McKinnon, W., Weisse, C.S., Reynolds, C.P.,
Bowles, C.A., & Baum, A. (1989). Chronic stress,
leukocyte subpopulations, and humoral response
to latent viruses. Health Psychology. 8, 389-402.
Meyer, R.J., & Haggerty, R.J. (1962). Streptococcal infections in families. Pediatrics. 29, 539549.
Rabin, B.S , Cohen, 5., Ganguli, R., I.vie,
D.T., & Cunnick, J.E. (1989). Bidirectional interaction between the central nervous system and
immune system. CRC Critical Rei'iewb in humunologu, 9, 279-312.
Stone, A.A., Bovbjerg, D.ll., Neale, J.M.,
Napoli, A., Valdimarsdottir, H., Cox, D., Hayden, E.G., &Gwaltney, J.M. (1993). Development
of common cold symptoms foUowmg expcrmiental rhinovirus infection is related to prior stressful
life events Behavioral Medicme, 8, 115-120.
Stone, A.A., Cox, D.S., Valdimarsdottir, H.,
Jandorf, L., & Neale, J.M. (1987). Evidence that
secretory igA antibody is a.ssocuited with daily
mood, journal of Personality and Social Psychology,
52, 988-993.
Stone, A.A., Neale, |.M., Cox, D.S., Napoli,
A., Valdimarsdottir, H., & Kennedy-Moore, F
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Possible Individuals in Language
and Cognition
Paul Bloom^
Department of Psychology, University of Arizona, Tucson, Arizona
One approach to the psychology of proper names and count
nouns explores the role these expressions play in our mental life.
Proper names such as fido correspond to entities we think of as individuals—entities that can be categorized, counted, and tracked
over space and time. Count nouns
such as dog correspond to kinds of
individuals. It makes sense to talk
of 2 dogs or 10 dogs, or to say that
a certain dog is the same one that I
saw yesterday, or to ask what happened to Fido. Not all parts of
speech refer to individuals; adjectives like hig and mass nouns like
water do not correspond to entities
that are countable or trackable in
the same sense.
This observation raises the
question of what sorts of entities
are naturally thought of as individuals. We count, name, and track
dogs—they are psychologically
natural individuals. As a result,
words that refer to this kind {dog)
and words that refer to particular
members of this kind {Fido) are
easily learned by children. But not
every logically possible individual
is acceptable from the standpoint
of human psychology. For in-
stance, construing the spatially
discontinuous entity composed of
my dog and his favorite bone as a
single individual is cognitively unnatural. We could not easily learn
a proper name {Fidobone, say) for
this entity, nor can we easily track
it over space and time. Why is it
that Fido is a psychologically possible individual, but Fidobone is
not?
One answer is that Fido is a discrete physical object—and discrete
physical objects are natural individuals. People count objects,
track them, categorize them as belonging to different kinds, and
learn names for these kinds. Psychologists typically concern themselves with objects when constructing theories of linguistic and
noniinguistic capacities, and many
theories of how we learn and understand words are restricted to
the learning and understanding of
object names, implicitly adopting
the view that, for humans, individuals just are discrete whole objects.
This view cannot be right, however. Children and adults do learn
words such as chapter, party, and
joke; we can count chapters, par-
Published hy Cambridge University i'ress
tory immune response Eo an oral antigen in men.
Health Psychology, 13. 440-446.
Recommended Reading
Cohen, S., & Herbert, T.B. (1996). Psychological factors and physical disease from the perspective of human psychoneuroimmunology. Annual
Rn'iavof P<ychologif. 47, 113-142.
Gkiser, R., & Kiecok-Claser, J (Eds.). (1994).
Handbook ol human stress and immunity. New York:
Academic Press.
ties, and jokes; we can track them,
categorize them, and so on. But to
say that Jane wrote two chapters
does not mean that she created
two objects. If she goes to two parties on Saturday night, and tells
two jokes at each party, what individuates the parties and jokes
rests on subtle intentional factors,
obvious enough intuitively, but
difficult to specify precisely. What
properties, if any, do these concepts share that make them all acceptable candidates for enumeration and naming? What makes
these nonobject entities psychologically natural individuals?
This issue is not special to word
learning. All theories of counting,
categorization, and tracking must
posit a domain over which these
operations work, that is, a domain
of individuals that get counted,
categorized, and tracked. This domain cannot be limited to objects;
many animals, including people,
pigeons, and rats, are capable of
quite complex computations over
distinct sounds, events, and actions (see Wynn, 1992). A similar
issue arises in social cognition.
When we attribute mental states
such as beliefs and goals, the targets of these attributions are not
necessarily physical objects. We
talk about a nation hesitating to
take action, a hockey team seeking
another chance for victory, and the
Internal Revenue Service becoming concerned about one's homeoffice deduction. Such attributions
are not merely metaphorical. In a
recent study, Csaba Veres and I
extended a classic experiment by
Heider and Simmel (1944) which
found that people exposed to movies of simple geometrical shapes
moving in a structured pattern will
describe these movies in terms of
purposeful and intentional action.
We redid this study with both individual shapes and groups of
shapes as stimuli, and found that
moving groups are naturally
viewed as intentional entities—as
"characters," with beliefs and desires—to the same extent as moving shapes are (Bloom & Veres,
1996). Within social cognition as
well, then, the question arises:
What are psychologically natural
individuals?
OBJECTS AND
OTHER INDIVIDUAtS
Some insight might emerge
from the study of development.
Infants are predisposed to parse
the physical world into bounded
units that move on continuous
paths, that is, into discrete physical objects (Spelke, 1994). Most of
the count nouns that 2-year-olds
know refer to objects, much more
so than for older children or
adults. When exposed to new
words, children tend to treat them
as object names, even if this interpretation is inconsistent with the
syntax, such as when a word is
presented as an adjective or a mass
noun (Markman, 1990). Moreover,
when asked to count different arrays, preschoolers are strongly biased to count the distinct objects,
even if explicitly asked to do otherwise. For instance, when shown
a display of five forks, one broken
into two separate pieces, and
asked "Can you count the forks?"
preschoolers typically say there
are six (Shipley & Shepperson,
1990).
Such results could be taken as
suggesting that children are conceptually enfeebled, and that objects are the only individuals they
can think about, count, track, and
name. But this is plainly not the
case. Even young infants can enumerate actions (Wynn, 1996) and
sounds (Starkey, Spelke, & Gelman, 1990). Many of children's
first words refer to nonobject individuals, such as nap, family, and
story, and these words arc used in
correct semantic and grammatical contexts (Nelson, Hampson,
& Shaw, 1993). In a few domains,
researchers have attempted to
teach names for nonobject individuals to young children. One set of
studies focused on words like
church, camp, and school, which
lead interesting double lives. A
word like church can refer to a
physical entity, as in "There is a
church on the corner," but it can
also be a proper name of a specific
cultural institution, as when one
says, "John goes to church regularly." Preschoolers understand
the multiple usage of such words,
and can learn new words that have
a similar abstract usage even on
the basis of only a few exposures
(Soja, 1994). A different domain is
that of collective nouns, such as
army and family, wbich refer to
groups of discrete physical objects.
Some such nouns are acquired
early, and preschoolers can learn
names for novel collections with
the aid of linguistic support. For
instance, if an adult points to a
group of objects and describes it
with the syntax associated with a
single individual (e.g., "This is a
fendle"), preschoolers will often
construe the new word as a collective noun, not as an object name
(Bloom & Kelemen, 1995).
These findings raise a puzzle: If
children can understand abstract
individuals, why are they so
drawn to objects in their word
learning and counting? Why are
objects so salient? One explanation
Cupyright i-^ 1996 American PsychologiiTji Society
appeals to the functional importance of objects. Humans and
other animals construe the world
in terms of objects that endure
over time and move cohesively
through space because animals
that do so are better able to track
prey, avoid predators, find shelter, and so on. Enduring objects
are extremely relevant causal entities from an ecological standpoint,
and this fact could have led to the
evolution of a hard-wired object
module that operates in essentially
the same fashion for children and
adults, and most likely exists
within other primates as well.
But objects are not the only individuals worth thinking about.
Just as making sense of the physical world motivated the evolutionary origins of object cognition, the
need to predict and understand
the social world motivates thinking about individuals like chapters, parlies, and jokes. Following
Carey (1988), we can view such individuals as emerging through a
process of theory construction.
The chiid who posits such individuals in the course of making sense
of the social world does so for the
same reason, and perhaps in the
same way, as the scientist who
posits individuals like electrons
and genes as part of the study of
the physical world.
It is conceivable that a single
mechanism parses the world into
both objects and nonobject individuals, but certain considerations
suggest otherwise. In particular,
the salience of whole objects for
children might result from the fact
that children's object module is
fully operational, whereas their capacity for individuation of at least
some abstract entities is less so, because of lack of knowledge or of
experience. A similar dissociation
is found in adult novices. A novice
watching a soccer game will track
only the moving objects, the players and the bail, whereas a soccer
aficionado watching a game can
track the movement of the teams—
spatially discontinuous entities—
as well as of the objects. The parsing of the world into objects is
involuntary and automatic; the
soccer expert can decide whether
to view the game as the interplay
of two distinct teams, but viewing
it in terms of moving objects is not
a matter of choice.
Another distinction between
object individuation and nonobject individuation is found in studies of apparent motion. When successive stimuli are presented at
very brief intervals, people perceive only the movement of spatially distinct entities. For instance,
if a row of three vertical lines is
shown alternately in two positions, so that the positions of the
two rightmost lines in one exposure coincide with the positions of
the two leftmost lines in the alternating exposure, people see a single line jumping back and forth
over two stationary lines. At
slower intervals, however, a sensitivity to nonobject individuals (defined through Cestalt principles
such as proximity) emerges. In this
example, the subjects construe the
group of three lines as an individual and see the entire group as
moving back and forth, even
though two of the lines do not actually change position across the
successive exposures (see Braddick, 1980).
Finally, the cues that identify
objects are distinct from those that
identify other types of individuals.
The perception of objects is a
highly inferential process (consider the problems posed by occlusion), but nevertheless the
mechanisms that typically govern
the on-line perception and tracking of objects are based on a limited set of unlearned principles
(see Spelke, 1994).^ In contrast, the
parsing of the world into other
sorts of individuals is a less encapsulated process, drawing upon
cues that emerge from a range of
different sources, including perception, language, and social cognition.
By saying that humans possess
two distinct modes of individuation, I do not mean to imply that
we possess only two. For instance,
there might exist dedicated systems for domains other than objects, such as a "person module"
that uses cues to animacy—
structural properties indicative of
faces or certain patterns of movement—to parse the world into
intentional beings that are not coextensive with objects (BaronCohen, 1995; Bloom & Veres,
1996). But we certainly do not have
specialized modules for chimneys,
or chapters, or families. How is it
that these nonobject entities are
treated as distinct individuals in
language and cognition?
SOME CUES TO
One cue that could cause us to
construe something other than a
discrete object as an individual is
the existence of perceived nonrandomness. For example, if a set
of objects is moving together
through space, this is seen as a
nonrandon:! state of affairs, and it
is natural to posit some connection
between the objects in order to explain their proximity and common
fate. As a result, a person might
construe the set of objects as a single individual, as with a flock or
pack. Similarly, certain discontinuities in contour are seen as the result of nonrandom processes, and
this inference can lead to the identification of some material individuals that are not discrete objects (Hoffman & Richards, 1984;
Leyton, 1992). These include fingers (created through biological
processes), mountains (created
through geological processes), and
Published by Cambridge University Press
chimneys (created through intentional processes). Intuitions of
nonrandomness can also apply in
the domain of actions, as when an
infant's sensitivity to systematic
patterns in motion can lead her to
count the jumps of a continually
moving puppet (Wynn, 1996).
A related cue to the existence ot
nonobject individuals is their participation (as agents, patients, or
goals) in intentional activities.
Chapters, parties, and jokes are individuals precisely because they
are created and regarded by other
people as singular entities. There
is no independent motivation for
treating them as such. Similarly, a
bikini can be viewed as a single individual because it is created and
used for a singular purpose, and
the world is divided into distinct
countries through social and historical facts, not physical ones.
One basic source of information
about the intentions of other people is linguistic. Our appreciation
that there exist individuals such as
specific countries emerges simply
by hearing people refer to such entities in their speech, and inferring
that some such entities must therefore exist.
It is not surprising that the cues
to nonobject individuals are abstract and diverse, given that they
pick out entities as disparate as
jokes and fingers. To make the investigation of such cues more tractable, my students and I have focused on a very specific question:
Exactly what is it about the collections named by count nouns in
natural language—individuals like
families and flocks—that makes
them natural individuals in language and cognition? Our experiments typically involve showing
children and adults displays of
three groups of several objects
each, either actual physical objects
or entities depicted on a computer
screen. The displays are described
using a novel word (e.g., "These
are fendles"); subjects are then
tested as to what they think the
new word means. We are interested in the factors that lead people to construe the groups of objects as individuals and thus to
interpret the new word as a collective name (Bloom & Kelemen,
1995; Bloom, Kelemen, Fountain,
&L Courtney, 1995).
Figure 1 shows some of the displays used in these experiments,
in schematic form. When subjects
are presented with a simple display of stationary objects (Fig. la),
they overwhelmingly construe the
word as an object name (i.e., there
are 15 "fendles"). Apparently the
bias to parse the scene into objects
overrides the Gestalt cue of proximity. However, if the same stationary groups are the recipients of
purposeful action, a very different
result obtains. Adults were shown
a display in which three "machines" rose up (Fig. Ibl), each
surrounding one of the groups.
Colored balloons popped out of
each machine when it made contact with a group (Fig. Ib2), and
the machines then gradually re11
rr
r
r r
r n
rn
c
r
rr
rr
rr
c
r
r r
rr
r
-^
i't
ri
r
11 r
i
rri
ir/
•''•
'
?
r fi
. 1
tr
rr
r
rr
r r
rr
rr
r
r
Fig. 1. Schematic representation of
the stimuli used in the collection studies: stationary groups of objects (a),
stationary groups that are the targets
of machines (bl) that react when they
contact the groups (b2), moving
groups of objects (c), and groups that
are perceived as moving because they
are resting on moving plates (d).
treated from the screen, leaving
the screen empty except for the
original, still stationary, groups. In
this condition, subjects tended to
interpret "fendle" as a collective
noun, referring either to each
group (the target of an action) or to
each group and its corresponding
machine (all of the participants in
an action). Thus, the object bias
disappears if a group is seen as a
participant in some structured interaction, even if the group remains stationary throughout.
The perceived intention of the
experimenter, signaled through
language or in some other fashion,
is also sufficient to guide people to
treat collections as individuals. For
instance, if each of three stationary
groups is described with a singular
count noun (e.g., if the experimenter says, "This is a fendle . . .
this is a fendle . . . and this is a
fendle," while pointing to each
group in turn), adults and 5-yearolds tend to treat the word as denoting the collections, sensitive to
the fact that the experimenter was
referring to them as individuals. A
similar effect obtains without syntactic cues. In one study, 4- and
5-year-olds watched while the experimenter carefully arranged
three groups of objects and described them with a plural count
noun ("These are fendles"). For
some of the children, a picture
frame was placed around each
group as it was being created (the
frame was removed before the
groups were named), giving the
impression that each group was an
independent artistic creation. The
children in this frame condition
gave collective interpretations of
"fendle" significantly more frequently than those not given this
intentional cue, suggesting that
these children inferred that the
groups were thought of as individuals in the mind of the experimenter and therefore construed
the groups as individuals.
Finally, people may be moti-
Copyright (C 1996 American Psychological S(iciL't\'
vated to treat collections as individuals when the collections themselves appear to be causally potent
entities. In one study, adults
viewed a computer screen showing three groups, each moving as a
single unit, tracing a path across
the screen, avoiding the other
groups, and so on (Eig. lc). These
subjects construed the groups as
individuals and interpreted "fendle" as a collective noun. This construal was not the result of the
movement of the groups per se. In
another study, other subjects were
shown the same moving groups,
but each group was surrounded by
a circle (Fig. Id). The experimenter
told the subjects, "These are fendles on plates," to make it clear that
the circles were defined as plates.
Placing the groups on "plates" explains the common movement of
the objects within a group without
appeal to any deeper shared properties of the objects. Without such
a motivation to treat the groups as
distinct causal entities, subjects
abandoned the collective interpretation and treated "fendle" as an
object name, despite the fact that
the groups were moving.
Future studies may reveal that
intentional and causal notions are
i m p o r t a n t not only for collections, as we have found, but
also for nonobject individuals
more generally. Such findings
would support the theory of individuation I proposed earlier: Although the functional motivations
for positing objects and positing
other individuals are identical, the
procedures responsible for their
individuation differ. Object individuation results from specialized
mechanisms that draw upon perceptual input. In contrast, the understanding of abstract individuals
emerges from more general aspects of our mental life: intuitions
about randomness and systematicity, inferences about which entities
count as participants in causal interactions, and our appreciation of
the beliefs and desires of other
people.
Acknowledgments—I am grateful to
Susan Carey, Emanuel Donchin, Tim
German, Mary Petersoti, Karen Wynn,
and an anonymous reviewer for helpfui
comments on a previous version of this
article and for discussion of the ideas
within. The research discussed here is
supported by grants from the Sloan
Foundation and the Spencer Foundation.
Notes
1. Address correspondence to Paul Bloom, Department of Psychology', Universitv' of Arizona, Tucson, AZ 85721; e-manl: bkxjmCfiu.arizona.edu.
2. Not all object individuation is plausibly
viewed as emerging from an innate object module, in particular, the identification of objects in a
static scene draws on a person's prior experience
with the objects and on sensitivity to cues such as
discontinuities in color and texture. These are the
same factors that apply for the individualion ol
nonobject entities such as parts, suggesting that
the procedures for nonobject individuation can
sometimes extend to objects as well. Note, however, that although infants are sensitive to objecl
properties such as spatiotemporal continuity, the
ability to exploit those other types of cues is not
present early in development (for discussion, seo
Baillargeon & Hanko-Summers, 199U; Spelke,
Breinlinger, Jacobson, & Phillips, 1993), This developmental dissociation suggests that although
the two modes of individuation might sometimes
apply to the same entities (objects), they are
nonetheless distinct.
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Integrating Information Across Saccadic
Eye Movements
David E. Irwin^
Department of Psychology, University of Illinois, Urbana-Champaign,
Champaign, Illinois
We make rapid eye movements
called saccades about three times
each second in order to examine
the world around us. The still periods between saccades are called
fixations. The average fixation is
approximately 300 ms in duration,
whereas the average saccade is
only 30 ms in duration. We make
saccades in order to direct the
fovea of the eye, which provides
our clearest vision, at objects of interest in the environment. Sac-
cadic eye movements create problems for perception because visual
information sweeps across the
back of the eyes during each saccade; as a consequence, objects in
the world have different positions
on the retina from one fixation to
the next. Even though the visual
input is continually changing in
this way, we ordinarily perceive
the world as a coherent whole,
with objects maintaining their positions in space. There is no feeling
Published by Cambridge University Press
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Recommended Reading
Bloom, P. (in press). Inlenlion, histor\, and
arlifart concepts Cognition.
Dennett, D 1199!). Real patterns, journal of
Philosophy, S8, 27-r-l.
Macnamara, |. (1994). Logic and cognition. In
), Macnamara & G E, Reyes (Eds.), The logical
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of "starting anew" with each fixation; rather, we remember the positions and the identities of at least
some of the objects in a scene,
even if we close our eyes.
Psychologists and vision researchers have wondered for more
than a century how this quality of
perception is achieved. One frequently proposed hypothesis is
that visual information acquired
during individual eye fixations is
accumulated across saccades. This
view assumes the existence of a
transsaccadic memory that combines
the information from successive
eye fixations in such a way that a
percept of a stable and continuous
visual world is produced. In this
article, I summarize research that
my colleagues and 1 have conducted during the past 15 years to