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Age decisions on familiar and unfamiliar faces
Behavioural Processes, 24 (1991) 21-35 0 1991 Elsevier Science Publishers B.V. 0376.6357/91/$03.50
21
BEPROC 00354
Age decisions on familiar R. Buyer Louvain
University
and unfamiliar
faces **
*, A. Lafalize and M. Distefano
(UCL), Psychology (NECO),
Department,
Unit& de Neuropsychologie
Louvain-la-Neuve,
(Accepted
27 February
Cognitive
Belgium
1991)
Abstract The extraction of age is among the “early visual processes” that operate on faces. Current cognitive models mention this operation, but data on the subject is rare. In the first experiment, a series of familiar and unfamiliar faces were displayed to subjects who were asked to make old/young categorizations. To test how early this operation occurs, the same material was used for familiarity decision. Finally, the stimuli were displayed centrally to 16 subjects and laterally to 32 subjects. The age decision was easier and quicker than the familiarity decision; the familiarity decision was unaffected by the age of the faces, while face familiarity affected the extraction of age. In a second experiment (40 subjects), we manipulated the ambiguity of the apparent age and conditional tasks were used, i.e., the subjects had to process both age and familiarity in a single task. The results suggest that age extraction is an operation that is mandatory for an efficient recognition process. Therefore, it is proposed to dissociate, within the semantic visually derived codes, the processing of age from the processing of sex and race.
Key words:
Age; Cognitive model; Conditional task; Face recognition; Familiarity
Introduction The cognitive models of face recognition include visual operations that precede the recognition stage and can be applied to unfamiliar as well as to familiar faces. Beyond the very first step of “facial decision” (Ellis, 1983, 1986), these operations, among other things,
* UCL-NECO, **
Voie du Roman
This study was presented,
Fransaise,
Paris, 1988.
Pays 20, 1348
Louvain-la-Neuve,
in part, at the meeting
of the Soci&
Belgium. de Neuropsychologie
de Langue
22
age of the extract characteristics concerning the sex, the race, and the approximate derived semantic codes” (Bruce & Young, perceived face. This extraction of “visually 1986) would not seem to be mandatory for face recognition. Two questions arise about these processes. The first is how early these operations occur with regard to the recognition step. The second question concerns their independence of face familiarity. Indeed, it could be that top-down mechanisms apply, so that familiarity could facilitate or inhibit decisions about the sex, age, or race of the face. In addition, we consider the possibility of lateral differences, i.e., the opportunity to demonstrate dissociations in the function of the stimulated portion of the visual field and, accordingly, of the stimulated cerebral hemisphere. However, given the small amount of published data, we also have to examine this question with centrally displayed stimuli. In normal subjects, Bruyer & Schweich (1987) used this neuropsychological procedure and showed that the “race decision” was an early operation and was not lateralized (see also Bruyer & Dujeux, 1988). However, only unfamiliar faces were used, so the effect of familiarity on this decision was not investigated. With regard to gender classification, several studies have shown that this operation was early, non-lateralized, and free of familiarity effects (Bruyer & Dujeux, 1988; Jones, 1979, 1980; Marzi, Tassinari, Tressoldi, Barry & Crabowska, 1985; Sergent, 1985). Finally, to our knowledge, there are no neuropsychological studies with normal subjects on “age classification” of faces. With brain-injured subjects, there are a few cases of prosopagnosia (i.e., a specific face agnosia) in which defects about face classification as a function of age (Beyn & Knyazeva, 1962; Bruyer, Rectem & Dupuis, 1986; Cloning, Cloning, Jellinger & Quatember, 1970; Michel, P&enin & %&off, 1986; Tiberghien & Clerc, 1986; Whiteley & Warrington, 1977), sex (Beyn & Knyazeva, 1962; Tiberghien & Clerc, 1986), or race (Cole & PerezCruet, 1964) have been clinically described. Nevertheless, prosopagnosics are more often than not able to perform these operations (e.g., Sergent & Villemure, 1989) and no pathological cases have been described in which these operations were defective while recognition was preserved. Therefore, there are precede and are independent of recognition. In this view. Tranel, Damasio & Damasio (1988) gender, age, and identity of faces to four severe defective in every task, while the remaining
reasons to suppose that these operations addition, more experimental data support applied recognition tests of expressions, cases of prosopagnosia. One subject was three were deficient for identity only.
Newcombe & Russell (1969) showed that a group of right-brain-injured, non-prosopagnosic subjects was impaired in a task of age and sex categorization of faces. However, the two scores were pooled in the results, and the faces used were only approximations of faces (Mooney faces). De Renzi, Bonacini & Faglioni (1989) have shown that damage to the posterior region of the right hemisphere impairs the classification of faces by age, more than it impairs face recognition. Finally, in a prosopagnosic subject, Sergent & Poncet (1990) found familiarity effects in the episodic recognition of faces whose age changed between encoding and test. The present study focusses on one of these visually derived semantic codes, namely, age. In the first experiment, normal subjects were presented with laterally or centrally displayed faces and asked to make old/young decisions. Two questions were considered, namely, (a) familiar and unfamiliar faces were intermixed in order to detect familiarity effects, and (b) a control recognition condition was provided to test how early is age evaluation. Indeed, little is known about the processing of age and the few published experiments have shown (a) that episodic recognition of faces is possible even if the age is changed between encoding and test, provided the change is not too large (Bruyer & Lafal-
23
ize, 19891, and the performance Seamon,
1982);
is facilitated
(b) that this episodic
encoding provided 1990); and (c) that parameter the three-dimensional
by face familiarity
recognition
is facilitated
(Bruyer
& Lafalize,
by the exposure
1989;
duration
at
the structural age changes are modest (Read, Vokey & Hammersley, the human perceiver can extract age changes by considering a single strain of a cardioidal function (Mark & Todd, 1985>, even on representations (Mark & Todd, 1983; see also Bruce, Burton,
Doyle & Dench, 1989 for both replication and slight qualifications). In the first experiment, we hypothesized that an advantage of familiar over unfamiliar faces in age decision would reflect top-down influence of face familiarity (face recognition units) on visual processes, and that age decision would be faster than familiarity decision. Bruce, Ellis, Gibling & Young (1987) used an elegant paradigm showing categorization was independent of recognition. This study will be presented we applied this methodology in our second experiment on age categorization, attempted
to precise the task effect observed
Experiment
that gender below since in which we
in the first experiment.
I
Method Subjects Forty-eight
(24 female,
24 male) young,
neurologically
intact,
right-handed
adults were
enrolled. There were no left-handed close relatives. They were randomly assigned to two displayed stimuli” condigroups: 16 subjects (8 females) were assigned to the “centrally tion; the remaining 32 took part in the “laterally displayed stimuli” condition (Actually, the lateral presentation was administered to 34 subjects. However, the data of two subjects had to be discarded because they were completely unable to recognize familiar faces in the familiarity decision task). Within each condition, two tasks, age decision tered to each subject in a balanced order. Stimuli A series of was submitted evaluated the 20 & 30; .; selected, with
and familiarity
decision,
were
adminis-
60 black-and-white photographs of familiar (well-known celebrities) faces to 40 judges who evaluated their celebrity on a seven-point scale; they also age on a seven-point scale (1 = less than 20 years old; 2 = between 7 = more than 70). Ten clearly familiar faces (mean score > 5) were then five being clearly “young” (values < 2: mean = 1.92; mean familiarity =
6.021, and five clearly “old” (values > 5: mean = 6.11; mean familiarity = 5.94). Another series of 47 black-and-white photographs of unfamiliar (unknown) faces was submitted to a similar process (n = 26 judges). This material had been collected from people who were invited to supply with two (or more) photographs of the same face taken at an interval of 15 years or more, with the youngest not less than 15 years old. We selected 10 clearly unfamiliar faces (mean score < 21, with five being clearly “young” (values < 2: mean = 1.63; mean familiarity = 1.38) and five clearly “old” (values > 5: mean = 6.22; mean familiarity = 1.39). Several slides were made of these 20 faces. The stimulus width was four degrees of the visual field. When laterally displayed, they were centered four degrees left or right of the fixation point.
24
Experimental design In the central condition, each task (age decision and familiarity decision) involved 60 items, i.e., three displays of each face in random order. In the lateral condition, each task 120 items, i.e., three displays of each face in each hemifield in random order. The subject was asked to respond as quickly as possible by depressing one of two push buttons (index fingers) indicating his/her choice: old/young or familiar/ unfamiliar. The involved
button assignment was balanced across the subjects. For the familiarity decision, the subject was asked to decide if the face was well known due to its episodic recurrence in the course of the or not (irrespective of its “familiarity” experimental session). For the age decision, some examples of old and young faces, not used in the experiment, were shown before beginning. This adaptation was provided since the notions of “old” and “young” can be relative to the current set of stimuli and/or to each subject. Procedure The subject sat facing the screen (viewing distance = 85.5 cm), the head supported on a chin rest. Each trial was sequenced as follows: auditory warning (500 msec) to invite the subject to focus on the central fixation point, delay (1000 msec), displaying of the stimulus during 150 msec, inter-item interval of five sec. The stimuli were back-displayed by projectors controlled by a microcomputer, the response device. The instructions stressed the speed of response. Statistical
as was
design
Central and lateral presentations were analyzed separately, since they were submitted to different subjects and differed in perceptual difficulty. In both cases, errors and correct latencies were studied separately by means of analyses of variance (ANOVAs). Post-hoc analyses of significant interactions were performed by using the Newman-Keuls test (p < 0.05).
Results Central presentation We computed 2 x 2 x 2, within-subject,
ANOVAs.
The factors were the task, the age of
the faces, and the face familiarity. As can be seen in Table 1, there were more errors in the familiarity decision than in the age decision (F(l ,I 5) = 29.38, p < 0.0001) and more errors for the familiar than for the
TABLE 1 Exp. I. Central
presentation:
errors (out
of 15, between
familiarity.
Means
mean
latency
parentheses)
of the correct
in function
responses
in msec and mean
number
of 16 subjects. Age decision
of
of the task, the age of the faces, and the face
Familiarity
decision
Old
Young
Old
Young
Familiar
678 (0.19)
661 (0.56)
831 (4.50)
732 (5.25)
Unfamiliar
699 (I .44)
729 (T.31)
776 (1.69)
783 (I .12)
25 TABLE
2
Exp. I. Lateral presentation: mean latency of the correct responses in msec and mean number of errors (out of 15, between parentheses) in function of the task, the age of the faces, the face familiarity, and the visual field (LVF = left, RVF = right). Means of 32 subjects. Age decision Old Familiar LVF RVF
Unfamiliar LVF RVF
Familiarity decision Young
Old
Young
729 (1.41)
729C1.75)
976C6.28)
936C5.12)
697c1.28)
713 (1.69)
923 (6.25)
863 (5.28)
730 (1.81) 728 (1.78)
795 (4.47)
911 (3.34)
884 (2.37)
818 (4.87)
886C3.06)
927 (2.47)
unfamiliar faces (F(1,15> = 9.83, p < 0.01). Moreover, these two factors interacted significantly (F(1 ,I 5) = 30.97, p < 0.0001). Post-hoc analysis of this interaction revealed a higher number of errors on the familiar faces for the familiarity decision condition than in the remaining three conditions. Thus, the task effect applied to the familiar faces only, and the familiarity effect applied to the familiarity decision only. No other main effect or interaction reached statistical significance. For the correct latencies (Table familiarity decision (F(1 ,I 5) = 9.1,
I), there p < 0.01).
was a significant There was also
advantage of age over a significant interaction
between the age and the familiarity of faces (F(1 ,I 5) = 6.2, p < 0.02). Post-hoc analysis of the interaction revealed that the young familiar faces were processed faster than both the young unfamiliar and the old familiar faces. There was no age effect for the unfamiliar people and no familiarity effect for the old faces. No other main effect or interaction reached
statistical
significance.
Lateral presentation We computed two
2 x 2 x 2 x 2, within-subject,
ANOVAs.
The factors were
the task,
the age of the faces, the face familiarity, and the visual hemifield of presentation. As shown in Table 2, accuracy was better for age than for familiarity decisions (F(1,31) = 42, p < 0.0001) and better for the old than for the young faces (F(1,31) = 5.3, p < 0.05). These two factors, however, interacted significantly (F(1,31) = 16.4, p < 0.001). Post-hoc analysis of this interaction showed that the age-decision advantage was observed for the old faces only. On the other hand, whereas the advantage of the old over the young faces appeared for age decision, the opposite advantage of the young over the old faces was significant in the familiarity decision task. There was also a significant task X familiarity interaction (F(1,31) = 44.4, p < 0.0001; see Fig. I). Post-hoc analysis of this interaction showed that the age-decision advantage was observed only for the familiar faces, and an advantage of the familiar over the unfamiliar faces appeared in the age-decision task, while accuracy was better for the unfamiliar than for the familiar faces in the familiarity decision task. Finally, the two factors involving the kinds of stimuli interacted significantly (F(1,31) = 8.6, p < 0.01). Post-hoc analysis of this age X familiarity interaction showed that old unfamiliar people were better processed than the other three series, which did not differ significantly from each other.
26
01
I
FAMILIAR Fig I. The taskxface
familiarity
UNFAMILIAR
interaction
for errors in Exp. I, lateral presentation.
While the field of presentation did not affect accuracy as a main effect or within interactions, the three remaining factors interacted significantly (F(1,31) = 7.02, p < 0.02). This interaction slightly modifies the effects already noted. (a) With the exception of the young unfamiliar faces, for which familiarity decisions were easier than age decisions, the age decision
was better
(b> An advantage decision when
task (for
the young
unfamiliar familiarity For
performed
than the familiarity
of the unfamiliar
both old and young faces were
faces,
the
decisions
old
faces
the correct
latencies
were
to the age decision. better
processed
faces, the young
(Table
2),
task for every
faces was revealed
faces) and of the familiar
submitted
on familiar
decision
over the familiar
there
than
faces were
was a main
over
Cc> For the
better
of face.
the unfamiliar age decisions
young;
faces on the
conversely,
processed
significant
kind
in the familiarity
for
than the old.
advantage
of the age
(F(1,31)= 46.9, p < 0.0001) and a bias favoring the right over the left field (F(1,31)= 3.5, p = 0.067). Three one-way interactions reached significance. For the first two (task X age: F(1,31) = 7.23, p < 0.01; task X familiarity:
decision
F(1,31)
over the familiarity
= 4.8,
p < 0.05),
significant
for
unfamiliar
faces.
familiarity), third
it can
both the old
be seen
and the young
Secondly,
while
significant
decision
the familiarity
the age decision
interaction
modified
F(1,31)= 14.24, p < 0.001)
since
in
Figure
2,
firstly,
faces as well decision
was affected
was
that
as for
unaffected
by face familiarity
the bias towards a significant
task
field
effect
advantage
was
and the
by age (as well (as well
as by
as by age). The
a main field effect (field
right
950
the
both the familiar
X familiarity:
for the familiar
but
n
-_____~‘~l!JRW
/----¤ w---
900 850 I
o
7oo%zE+-xFig 2. The taskxage
(left)
and taskxfamiliarity
-
FAMILIAR (right)
I
UNFAMILIAR
interactions
lateral presentation.
FlGI DECISION
for correct
latencies
in Exp. I,
27
not the unfamiliar faces emerged. Complementarily, faster than the unfamiliar in the right field only.
the familiar
faces were processed
Discussion One purpose of this experiment was to decide whether age processing is earlier than face recognition. It seems that a positive answer can be given. Indeed, this expected kind of result appeared for latencies on both centrally and laterally displayed faces, and a similar pattern appeared for accuracy. Therefore, these results tend to support the theoretical models that locate the age decision in the cognitive stages (“visual processing”) that precede the recognition stages (e.g., Bruce & Young, 1986). One could argue that even though the same faces have been used in both tasks the task difficulty was not identical, since the stimuli were selected on the criteria of the ease to be discriminated for age. In this respect, it should be mentioned, firstly, that the stimuli were also selected on the basis of the ease to be discriminated for familiarity. Secondly, this facility of age discrimination will be manipulated in the second experiment. Another purpose of this study concerned the relative dependency between these two stages of processing, i.e., whether familiarity affects decisions on age. Provided the task demands were hard enough i.e., the lateral mode of presentation it appeared that familiarity influenced the age decision, while the speed of familiarity decision was unaffected by age. This observation suggests top-down effects of the face recognition units on the decisions taken at the visual processing level. That is to say, when faces were recognizable, the decision on age was more easily (or quickly) taken than when they were not. In a companion paper using an episodic recognition procedure, we (Bruyer & Lafalize, 1989) noted that it was almost impossible to recognize unfamiliar faces strongly modified by age, while such a decision was much easier for familiar faces (see also Seamon, 1982). It was suggested that only the familiar faces activated semantic nodes about the person seen (Bruce & Young, 1986) so that the abstraction of age appearance became useless. Another interpretation, however, could be that face recognition units are “instance based”, i.e., they can vary in age or expression and, in this way, there is no need to resort to any semantic node effect. Finally, lateral differences emerged favoring the right visual hemifield that were due to familiar faces, irrespective of the task. Such a left hemispheric superiority has already been reported when known faces are involved, as compared to the “classical” right hemisphere advantage for unfamiliar faces. It has also been shown that this asymmetry results more from familiarity than from access to name representation (Umilta, Brizzolara, Tabossi & Fairweather, 1978). This result could also suggest that the left-hemisphere advantage in the processing of familiar faces emerges at the “visual processing” stage of the stimuli before the recognition stage. Since this laterality effect did not interact with the task, the lateral mode of presentation was not used in the second experiment. In short, the data collected in Exp.1 suggest that age decision precedes the recognition, and is affected - at least in some conditions - by face familiarity, in a top-down manner. However, as will be developed below, we have to check for possible methodological (task constraints) bias of this asymmetrical effect: age categorization was not required to take the familiarity decision. Exp. II has been planned to envisage this possibility. Moreover and more generally, even if an operation is faster than and is influenced by another one, it
28 remains to determine whether the two operations function sequentially
or in parallel. Exp.
II was designed to solve this question.
Experiment
II
The studies of Bruyer & Dujeux (19881, Jones (1979, 19801, Marzi et al. (1985) and Sergent (1985) have shown that gender classification of faces was independent of face familiarity. However, Bruce (I 986) showed that face familiarity facilitated sex categorization as we did in Exp. I regarding age categorization (Obviously, there is a lack of clinical and experimental data supporting the contention that sex and age [and race] classifications resort to identical mechanisms, even Bruyer & Dujeux [I 9881 suggested that Additional experiments are required to tions differ on at least one major point:
though authors tend to make such an analogy. sex and race categorizations should be dissociated. test this point. In addition, sex and age categorizathe former refers to a discrete dichotomy, while the
latter taps a continuous scale). Moreover, Bruce (1986) suspected that this familiarity effect was particularly evident when the gender of the face was someone ambiguous. This has since been confirmed (Bruce et al., 1987). This may be linked to our results showing that familiarity influences age decisions provided that perceptual conditions are difficult enough. According to Bruce, this result is not consistent with a strict perceptual hierarchy where one process should be completed before the next one begins. In the study of Bruce et al. (19871, it was questioned whether this lack of hierarchical relationship could have resulted from methodological biases, i.e., sex categorization was not a mandatory step for face recognition. Therefore, the authors designed a second experiment in which sex and familiarity were made to be relevant to each other, i.e., in the disjunctive condition, the subjects had to decide if the face seen was male (female) or known (unknown) and, in the conjunctive condition, they had to decide if the face was male (female) and known (unknown). According to the authors, the conjunctive condition provided a strong test of the model: if gender classification precedes the familiarity decision, “then a factor which slows up the sex judgement should also slow up conjunction decision. Such a consequence would be unlikely faces
in
decision
parallel
with
their
was unaffected
model
was claimed
In our second
familiarity”
(p.
by face ambiguity,
in a system which processed the sex of
516).
while
In
their
experiment,
the disjunctive
the
decision
conjunctive
was. The
parallel
to be supported.
experiment,
we used the disjunctive
et al. for age and familiarity
decisions.
We
and conjunctive
also tested
conditions
the age decision
of Bruce
and the familiarity
alone to search for effects of ambiguity. Furthermore, since, in Exp. I, the effects of interest were found when the task was difficult (lateral presentation), then, in Exp. II, we had the opportunity to examine the effect of another kind of perceptual difficulty by using
decision
ambiguous faces. Contrary to the opinion of Bruce et al. (19871, ambiguity for parallel young
does
processing.
(disjunction)
(by pressing and
not affect the response
such
we consider that, if age a result
a subject
has to decide whether
to give a positive
response,
he/she
button)
old (conjunction).
fore,
in the disjunctive
were
conjunctive,
and negative
conditions,
when
the other
Indeed,
in both
The
condition,
while,
answers
if the face is neither same
in reverse
positive
answers
in the conjunctive
were
disjunctive.
nor young,
i.e.,
for the conjunctive were
condition,
still
argue or
has also to give a negative response
familiar
applies
would
the face is familiar
disjunctive, positive
if it is unfamiliar condition.
There-
and negative answers
answers
were
conjunctive,
29
Method Subjects The experiment was submitted selected as in Exp. I.
to 40 (20
female, 20
male) young, normal adults,
Stimuli We used 16 faces from a set of 50 faces that had been submitted to ten judges for two tasks. In the familiarity judgment, they were asked to evaluate the celebrity on a seven-point scale: we selected faces with a mean evaluation greater than five (familiar faces) and less than three (unfamiliar faces). In the age judgment, the same faces had to be categorized in four classes: “very young”, “relatively young”, “elderly”, and “very old”. The judges had to sort the faces into four classes and corrections were authorized. We retained those faces that received the same classification by at least seven judges. The resulting set of stimuli was formed with eight familiar and eight unfamiliar faces. Each subset was composed of four young and four old people with two unambiguous (very young or very old) and two ambiguous (relatively young or elderly) faces. Four main sets of four faces resulted: familiar ambiguous, familiar unambiguous, unfamiliar ambiguous, and unfamiliar unambiguous. The mean familiarity ratings of these four sets were 6.05, 5.97, 1.94 and 1.78, respectively. Experimental
design
Ten slides of each face were prepared. Therefore, for each of the two between-subject conditions (below), 160 trials resulted, 40 for each of the four sets of faces. Sixteen subjects were randomly submitted to the disjunctive condition. They had to press one button when the face seen was either young (old) or familiar (unfamiliar), and the other button in the other cases (index fingers were used). The four possible disjunctions were crossed with four subjects for each. The button assignment was also balanced across the subjects within each subsample. Sixteen other subjects were submitted to the conjunctive condition. They had to push one button when the face seen was young (old) and familiar (unfamiliar) and the other button in the other cases. The four possible conjunctions were crossed with four subjects for each. The button assignment was also balanced across the subjects within each subsample. The remaining eight subjects were given “single tasks”. As in Exp. I, they had to decide whether the face was that of a young or an old person and whether it was familiar or unfamiliar, in two successive conditions. The order of conditions was balanced across the subjects, as was the button assignment. Procedure The procedure was identical to that of Exp.1, with two modifications: the instructions for the disjunctive and conjunctive conditions (see above) and the exposure duration of the stimulus which lasted until a response was given.
Results Single tasks There were 5.4% errors (Table 3) and the analysis revealed only that familiar faces were better processed than unfamiliar faces (F(1,7) = 12.7, p < 0.01). The correct latencies
30 TABLE 3 Exp. II. Single tasks: mean of 40, between Means
latency
parentheses)
of the correct
in function
responses in msec and mean number
of the task, the face familiarity,
of errors (out
and the ambiguity
of age.
of eight subjects. Age decision
Familiarity
decision
Familiar
Unfamiliar
Familiar
Unfamiliar
Ambiguous
958 (I ,251
1007
(5.00)
870 (0.62)
1057
(3.50)
Unambiguous
878 (0.87)
834 (1.37)
814 (2.25)
1022
(2.50)
llOO1050,-
n
FAMILIARITY DECISION
looo~950 I’ AGE DECISION
0 900 I’ 850
.A
-
,
800 * UNFAMILIAR
FAMILIAR Fig. 3. The task X familiarity
(Table
3) were
submitted
to
interaction
for correct
a within-subject,
latencies
in Exp. II, single tasks.
2 x 2 x 2 ANOVA.
The
factors
were
familiarity, age ambiguity, and task. There appeared a main significant advantage of familiar over unfamiliar faces (F(1,7) = 13.16, p < 0.01) and of unambiguous over ambiguous faces (F(1,7) = 24.55, p < 0.002). The task X familiarity interaction was significant (F(1,7) = 13.26, p < 0.01; see Fig. 3), i.e., familiarity decisions on familiar faces were faster than the other three conditions, and familiarity judgments than the remaining three conditions (the face familiarity
on unfamiliar faces were slower did not affect age evaluations).
There was a strong bias toward a task x ambiguity interaction (F(1,7) = 4.95, p = 0.06): age decisions on unambiguous faces were si,gnificant/y faster than in the remaining three conditions (see Fig. 4). -
lOOOr
n 0
900 g50:j
850
k
n
FPlMl LIARITY DECISION
0 AGE DECISION
1
800. AMBIGUOUS Fig. 4. The taskxambiguity
interaction
UNAMBIGUOUS for correct
latencies
in Exp. II, single tasks.
31 TABLE 4 Exp. Il. Conditional (out
tasks: mean latency
of 40, between
parentheses)
age. Means of 16 subjects
of the correct
in function
responses (msec) and mean number
of the task, the face familiarity
of errors
and the ambiguity
of
per task.
Disjunctive
task
Conjunctive
task
Familiar
Unfamiliar
Familiar
Unfamiliar
Ambiguous
945 (7.25)
1033
869 (4.44)
896 (8.00)
Unambiguous
911 (4.62)
849 (2.82)
855 (5.19)
(12.19)
933 (6.06)
Conditional tasks The correct latencies (Table 4) were studied by means of a mixed 2 x 2 X 2 ANOVA. The between-subject factor was the condition (conjunctive vs. disjunctive), and the within-subject factors were face familiarity and age ambiguity. Familiar faces were processed faster than unfamiliar faces (F(1,30) = 4.41, p < 0.05), and unambiguous faces were judged faster than ambiguous faces (F(1,30) = 8.41, p < 0.01). Errors (Table 4) were not rare (15.8%) and were submitted to the same ANOVA as latencies. Errors were less frequent on familiar than on unfamiliar faces (F(1,30) = 4.38, p < 0.05) and on unambiguous than on ambiguous faces (F(1,30) = 9.05, p < 0.01). Ideally, the statistical analyses should have included the kind of response as a factor. However, such a design was virtually impossible since, in the disjunctive task, each subject gave positive responses to the familiar and unfamiliar faces but half of them gave negative responses to the familiar faces and the other half to the unfamiliar faces. In the conjunctive task, a mirror image applied. One manner to solve this technical difficulty was to compute an index of ambiguity. We computed an index on correct latencies, for each subject, each kind of face familiarity, and each kind of response (conjunctive responses, i.e., positive responses in the conjunctive task and negative responses in the disjunctive task, vs disjunctive responses, i.e., positive responses in the disjunctive task and negative responses in the conjunctive task). The index was computed as (A - nA)/(A + nA), where A and nA represent the mean correct latency for the ambiguous and the unambiguous faces respectively. The four indexes (see Fig. 5) were tested against zero, i.e., against the absence of ambiguity effect: the ambiguity effect was significant for disjunctive responses to unfamiliar (0.034: t(31) = 2.3, p < 0.025) but not to familiar faces (0.009), and for
0,4T
Fig. 5. The index
of ambiguity
DISJUNCTIVE
for correct
(disjunctive,
latencies
conjunctive)
COWJNCTIVE
in Exp. II, conditional and the face familiarity.
tasks, according
to the task
32
conjunctive responses to both familiar (0.350: (0.103: t(15> = 3.92, p < 0.001 I
t(l5)
=
2.7, p < 0.01) and unfamiliar faces
In considering the single tasks, two conclusions derived from the Exp. I should be revised. On the one hand, age decisions were faster than familiarity decisions in certain conditions only, i.e., when the unfamiliar faces were considered (either ambiguous or not) and when easy, unambiguous faces were processed (either familiar or not). Two speculative comments can be proposed, which would require additional experiments. Firstly, the task difficulty could explain that age decision was not faster than familiarity decision on ambiguous faces: indeed, faces were selected as easily discriminable in the familiarity dimension while, by definition, ambiguous faces were selected as not easily discriminable in the age dimension. Secondly, age decision was not faster than familiarity decision when familiar faces were seen: this could suggest that the recognition is unavoidable and that the response (age decision) is mandatorily delayed up to the activation of a face recognition unit. We acknowledge, however, that this was not observed in Exp. I or in other studies dealing with gender classification or expression analysis. On the other hand, when both the ambiguous and the unambiguous faces were mixed together, the effect of face familiarity on age decision disappeared. It could be, therefore, that the suggested top-down effects of familiarity on visual, earlier processes was due only to the easy, unambiguous faces like those used in Exp. I (see Fig. 2, right panel, vs. Fig. 3). This observation is contrary to what is argued by Bruce (1986) and Bruce et al. (1987). They suggest that gender classification is facilitated by face familiarity when the gender is ambiguous. This constitutes another argument supporting dissociations within the “visually derived semantic codes” (Bruce & Young, 1986). The present controversy suggests a dissociation between sex attribution and age categorization, just as the study of Bruyer & Dujeux (I 988) suggested a dissociation between sex attribution and race categorization. The single tasks revealed two other points. Firstly, as expected, age judgment was affected by the ambiguity, i.e., for ambiguous faces, age decisions were as slow as familiarity decisions. Secondly, it confirmed that the familiarity decisions are not influenced by age. Whatever the kind of task and for both dependent variables, the pattern emerging from the conditional tasks was clear: the familiar faces were processed better than the unfamiliar and the unambiguous faces better than the ambiguous. Thus, there was no sign of a difference between the two tasks, which was to be expected since, in both cases, 75% of stimuli gave rise to “disjunctive decisions” and one quarter of trials should have induced “conjunctive judgments”. The ambiguity of age affected both conditional tasks. Thus, when the subject could “choose” either the apparent age or the familiarity of faces (disjunctive responses), he/she voted for age and was therefore affected by the age ambiguity. Such a choice would be plausible if one recalls that, in general, age decisions are easier and faster than familiarity decisions. However, when the subject was forced to process both age and familiarity (conjunctive responses), he/she was still affected by the ambiguity. Finally, the analysis of the ambiguity index supports a sequential model in which age decision is an early visual stage within the series of operations aimed at recognizing the face.
33
General
Discussion
and Conclusion
The extraction of age precedes the familiarity decision, at least for unfamiliar or unambiguous faces. Face familiarity affects the judgment of age, at least when unambiguous faces are employed. The single tasks could suggest that age ambiguity does not influence the familiarity decision, but the conditional tasks show that it does. This leads us to conclude that age evaluation is a visual operation that precedes and is mandatory for an efficient recognition process, and that the output of the recognition stage can affect, in a top-down way, the evaluation of the apparent age (at least when the evaluation is easy). In other words, since familiarity was considered as celebrity in the present study, the subjects could respond more easily to the age question concerning familiar faces because they already knew the age: this is precisely the meaning of a familiarity effect. This statement is paradoxical, since it suggests that an operation (age decision) that must be completed before the next one begins (familiarity decision) can be influenced back by this next operation. This paradox reveals the weakness of strictly serial models, but it disappears when a more dynamic, cascade model, framework is accepted (McClelland, 1979). Gender categorization, age evaluation, and race classification are often taken as examples of semantic codes that are derived from the visual processing of faces, familiar or not 1986) and, in this respect, they differ from the “deep” semantic (Bruce & Young, representations, like activities or addresses, which are not visually derivable and concern derived semantic codes”, is conceived as familiar faces only. This box, the “visually activated only when the task requires it and is considered not necessary for efficient recognition and these visual computations function in parallel with the visual operations leading to recognition. As regards gender categorization, the data of Bruce (I 986; Bruce et al., 1987) seem to support this view. However, as regards age evaluation, our data does not support this view. We suggest that these three operations should not be maintained in a single box. Firstly, there are cases of prosopagnosia (reviewed in the Introduction) in which one of these operations is defective while the others are not. Secondly, the work of Bruce and her coworkers indicates that sex categorization operates independently from the recognition process and, according to Roberts & Bruce (1988), both operations depend on different facial features. On the other hand, our present data indicate that age evaluation is dependent on the recognition process. Thirdly, Bruyer & Dujeux (1988) suggested that sex classification should be dissociated from race categorization. Finally, the age decision seems to be affected by face familiarity while the other operations are not. Therefore, it is proposed that the age decision differs from the other visually derived semantic processes. Such a dissociation is plausible for structural reasons. Sex and race are definitive semantic properties while age is not. Moreover, the structural encoding preceding the access to face recognition units is conceived as the extraction of invariant properties of the faces (Bruce, 1988; Bruce & Young, 1986), i.e., the face must be recognized irrespective of its distance, pose or expression. In this respect, one can imagine that the structural encoding elaborates a representation independent of the apparent age. Finally, this apparent age must be kept independent of facial expression (and facial actions), since it denotes slow and irreversible modifications, which is not the case with facial expressions.
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21
BEPROC 00354
Age decisions on familiar R. Buyer Louvain
University
and unfamiliar
faces **
*, A. Lafalize and M. Distefano
(UCL), Psychology (NECO),
Department,
Unit& de Neuropsychologie
Louvain-la-Neuve,
(Accepted
27 February
Cognitive
Belgium
1991)
Abstract The extraction of age is among the “early visual processes” that operate on faces. Current cognitive models mention this operation, but data on the subject is rare. In the first experiment, a series of familiar and unfamiliar faces were displayed to subjects who were asked to make old/young categorizations. To test how early this operation occurs, the same material was used for familiarity decision. Finally, the stimuli were displayed centrally to 16 subjects and laterally to 32 subjects. The age decision was easier and quicker than the familiarity decision; the familiarity decision was unaffected by the age of the faces, while face familiarity affected the extraction of age. In a second experiment (40 subjects), we manipulated the ambiguity of the apparent age and conditional tasks were used, i.e., the subjects had to process both age and familiarity in a single task. The results suggest that age extraction is an operation that is mandatory for an efficient recognition process. Therefore, it is proposed to dissociate, within the semantic visually derived codes, the processing of age from the processing of sex and race.
Key words:
Age; Cognitive model; Conditional task; Face recognition; Familiarity
Introduction The cognitive models of face recognition include visual operations that precede the recognition stage and can be applied to unfamiliar as well as to familiar faces. Beyond the very first step of “facial decision” (Ellis, 1983, 1986), these operations, among other things,
* UCL-NECO, **
Voie du Roman
This study was presented,
Fransaise,
Paris, 1988.
Pays 20, 1348
Louvain-la-Neuve,
in part, at the meeting
of the Soci&
Belgium. de Neuropsychologie
de Langue
22
age of the extract characteristics concerning the sex, the race, and the approximate derived semantic codes” (Bruce & Young, perceived face. This extraction of “visually 1986) would not seem to be mandatory for face recognition. Two questions arise about these processes. The first is how early these operations occur with regard to the recognition step. The second question concerns their independence of face familiarity. Indeed, it could be that top-down mechanisms apply, so that familiarity could facilitate or inhibit decisions about the sex, age, or race of the face. In addition, we consider the possibility of lateral differences, i.e., the opportunity to demonstrate dissociations in the function of the stimulated portion of the visual field and, accordingly, of the stimulated cerebral hemisphere. However, given the small amount of published data, we also have to examine this question with centrally displayed stimuli. In normal subjects, Bruyer & Schweich (1987) used this neuropsychological procedure and showed that the “race decision” was an early operation and was not lateralized (see also Bruyer & Dujeux, 1988). However, only unfamiliar faces were used, so the effect of familiarity on this decision was not investigated. With regard to gender classification, several studies have shown that this operation was early, non-lateralized, and free of familiarity effects (Bruyer & Dujeux, 1988; Jones, 1979, 1980; Marzi, Tassinari, Tressoldi, Barry & Crabowska, 1985; Sergent, 1985). Finally, to our knowledge, there are no neuropsychological studies with normal subjects on “age classification” of faces. With brain-injured subjects, there are a few cases of prosopagnosia (i.e., a specific face agnosia) in which defects about face classification as a function of age (Beyn & Knyazeva, 1962; Bruyer, Rectem & Dupuis, 1986; Cloning, Cloning, Jellinger & Quatember, 1970; Michel, P&enin & %&off, 1986; Tiberghien & Clerc, 1986; Whiteley & Warrington, 1977), sex (Beyn & Knyazeva, 1962; Tiberghien & Clerc, 1986), or race (Cole & PerezCruet, 1964) have been clinically described. Nevertheless, prosopagnosics are more often than not able to perform these operations (e.g., Sergent & Villemure, 1989) and no pathological cases have been described in which these operations were defective while recognition was preserved. Therefore, there are precede and are independent of recognition. In this view. Tranel, Damasio & Damasio (1988) gender, age, and identity of faces to four severe defective in every task, while the remaining
reasons to suppose that these operations addition, more experimental data support applied recognition tests of expressions, cases of prosopagnosia. One subject was three were deficient for identity only.
Newcombe & Russell (1969) showed that a group of right-brain-injured, non-prosopagnosic subjects was impaired in a task of age and sex categorization of faces. However, the two scores were pooled in the results, and the faces used were only approximations of faces (Mooney faces). De Renzi, Bonacini & Faglioni (1989) have shown that damage to the posterior region of the right hemisphere impairs the classification of faces by age, more than it impairs face recognition. Finally, in a prosopagnosic subject, Sergent & Poncet (1990) found familiarity effects in the episodic recognition of faces whose age changed between encoding and test. The present study focusses on one of these visually derived semantic codes, namely, age. In the first experiment, normal subjects were presented with laterally or centrally displayed faces and asked to make old/young decisions. Two questions were considered, namely, (a) familiar and unfamiliar faces were intermixed in order to detect familiarity effects, and (b) a control recognition condition was provided to test how early is age evaluation. Indeed, little is known about the processing of age and the few published experiments have shown (a) that episodic recognition of faces is possible even if the age is changed between encoding and test, provided the change is not too large (Bruyer & Lafal-
23
ize, 19891, and the performance Seamon,
1982);
is facilitated
(b) that this episodic
encoding provided 1990); and (c) that parameter the three-dimensional
by face familiarity
recognition
is facilitated
(Bruyer
& Lafalize,
by the exposure
1989;
duration
at
the structural age changes are modest (Read, Vokey & Hammersley, the human perceiver can extract age changes by considering a single strain of a cardioidal function (Mark & Todd, 1985>, even on representations (Mark & Todd, 1983; see also Bruce, Burton,
Doyle & Dench, 1989 for both replication and slight qualifications). In the first experiment, we hypothesized that an advantage of familiar over unfamiliar faces in age decision would reflect top-down influence of face familiarity (face recognition units) on visual processes, and that age decision would be faster than familiarity decision. Bruce, Ellis, Gibling & Young (1987) used an elegant paradigm showing categorization was independent of recognition. This study will be presented we applied this methodology in our second experiment on age categorization, attempted
to precise the task effect observed
Experiment
that gender below since in which we
in the first experiment.
I
Method Subjects Forty-eight
(24 female,
24 male) young,
neurologically
intact,
right-handed
adults were
enrolled. There were no left-handed close relatives. They were randomly assigned to two displayed stimuli” condigroups: 16 subjects (8 females) were assigned to the “centrally tion; the remaining 32 took part in the “laterally displayed stimuli” condition (Actually, the lateral presentation was administered to 34 subjects. However, the data of two subjects had to be discarded because they were completely unable to recognize familiar faces in the familiarity decision task). Within each condition, two tasks, age decision tered to each subject in a balanced order. Stimuli A series of was submitted evaluated the 20 & 30; .; selected, with
and familiarity
decision,
were
adminis-
60 black-and-white photographs of familiar (well-known celebrities) faces to 40 judges who evaluated their celebrity on a seven-point scale; they also age on a seven-point scale (1 = less than 20 years old; 2 = between 7 = more than 70). Ten clearly familiar faces (mean score > 5) were then five being clearly “young” (values < 2: mean = 1.92; mean familiarity =
6.021, and five clearly “old” (values > 5: mean = 6.11; mean familiarity = 5.94). Another series of 47 black-and-white photographs of unfamiliar (unknown) faces was submitted to a similar process (n = 26 judges). This material had been collected from people who were invited to supply with two (or more) photographs of the same face taken at an interval of 15 years or more, with the youngest not less than 15 years old. We selected 10 clearly unfamiliar faces (mean score < 21, with five being clearly “young” (values < 2: mean = 1.63; mean familiarity = 1.38) and five clearly “old” (values > 5: mean = 6.22; mean familiarity = 1.39). Several slides were made of these 20 faces. The stimulus width was four degrees of the visual field. When laterally displayed, they were centered four degrees left or right of the fixation point.
24
Experimental design In the central condition, each task (age decision and familiarity decision) involved 60 items, i.e., three displays of each face in random order. In the lateral condition, each task 120 items, i.e., three displays of each face in each hemifield in random order. The subject was asked to respond as quickly as possible by depressing one of two push buttons (index fingers) indicating his/her choice: old/young or familiar/ unfamiliar. The involved
button assignment was balanced across the subjects. For the familiarity decision, the subject was asked to decide if the face was well known due to its episodic recurrence in the course of the or not (irrespective of its “familiarity” experimental session). For the age decision, some examples of old and young faces, not used in the experiment, were shown before beginning. This adaptation was provided since the notions of “old” and “young” can be relative to the current set of stimuli and/or to each subject. Procedure The subject sat facing the screen (viewing distance = 85.5 cm), the head supported on a chin rest. Each trial was sequenced as follows: auditory warning (500 msec) to invite the subject to focus on the central fixation point, delay (1000 msec), displaying of the stimulus during 150 msec, inter-item interval of five sec. The stimuli were back-displayed by projectors controlled by a microcomputer, the response device. The instructions stressed the speed of response. Statistical
as was
design
Central and lateral presentations were analyzed separately, since they were submitted to different subjects and differed in perceptual difficulty. In both cases, errors and correct latencies were studied separately by means of analyses of variance (ANOVAs). Post-hoc analyses of significant interactions were performed by using the Newman-Keuls test (p < 0.05).
Results Central presentation We computed 2 x 2 x 2, within-subject,
ANOVAs.
The factors were the task, the age of
the faces, and the face familiarity. As can be seen in Table 1, there were more errors in the familiarity decision than in the age decision (F(l ,I 5) = 29.38, p < 0.0001) and more errors for the familiar than for the
TABLE 1 Exp. I. Central
presentation:
errors (out
of 15, between
familiarity.
Means
mean
latency
parentheses)
of the correct
in function
responses
in msec and mean
number
of 16 subjects. Age decision
of
of the task, the age of the faces, and the face
Familiarity
decision
Old
Young
Old
Young
Familiar
678 (0.19)
661 (0.56)
831 (4.50)
732 (5.25)
Unfamiliar
699 (I .44)
729 (T.31)
776 (1.69)
783 (I .12)
25 TABLE
2
Exp. I. Lateral presentation: mean latency of the correct responses in msec and mean number of errors (out of 15, between parentheses) in function of the task, the age of the faces, the face familiarity, and the visual field (LVF = left, RVF = right). Means of 32 subjects. Age decision Old Familiar LVF RVF
Unfamiliar LVF RVF
Familiarity decision Young
Old
Young
729 (1.41)
729C1.75)
976C6.28)
936C5.12)
697c1.28)
713 (1.69)
923 (6.25)
863 (5.28)
730 (1.81) 728 (1.78)
795 (4.47)
911 (3.34)
884 (2.37)
818 (4.87)
886C3.06)
927 (2.47)
unfamiliar faces (F(1,15> = 9.83, p < 0.01). Moreover, these two factors interacted significantly (F(1 ,I 5) = 30.97, p < 0.0001). Post-hoc analysis of this interaction revealed a higher number of errors on the familiar faces for the familiarity decision condition than in the remaining three conditions. Thus, the task effect applied to the familiar faces only, and the familiarity effect applied to the familiarity decision only. No other main effect or interaction reached statistical significance. For the correct latencies (Table familiarity decision (F(1 ,I 5) = 9.1,
I), there p < 0.01).
was a significant There was also
advantage of age over a significant interaction
between the age and the familiarity of faces (F(1 ,I 5) = 6.2, p < 0.02). Post-hoc analysis of the interaction revealed that the young familiar faces were processed faster than both the young unfamiliar and the old familiar faces. There was no age effect for the unfamiliar people and no familiarity effect for the old faces. No other main effect or interaction reached
statistical
significance.
Lateral presentation We computed two
2 x 2 x 2 x 2, within-subject,
ANOVAs.
The factors were
the task,
the age of the faces, the face familiarity, and the visual hemifield of presentation. As shown in Table 2, accuracy was better for age than for familiarity decisions (F(1,31) = 42, p < 0.0001) and better for the old than for the young faces (F(1,31) = 5.3, p < 0.05). These two factors, however, interacted significantly (F(1,31) = 16.4, p < 0.001). Post-hoc analysis of this interaction showed that the age-decision advantage was observed for the old faces only. On the other hand, whereas the advantage of the old over the young faces appeared for age decision, the opposite advantage of the young over the old faces was significant in the familiarity decision task. There was also a significant task X familiarity interaction (F(1,31) = 44.4, p < 0.0001; see Fig. I). Post-hoc analysis of this interaction showed that the age-decision advantage was observed only for the familiar faces, and an advantage of the familiar over the unfamiliar faces appeared in the age-decision task, while accuracy was better for the unfamiliar than for the familiar faces in the familiarity decision task. Finally, the two factors involving the kinds of stimuli interacted significantly (F(1,31) = 8.6, p < 0.01). Post-hoc analysis of this age X familiarity interaction showed that old unfamiliar people were better processed than the other three series, which did not differ significantly from each other.
26
01
I
FAMILIAR Fig I. The taskxface
familiarity
UNFAMILIAR
interaction
for errors in Exp. I, lateral presentation.
While the field of presentation did not affect accuracy as a main effect or within interactions, the three remaining factors interacted significantly (F(1,31) = 7.02, p < 0.02). This interaction slightly modifies the effects already noted. (a) With the exception of the young unfamiliar faces, for which familiarity decisions were easier than age decisions, the age decision
was better
(b> An advantage decision when
task (for
the young
unfamiliar familiarity For
performed
than the familiarity
of the unfamiliar
both old and young faces were
faces,
the
decisions
old
faces
the correct
latencies
were
to the age decision. better
processed
faces, the young
(Table
2),
task for every
faces was revealed
faces) and of the familiar
submitted
on familiar
decision
over the familiar
there
than
faces were
was a main
over
Cc> For the
better
of face.
the unfamiliar age decisions
young;
faces on the
conversely,
processed
significant
kind
in the familiarity
for
than the old.
advantage
of the age
(F(1,31)= 46.9, p < 0.0001) and a bias favoring the right over the left field (F(1,31)= 3.5, p = 0.067). Three one-way interactions reached significance. For the first two (task X age: F(1,31) = 7.23, p < 0.01; task X familiarity:
decision
F(1,31)
over the familiarity
= 4.8,
p < 0.05),
significant
for
unfamiliar
faces.
familiarity), third
it can
both the old
be seen
and the young
Secondly,
while
significant
decision
the familiarity
the age decision
interaction
modified
F(1,31)= 14.24, p < 0.001)
since
in
Figure
2,
firstly,
faces as well decision
was affected
was
that
as for
unaffected
by face familiarity
the bias towards a significant
task
field
effect
advantage
was
and the
by age (as well (as well
as by
as by age). The
a main field effect (field
right
950
the
both the familiar
X familiarity:
for the familiar
but
n
-_____~‘~l!JRW
/----¤ w---
900 850 I
o
7oo%zE+-xFig 2. The taskxage
(left)
and taskxfamiliarity
-
FAMILIAR (right)
I
UNFAMILIAR
interactions
lateral presentation.
FlGI DECISION
for correct
latencies
in Exp. I,
27
not the unfamiliar faces emerged. Complementarily, faster than the unfamiliar in the right field only.
the familiar
faces were processed
Discussion One purpose of this experiment was to decide whether age processing is earlier than face recognition. It seems that a positive answer can be given. Indeed, this expected kind of result appeared for latencies on both centrally and laterally displayed faces, and a similar pattern appeared for accuracy. Therefore, these results tend to support the theoretical models that locate the age decision in the cognitive stages (“visual processing”) that precede the recognition stages (e.g., Bruce & Young, 1986). One could argue that even though the same faces have been used in both tasks the task difficulty was not identical, since the stimuli were selected on the criteria of the ease to be discriminated for age. In this respect, it should be mentioned, firstly, that the stimuli were also selected on the basis of the ease to be discriminated for familiarity. Secondly, this facility of age discrimination will be manipulated in the second experiment. Another purpose of this study concerned the relative dependency between these two stages of processing, i.e., whether familiarity affects decisions on age. Provided the task demands were hard enough i.e., the lateral mode of presentation it appeared that familiarity influenced the age decision, while the speed of familiarity decision was unaffected by age. This observation suggests top-down effects of the face recognition units on the decisions taken at the visual processing level. That is to say, when faces were recognizable, the decision on age was more easily (or quickly) taken than when they were not. In a companion paper using an episodic recognition procedure, we (Bruyer & Lafalize, 1989) noted that it was almost impossible to recognize unfamiliar faces strongly modified by age, while such a decision was much easier for familiar faces (see also Seamon, 1982). It was suggested that only the familiar faces activated semantic nodes about the person seen (Bruce & Young, 1986) so that the abstraction of age appearance became useless. Another interpretation, however, could be that face recognition units are “instance based”, i.e., they can vary in age or expression and, in this way, there is no need to resort to any semantic node effect. Finally, lateral differences emerged favoring the right visual hemifield that were due to familiar faces, irrespective of the task. Such a left hemispheric superiority has already been reported when known faces are involved, as compared to the “classical” right hemisphere advantage for unfamiliar faces. It has also been shown that this asymmetry results more from familiarity than from access to name representation (Umilta, Brizzolara, Tabossi & Fairweather, 1978). This result could also suggest that the left-hemisphere advantage in the processing of familiar faces emerges at the “visual processing” stage of the stimuli before the recognition stage. Since this laterality effect did not interact with the task, the lateral mode of presentation was not used in the second experiment. In short, the data collected in Exp.1 suggest that age decision precedes the recognition, and is affected - at least in some conditions - by face familiarity, in a top-down manner. However, as will be developed below, we have to check for possible methodological (task constraints) bias of this asymmetrical effect: age categorization was not required to take the familiarity decision. Exp. II has been planned to envisage this possibility. Moreover and more generally, even if an operation is faster than and is influenced by another one, it
28 remains to determine whether the two operations function sequentially
or in parallel. Exp.
II was designed to solve this question.
Experiment
II
The studies of Bruyer & Dujeux (19881, Jones (1979, 19801, Marzi et al. (1985) and Sergent (1985) have shown that gender classification of faces was independent of face familiarity. However, Bruce (I 986) showed that face familiarity facilitated sex categorization as we did in Exp. I regarding age categorization (Obviously, there is a lack of clinical and experimental data supporting the contention that sex and age [and race] classifications resort to identical mechanisms, even Bruyer & Dujeux [I 9881 suggested that Additional experiments are required to tions differ on at least one major point:
though authors tend to make such an analogy. sex and race categorizations should be dissociated. test this point. In addition, sex and age categorizathe former refers to a discrete dichotomy, while the
latter taps a continuous scale). Moreover, Bruce (1986) suspected that this familiarity effect was particularly evident when the gender of the face was someone ambiguous. This has since been confirmed (Bruce et al., 1987). This may be linked to our results showing that familiarity influences age decisions provided that perceptual conditions are difficult enough. According to Bruce, this result is not consistent with a strict perceptual hierarchy where one process should be completed before the next one begins. In the study of Bruce et al. (19871, it was questioned whether this lack of hierarchical relationship could have resulted from methodological biases, i.e., sex categorization was not a mandatory step for face recognition. Therefore, the authors designed a second experiment in which sex and familiarity were made to be relevant to each other, i.e., in the disjunctive condition, the subjects had to decide if the face seen was male (female) or known (unknown) and, in the conjunctive condition, they had to decide if the face was male (female) and known (unknown). According to the authors, the conjunctive condition provided a strong test of the model: if gender classification precedes the familiarity decision, “then a factor which slows up the sex judgement should also slow up conjunction decision. Such a consequence would be unlikely faces
in
decision
parallel
with
their
was unaffected
model
was claimed
In our second
familiarity”
(p.
by face ambiguity,
in a system which processed the sex of
516).
while
In
their
experiment,
the disjunctive
the
decision
conjunctive
was. The
parallel
to be supported.
experiment,
we used the disjunctive
et al. for age and familiarity
decisions.
We
and conjunctive
also tested
conditions
the age decision
of Bruce
and the familiarity
alone to search for effects of ambiguity. Furthermore, since, in Exp. I, the effects of interest were found when the task was difficult (lateral presentation), then, in Exp. II, we had the opportunity to examine the effect of another kind of perceptual difficulty by using
decision
ambiguous faces. Contrary to the opinion of Bruce et al. (19871, ambiguity for parallel young
does
processing.
(disjunction)
(by pressing and
not affect the response
such
we consider that, if age a result
a subject
has to decide whether
to give a positive
response,
he/she
button)
old (conjunction).
fore,
in the disjunctive
were
conjunctive,
and negative
conditions,
when
the other
Indeed,
in both
The
condition,
while,
answers
if the face is neither same
in reverse
positive
answers
in the conjunctive
were
disjunctive.
nor young,
i.e.,
for the conjunctive were
condition,
still
argue or
has also to give a negative response
familiar
applies
would
the face is familiar
disjunctive, positive
if it is unfamiliar condition.
There-
and negative answers
answers
were
conjunctive,
29
Method Subjects The experiment was submitted selected as in Exp. I.
to 40 (20
female, 20
male) young, normal adults,
Stimuli We used 16 faces from a set of 50 faces that had been submitted to ten judges for two tasks. In the familiarity judgment, they were asked to evaluate the celebrity on a seven-point scale: we selected faces with a mean evaluation greater than five (familiar faces) and less than three (unfamiliar faces). In the age judgment, the same faces had to be categorized in four classes: “very young”, “relatively young”, “elderly”, and “very old”. The judges had to sort the faces into four classes and corrections were authorized. We retained those faces that received the same classification by at least seven judges. The resulting set of stimuli was formed with eight familiar and eight unfamiliar faces. Each subset was composed of four young and four old people with two unambiguous (very young or very old) and two ambiguous (relatively young or elderly) faces. Four main sets of four faces resulted: familiar ambiguous, familiar unambiguous, unfamiliar ambiguous, and unfamiliar unambiguous. The mean familiarity ratings of these four sets were 6.05, 5.97, 1.94 and 1.78, respectively. Experimental
design
Ten slides of each face were prepared. Therefore, for each of the two between-subject conditions (below), 160 trials resulted, 40 for each of the four sets of faces. Sixteen subjects were randomly submitted to the disjunctive condition. They had to press one button when the face seen was either young (old) or familiar (unfamiliar), and the other button in the other cases (index fingers were used). The four possible disjunctions were crossed with four subjects for each. The button assignment was also balanced across the subjects within each subsample. Sixteen other subjects were submitted to the conjunctive condition. They had to push one button when the face seen was young (old) and familiar (unfamiliar) and the other button in the other cases. The four possible conjunctions were crossed with four subjects for each. The button assignment was also balanced across the subjects within each subsample. The remaining eight subjects were given “single tasks”. As in Exp. I, they had to decide whether the face was that of a young or an old person and whether it was familiar or unfamiliar, in two successive conditions. The order of conditions was balanced across the subjects, as was the button assignment. Procedure The procedure was identical to that of Exp.1, with two modifications: the instructions for the disjunctive and conjunctive conditions (see above) and the exposure duration of the stimulus which lasted until a response was given.
Results Single tasks There were 5.4% errors (Table 3) and the analysis revealed only that familiar faces were better processed than unfamiliar faces (F(1,7) = 12.7, p < 0.01). The correct latencies
30 TABLE 3 Exp. II. Single tasks: mean of 40, between Means
latency
parentheses)
of the correct
in function
responses in msec and mean number
of the task, the face familiarity,
of errors (out
and the ambiguity
of age.
of eight subjects. Age decision
Familiarity
decision
Familiar
Unfamiliar
Familiar
Unfamiliar
Ambiguous
958 (I ,251
1007
(5.00)
870 (0.62)
1057
(3.50)
Unambiguous
878 (0.87)
834 (1.37)
814 (2.25)
1022
(2.50)
llOO1050,-
n
FAMILIARITY DECISION
looo~950 I’ AGE DECISION
0 900 I’ 850
.A
-
,
800 * UNFAMILIAR
FAMILIAR Fig. 3. The task X familiarity
(Table
3) were
submitted
to
interaction
for correct
a within-subject,
latencies
in Exp. II, single tasks.
2 x 2 x 2 ANOVA.
The
factors
were
familiarity, age ambiguity, and task. There appeared a main significant advantage of familiar over unfamiliar faces (F(1,7) = 13.16, p < 0.01) and of unambiguous over ambiguous faces (F(1,7) = 24.55, p < 0.002). The task X familiarity interaction was significant (F(1,7) = 13.26, p < 0.01; see Fig. 3), i.e., familiarity decisions on familiar faces were faster than the other three conditions, and familiarity judgments than the remaining three conditions (the face familiarity
on unfamiliar faces were slower did not affect age evaluations).
There was a strong bias toward a task x ambiguity interaction (F(1,7) = 4.95, p = 0.06): age decisions on unambiguous faces were si,gnificant/y faster than in the remaining three conditions (see Fig. 4). -
lOOOr
n 0
900 g50:j
850
k
n
FPlMl LIARITY DECISION
0 AGE DECISION
1
800. AMBIGUOUS Fig. 4. The taskxambiguity
interaction
UNAMBIGUOUS for correct
latencies
in Exp. II, single tasks.
31 TABLE 4 Exp. Il. Conditional (out
tasks: mean latency
of 40, between
parentheses)
age. Means of 16 subjects
of the correct
in function
responses (msec) and mean number
of the task, the face familiarity
of errors
and the ambiguity
of
per task.
Disjunctive
task
Conjunctive
task
Familiar
Unfamiliar
Familiar
Unfamiliar
Ambiguous
945 (7.25)
1033
869 (4.44)
896 (8.00)
Unambiguous
911 (4.62)
849 (2.82)
855 (5.19)
(12.19)
933 (6.06)
Conditional tasks The correct latencies (Table 4) were studied by means of a mixed 2 x 2 X 2 ANOVA. The between-subject factor was the condition (conjunctive vs. disjunctive), and the within-subject factors were face familiarity and age ambiguity. Familiar faces were processed faster than unfamiliar faces (F(1,30) = 4.41, p < 0.05), and unambiguous faces were judged faster than ambiguous faces (F(1,30) = 8.41, p < 0.01). Errors (Table 4) were not rare (15.8%) and were submitted to the same ANOVA as latencies. Errors were less frequent on familiar than on unfamiliar faces (F(1,30) = 4.38, p < 0.05) and on unambiguous than on ambiguous faces (F(1,30) = 9.05, p < 0.01). Ideally, the statistical analyses should have included the kind of response as a factor. However, such a design was virtually impossible since, in the disjunctive task, each subject gave positive responses to the familiar and unfamiliar faces but half of them gave negative responses to the familiar faces and the other half to the unfamiliar faces. In the conjunctive task, a mirror image applied. One manner to solve this technical difficulty was to compute an index of ambiguity. We computed an index on correct latencies, for each subject, each kind of face familiarity, and each kind of response (conjunctive responses, i.e., positive responses in the conjunctive task and negative responses in the disjunctive task, vs disjunctive responses, i.e., positive responses in the disjunctive task and negative responses in the conjunctive task). The index was computed as (A - nA)/(A + nA), where A and nA represent the mean correct latency for the ambiguous and the unambiguous faces respectively. The four indexes (see Fig. 5) were tested against zero, i.e., against the absence of ambiguity effect: the ambiguity effect was significant for disjunctive responses to unfamiliar (0.034: t(31) = 2.3, p < 0.025) but not to familiar faces (0.009), and for
0,4T
Fig. 5. The index
of ambiguity
DISJUNCTIVE
for correct
(disjunctive,
latencies
conjunctive)
COWJNCTIVE
in Exp. II, conditional and the face familiarity.
tasks, according
to the task
32
conjunctive responses to both familiar (0.350: (0.103: t(15> = 3.92, p < 0.001 I
t(l5)
=
2.7, p < 0.01) and unfamiliar faces
In considering the single tasks, two conclusions derived from the Exp. I should be revised. On the one hand, age decisions were faster than familiarity decisions in certain conditions only, i.e., when the unfamiliar faces were considered (either ambiguous or not) and when easy, unambiguous faces were processed (either familiar or not). Two speculative comments can be proposed, which would require additional experiments. Firstly, the task difficulty could explain that age decision was not faster than familiarity decision on ambiguous faces: indeed, faces were selected as easily discriminable in the familiarity dimension while, by definition, ambiguous faces were selected as not easily discriminable in the age dimension. Secondly, age decision was not faster than familiarity decision when familiar faces were seen: this could suggest that the recognition is unavoidable and that the response (age decision) is mandatorily delayed up to the activation of a face recognition unit. We acknowledge, however, that this was not observed in Exp. I or in other studies dealing with gender classification or expression analysis. On the other hand, when both the ambiguous and the unambiguous faces were mixed together, the effect of face familiarity on age decision disappeared. It could be, therefore, that the suggested top-down effects of familiarity on visual, earlier processes was due only to the easy, unambiguous faces like those used in Exp. I (see Fig. 2, right panel, vs. Fig. 3). This observation is contrary to what is argued by Bruce (1986) and Bruce et al. (1987). They suggest that gender classification is facilitated by face familiarity when the gender is ambiguous. This constitutes another argument supporting dissociations within the “visually derived semantic codes” (Bruce & Young, 1986). The present controversy suggests a dissociation between sex attribution and age categorization, just as the study of Bruyer & Dujeux (I 988) suggested a dissociation between sex attribution and race categorization. The single tasks revealed two other points. Firstly, as expected, age judgment was affected by the ambiguity, i.e., for ambiguous faces, age decisions were as slow as familiarity decisions. Secondly, it confirmed that the familiarity decisions are not influenced by age. Whatever the kind of task and for both dependent variables, the pattern emerging from the conditional tasks was clear: the familiar faces were processed better than the unfamiliar and the unambiguous faces better than the ambiguous. Thus, there was no sign of a difference between the two tasks, which was to be expected since, in both cases, 75% of stimuli gave rise to “disjunctive decisions” and one quarter of trials should have induced “conjunctive judgments”. The ambiguity of age affected both conditional tasks. Thus, when the subject could “choose” either the apparent age or the familiarity of faces (disjunctive responses), he/she voted for age and was therefore affected by the age ambiguity. Such a choice would be plausible if one recalls that, in general, age decisions are easier and faster than familiarity decisions. However, when the subject was forced to process both age and familiarity (conjunctive responses), he/she was still affected by the ambiguity. Finally, the analysis of the ambiguity index supports a sequential model in which age decision is an early visual stage within the series of operations aimed at recognizing the face.
33
General
Discussion
and Conclusion
The extraction of age precedes the familiarity decision, at least for unfamiliar or unambiguous faces. Face familiarity affects the judgment of age, at least when unambiguous faces are employed. The single tasks could suggest that age ambiguity does not influence the familiarity decision, but the conditional tasks show that it does. This leads us to conclude that age evaluation is a visual operation that precedes and is mandatory for an efficient recognition process, and that the output of the recognition stage can affect, in a top-down way, the evaluation of the apparent age (at least when the evaluation is easy). In other words, since familiarity was considered as celebrity in the present study, the subjects could respond more easily to the age question concerning familiar faces because they already knew the age: this is precisely the meaning of a familiarity effect. This statement is paradoxical, since it suggests that an operation (age decision) that must be completed before the next one begins (familiarity decision) can be influenced back by this next operation. This paradox reveals the weakness of strictly serial models, but it disappears when a more dynamic, cascade model, framework is accepted (McClelland, 1979). Gender categorization, age evaluation, and race classification are often taken as examples of semantic codes that are derived from the visual processing of faces, familiar or not 1986) and, in this respect, they differ from the “deep” semantic (Bruce & Young, representations, like activities or addresses, which are not visually derivable and concern derived semantic codes”, is conceived as familiar faces only. This box, the “visually activated only when the task requires it and is considered not necessary for efficient recognition and these visual computations function in parallel with the visual operations leading to recognition. As regards gender categorization, the data of Bruce (I 986; Bruce et al., 1987) seem to support this view. However, as regards age evaluation, our data does not support this view. We suggest that these three operations should not be maintained in a single box. Firstly, there are cases of prosopagnosia (reviewed in the Introduction) in which one of these operations is defective while the others are not. Secondly, the work of Bruce and her coworkers indicates that sex categorization operates independently from the recognition process and, according to Roberts & Bruce (1988), both operations depend on different facial features. On the other hand, our present data indicate that age evaluation is dependent on the recognition process. Thirdly, Bruyer & Dujeux (1988) suggested that sex classification should be dissociated from race categorization. Finally, the age decision seems to be affected by face familiarity while the other operations are not. Therefore, it is proposed that the age decision differs from the other visually derived semantic processes. Such a dissociation is plausible for structural reasons. Sex and race are definitive semantic properties while age is not. Moreover, the structural encoding preceding the access to face recognition units is conceived as the extraction of invariant properties of the faces (Bruce, 1988; Bruce & Young, 1986), i.e., the face must be recognized irrespective of its distance, pose or expression. In this respect, one can imagine that the structural encoding elaborates a representation independent of the apparent age. Finally, this apparent age must be kept independent of facial expression (and facial actions), since it denotes slow and irreversible modifications, which is not the case with facial expressions.
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