Perceptualand Motor Skills, 1992, 74, 339-343. O Perceptual and Motor Skills 1992
VEKBAL MEMORY ELICITED BY AMBIENT ODOR '
DAVID G. SMITH, LIONEL STANDING, AND ANTON DE MAN
Bishop's University
Summary.-This study examined whether an ambient odor can act as a contextual
cue for retrieval of verbal stimuli. Subjects (N = 47) learned a list of 24 words while
exposed to one of two odors (either jasmine incense or Lauren perfume) and subsequently relearned the list with either the same or the alternative odor present. Superior memory for the word list was found when the odor present during the relearning session was the same one that had been present at the time of initial learning, thereby demonstrating context-dependent memory. There were no differences in initial learning between the two odor conditions. No differences in pleasantness or intensity were
found between the odors.
According to the encoding specificity principle (Tulving, 1983), verbal
memory performance is enhanced when the contextual, or incidental, stimuli
present at the time of retrieval are the same as those which were present during the initial learning. This effect may be demonstrated not only by changes
to the contextual learning stimuli, e.g., associated category names (Tulving &
Pearlstone, 1966) but also by changes to the general environment experienced by the subject during the learning task. Context dependency has thus
been demonstrated, for instance, using underwater/terrestrial changes of location between learning and retest (Godden & Baddeley, 1975) as well as
changes in room location or setting (Smith, 1979; Smith, Glenberg, & Bjork,
1978).
The present study examined whether contextual effects may be produced by odor. In accordance with the general principle of context dependency, it was predicted that, if subjects learn a word list while one odor is
present and subsequently retrieve this information while exposed to a different odor, performance should be depressed, compared to conditions where
the same odor is present for both the learning and retrieval sessions.
Anecdotal accounts of memories elicited by odors are widespread, but
few published studies bear directly on this point. Laird (1935) reported that
90% of women and 79% of men had at some point experienced an odor
that brought back vivid contextual memories. Two recent studies appear to
show the phenomenon more directly. Cann and Ross (1989) showed subjects
photographs in the presence of a pleasant or an unpleasant odor. Two days
later, subjects recognized these photographs more accurately if, during the
memory test, they were again exposed to the original odor rather than the
'Reprints may be obtained from L. Standing, Department of Psychology, Bishop's University,
Lemoxville, PQ, Canad:! JIM 127.
340
D. G. SMITH, E T A L .
alternative one. Schab (1990; Exp. 3), using verbal learning, also found that
memory was improved when the original odor was present during the memory test. In this case, free recall after a period of 24 hours was used as the
dependent measure.
It should be noted that the present situation differs from the paired-associate task wherein several odors are used, each associated with a particular
stimulus word. Eich (1978) used odors as paired-associate cue items and
reported that odor was ineffective as a retrieval cue unless it was semantically related to the word which was to be recalled (the semantic cue
'cowhide,' for example, elicited memory for the stimulus LEATHER more
often than did the odor of leather). Also, Ludvigson and Rottman (1989)
attempted to demonstrate the odor-dependent memory effect but did not
succeed. Two factors, however, could have masked the phenomenon. Their
subjects learned a list only once, with recall a week later, so that they may
not have had time to establish an association between odor and words.
Further, the words used were not emotion producing; odor may work best as
a retrieval cue if the related event is emotional (Laird, 1935).
The present study employed a different measure of learning (relearning),
and both pleasant and unpleasant verbal stimuli, to test the generality of the
effect.
METHOD
Subjects
Forty-seven college and university students (16 men and 31 women)
were used as volunteer subjects. Their mean age was 20.5 years (range 17 to
25). Participation was rewarded with a lottery ticket.
Materials
The two odors used were jasmine incense (Ligne Noire) and 'Lauren'
perfume by Ralph Lauren.
Twenty-four words (12 pleasant, 12 unpleasant) were used as learning
stimuli. The words were selected from a set of 132 common nouns and adjectives by another group of 20 subjects, who classified them as pleasant or
unpleasant and rated them for emotionality on a scale from 1 to 10. The 12
most pleasant and 12 most unpleasant words were selected in this way.
The words were displayed on separate white 8- x 5.5-inch cards in a ring
binder.
Procedure
All subjects were tested in the same room, which was about 10 x 18
feet. The incense odor was produced by lighting a stick of incense for 5 min.
before the subjects arrived. Alternatively about 2 rnl of perfume was sprayed
about the room in advance.
Subjects were randomly formed into four treatment groups, constrained
ODOR AND MEMORY
341
by their availability and the need to balance the malelfemale composition of
each group. Each subject was tested with a learning session, followed by a
relearning session two days later as a measure of retention. The odors present
for the learning and retest sessions were, respectively, incense-incense, incense-perfume, perfume-perfume, and perfume-incense in the four groups.
I n the learning session, the words were presented in random order for 6
sec. each and shuffled between trials. An interval of 2 rnin., 30 sec. was allowed for free verbal recall. A recall trial was considered successful if 20 of
the 24 words were correctly recalled without regard to order. Each subject
completed six trials.
Two days later, subjects returned to the laboratory (to minimise rehearsal, subjects were told to expect a problem-solving task) and were given a
relearning task. This was identical to the original learning task, except that a
maximum of four trials was given.
A postexperimental questionnaire was given to all subjects after Session
2 to evaluate the relative intensity and pleasantness of the odors. Subjects
were then debriefed.
RESULTS
The data were first checked for a possible differential effect of the two
odors on initial learning. Trials to criterion in Session 1 for the two perfume
groups pooled did not differ from the two incense groups (t,, = 1.21, p > .lo).
Therefore, the rate of learning as measured by trials to criterion may be
taken as equal under the two odor conditions.
A two-way analysis of variance (learning environment odor x word pleasantness) was performed to assess whether the learning environment affected
the number of words recalled on the sixth trial. The analysis indicated no effect of the learning environment odor (F,,,, = .04) or of the words' pleasantness (F,,,, = 0.22), and no inreraction between them (F,,4,= 2.54, all ps>
.05). These analyses justified using the number of trials to criterion and
number of words recalled as dependent variables.
The mean number of trials to criterion and the number of words recalled are shown in Table 1 as a function of experimental group. The effect
of odor conditions on trials to criterion in the relearning task was examined
by means of a two-way analysis of variance. (Two subjects were excluded
from the analysis since they did not reach criterion.) No main effects were
found for either learning session odor (F,,,, = .09, p > .05) or relearning session odor (F,,.,, = 1.42, p > .05); however, the interaction between learning
and recall odors was significant, such that relearning performance was best
when the relearning odor was the same as the learning odor (F,,,,= 11.05,
p < .01).
A three-way analysis of variance was performed on the number of words
recalled in Session 2 to assess the effect of congruent and incongruent learn-
342
D. G. SMITH. ETAL.
TABLE 1
AN NUMBEROF T m s TO CRITERION,AND NUMBEROF WORDSRECALLED,
AS A FUNCTION
OF LEARNING
A N D RECALLODOR
Recall Odor
Learning Odor
n
Incense
Perfume
Incense
Perfume
Incense
Perfume
Trials to Criterion
M
SD
10
11
12
12
1.50
2.09
2.33
1.08
0.71
0.94
1.37
0.28
Mean Words Recalled
n
M
SD
11
12
12
12
19.1
17.7
16.8
21.8
3.88
2.68
4.07
1.74
inglrecall environments on recall of pleasant and unpleasant words. No main
effects were found for type of odor (perfume versus incense) in either the
learning or the recall environment (F,,,, = 0.93 and F,,,, = 3.72, respectively,
both ps > .05); however, the interaction of the learning odor x recall odor was
significant (F,,,, = 11.78, p<.01). Thus, congruent rather than incongruent
environments produced the higher learning. The incense-perfume and perfume-incense conditions did not differ (q,, = 0.96, p > -2); however, it was
also observed that the perfume-perfume condition gave higher scores than
the incense-incense condition (q,,= 2.8, p < .05).
No main effect was noted for the pleasantness of the stimulus words
(F,,4,= 0.13, p > .05). No interaction of recall odor x pleasantness occurred
(F,,,, = ,002, p>.05), and there was no three-way interaction of learning
odor x recall odor x word pleasantness (F,,,, = .025, p > .05).
An interaction for learning odor x word pleasantness was observed (F,,,,
= 4.77, p c . 0 5 ) . An analysis of simple main effects shows that the type of
learning odor had no effect on the number of unpleasant words recalled
(F,,,, = .0002) or the number of pleasant words recalled (F,,,,= 3.06, both
ps > .05). A trend was noted for the women over-all to score higher on recall
than the men (19.61 vs 17.38; t,, = 2.38, p < .01).
The mean perceived intensity rating for incense was 6.3 on a 10-point
scale; three of 22 subjects (7 men, 15 women) who responded did not notice
the incense odor at all (two of these were women). The mean rated intensity
for perfume was 7.8; three of 19 respondents (9 men, 10 women) did not
notice the odor (two of these were men). The intensity means did not differ
significantly (t,, = 1.90, p > .05). The pleasantness scores were randomly distributed across unpleasant, neutral, and pleasant categories for both perfumes rXZ2(N= 35) = 0.79, p > . l o ] The median judgement for both odors
was 'neutral.' There was no correlation between perceived odor intensity and
words recalled, either For congruent or for incongruent conditions (r,, = .12,
and r , , = -.31, both ps> ,051.
DISCUSSION
The experimental hypothesis that odor can act as a contextual cue to facilitate the retrieval of verbal stimuli from memory is supported by the data.
O D O R A N D MEMORY
343
Relearning in a same-odor environment is superior to performance when the
relearning session incorporates an odor different from that of the learning
session.
Although this outcome contradicts the results of Ludvigson and Rottman (1989), it represents a replication of the essential findings of Cann and
Ross (1989) and of Schab (1990). Since the details of the present experiment, especially the learning task, differ from those of the prior studies, the
effect appears to be robust.
The results are also in accord with the general literature on context-dependent memory. The simplest interpretation of this effect is to say that
incidental elements of the learning environment (e.g., room odor) become associated with the learning stimuli. I n accordance with the classical doctrine
of associationism, proximity in time and space is sufficient to produce this
effect. Subsequently, reinstating any of these elements such as odor is sufficient to improve recall of the learned stimuli, presumably through facilitating
the retrieval process rather than strengthening the memory trace per se.
Although alternative explanations for the present data might be attempted in terms of odor-enhanced arousal or mood-dependent memory,
these appear unlikely to be of appreciable significance and are specifically
countered by the detailed results of Schab (1990). However, the question remains whether the memory-enhancing- effects of odor represent a direct link
between the odor and the verbal items in memory or one between the verbal
associates of the odor and the stored items. The latter possibihty appears
likely, since Eich (1978) found that the effect of fragrance cues was strongly
mediated by verbal associations to those cues.
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Accepted February 3, 1992.