VOL. 84, No. 3
MAY 1977
Psychological Bulletin
Copyright © 1977 by the American Psychological Association, Inc.
Left-Handedness
Curtis Hardyck
Lewis F. Petrinovich
Institute of Human Learning
University of California, Berkeley
University of California, Riverside
The phenomenon of left-handedness is reviewed from prehistoric man through
contemporary studies of lateralization of cerebral function. The following conclusions seem warranted: Handedness is most appropriately regarded as a continuum ranging from strong right-handedness across mixed-handedness to strong
left-handedness. Left-handedness, ranging from moderate through strongly lefthanded, is found in approximately 10% of the population. Evidence for a
genetic basis of handedness remains positive, but with no direct link established.
There is remarkably little evidence for any association of left-handedness with
deficit, as has often been suggested. The familial left-handed show greater recovery of functioning following unilateral cerebral insult than do nonfamilial
right-handed and nonfamilial left-handed. Both behavioral and clinical lesion
studies indicate systematic differences in lateralization of cerebral function between the right- and left-handed and the familial and nonfamilial left-handed.
A classification of handedness and lateralization of cerebral function is suggested, with the right-handed with no family history of left-handedness being
the most strongly lateralized and the left-handed with a positive family history
of left-handedness showing bilateral localization of functions. The left-handed
with no family history of left-handedness are classified as identical in cerebral
lateralization with the right-handed with no family history of left-handedness.
The possibilities exist that bilaterality of cerebral functioning is either stable in
the human race or is changing at an extremely slow rate.
In the Old Testament, in the Book of
Psalms (Joint Committee on the New Translation of the Bible, 1970), the statement is
made that the Lord's "right hand is full of
righteousness" (48:10); in the Book of Isaiah,
that his "right hand shall spread out the
heavens" (48:13); and again in Psalms, that
his "right hand shall hold me" (139:10).
„,,
/-\u rn i
i.
-j
-c.
The Old Testament provides no specific
Lord's left hand, what part, if any, it played
in the creation of the heavens, and who is
held in the left hand. However, in the New
Testament, the Book of Matthew (Joint
Committee, 1970) provides some fairly specific
information on the fate of those individuals
at the left hand:
. ,. ,
, „
c
When the Son of Man comes in his glory and all
the angels with ^ he will sit in gtate *n 4 thronC|
information as to what is contained in the
w;th
This work was supported in part by , funds from
the Spencer Foundation and from the Committee on
Research, University of California, Berkeley.
Requests for reprints should be sent to Curtis
Hardyck, Institute of Human Learning, University
of California, Berkeley, California 94720.
separate men into two groups, as a shepherd separates
the sheep from the goats and he will place the sheep
on his right hand and the goats on his left. Then
the king will say to those on his right hand, "You
have my father's blessing; come enter and possess the
kingdom that has been ready for you since the world
was made." . . . Then he will say to those on his
left hand, "The curse is upon you; go from my sight
385
all the nations gathered before him. He will
386
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
to the eternal fire that is ready for the devil and his
angels." (Matthew, 25)
The above quotations, selected from the
80 Biblical references to the right hand, are
not atypical; honors, virtues, and powers are
all ascribed to the right hand. By contrast,
as Wile (1934, p. 340) notes, "there is not
one honorable reference to the left hand."
Even if the picturesque language is ignored,
evidence seems convincing that in Biblical
times, negative qualities were attributed to
the left hand. By implication, those individuals
who carry out a variety of actions using the
left hand are different and probably suspect.
However, the outlook is not limited to antiquity. Among the contemporary ideological
descendants of the Biblical scribe who, along
with their ancestor, would be eager to consign the left-handed to burn in hell forever,
would be found a good many neurologists,
neurosurgeons, and neuropsychologists, sharing
among themselves the frustrations of seeing
their theories of cerebral function unable to
account for the bilateral cerebral organization
found in many of the left-handed. Their
frustrations have been aptly characterized by
Subirana (1969):
If the difference between the left and right hemispheres were to stick to an exact pattern in human
beings, it would have been relatively easy for the
investigators who from the second half of the last
century have worked unceasingly on the matter to
find out the relative functions of each hemisphere;
but not all people have a right hand preference and
a dominant left hemisphere for language function,
since left-handers are not included in this pattern and
seem to have been created on purpose to upset all
the different conceptions which have prevailed during
the last century in connection with the pathology and
physiology of the two hemispheres, (p. 248)
Reaction to the problems of explanation
posed by the left-handed has followed two
courses. Perhaps the most common approach
has been to assume that left-handedness is
a signal that something is wrong—that the
left-handed represent an aberrancy or abnormality and can thus be excluded from
consideration in theories of normal cerebral
functioning. Certainly the search for deficit
associated with left-handedness has been both
extensive and unceasing. Attempts have been
made to link left-handedness with mental
deficiency, dyslexia, speech disturbances, birth
defects, emotional instability, motor awkwardness, and alcoholism, to provide only a partial
list. A variant of this position has been the
suggestion that the left-handed represent an
evolutionary retrogression (Levy, 1969; Miller,
1971; Nebes, 1971)—a phylogenetic step
backward.
A second approach has been to disregard
the left-handed, usually by ignoring the observed differences in cerebral organization or
by assuming that they are the simple mirror
images of the right-handed. Broca, in 1861,
seems to have been the first to suggest the
mirror image hypothesis, only to have case
reports appear almost immediately that prevented his formulation from being considered
absolute. However, belief that the left-handed
are mirror images of the right-handed survived in the clinical neurological literature
until at least 1936 and still has adherents
today (Sperry, 1973).
Those who disregard the left-handed usually
describe the characteristic form of cerebral
organization for the right-handed, noting
briefly in the process that there are some
exceptions, such as the left-handed. A contemporary example has been given in Ornstein's (1972, 1973) writings on the psychology
of consciousness. In two volumes on the
subject of consciousness, including a discussion
of the nature of functions performed by the
right and left cerebral hemispheres, the delineation of function is represented as being
straightforward, with the left hemisphere
specialized for "analysis" and the right hemisphere specialized for "holistic mentation."
In the course of this discussion is the following footnote: "This right-left specialization is based on righthanders. Lefthanders,
who are about 5 percent of the population,
are less consistent; some have reversed
specialization of the hemispheres, but some
have mixed specialization—e.g., language in
both sides" (p. 53). This "5 percent" is not
mentioned again in the discussion of consciousness and cerebral specialization—a procedure that is not as extreme as consigning
the left-handed to hell, but does seem to
leave them, at least, in purgatory.
Formulations on the relation of handedness
to magic, religion, and cultural symbolism
can be found in the collection edited bv
LEFT-HANDEDNESS
Needham (1973). In general, scientific outlooks on left-handedness are consistent with
philosophical formulations.
Faced with what is essentially a harmonious
outlook in scientific thought and in philosophical speculation, some justification should
be offered for considering the left-handed,
whatever percentage of the population they
may be, as a problem worthy of detailed study.
1. The evidence for the association of lefthandedness and deficit is based largely on
accumulated clinical impressions rather than
on systematic study. It seems appropriate to
review this evidence and the conclusions that
have been drawn from it.
2. The left-handed of high ability are
usually conveniently forgotten in discussions
of handedness and deficit. Among notable
examples of left-handed individuals of high
ability are Michelangelo, Leonardo da Vinci,
Benjamin Franklin, and Pablo Picasso. A recent evaluation of characteristics common to
left-handed children (T. H. Blau, Note 1)
reported that left-handed children may be
more creative than their right-handed counterparts, although the evidence is only suggestive.
3. Much has been made of the deficit of
the left-handed in certain types of cognitive
tasks, such as spatial ability (Levy, 1969;
Miller, 1971; Nebes, 1971), where the evidence
is based on small and highly selected samples.
Attempts to replicate these findings (FaganDubin, 1974; Hardyck, in press-a; Hardyck,
Petrinovich, & Goldman, 1976; Kutas, McCarthy, & Donchin, 1975; Newcombe &
Ratcliff, 1973) have not been successful.
4. The strengths specific to the left-handed
have not, in general, been included in any
overall evaluation. Extensive analyses of patterns of recovery from the effects of cerebral
lesions indicate that the left-handed recover
functions more quickly and show fewer longterm effects of brain lesions than do the
right-handed. Such effects are not limited to
the phenotypically left-handed. As Subirana
(1969) has pointed out, "The cases seen in
last years authorize me to write that the
aphasics with a left-handed sibling are nearly
always the champions of the language rehabilitation division" (p. 268).
5. The left-handed have frequently been
categorized as a group requiring special
387
education or presenting special educational
problems, these opinions again being based
primarily on accumulated clinical impressions.
These considerations persuaded us, following
an examination of handedness and its relationship to intellectual functioning in 7,686
school children (Hardyck, Petrinovich, &
Goldman, 1976), to review in detail the
problem of handedness and its relationship
to intellectual functioning and cerebral
dominance.
The Ontogeny of Handedness
Theories of the causation of handedness are
plentiful, although the majority of early suggestions can be dismissed on the basis of
known anatomical evidence. The evidence
favors a genetic basis, but existing genetic
models are all limited by the fact that data
on the incidence of handedness are extremely
variable.
Psychological-Social (Nongenetic)
Theories
Explanations for the preference habits of
man are so extensive that any detailed account is impractical. Extensive reviews of
social and psychological theories of handedness were given by Jackson (1905), Wile
(1934), and A. Blau (1946). Jackson's approach is illustrative of the purely social
outlook. He argued that handedness was
entirely a matter of habit and that all children
should be taught to use either hand interchangeably. A. Blau (1946), using a psychoanalytic framework, argued that left-handedness is a result of emotional negativism and
has no biological basis whatever, a point of
view also advocated by Domhoff (1969-1970)
and Thass-Thienemann (1955), who focused
on the negative qualities associated with the
term left.
A variety of social evolution explanations
have been suggested, perhaps the most common one being the "sword and shield" theory.
This explanation, attributed to Thomas Carlyle, among others, has had numerous advocates (Gould, 1908; Harman, 1905; PyeSmith, 1871; Woodruff, 1909). The basic
argument is that the soldier who held his shield
in his left hand offered his heart better
388
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
protection and thus had a better chance of
survival. By the same process, the right hand
grew more skilled in manipulative movement
and eventually came to be used for all skilled
manipulative activities.1
Anatomical Theories
Organ asymmetry has often been suggested
as an explanation for handedness. Aristotle
(1941) believed that the organs for the right
side of the body were more powerful than
those for the left. Sir Francis Bacon (1875)
was more specific in his formulations, offering
the opinion that the liver being located predominantly on the right side was the basis
for handedness.
It is difficult to identify origins of the idea
that the two sides of the brain might differ
and be related to handedness. The idea that
one side of the brain had a direct relationship
to the opposite side of the body seems to
have originated at least during the first
century A.D., according to Gianntrapani
(1969). In 1871, Ogle gave an account of his
investigations, including detailed descriptions
of an independent investigator's assessment
of the differences present in the brains of two
left-handed women as compared with the
brains of right-handed individuals, stating
that many features appeared to be reversed.
Heschl, in 1878, provided a detailed description of organic asymmetry.
Contemporary opinion on the topic is divided. Von Benin's (1962) detailed review of
anatomical differences led him to conclude that
any observable differences are so insignificant
as to be totally inadequate to account for
any differences in specialization of function.
Geschwind and Levitsky (1968), in an analysis
of 100 brains, reported that the area behind
Heschl's gyrus was larger on the left in 65%
of the brains examined and larger on the
right in 11%. Unfortunately, neither von
Bonin nor Geschwind and Levitsky had
handedness data to accompany their
investigations.
A variant on the idea of brain differences
is the proposal that the left side of the brain
is better vascularized. Gratiolet (1839-1857)
suggested that the left side of the brain had
a more rapid flow of blood, based on the
claim that the left carotid artery, arising
directly from the aorta, had a faster blood
flow than did the right carotid artery, being
separated from the aorta by the innominate
artery. This position was developed and
elaborated by Hyrtl (1871). In general, these
positions were discredited by advances in
anatomical knowledge, particularly when it
was shown that the circle of Willis provides
for the equalization of blood supply to both
hemispheres.
In this context, a more recent study by
Di Chiro (1962) is of interest. He took angiograms of predominant venous drainage on
46 patients, noting reported handedness and
determining localization of speech by means
of Wada and Rasmussen's (1960) technique
of injecting sodium amytal into the carotid
arteries. Our recalculation of his data, removing ambiguous cases of handedness, indicates that the relationship between handedness
and predominant venous drainage is within
the limits expected by chance.
Genetic Theories
There have been many attempts to develop
genetic models for handedness (Annett, 1964,
1967, 1972, 1973a, 1973b, 1974, 1975; Bradbury, 1912; Chamberlain, 1928; Falek, 1959;
Hudson, 1975; Jordan, 1911, 1914; Levy &
Nagylaki, 1972; Newman, 1931; Ramaley,
1912, 1913; Rife, 1940, 1950; Schott, 1931;
Trankell, 1950, 1955), but not a great deal
1
The problem common to all social evolutionary
explanations is that disproof is impossible. The "sword
and shield" theory should, to be comprehensive, offer
some explanation as to why women, who did not
usually carry swords and shields, have an even lower
incidence of left-handedness than do men. To illustrate the ease with which such explanations can be
constructed, we may take the data of Salk (1966),
showing that women tend to hold neonates with the
left arm, whether right- or left-handed. Salk suggests
that this places the neonate in closer contact with
the mother's heartbeat and results in a greater feeling
of security for the infant. As a social evolution explanation for handedness, it will work just as well
as the sword and shield theory. In fact, since it seems
safe to postulate that more women have held more
infants than men have held shields and swords, it is
even possible to "explain" the lower incidence of
left-handedness in women.
LEFT-HANDEDNESS
of success. The majority of views argue that
left-handedness is carried as a Mendelian
recessive, but the data base for these arguments is far from adequate. Trankell (1950)
collected data on all seventh-grade children
and their parents in the city schools of
Stockholm, allowing him to standardize his
measures on 800 children and to test over
800 more. However, his incidence data from
parents were collected by questionnaire, and
the unreliability of such data collection for
handedness has been shown in several studies
(Benton, Meyers, & Polder, 1962; Satz,
Achenbach, & Fennell, 1967). Falek's (1959)
study, which used interviews and behavioral
testing to determine incidence and preference,
produced an inconclusive result, possibly by
discarding those individuals who had no strong
hand preference. Findings from both lesion
(Hecaen & Sauget, 1971) and behavioral
studies (Dee, 1971) suggest that those individuals who have a family history of lefthandedness are also less likely to be strongly
left-handed. Falek, by attempting to select
clearly defined groups, may have discarded
the genetically meaningful portion of his data.
The ambiguity of many data in this area
has been pointed out by Fuller (I960), who
noted that the same data have been used to
support and to disprove genetic theories.
The most recent attempts to develop genetic models of handedness have been those
of Annett (1964, 1967, 1972, 1973a, 1973b,
1974, 1975) and Levy and Nagylaki (1972).
The Annett model argues that handedness is
distributed binomially as left, mixed, and
right, in the proportions .04, .30, and .66,
respectively, and is due to the presence or
absence of a Right Shift factor. In Annett's
model, the presence of this factor will produce
both a localization of speech in the left
cerebral hemisphere and a bias toward righthandedness. Annett has reported a series of
studies in support of this model. However,
her model is dependent on the acceptance of
the conditions she has developed. The model
does not seem to fit the data of Hecaen and
Sauget (1971) on either strength of handedness
or on bilateral speech representation in many
left-handed. In her most recent account (1975)
Annett reviewed a number of lesion studies
with respect to her model, arguing that three
389
of the studies (Bingley, 1958; Newcombe &
Ratcliff, 1973; Penfield & Roberts, 1959) were
in accord with the results of her genetic model.
Unfortunately, the studies of Conrad (cited
in Zangwill, 1967) and Hecaen and de Ajuriaguerra (1964) show significant discrepancies.
Annett also failed to include in her analysis
the extensive study done by Hecaen and
Sauget (1971). Since Hecaen and Sauget
took great care to evaluate both preferred
handedness and family history of handedness,
this omission is not easily dismissed. Also,
Annett's model requires a lateralization of
speech to either the left or the right hemisphere, which requires dismissing the considerable body of both lesion (Branch, Milner,
& Rasmussen, 1964; Hecaen & Sauget, 1971;
Wada & Rasmussen, 1960) and behavioral
(Lomas & Kimura, 1976) evidence for bilateral
speech representation in many left-handed.
The two-gene, four-allele model presented
by Levy and Nagylaki (1972) is undoubtedly
the most detailed and comprehensive of the
genetic models. However, it has recently
been critically evaluated by Hudson (1975)
who argued that the model is unable to
account for observed distributions of handedness in three sets of data.
The Levy-Nagylaki model does attempt to
account for bilateralization of function, but
argues that only half the population of familial
left-handed should show bilaterality. In view
of the large number of studies reporting that
interhemispheric differences are less pronounced in the left-handed than in the righthanded (see Handedness and Cerebral Dominance, this review), this aspect of the model
seems suspect.
Perhaps the principal proponent of a nongenetic explanation is Collins (1968, 1969,
1970, 1975), who has argued that handedness
can be accounted for without any recourse
to genetic considerations, a position strongly
contested by proponents of genetic models
(Nagylaki & Levy, 1973).
In summarizing this area, the most appropriate conclusion seems to be that a genetic
model is a more probable explanation. Such
a conclusion has to be based more on the
cumulative body of data on the left-handed
than on the strictly genetic evidence. The
most compelling evidence is the systematic
390
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
behavioral differences in hemispheric specialization that have been reported on the lefthanded. A final comment on the evidence for
a genetic base is reserved until behavioral
and lesion studies are reviewed.
Developmental Status
Evidence on developmental patterns of hand
preferences has largely been accumulated
through the study of individual children
(Baldwin, 1895; G. V. N. Dearborn, 1913;
Fenton, 1925; Gesell & Ames, 1947; Giesecke,
1936; Halverson, 1931; Heinlein, 1930; Lippman, 1927; Major, 1906; Seth, 1973; Shinn,
1914; Updegraff, 1932; Voelkel, 1913; Wooley,
1910). Giesecke's (1936) study of infants
ranging in age from 5 days to 17 months
can serve as an illustration of this class of
studies. She observed the manipulative activities of her subjects, combining this with the
presentation to the infant of brightly colored
objects, such as blocks, in a medial plane
and alternatively to the right and left sides.
In four subjects, ranging in age from 7 to
14 months, she found three subjects to carry
out a predominance of activities with the
right hand and one with the left.
Some interesting neurophysi9logical relationships are suggested by the work of Cernacek and Podivinsky (1971), who studied
evoked cortical potentials in response to mild
electrical shock administered to right and left
hands in infants and children. They found
evoked cortical potential in the left hemisphere to be significantly larger for right-hand
stimulation in dextrals. There were no differences found for children classified as ambidextrous, and there was considerable variability in the size of the evoked response for
those children classified as left-handed. The
researchers speculated that for the righthanded, cortical representation of the right
hand is much more focally concentrated
within the somatosensory regions of the left
hemisphere, whereas the left hand may
project more diffusely to the right hemisphere,
or even to both hemispheres. A similar finding
has been reported by Kutas and Donchin
(1974). This work is also supported by the
findings of Wyke (1969), who, in lesion
studies, found tapping and manipulative skills
to be impaired in both arms in subjects with
left-side lesions, but only contralateral impairment with right-side lesions. The model
of hemispheric functioning proposed by Semmes (1968) is also compatible with these
ideas. A survey of results of these studies
indicates that knowledge of the ontogeny of
handedness and of its pattern of development
is still ambiguous and incomplete, particularly
for the left-handed.
The problem is further complicated by the
fact that societies have had, at different
times, quite different degrees of tolerance for
the phenomenon of left-handedness. The extent to which this affects the tendency toward
left-handedness is difficult to assess; but the
data of Dawson (Note 2) on societies with
varying degrees of permissiveness toward lefthandedness provide average percentages of
10.4% for societies that Dawson characterized
as "extremely permissive," 5,9% for "permissive," and 1.8% for "harsh, restrictive"
societies.
The Incidence of Handedness
Handedness in Early Man—Archeological and
Anthropological Evidence
Although the amount of evidence is limited,
existing data suggest that the incidence of
handedness in early man was not essentially
different from the ratios found today. Dart
(1949), in an analysis of 47 fossil baboon
skulls found under circumstances indicating
they had been killed as food by Australopithecus, found 7 skulls clearly identifiable
as fractured on the left side by a blow from
the front, indicating that the implement used
to strike the blow had been held in the assailant's right hand. Only 2 skulls were found
with similar fractures on the right side.
Although such data are hardly sufficient for
any stable determination of incidence, the
evidence suggests a predominance of righthandedness. Black, Young, Pei, and de Chardin
(1933) suggested that the stone implements
used by Peking man fit the right hand better
than the left. By contrast, both Sarasin
(1882) and de Mortillet (1882) reported the
incidence of stone scraping tools to be about
equal for both hands, concluding that early
LEFT-HANDEDNESS
391
Table 1
Incidence of Handedness
Type of data
Studies
Range of
incidence
(%)
Mean Median
(%)
(%)
Incidence figures
unsupported by data
Baldwin (1901-02), Gould (1908),
Hyrtl (1871), Kapustin (cited in
Schiller, 1932), Lombroso (1903),
Morro (cited in Ellis, 1890),
Songues (cited in Gordon, 1920)
2-8
Indirect measures
of handedness
Dennis (1958), W. F. Jones (1918),
Parsons (1924), Selzer (1933),
Van Biervliet (1897), Wile (1934),
Woo & Pearson (1927)
3.9-29.3
Self-report and
questionnaire studies
Blau (1946), Burt (1937),
Carrothers (1947), Clark (1957),
Komai & Fukuoka (1934), Pyle &
Drouin (1932), Ramaley (1912),
Smith (1917), Wallin (1916),
M. 0. Wilson &Dolan (1931)
5.5-15.8
8.64
Performance tests and
behavioral measures
Daniels (1940), Durost (1934),
Gordon (1920), Haefner (1929),
Hardyck, Petrinovich, &
Goldman (1976), Hildreth (1949a, 1949b),
Jasper & Raney (1937),
H. E. Jones (1931), Newcombe &
Ratcliff (1973), Ojemann (1930a, 1930b),
Oldfield (1971), Quinan (1930),
Schiller (1932), Updegraff (1932)
3.3-11.4
8.58
man was equally skilled with both hands,
a conclusion also reached by D. Wilson (1904).
Magoun (1966) has noted that in Cro-Magnon
paintings, silhouettes of the human hand are
common, with the left hand occurring about
80% of the time. If it can be assumed that
the preferred hand was used to trace the
silhouette, then it seems safe to assume that
Cro-Magnon man was predominantly righthanded. Similar evidence for the predominance of right-handedness was provided by
Brinton (1896) in a commentary on North
American aboriginal art and by Mason (1896)
in an examination of throwing sticks.
An unusual measure of incidence was developed by Dennis (1958), who examined the
frequencies of handedness as depicted in
paintings in the tombs of Beni Hasan and
Thebes, spanning the eras from about 2500
B.C. to 1500 B.C. Dennis noted the frequency
with which the right or left hand was used
for activities requiring skill, excluding un-
4.8
5.0
12.2
18.0
8.0
skilled activities such as carrying or instances
of bimanual acts. His results are not drastically different from many contemporary
incidence figures.
The first written record of the incidence
of left-handedness, as von Bonin (1962), Brain
(1945), and Burt (1937), among others, have
noted, is in the Book of Judges (Joint Committee, 1970) and describes the Benjamite
army of 26,700 men. Within this army was
a battalion of 700 men described as "seven
hundred picked men from Gibeah, left-handed
men, who could sling a stone and not miss
by a hair's breadth" (20:15). If this information is used to calculate an incidence ratio,
the figure of 2.6% is obtained—a rather low
ratio of left-handed, until the rather demanding selection factors are considered, entirely
apart from the consideration that there is no
evidence that the other 26,000 soldiers were
all right-handed.
392
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
Contemporary Estimates of the Incidence of
Left-Handedness
When contemporary estimates of the incidence of left-handedness such as those presented by Wile (1934) and Hecaen and de
Ajuriaguerra (1964) are examined, an astonishing range of values appears. Estimates of
left-handedness in the population at large
range from a low of 1% to a high of 30%.
However, examination of the methods used
to arrive at incidence figures reveals that
(a) many incidence estimates are actually
opinions unsupported by any data, and (b)
incidence of handedness is closely related to
methods of determination.
In Table 1, a classification of incidence
figures is given, categorized by the methods
used to determine them. Examination of this
table indicates that estimates that are either
extremely high or extremely low tend to be
those based either on opinion unsupported
by data or on indirect determinations of
handedness, such as eyedness or strength of
grip—measures that have a positive but far
from perfect correlation with preferred
handedness.
When performance measures have been
taken, results have been much more stable,
with the incidence of left-handedness centering
around 9%-10%. Within this group of studies,
there is only one striking deviation: Newcombe and Ratcliff (1973) reported an incidence of only 3%. This low figure seems to
have been produced by an extremely stringent
criterion, which required that all seven performance tasks be done with the same hand.
On the basis of the accumulated performance
studies, a population estimate of 8%-10%
seems most appropriate. However, it should
be kept in mind that this figure represents
a range of preference rather than an absolute,
with preferred handedness ranging from those
few individuals who are totally left-lateralized
to the individuals who use either hand with
almost equal skill.
The Measurement of Handedness
Viewed phenomenologically, the measurement of handedness would seem to be simplicity itself. However, in a technological
society, most devices are designed for the
right-handed. Simple use of devices such as
can openers made to be turned with the right
hand, scissors angled so that the cutting
edge is appropriate for right-hand usage, and
other such devices undoubtedly has some
effect on the incidence of certain types of
hand activities.
Self-report is certainly the most common
method used to assess handedness, whether
by simple self-categorization or by means of
detailed questionnaires. Next to self-report,
the next most common determination is made
on the basis of writing hand. As a measure
of handedness this particular measure has
several drawbacks, being subject to cultural
pressure, both by parents and by the educational system. The beginning left-handed
writer is frequently reported to be a source
of annoyance and frustration to the primary
school teacher and probably continues to be
pressured to learn to write with the right
hand, even in today's era of more permissive
school systems.
There has also been a tendency to equate
strength with handedness. Woo and Pearson
(1927) analyzed Sir Francis Gallon's dynamometer grip data to arrive at an estimate
of left-handedness. Woo and Pearson apparently assumed that strength of grip could
be equated with handedness, an assumption
that was brought into serious question by the
study of Koch (1933), who showed that
dexterity and strength of grip were not
closely related and that for her left-handed
subjects, about 28% had stronger grips with
their right hands.
Handedness has also been equated with
sensitivity of discrimination, although the
techniques used at times are difficult to
fathom. Van Biervliet (1897) suspended equal
weights from his subjects' right and left index
fingers and had them make repeated judgments as to which weight was heavier. Subjects who consistently reported the right side
weight as heavier were judged as left-handed.
A variant on this approach was the brachiometer test of E. Jones (1911), in which a variety of
bone measurements were taken on both arms.
Parsons (1924) was firmly committed to the
belief that handedness was completely determined by dominant eyedness and developed
LEFT-HANDEDNESS
393
a device called the Manuscope to use in de- reliably determined by questionnaire measures
termining the preferred hand. (Later studies alone and that behavioral measures are neceshave indicated that handedness and eyedness sary to insure accurate classification. In this
are correlated only about .53, based on the context, the studies of Benton et al. (1962)
average relationships found among several and Satz et al. (1967) are of particular interest,
since they tested subjects self-classified as
studies.)
A variety of questionnaires have been con- left-handed on behavioral measures of manual
structed at various times to assess handedness dexterity. Benton et al. gave subjects the
(Annett, 1970; Benton, Meyers, & Polder, Crawford and Crawford (1956) Small Parts
1962; Crovitz & Zener, 1962; Hildreth, 1949a, Dexterity Test and two paper-cutting tasks,
1949b, 1950; Oldfield, 1971; Satz, Achenbach, deriving a composite score of skill with each
Pattishall, & Fennell, 1965). The majority of hand. A similar procedure was used by Satz
these questionnaires cover the same items and et al., who also used the Crawford measure
differ primarily in the type of answer option and the Reitan (1959) finger oscillation
given to the respondent. A variation on hand- (tapping) test. In these two studies, those
edness questionnaires have been the so-called subjects who classified themselves as lefttests of laterality (Belmont & Birch, 1965; Ber- handed were classified by the performance
man, 1971; Crinella, Beck, & Robinson, 1971; measures as follows:
Harris, 1955; Sabatino & Becker, 1971), which
Benton, Meyers, and Polder (1962)
differ from handedness measures primarily in
that determinations of eye and foot dominance
Predominantly left-handed 44% (22)
35% (14)
Ambilateral
are also measured and an overall indicator
of "lateral dominance" is derived. PerformPredominantly right-handed 10% ( 4)
ance measures of handedness have in general
Satz, Achenbach, and Fennell (1967)
been behavioral demonstrations of the activities listed in questionnaires. Formal routines
Predominantly left-handed 61% (33)
have been devised by a number of investi22% (12)
Ambilateral
gators (Roudinesco & Thyss, 1948; Subirana,
Predominantly right-handed 17% ( 9)
1961;Zazzo, 1960).
By contrast, of the 69 self-classified rightOnly a few comparisons of questionnaires
and behavioral measures exist. One of the handed in the Satz et al. study, 3% (2) were
most comprehensive comparisons was done left-handed and 4% (3) were ambilateral. For
by Koch (1933), who compared observations Benton et al., of the 66 self-classified rightof performance on 105 tasks with responses handed, 3% (2) were left-handed and 30%
to a questionnaire asking for preferred hand (20) were ambilateral.
This evidence suggests that the probability
usage on the same tasks. Her set of tasks
of
misclassification in self-reports of handedincluded both frequently occurring items, such
ness
is much higher for the left-handed than
as writing hand or hand used to deal cards,
and less frequent activities, such as hand for the right-handed. Such a possible misused to manipulate the clasp on an umbrella classification may aid in explaining some of
or hand used to pull the string when using the inconsistent results found in studies of
a bow and arrow. The subjects were observed handedness as related to intellectual or cogon each of these activities and then given nitive deficiency, and in studies of cerebral
a questionnaire. After a 1-week interval, the dominance.
questionnaire was given again, resulting in a
test-retest reliability of .81 overall.
Handedness and Deficit
Similar comparisons, though not as detailed
Left-handedness has been linked with a
in scope, have been done by other investigators (Benton et al., 1962; Raczkowski, variety of deficits. In reviewing what has
Kalat, & Nebes, 1974; Satz et al., 1967). come to be an enormous literature, the
The results have been, in general, consistent; teasingly suggestive nature of this relationthe conclusion is that handedness is not ship is rather striking in its persistence
394
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
through generations of research workers. no difference (Fagan-Dubin, 1974; Hardyck
There is usually just enough of a relationship et al., 1976; Keller, Croake, & Riesenman,
to suggest a possible link and never enough 1973; Miller, 1971; Newcombe et al., 1973;
of one to establish firmly a solid correlation. Orme, 1970; M. O. Wilson & Dolan, 1931)
To evaluate this material, it is necessary to and 1 (Levy, 1969) found left-handed to do
assess the validity of methods of classification less well on Wechsler Adult Intelligence Scale
of handedness. As mentioned earlier, the pos- performance items. Since the comparison in
sibility of misclassifying the left-handed on Levy's study was between two groups of
the basis of self-report is considerably higher graduate students in scientific and engineering
fields, "less well" cannot be interpreted in
than that for the right-handed.
A second distinction that must be kept in relation to usual test norms. A questionnaire
mind is the population from which the groups study reported left-handed girls in a juvenile
being examined are drawn. Studies postu- detention home to be more unstable than
lating relationships between handedness and right-handed ones (Orme, 1970), and another
deficit have been largely based on samples questionnaire study (Bakan, Dibb, & Reid,
drawn from clinics where children have been 1973) found that left-handed college students
referred because of speech, language, or other reported more parental accounts of stressful
births. Three studies (Flick, 1966; Nebes,
kinds of problems.
Still another type of problem exists. The 1971; Silverman, Adevai, & McGough, 1966)
emphasis placed on the testing of hypotheses reported poorer performance for the leftby the approach of determining statistically handed on perceptual tasks. The studies by
"significant differences" may well have led to Flick and by Silverman et al. have not been
an overcapitalization of chance relations. In replicated, to our knowledge; however, four
the studies reviewed for this paper, we found replications of the Nebes study (Hardyck,
relatively little emphasis on the extent to in press-a; Kutas, McCarthy, & Donchin,
which handedness as a variable is associated 1975) found no differences between right- and
with variance in other variables under ques- left-handed subjects. Three studies reported
tion. When reviewed as a problem in ac- a larger percentage of left-handed among
counting for variance in performance on a mentally defective children than among norvariety of test measures, handedness turns mal children (Burt, 1937; Gordon, 1920;
out to account for remarkably little vari- M. O. Wilson & Dolan, 1931) and one study
ance—far less, in fact, than the emphasis (Wile, 1934) found no difference. Finally, one
placed on small but statistically significant study reported a high incidence of lefthandedness among patients in an alcoholic
differences would warrant.
A detailed review of studies comparing the ward (Bakan, 1973). It appears that the data
performance of the left- and the right-handed indicating that left-handedness is associated
is precluded by space limitations. A summary with deficits of various kinds is far from
does, however, indicate the overall trend of compelling.
results. Of 14 studies of reading ability,
Handedness and Cerebral Dominance
13 reported no differences (Allison, 1966;
Speculations about the relation of handedBalow, 1963; Balow & Balow, 1964; Coleman
& Deutsch, 1964; W. F. Dearborn, 1931; ness to cerebral dominance are at least as old
Gilkey & Parr, 1944; Hildreth, 1934; Koos, as the initial speculation that the two hemi1964; Sabatino & Becker, 1971; Wittenborn, spheres of the brain perform different func1946; Witty & Kopel, 1936; Wolfe, 1941a, tions. Credit for the idea of cerebral speciali1941b; Woody & Phillips, 1934), and 1 found zation is usually given to Dax (1865) and to
the left-handed to be superior (M. M. W. Broca (1861), who seem to have presented
Jones, 1944). In two studies of academic the first specific set of statements concerning
achievement, one found no difference (Saba- localization of function in relation to handedtino & Becker, 1971), and the other (Gilbert, ness. The concept of cerebral dominance seems
1973) found the strongly left-handed to do to have begun with Jackson (1958) and to
less well on a college entrance examination. have been given added credence by the work
Of 8 studies of measured intelligence, 7 found of Bastian (1868).
LEFT-HANDEDNESS
The study of specialization of functions
within the hemispheres has, in recent years,
been stimulated by the studies of Sperry,
Gazzaniga, and Bogen (Sperry, 1968a, 1968b;
Sperry, Gazzaniga, & Bogen, 1969) on patients
who have undergone cerebral commissurotomy. Studies on these patients led to the
conclusions that ". . . the disconnected left
hemisphere processing information from the
right hand and the right half visual field is
the hemisphere that does essentially all the
talking, reading, writing, and mathematical
concepts in the right hand subjects . . . "
(Sperry, 1973, p. 212). The right hemisphere
is superior at form relations and perceptual
organizations, but, in Sperry's terms, "the
disconnected right hemisphere on the other
hand remains essentially mute, alexic, agraphic,
and unable to carry out calculations beyond
simple additions to sums under 20 . . . "
(1973, p. 212).
The results of these studies have stimulated
a flood of investigations into the nature and
function of cerebral dominance and localization. In particular, the discovery of specialized
nonverbal processing centers has sparked a
variety of speculations, ranging from questions
on current educational practices to the somewhat metaphysical speculations of consciousness and brain function typified by the work
of Ornstein (1972, 1973).
The value of the commissurotomy studies
can scarcely be overestimated. At the same
time, it is quite possible that generalizations
made from nine patients suffering from severe
epileptic disorders of unknown etiology may
not be completely applicable to the population at large. In this context, the studies of
visual-field differences in normal subjects
stimulated by the Sperry et al. studies of
visual half-field differences in the commissurotomy patients and the dichotic listening
studies stemming from Kimura's applications
of Broadbent's techniques (Broadbent, 1954,
1956; Kimura, 1963, 1964, 1967; Kimura &
Folb, 1968) are of particular interest, especially in relation to handedness. In these
studies, handedness was usually considered to
be an indicator of cerebral dominance. Differences in efficiency of visual-field localization and in accuracy of report in dichotic
listening were measured in relation to
handedness.
395
The number of studies currently reported
is too extensive to review in any detail.
A summary reveals the following trends:
Of studies of visual-field preference that
report no data on family history, six found
the right-handed to show a right visual-field
preference (Bryden, 1973; Dimond, 1971;
Dimond & Beaumont, 1974; McKeever & Gill,
1972; Orbach, 1967; Zurif & Bryden, 1969),
and four reported no visual-field differences
(Beaumont & Dimond, 1973; Groberg, Dustman, & Beck, 1969; Hines & Satz, 1974;
McKinney, 1967). One study (Orbach, 1967)
reported that the left-handed recognize Hebrew
words better in the left visual field, and
English words better in the right visual field.
Another study (Lomas & Kimura, 1976) found
that concurrent manual activity (rhythmic
tapping) with the right hand interfered with
speech in right-handed subjects but that lefthand activity had no effect on speech. Lefthanded subjects showed equal interference
with speech activity when tapping with
either hand.
When family history is taken into consideration, the right-handed with both a positive and a negative family history of lefthandedness have higher accuracy scores and
show faster reaction times in the right visual
field (Cohen, 1972; Dirnond Ik Beaumont,
1974; Hines & Satz, 1971; McKeever, Gill,
& Van Deventer, 1975; McKeever, Van
Deventer, & Suberi, 1973). The left-handed
with a family history of left-handedness have
better word recognition in the left visual field
than do the left-handed with no family history
of left-handedness (Bryden, 1965; Zurif &
Bryden, 1969). When differences between
visual fields were examined, several studies
(Beaumont & Dimond, 1975; Buffery, 1974;
Cohen, 1972; Davidoff, 1975; Dimond &
Beaumont, 1972, 1974; Efron, 1962; McKeever, Gill, & Van Deventer, 1975; Moscovitch
& Catlin, 1970; Provins and Jeeves, 1975)
reported inter- and intra-visual-field differences
in reaction time to be less for the left-handed.
Studies of dichotic listening have revealed
a similar pattern. Of those studies that
reported no family history, three found a
smaller difference between the left and right
ear for the left-handed, as compared with the
right-handed (Curry, 1967; Curry & Rutherford, 1967; Satz et al., 1965), and three found
396
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
that the right ear was dominant for the righthanded (Curry, 1967; Knox & Boone, 1970;
Zurif & Bryden, 1969). One investigator found
the latter results only for those with a strong
hand dominance (Dee, 1971), one reported
left-ear dominance for the left-handed (Knox
& Boone, 1970), and another found this only
for those individuals who had a moderate
degree of left-handedness; for individuals who
were strongly left-handed, the right ear was
dominant (Dee, 1971). Three studies found
no differences (Cyr, Daniloff, & Berry, 1971;
Hines & Satz, 1971; Satz et al., 1965). One
complicating factor was suggested by Bryden
(1965), who reported that right-ear dominance increased with age for the right-handed
and decreased with age for the left-handed.
Thus, developmental age may be a confounding factor in some of these studies.
Finally, when family history was recorded,
it was found that the left-handed with a
positive history of left-handedness showed
a left-ear dominance (Dee, 1971; Zurif &
Bryden, 1969), whereas those with a negative
family history of left-handedness showed a
right-ear dominance (Zurif & Bryden, 1969).
When these studies are examined for common
trends, the variability shown by the lefthanded is again striking. The right-handed
groups display a clear-cut pattern of function
in most cases. The left-handed are sometimes
identical in performance with the righthanded, but more often than not, usually
show smaller interhemisphere differences.
The results of these studies lead to the
following conclusions: First of all, the systematic differences found in visual field and
dichotic listening experiments for familial
left-handed raise serious questions about nongenetic explanations of handedness, such as
that put forth by Collins (1970). If, as Collins
argued, an unspecified environmental mechanism is adequate to explain the fact that
offspring resemble their parents in handedness, such a mechanism would have to work
in a rather strange manner, since it would be
in effect for the familial left-handed, but not
for the nonfamilial left-handed.
The evidence from the few studies in which
familial handedness has been carefully evaluated suggests that bilaterality of cerebral
organization is not a characteristic of the
nonfamilial left-handed and that as a group,
they are organized for cerebral specialization
exactly as are the right-handed. Such individuals may be left-handed owing to some
early brain insult, as hypothesized by Bakan
et al. (1973), or perhaps some unspecified
environmental effect, as Collins (1970) suggested, or perhaps even a basis such as the
extreme negativism proposed by A. Blau
(1946).
Bilaterality of cerebral function seems to be
present in the left-handed only when there is
a family history of left-handedness; measures
of dichotic listening and visual-field differences
in these individuals show a consistent lack
of difference in both visual field and ear
preferences. In the 15 studies reviewed in
which familial handedness was used as a classificatory variable, 10 reported smaller between-hemisphere differences for the familial
left-handed and 5 found no difference when
compared with the right-handed. No studies
reported larger between-hemisphere differences
for the left-handed.
Lesion Studies
Concern with localization of function and
the characteristics of cerebral dominance
began with studies of patients who had suffered various types of cortical lesions. Broca
(1861) provided a dramatic demonstration of
the localization of speech in an aphasic
patient and originated the notion that lefthandedness is related to localization of language in the right hemisphere. However, for
some time after Broca, case reports continued
to appear citing instances of aphasia for lefthemisphere lesions in left-handed patients and,
very rarely, aphasia following a right-side
lesion in a right-handed patient. It was quite
some time before these cases were considered
as other than simple exceptions to Broca's
formulations.
Since the clinical literature on this topic
is huge and has been adequately summarized
by a number of investigators, we limit the
present review to those contemporary reports
based on reasonable numbers of cases (Branch,
Milner, & Rasmussen, 1964; Cloning, Gloning,
Haub, & Quatember, 1969; Goodglass &
Quadfasel, 1954; Hecaen & Piercy, 1956;
Hecaen & Sauget, 1971; Luria, 1970; Penfield
& Roberts, 1959; Subirana, 1958). The results
LEFT-HANDEDNESS
can be summarized rather succinctly. About
24% of right-handed individuals with left-side
cortical lesions develop language disorders, as
compared with 6.7% of right-handed with
right-side lesions (data taken as a median
percentage over all studies in which data are
roughly comparable, and summing over all
categories of verbal disorders—oral language,
reading, writing, etc.). The left-handed with
left-side cortical lesions show language disorders in 22.4%, and for right-side lesions,
13.7%.
These between-hemisphere differences are
not as extreme for visual measures: For the
right-handed, the percentage of visual disorders for left-side lesions is 7.1%, and for
right-side lesions, 10.8%. For the left-handed,
the percentage of disorders for left-side lesions
is 7.8%, and for right-side lesions, 10.1%.
Another way of examining these differences
is by comparison of the frequency of statistically significant differences in occurrence of
deficits in performance, as related to lesion
sites in the right- and left-handed. For the
right-handed, disorders in relation to lesion
site are almost always statistically significant—
for example, language disorders occur frequently with left-side lesions and rarely with
right-side lesions. For the left-handed, the
lack of significance in relation to lesion site
is the most usual finding-—disorders associated with one hemisphere seem to occur at
no more than chance levels of significance.
Hecaen and Sauget (1971) assessed 50 types
of symptoms in relation to lesion site—right
or left hemisphere—on right- and left-handed
patients. For the right-handed, they reported
47 out of SO between-hemisphere differences
as statistically significant at a probability of
.05 or less. The corresponding number of
significant differences for the left-handed
patients was 4 out of 50.
The evidence again supports the view that
the left-handed have a more bilateral functional organization, both verbally and visually, than do the great majority of the righthanded. However, 'as the study of Hecaen
and Sauget (1971) indicated, both the family
history of left-handedness and the behavioral
tendency of left-handedness must be carefully
assessed, since there are some rather striking
differences between the familial left-handed
and the nonfamilial left-handed. There are
397
no differences in the verbal performances of
the familial left-handed who have suffered
either right or left cortical lesions—the frequency of language difficulties of all types is
virtually identical for right- and left-side
lesions. For the nonfamilial left-handed, the
frequency of language difficulties of all types
is always greater with left-side lesions. To
further complicate the analysis, the pattern
of deficit as a function of lesion site for the
weakly left-handed—those subjects who do
not show extremely strong left-handed preferences in the behavioral measures—is almost
identical with that shown for the familial
left-handed, no matter what the degree of
left-handedness. For the strongly left-handed-—
those subjects who perform almost all activities with the left hand—the pattern of deficit
is almost identical with that of the nonfamilial left-handed, with the majority of
disturbances of language associated with a
left-side lesion. When the frequency of familial
to nonfamilial handedness is assessed in relation to the degree of handedness, the familial
cases are more often associated with moderate
than with extreme left-handedness. Although
Hecaen and Sauget cautioned that these
findings should be replicated, the data are
nonetheless striking, especially in view of the
differences found by Zurif and Bryden (1969)
between familial and nonfamilial handedness
in visual field and dichotic listening
performance.
In reviewing these studies of handedness,
it is easy to understand Subirana's (1969)
lament that the left-handed seem to have
been put on earth to plague and to complicate
straightforward interpretations of human cortical functioning. They are both a fascination
and an annoyance, and although our review
of handedness leads us to wonder why the
left-handed have been viewed so darkly
throughout history, it is possible to understand the researcher who, having his neat
theoretical formulations concerning cortical
functioning reduced to absurdity by the lefthanded, argues that left-handedness is the
simple reverse of right-handedness, or else
pretends that the left-handed do not really
exist.
Discussion
Several conclusions seem evident:
1. One conclusion has been reached by
398
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
every researcher who has studied the problem
of handedness. Though obvious, it still needs
emphasis: Handedness is not a simple phenomenon that is easily determined phenomenologically or by self-report. The development
of preferred handedness can be markedly
affected by such factors as family and cultural
preferences, educational practices, the prevalence of certain types of devices more
suitable for one hand than the other, genetic
factors, and specific brain damage, to mention
only the immediately obvious items.
2. Left-handedness, even when behaviorally
established, is not a unitary trait. As several
studies (Bryden, 1973; Hecaen & Sauget,
1971; Hines & Satz, 1971; McKeever et al,
1973; Zurif & Bryden, 1969) suggest, the
left-handed with a positive family history of
left-handedness are different in many ways
from the left-handed who are solitary within
a family of right-handed. These left-handed
with no family history are, paradoxically, the
most strongly left-handed and most often
show a pattern of cerebral localization that is
characteristic of the right-handed.
The left-handed with a family history of
left-handedness range from those with strong
(but not absolute) left-hand preferences to
those who are approximately equally skilled
with either hand. These individuals most
frequently show the bilateralized cerebral
organization that was characteristic of the
patients of Hecaen and Sauget (1971), in
whom the incidence of dysphasias and spatial
disturbances was approximately equal, regardless of lesion site. However, as Luria (1970)
has shown, individuals with this bilateral
organization also recover function following
brain damage much more quickly and show
fewer lasting after-effects from lesions than
do the more lateralized right-handed.
3. The tendency of the left-handed to be
less strongly handed than their right-handed
counterparts is, in view of the other evidence,
not surprising. This could be the result either
of having to cope with a world organized for
the right-handed or of an intrinsic bilateral
organization. Given the patterns of bilateralization shown by many left-handed, an ability
to use either hand would be a natural corollary
of such organization. A few studies (Bryden,
1970; Curry & Gregory, 1969; McFie, 1952;
Witelson & Rabinovitch, 1972; Zurif & Carson,
1970) have suggested that certain types of
verbal deficit, such as dyslexia, are linked to
incomplete cerebral lateralization, but these
relationships are far from firmly established.
It is possible that the left-handed, as a group,
do differ in maturational rate of lateralization.
Thus, if cognitive functions are bilaterally
located, then the time period taken to establish predominant usage might require a longer
period of development.
4. The relationship between handedness and
cerebral organization seems definite, though
far from precise. Those reports that have
included handedness as a selection variable
in studies of dichotic listening or visual halffield differences indicate that the relationship
is systematic, though not straightforward. The
few studies that have assessed family history
of handedness have, in general, increased the
precision of the relationships under study.
Given these obtained relationships and the
systematic nature of the differences found in
both the behavioral and clinical lesion studies,
a tentative classification of individual differences in handedness and cerebral organization can be offered. It is suggested that
lateralization of cerebral function in humans
can be organized along a continuum of
handedness, with those individuals who are
strongly right-handed and have no family
history of left-handedness being more highly
lateralized for speech and visual functions,
the verbal functions being left-hemisphere
lateralized and the spatial functions righthemisphere lateralized. At the opposite end
of the continuum are the left-handed with a
positive family history of left-handedness who
have both speech and visual functions bilaterally localized. Bridging these two groups
are the right-handed with a family history of
left-handedness, whom one would expect to
show greater bilateralization of function than
do the right-handed with negative family
history, but less than do the familial
left-handed.
One group remains unaccounted for—the
left-handed with no family history of lefthandedness. Since the available evidence suggests that localization of function is identical
with that of the right-handed with no family
history of left-handedness, this group will be
classified as identical with the right-handed.
The validity of such a classification remains
LEFT-HANDEDNESS
to be established (see Hardyck, in press-b,
for a more extensive treatment of this problem), but is experimentally testable.
5. The conclusion that the left-handed are
cognitively deficient, or are the products of a
high incidence of early brain insult seems to
be an artifact of observations on clinic populations with whom self-report and casual observation have usually been used to determine
handedness.
It is, of course, quite possible that a deficient subpopulation that is characteristically
left-handed may exist. The studies of lefthandedness and cognitive deficit offer little
support for such a hypothesis, as regards the
general population of left-handed. However,
the studies of left-handedness in mentally
retarded populations (Burt, 1937; Gordon,
1920; M. 0. Wilson & Dolan, 1931) indicate a
systematically higher incidence.
6. The items reviewed to date suggest a
hypothesis-—at present, highly speculative—
about the possible relationships of observed
findings to a genetic basis for both handedness
and cerebral organization. The greater flexibility of the familial left-handed individual
in recovering from unilateral cerebral insult
seems well documented. It is reasonable to
argue for a genetic basis for such mechanisms,
as opposed to an environmental determination, since an environmental influence that
affects cerebral organization for the familial
left-handed and not the nonfamilial seems
highly improbable at best. However, if the
bilateral organization of the familial lefthanded provides an evolutionary advantage,
then the problem of apparent stability within
the population must be faced. The evidence,
though fragmentary, suggests that the incidence of left-handedness is relatively unchanged from Australopithecus through the
Egyptians of 2500 B.C. to the present. By
contrast, studies of population genetics (Cavalli-Sforza & Bodmer, 1971) indicate that a
malaria-resistant gene such as Thalassemia
can appear and reach stability in a population
in about 70 generations.
A possible explanation for the apparent
stability of left-handedness may reside in the
fact that the relatively low incidence of
cerebral injury does not have a strong effect
on reproductive success. Thus, the particular
gene complexes that give the left-handed an
399
advantage in terms of protection from the
lasting effects of cerebral trauma cannot
become fixed in the population. In this context, Dobzansky (1970) has shown that a trait
that is present in a small proportion of the
population and that affords only a slight
selective advantage will be subject only to
the effects of genetic drift. However, it is
also possible that bilaterality of cerebral
organization and associated left- or mixedhandedness may be increasing in frequency
in the human race, but at such a slow rate
that changes are difficult to detect.
7. Some consequences of recent work (Levy,
1969; Miller, 1971; Nebes, 1971) have been
tendencies to oversimplify findings and to
produce overextended generalizations about
the nature of human cortical functioning.
Speculations about the function of the "left
brain" and the "right brain" are an illustration of this tendency (Ornstein, 1972, 1973).
Similarly, positions are taken on the "value"
of lateralization, arguing that increased lateralization represents a superior cortical organization (Sperry, 1973).
There seems to be no basis whatever for
continuing to regard the left-handed with the
appellations and stigmata that seem to have
characterized them since Biblical times. In
fact, a reasonable case can be made for the
opposite viewpoint, since the evidence for
deficit is minimal and the advantages of
recovery of function in the event of brain
damage are considerable. The phrase, "Two
heads are better than one," might well be
applied to the unique advantages possessed
by many of the left-handed.
Reference Notes
1. Blau, T. H. The sinislral child. Paper presented at
the meeting of the American Psychological Association, New Orleans, September 1975.
2. Dawson, J. L. M. Eskimo laleralily and cognitive
style. Paper presented at the Second International
Conference of the International Association for
Cross-Cultural Psychology, Queen's University,
Kingston, Ontario, 1974.
References
Allison, R. B. The relationship between handedness in
elementary school children and reading skills, school
achievement, and perceptual-motor development.
Dissertation Abstracts, 1966, 27. 1256A.
400
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
Annett, M. A model of the inheritance of handedness
and cerebral dominance. Nature, 1964, 204, 59-60.
Annett, M. The binomial distribution of right, mixed
and left handedness. Quarterly Journal of Experimental Psychology, 1967, 19, 327-333.
Annett, M. A classification of hand preference by
association analysis. British Journal of Psychology,
1970, 61, 303-321.
Annett, M. The distribution of manual asymmetry.
' British Journal of Psychology, 1972, 63, 343-348.
Annett, M. Handedness in families. Annals of Human
Genetics, 1973, 37, 93-105. (a)
Annett, M. Laterality of childhood hemiplegia and
the growth of speech and intelligence. Cortex, 1973,
9, 4-33. (b)
Annett, M. Handedness in the children of two lefthanded parents. British Journal of Psychology, 1974,
65, 129-131.
Annett, M. Hand preference and the laterality of
cerebral speech. Cortex, 1975, 11, 305-328.
Aristotle. De partibus animalium. In R. P. McKeon
(Ed.), The basic works of Aristotle. New York:
Random House, 1941.
Bacon, F. The works of Francis Bacon (J. Speddin,
R. L. Ellis, & D. D. Heath, Eds.). London: Longmans, 1875.
Bakan, P. Left-handedness and alcoholism. Perceptual
& Motor Skills, 1973, 36, 514.
Bakan, P., Dibb, G., & Reid, P. Handedness and
birth stress. Neuropsychologia, 1973, 11, 363-366.
Baldwin, J. M. Mental development in the child and
the race, methods and processes. New York: Macmillan, 1895.
Baldwin, J. M. Dictionary of philosophy and psychology
(3 vols.). New York: Macmillan, 1901-1902.
Balow, I. H. Lateral dominance characteristics and
reading achievement in first grade. Journal of Psychology, 1963, 55, 323-328.
Balow, I. H., & Balow, B. Lateral dominance and
reading achievement in the second grade. American
Educational Research Journal, 1964, /, 139-143.
Bastian, H. C. A treatise on aphasia and other speech
defects. London: Lewis, 1868.
Beaumont, J. G., & Dimond, S. J. Transfer between
the cerebral hemispheres in human learning. Ada
Psychologica, 1973, 37, 87-91.
Beaumont, J. G., & Dimond, S. J. Interhemispheric
transfer of figural information in right- and nonright-handed subjects. Ada Psychologica, 1975, 39,
97-104.
Belmont, L., & Birch, H. G. Lateral dominance,
lateral awareness, and reading disability. Child
Development, 1965, 36, 57-71.
Benton, A. L., Meyers, R., & Polder, G. J. Some
aspects of handedness. Psychiatric Neurology, Basel,
1962, 144, 321-337.
Berman, A. The problem of assessing cerebral dominance and its relationship to intelligence. Cortex,
1971, 7, 372-386.
Bingley, T. Mental symptoms in temporal lobe epilepsy
and temporal lobe gliomas with special reference
to laterality of lesion and the relationship between
handedness and brainedness. Ada Psychialrka et
Neurologica, 1958, 33, Supplement 120.
Black, D., Young, C. C., Pei, W. C., & de Chardin, T-
Fossil man in China. Memoirs of the Geological
Survey of China, 1933, Series A, No. 11.
Blau, A. The master hand; a study of right and left
sidedness and its relation to laterality and language.
Research Monographs of the American Orthopsychialric Association, 1946, No. 5.
Bradbury, K. Mendelian heredity in man. Eugenics
Review, 1912, 4, 200-202.
Brain, W. R. Speech and handedness. Lancet, 1945,
249, 837-843.
Branch, C., Milner, B., & Rasmussen, T. Intracarotic
sodium amytal for the lateralization of cerebral
speech dominance. Journal of Neurosurgery, 1964,
21, 399-465.
Brinton, D. Left-handedness in North American
aboriginal art. American Anthropologist, 1896, 9,
175-181.
Broadbent, D. E. The role of auditory localization
in attention and memory span. Journal of Experimental Psychology, 1954, 47, 191-196.
Broadbent, D. E. Successive responses to simultaneous
stimuli. Quarterly Journal of Experimental Psychology, 1956, 8, 145-152.
Broca, P. Remarques sur le siege de la facultfi du
langage articule1, suivi d'une observation d'apheme.
Bulletin SocielU Anthropologie, 1861, 6, 330-357.
Bryden, M. P. Tachistoscopic recognition, handedness,
and cerebral dominance. Neuropsychologia, 1965,
3, 1-8.
Bryden, M. P. Laterality effects in dichotic listening:
Relations with handedness and reading ability in
children. Neuropsychologia, 1970, 8, 443-450.
Bryden, M. P. Perceptual asymmetry in vision: Relation to handedness, eyedness, and speech lateralization. Cortex, 1973, 9, 419-435.
Buffery, A. W. H. Asymmetrical lateralization of cerebral functions and the effects of unilateral brain
surgery in epileptic patients. In S. J. Dimond &
J. G. Beaumont (Eds.), Hemisphere function in the
human brain. New York: Wiley, 1974.
Burt, C. The backward child. New York: Macmillan,
1937.
Carrothers, G. E. Left-handedness among school
pupils. American School Board Journal, 1947, 114,
17-19.
Cavalli-Sforza, L. L., & Bodmer, W. F. The genetics
of human populations. San Francisco: Freeman, 1971.
Cernacek, J., & Podivinsky, F. Ontogenesis of handedness and somatosensory cortical response. Neuropsychologia, 1971, 9, 219-232.
Chamberlain, H. D. Inheritance of left-handedness.
Journal of Heredity, 1928, 19, 557-559.
Clark, M. M. Left-handedness; laterality characteristics
and their educational implications. London: University of London Press, 1957.
Cohen, G. Hemispheric differences in a letter classification task. Perception &• Psychophysics, 1972,
11, 139-142.
Coleman, R. L, & Deutsch, G. P. Lateral dominance
and right-left discrimination: A comparison of
normal and retarded readers. Perceptual 6* Motor
Skills, 1964, 19, 43-50.
Collins, R. L. On the inheritance of handedness:
I. Laterality in inbred mice. Journal of Heredity,
1968., 59, 9-12
LEFT-HANDEDNESS
Collins, R. L. On the inheritance of handedness:
II. Selection for sinistrality in mice. Journal of
Heredity, 1969, 60, 117-119.
Collins, R. L. The sound of one paw clapping: An
inquiry into the origin of left-handedness. In G.
Lindzey & D. D. Thiessen (Eds.), Contributions to
behavior-genetic analysis: The mouse as prototype.
New York: Appleton-Century-Crofts, 1970.
Collins, R. L. When left-handed mice live in righthanded worlds. Science, 1975, 187, 181-184.
Crawford, J. E., & Crawford, D. M. Small Parts
Dexterity Test. New York: Psychological Corporation, 19S6.
Crinella, F. M., Beck, F. W., & Robinson, J. W.
Unilateral dominance is not related to neuropsychological integrity. Child Development, 1971, 42,
2033-2054.
Crovitz, H. F., & Zener, K. A group-test for assessing
hand- and eye-dominance. American Journal of
Psychology, 1962, 75, 271-276.
Curry, F. K. A comparison of left-handed and righthanded subjects on verbal and non-verbal dichotic
listening tasks. Cortex, 1967, 3, 343-352.
Curry, F. K., & Gregory, H. H. The performance of
stutterers on dichotic listening tasks thought to
reflect cerebral dominance. Journal of Speech &•
Hearing Research, 1969, 12, 73-82.
Curry, F. K., & Rutherford, D. R. Recognition and
recall of dichotically presented verbal stimuli by
right- and left-handed persons. Neuropsychologia,
1967,5, 119-126.
Cyr, D., Daniloff, R., & Berry, R. The perception
of clicks embedded in sentences as a function of
handedness and mode of presentation. Journal of
Auditory Research, 1971, 11, 251-259.
Daniels, E. M. An analysis of the relation between
handedness and stuttering, with special reference
to the Orton-Travis theory of cerebral dominance.
Journal of Speech Disorders, 1940, 5, 309-329.
Dart, R. A. The predatory implemental technique of
Australopithecus. American Journal of Physical
Anthropology, 1949, 7, 1-38.
Davidoff, J. B. Hemispheric differences in the perception of lightness. Neuropsychologia, 1975, 13,
121-124.
Dax, M. Lesions de la moitie gauche de 1'encephale
coincident avec 1'oubli des signes de la pense'e.
Gazette Hebdomadaire, 1865, 2, 259-260.
Dearborn, G. V. N. Moto-sensory development. Baltimore, Md.: Warwick & York, 1913.
Dearborn, W. F. Ocular and manual dominance in
dyslexia. Psychological Bulletin, 1931, 28, 704.
Dee, H. L. Auditory asymmetry and strength of
manual preference. Cortex, 1971, 7, 236-245.
de Mortillet, Gabriel. Le prehistorique antiquite de
I'homme. Paris: Reinwald, 1882.
Dennis, W. Early graphic evidence of dextrality in
man. Perceptual &• Motor Skills, 1958, 8, 147-149.
Di Chiro, G. Angiographic patterns of cerebral convexity veins and superficial dura] sinuses. American
Journal of Roentgenology, 1962, 87, 308-321.
Dimond, S. J. Hemisphere function and word registration. Journal of Experimental Psychology, 1971,
87, 183-186.
Dimond, S. J., & Beaumont, J. G. Hemisphere func-
401
tion and color naming. Journal of Experimental Psychology, 1972, 96, 87-91.
Dimond, S. J., & Beaumont, J. G. Hemisphere function and paired-associate learning. British Journal
of Psychology, 1974, 65, 275-278.
Dobzhansky, T. Genetics of the evolutionary process.
New York: Columbia University Press, 1970.
Domhoff, G. W. But why did they sit on the king's
right in the first place? Psychoanalytic Review,
1969-1970, 56, 586-596.
Durost, W. N. The development of a battery of
objective group tests of manual laterality, with the
results of their application to 1300 children. Genetic
Psychology Monographs, 1934, 16, 229-235.
Efron, R. The effect of handedness on the perception
of sumultaneity and temporal order, Brain, 1962,
86, 261-284.
Ellis, Havelock. The criminal. London: Walter Scott,
1890.
Fagan-Dubin, L. Lateral dominance and development
of cerebral specialization. Cortex, 1974, 10, 69-74.
Falek, A. Handedness: A family study. American
Journal of Human Genetics, 1959, 11, 52-62.
Fenton, J. C. A practical psychology of babyhood. New
York: Houghton Mifflin, 1925.
Flick, G. Sinistrality revisited: A perceptual-motor
approach. Child Development, 1966, 37, 613-622.
Fuller, J. L. Behavior genetics. Annual Review of
Psychology, 1960, 11, 41-70.
Geschwind, N., & Levitsky, W. Human brain: Leftright asymmetries in temporal speech region.
Science, 1968, 161, 186-187.
Gesell, A., & Ames, L. B. The development of
handedness. Journal of Genetic Psychology, 1947, 70,
155-167.
Gianntrapani, D. Developing concepts of lateralization of cerebral functions. Cortex, 1969, 5, 353-370.
Giesecke, M. The genesis of hand preference. Monographs of the Society for Research in Child Development, 1936, 1, pp. vii; 102,
Gilbert, C. Strength of left-handedness and facial
recognition ability. Cortex, 1973, 9, 145-151.
Gilkey, B. G., & Parr, F. W. An analysis of the
reversal tendencies of fifty selected elementary
school pupils. Journal of Educational Psychology,
1944, 35, 284-292.
Gloning, L, Cloning, K., Haub, G., & Quatember, R.
Comparison of verbal behavior in right-handed and
non right-handed patients with anatomically verified
lesion of one hemisphere. Cortex, 1969, 5, 43-52.
Goodglass, H., & Quadfasel, F. A. Language laterality
in left-handed aphasics. Brain, 1954, 77, 521-548.
Gordon, H. Left-handedness and mirror writing. Brain,
1920, 43, 313-368.
Gould, G. M. Righthandedness and leflhandedness.
Philadelphia, Pa.: Lippincott, 1908.
Gratiolet, P. In F. Leuret & P. Gratiolet, Anatomic
comparte du systeme nerveux, considers dans ses
rapports awe ('intelligence (Vol. 2). Paris: Balliere,
1839-1857.
Groberg, D. H., Dustman, R. E., & Beck, E. C.
The effect of body and head tilt in the perception
of vertical: Comparison of body and head tilt with
left and right handed, male and female subjects.
Neuropsychologia, 1969, 7, 89-100.
402
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
Haefner, R. The educational significance of left-handedness. New York: Teachers College, Columbia University Press, 1929.
Halverson, H. M. An experimental study of prehension in infants by means of systematic cinema
records. Genetic Psychology Monographs, 1931, 10,
107-286.
Hardyck, C. Handedness and part-whole relationships : A replication. Cortex, in press, (a)
Hardyck, C. A model of individual differences in
hemispheric functioning. In H. Avakaian-Whitaker
& H. A. Whitaker (Eds.), Studies in neurolinguistics
(Vol. 3). New York: Academic Press, in press, (b)
Hardyck, C., Petrinovich, L., & Goldman, R. Lefthandedness and cognitive deficit. Cortex, 1976, 12,
266-279.
Harman, N. B. Ambidexterity. British Medical Journal,
1905, 7, 15-16.
Harris, A. J. The Harris tests of lateral dominance.
New York: Psychological Corporation, 1955.
He'caen, H., & de Ajuriaguerra, J. Left-handedness;
manual superiority and cerebral dominance. New
York: Grune & Stratton, 1964.
He'caen, H., & Piercy, M. Paroxysmal dysphasia and
the problem of cerebral dominance. Journal of
Neurology, Neurosurgery &• Psychiatry, 1956, 19,
194-201.
Hecaen, H,, & Sauget, J. Cerebral dominance in lefthanded subjects. Cortex, 1971, 7, 19-48.
Heinlein, J. H. Preferential manipulation in children.
Baltimore: Johns Hopkins University Press, 1930.
Heschl, R, Uber de wrdere quere Schlafenwindung des
Menschlichen Grosshirns. Vienna, Austria: Braumuller, 1878.
Hildreth, G. Reversals in reading and writing. Journal
of Educational Psychology, 1934, 25, 1-20.
Hildreth, G. The development and training of hand
dominance: II. Developmental tendencies in handedness. Journal of Genetic Psychology, 1949, 75, 221254. (a)
Hildreth, G. The development and training of hand
dominance: III. Origins of handedness and lateral
dominance. Journal of Genetic Psychology, 1949, 75,
255-275. (b)
Hines, D., & Satz, P. Superiority of right visual halffields in right-handers for recall of digits presented
at varying rates. Neuropsychologia, 1971, 9, 21-25.
Hines, D., & Satz, P. Cross-modal asymmetries in
perception related to asymmetry in cerebral function. Neuropsychologia, 1974, 12, 239-247.
Hudson, P. T. W. The genetics of handedness: A reply
to Levy and Nagylaki. Neuropsychologia, 1975, 13,
331-339.
Hyrtl, J. Handbuch der topographischen anatomic.
Vienna, Austria: Aufflacher, 1871.
Jackson, H. Ambidexterity. London: Kegan Paul, 1905.
Jackson, J. H. Selected writings of John Hughlings
Jackson (2 vols., J. Taylor, Ed.). New York: Basic
Books, 1958.
Jasper, H. H., & Raney, E. J. The phi test of lateral
dominance. American Journal of Psychology, 1937,
49, 450^57.
Joint Committee on the New Translation of the
Bible. The New English Bible. London: Oxford
University Press, 1970.
Jones, E. Right- and left-handedness. Psychological
Bulletin, 1911,*, 385-386.
Jones, H. E. Dextrality as a function of age. Journal
of Experimental Psychology, 1931, 14, 125-144.
Jones, M. M. W. The relationship between reading
deficiencies and left-handedness. School and Society,
1944, 60, 238-239.
Jones, W. F. Study of handedness. Los Angeles: University of Southern California, 1918.
Jordan, H. E. The inheritance of left-handedness.
American Breeder's Magazine, 1911, 2, Nos. 1, 2.
Jordan, H. E. Hereditary left-handedness with a note
on twinning. Journal of Genetics, 1914, 4, 67-81.
Keller, J. F., Croake, J. W., & Riesenman, E. Relationships among handedness, intelligence, sex, and
reading achievement of school age children. Perceptual &• Motor Skills, 1973, 37, 159-162.
Kimura, D. Speech lateralization in young children
as determined by an auditory test. Journal of
Comparative and Physiological Psychology, 1963, 56,
899-902.
Kimura, D. Left-right differences in the perception
of melodies. Quarterly Journal of Experimental Psychology, 1964, 16, 355-358.
Kimura, D. Functional asymmetry of the brain in
dichotic listening. Cortex, 1967, J, 163-178.
Kimura, D., & Folb, S. Neural processing of backwards speech sounds. Science, 1968, 161, 395-396.
Knox, A. W., & Boone, D. R. Auditory laterality and
tested handedness. Cortex, 1970, 6, 164-173.
Koch, H. L. A study of the nature, measurement,
and determination of hand preference. Genetic
Psychology Monographs, 1933, 13, 117-221.
Komai, T., & Fukuoka, G. A study on the frequency
of left-handedness and left-footedness among Japanese school children. Human Biology, 1934, 6, 33-41.
Koos, E. M. Manifestations of cerebral dominance
and reading retardation in primary grade children.
Journal of Genetic Psychology, 1964, 104, 155-166.
Kutas, M., & Donchin, E. Studies of squeezing:
Handedness, responding hand, response force, and
symmetry of readiness potential. Science, 1974, 186,
545-548.
Kutas, M., McCarthy, G., & Donchin, E. Differences
between sinistrals' and dextrals' ability to infer a
whole from its parts: A failure to replicate. Neuropsychologia, 1975, 13, 455-464.
Levy, J. Possible basis for the evolution of lateral
specialization of the human brain. Nature, 1969,
224, 614-615.
Levy, J., & Nagylaki, T. A model for the genetics
of handedness. Genetics, 1972, 72, 117-128.
Lippman, H. S. Certain behavior responses in early
infancy. Pedagogical Seminary and Journal of Genetic
Psychology, 1927, 34, 424-440.
Lomas, J., & Kimura, D. Intrahemispheric interaction
between speaking and sequential manual activity.
Neuropsychologia, 1976, 14, 23-33.
Lombroso, C. Left-handedness and left-sidedness.
North American Review, 1903, 777, 440-444.
Luria, A. R. Traumatic aphasia. The Hague, The
Netherlands: Mouton, 1970.
LEFT-HANDEDNESS
Magoun, H. W. Discussion of brain mechanisms in
speech. In E. C. Carterette (Ed.), Brain function:
Speech, language and communication (Vol. 3). Los
Angeles: University of California Press, 1966.
Major, D. R. First steps in mental growth. New York:
Macmillan, 1906.
Mason, O. T. Throwing sticks. American Anthropologist, 1896, 9, 226-232.
McFie, J. Cerebral dominance in cases of reading
disability. Journal of Neurology, Neurosurgery 6*
Psychiatry, 1952, 15, 194-199.
McKeever, W. F., & Gill, K. Visual half-field differences in masking effects for sequential letter
stimuli in the right and left handed. Neuropsychologia, 1972, 10, 111-117.
McKeever, W. F., Gill, K. M., & Van Deventer,
A. D. Letter versus dot stimuli as tools for "splitting the normal brain with reaction time." Quarterly
Journal of Experimental Psychology, 1975, 27,
363-373.
McKeever, W. F., Van Deventer, A. D., & Suberi, M.
Avowed, assessed, and familial handedness and differential hemispheric processing of brief sequential
and non-sequential visual stimuli. Neuropsychologia,
1973,11, 235-238.
McKinney, J, P. Handedness, eyedness and perceptual
stability of the left and right visual fields. Neuropsychologia, 1967, 5, 339-344.
Miller, E. Handedness and the pattern of human
ability. British Journal of Psychology, 1971, 62,
111-112.
Moscovitch, M., & Catlin, J. Interhemispheric transmission of information: Measurement in normal
man. Psychonomic Science, 1970, 18, 211-213.
Nagylaki, T., & Levy, J. "The sound of one paw
clapping" isn't sound. Behavior Genetics, 1973, 3,
279-292.
Nebes, R. D. Handedness and the perception of partwhole relationships. Cortex, 1971, 7, 350-356.
Needham, R. (Ed.). Right and left. Chicago: University of Chicago Press, 1973.
Newcombe, F., & Ratcliff, G. Handedness, speech
lateralization and ability. Neuropsychologia, 1973,
;;, 399-407.
Newman, H. H. Differences between conjoined twins:
In relation to a general theory of twinning. Journal
of Heredity, 1931, 22, 201-207.
Ogle, W. On dextral pre-eminence. Royal MedicoChirurgical Society of London Transactions, 1871,
54, 279-301.
Ojemann, R. H. Studies in handedness: I. A technique
for testing unimanual handedness. Journal of Educational Psychology, 1930, 21, 597-611. (a)
Ojemann, R. H. Studies in handedness: II. Testing
bimanual handedness. Journal of Educational Psychology, 1930, 21, 695-702. (b)
Oldfield, R. C. The assessment and analysis of handedness: The Edinburgh Inventory. Neuropsychologia,
1971, 9, 97-113.
Orbach, J. Differential recognition of Hebrew and
English words in right and left visual fields as a
function of cerebral dominance and reading habits.
Neuropsychologia, 1967, 5, 127-134.
Orme, J. E. Left-handedness, ability and emotional
403
instability. British Journal of Social and Clinical
Psychology, 1970, 9, 87-88.
Ornstein, R. E. The psychology of consciousness. San
Francisco: Freeman, 1972.
Ornstein, R. E. The nature of human consciousness:
A book of readings. San Francisco: Freeman, 1973.
Parsons, B. S. Lefthandedness. New York: Macmillan,
1924.
Penfield, W., & Roberts, L. Speech and brain mechanisms. Princeton, N.J.: Princeton University Press,
1959.
Provins, K. A., & Jeeves, M. A. Hemisphere differences in response time to simple auditory stimuli.
Neuropsychologia, 1975, 13, 207-211.
Pye-Smith, P. H. On left-handedness. Guy's Hospital
Reports, 1871, 16, 141.
Pyle, W. H., & Drouin, A. Left-handedness: An experimental and statistical study. School and Society,
1932, 36, 253-256.
Quinan, C. The principal sinistral types: An experimental study particularly as regards their relation
to the so-called constitutional psychopathic states.
Archives of Neurology and Psychiatry, 1930, 24,
35-47.
Raczkowski, D., Kalat, J. W., & Nebes, R. W. Reliability and validity of some handedness questionnaire items. Neuropsychologia, 1974, 12, 43-48.
Ramaley, F. Inheritance of left-handedness. American
Naturalist, 1912, 46, 730-738.
Ramaley, F. Mendelian proportions and the increase
of recessives. American Naturalist, 1913, 47, 334-339.
Reitan, R. M. Differential effects of lateralized brain
lesions in the Trail Making Test. Journal of Nervous
&• Mental Disease, 1959, 129, 257-262.
Rife, D. C. Handedness with a special reference to
twins. Genetics, 1940, 25, 178-186.
Rife, D. C. An application of gene frequency analysis
to the interpretation of data from twins. Human
Biology, 1950, 22, 136-145.
Roudinesco, J., & Thyss, J. L'enfant gaucher Stude
clinique; signification physiologique; problemes
pedagogiques. Enfance, 1948, ;, 8-28; 126-141.
Sabatino, D., & Becker, J. T. Relationship between
lateral preference and selected behavioral variables
for children failing academically. Child Development,
1971, 42, 2055-2060.
Salk, L. Thoughts on the concept of imprinting and
its place in early human development. Canadian
Psychiatric Association Journal, 1966, 11, 295-305.
Sarasin, P. Ueber Rechts- und Links-Haendigkeit in
der Praehistorie und die Rechtshandigkeit in Historiche Zeit. Naturforschende Gesellschaft in Basel Verhtmdlungen, 1882, 29, 122-196.
Satz, P., Achenbach, K., & Fennell, E. Correlations
between assessed manual laterality and predicted
speech laterality in a normal population. Neuropsychologia, 1967, 5, 295-310.
Satz, P., Achenbach, K., Pattishall, E., & Fennell, E.
Order of report, ear asymmetry, and handedness
in dichotic listening. Cortex, 1965, 1, 377-396.
Schiller, M. Problem um due Linkshandigkeit mit
Untersuchunger an Stuttgarter Schulkindern. Zeitschrift fur die Gesamte Neurologic und Psychiatric,
1932, 14, 496-512.
404
CURTIS HARDYCK AND LEWIS F. PETRINOVICH
Schott, A. [Left-handedness and heredity.] Zeitschrift
fur die Gesamte Neurologic und Psychialrie, 1931,
135, 1-322.
Selzer, C. A. Lateral dominance and visual fusion.
Cambridge, Mass.: Harvard University Press, 1933.
Semmes, J. Hemispheric specialization: A possible
clue to mechanism. Neuropsychologia, 1968, 6, 11-26.
Seth, G. Eye-hand coordination and "handedness":
A developmental study of visuo-motor behavior in
infancy. British Journal of Educational Psychology,
1973, 43, 35-49.
Shinn, M. W. Notes on the development of a child.
Berkeley, Calif.: University of California, 1914.
Silverman, A. J., Adevai, G., & McGough, E. W.
Some relationships between handedness and perception. Journal of Psychosomatic Research, 1966,
10, 151-158.
Smith, L. G. A brief survey of right- and left-handedness. Pedagogical Seminary and Journal of Genetic
Psychology, 1917, 24, 19-35.
Sperry, R. W. Hemisphere deconnection and unity
in conscious awareness. American Psychologist, 1968,
23, 723-733. (a)
Sperry, R. W. Mental unity following surgical disconnection of the cerebral hemispheres. Harvey
Lectures, Series 62. New York: Academic Press,
1968. (b)
Sperry, R. W. Lateral specialization of cerebral function in surgically separated hemispheres. In F. J.
McGuigan & R. A. Schoonover (Eds.), The psychophysiology of thinking. New York: Academic Press,
1973.
Sperry, R. W., Gazzaniga, M. S., & Bogen, J. E.
Interhemispheric relationships: The neocortical commissures; syndromes of hemisphere disconnection.
In P. J. Vinken & G. W. Bruyn (Eds.), Handbook
of clinical neurology (Vol. 4). Amsterdam, The
Netherlands: North Holland, 1969.
Subirana, A. The prognosis in aphasia in relation to
cerebral dominance and handedness. Brain, 1958,
81, 415-425.
Subirana, A. The relationship between handedness
and language function. Logos (Bulletin of the New
York Hospital for Speech Disorders), 1961, 4, 67-83.
Subirana, A. Handedness and cerebral dominance. In
P. J. Vinken & G. W. Bruyn (Eds.), Handbook of
clinical neurology. Amsterdam, The Netherlands:
North Holland, 1969.
Thass-Thienemann, T. Left-handed writing: A study
in the psychoanalysis of language. Psychoanalytic
Review, 1955, 42, 239-261.
Trankell, A. Vdnsterhanthel has barn i skol&ldern.
Helsinki, Finland: Forum, 1950.
Trankell, A. Aspects of genetics in psychology.
American Journal of Human Genetics, 1955, 7,
264-276.
Updegraff, R. Preferential handedness in young
children. Journal of Experimental Education, 1932,
1, 134-139.
Van Biervliet, J. J. L'asymetrie sensouielle. Bulletin
de I'Academie Royale de Belgique, 1897.
Voelkel, E. Unterschuengen tiber die Rechtshandigkeit
beim Saugling. Zeitschrift fur Kinderheilkunde, 1913,
8, 351-358.
von Bonin, G. Anatomical asymmetries of the cerebral
hemispheres. In V. B. Mountcastle (Ed.), Interhemispheric relations and cerebral dominance. Baltimore, Md.: Johns Hopkins University Press, 1962.
Wada, J. A., & Rasmussen, T. Intracarotic injection
of sodium amytal for the lateralization of cerebral
speech dominance. Experimental and clinical observations. Journal of Neurosurgery, 1960, 17,
266-282.
Wallin, J. E. W. A census of speech defectives among
89,057 public-school pupils—A preliminary report.
School and Society, 1916, 3, 213-216.
Wile, I. S. Handedness: Right and left. Boston: Lothrop,
Lee & Shepard, 1934.
Wilson, D. Paleolithic dexterity. Transactions of the
Royal Society of Canada, 1904, J, 119-133.
Wilson, M. 0., & Dolan, L. B. Handedness and
ability. American Journal of Psychology, 1931, 43,
261-268.
Witelson, S. F., & Rabinovitch, M. S. Hemispheric
speech lateralization in children with auditorylinguistic deficits. Cortex, 1972, 8, 412-426.
Wittenborn, J. R. Correlates of handedness among
college freshmen. Journal of Educational Psychology,
1946, 37, 161-170.
Witty, P. A., & Kopel, D. Sinistral and mixed manualocular behavior in reading disability. Journal of
Educational Psychology, 1936, 27, 119-134.
Wolfe, L. S. Differential factors in specific reading
disability: I. Laterality of function. Journal of
Genetic Psychology, 1941, 58, 46-56. (a)
Wolfe, L. S. Differential factors in specific reading
disability: II. Audition, vision, verbal association,
and adjustment. Journal of Genetic Psychology, 1941,
58, 57-70. (b)
Woo, T. L., & Pearson, K. Dextrality and sinistrality.
Biomelrika, 1927, 19, 192-198.
Woodruff, C. (Ed.). Expansion of races. New York:
Rebman, 1909.
Woody, C., & Phillips, A. J. The effects of handedness
on reversals in reading. Journal of Educational
Research, 1934, 27, 651-652.
Wooley, H. T. The development of right-handedness
in a normal infant. Psychological Review, 1910,
17, 37-41.
Wyke, M. Influence of direction on the rapidity of
bilateral arm movements. Neuropsychologia, 1969,
7, 189-194.
Zangwill, O. L. Speech and the minor hemisphere.
Ada Neurologica el Psychialrica Belgica, 1967, 67,
1013-1020.
Zazzo, R. Les jumeaux, le couple et la personne. Paris:
Presses Universitaires de France, 1960.
Zurif, E. B., & Bryden, M. P. Familial handedness
and left-right differences in auditory and visual
perception. Neuropsychologia, 1969, 7, 179-187.
Zurif, E. B., & Carson, G. Dyslexia in relation to
cerebral dominance and temporal analysis. Neuropsychologia, 1970, 8, 351-362.
Received January 5, 1976