Infant and Child Development
Inf. Child Dev. 10: 39–45 (2001)
DOI: 10.1002/icd.245
Recognition of Faces of Different
Species: A Developmental Study
Between 5 and 8 Years of Age
Olivier Pascalisa,*, Elisabeth Demontb, Michelle de Haanc
and Ruth Campbelld
a
The University of Sheffield, Department of Psychology, Sheffield, UK
Université Louis Pasteur, Strasbourg, France
c
Institute of Child Health, UCL, London, UK
d
Human Communication and Science Department, UCL, London, UK
b
There is developmental progression in the ability to recognize
human faces (HF) during childhood, accompanied by qualitative
differences in what children perceive and remember. The best
known example is that of sensitivity to vertical orientation:
while there is age-related improvement in recognizing upright
faces, upside-down ones show no recognition improvement. It is
believed by some investigators to be a sign of developing faceexpertise over the first 10 years or so of life. If expertise, based
on experience with many individuals, is the basis for the development of the inversion-effect, faces from other species should
not induce inversion-effects. In two experiments, we explored
the expertise phenomenon by testing recognition of faces of
different animal species with children between 5 and 10 years of
age. Our results failed to show any developmental changes in
the processing of faces of own- and other-species. Copyright
© 2001 John Wiley & Sons, Ltd.
Key words: children; faces; force choice task
A dramatic developmental progression is observed in face recognition from
infancy to adulthood. If numerous changes occur during the first year of life (de
Haan and Halit, 2001), a developmental enhancement in the ability to recognize
human faces (HF) is still observed during childhood (Carey, 1992; Campbell et
al., 1995, 1999). The exact nature and causes of the changes, however, are still
not well understood.
Nelson (this issue) draws a parallel between the development of language and
the development of face recognition. He proposes that the face-processing
system develops during the first years of life from a broad non-specific system
to a human-tuned face processor. In his view, the specificity of the face
recognition system to HF will increase with age, and with experience in
processing HF.
* Correspondence to: The University of Sheffield, Department of Psychology, Sheffield S10 2TP, UK.
Copyright © 2001 John Wiley & Sons, Ltd.
40
O. Pascalis et al.
One change in face-processing that occurs during childhood is the emergence
of the inversion-effect— the phenomenon that inversion disproportionately impairs recognition of HF relative to recognition of other objects. There is debate
concerning the specific factor(s) responsible for the ‘facial inversion-effect’.
Rhodes (1995) claims that relational or higher-order-feature information, such as
the distance between the eyes, or between lips and chin, is orientation-sensitive.
In Rhodes’ view, what develops in childhood is the ability to use representations of faces that make use of relational features. By contrast, work by Farah et
al. (1995) suggests that the holistic or global aspect (captured, for instance, by
coarse quantization of the face or by low-spatial frequency filtering) is orientation-sensitive —and that this is sufficient to account for inversion-effects in face
recognition. Diamond and Carey (1977) initially found that this effect did not
emerge until 10 years of age, and showed that the development progression was
a result of age-related improvements in recognizing upright, but not inverted,
faces. Since then, further studies have shown that, under certain circumstances,
even children as young as 7 years of age (Flin, 1985) are better at recognizing
upright than inverted HF. Diamond and Carey (1986) argued that the emergence of the inversion-effect is based on experience in processing many individual faces. If so, then non-HF, even if they share similarities with HF, need not
induce inversion-effects.
We have recently investigated this hypothesis by testing adults’ recognition
for individual faces of other species with a forced choice task (Pascalis et al.,
1998). Adults were good at recognizing HF, monkey faces (MF) and sheep faces
(SF). However, the results pointed to qualitatively different processing of
primate faces compared with SF. An inversion-effect was found for HF and MF,
but not for SF. This suggests that adults process primate faces in a qualitatively
different way from SF. We suggested that our results might reflect that, even
though the adults were not experts in recognizing MF, they might have used
their HF ‘template’ to process the MF, thereby inducing an inversion-effect. The
HF template is, however, not designed to be efficient in processing other
primate faces. We showed, with a visual paired-comparison task, administered
in identical fashion to both humans and monkeys, that human participants were
more skilled at recognizing individual HF than MF, while the opposite was true
for monkeys (Pascalis and Bachevalier, 1998).
The aim of the present study was to determine whether children, who have
less experience with faces than adults, would show a different pattern of
responding to HF and MF than did adults. In two experiments, we explored the
recognition of upright and inverted faces of different animal species by children
between 5 and 8 years of age. We predicted that the youngest group, who have
relatively more limited experience with (human) faces, should present a pattern
of results different from the other groups tested. They may fail to show an
inversion-effect for any type of face, whereas the older group should give an
inversion-effect for both HF and MF, but possibly not for SF.
EXPERIMENT I
Method
Participants
Thirty-seven children from the Ziegleau School in Strasbourg, who had
volunteered to take part in the study, and for whom written parents’ consent
Copyright © 2001 John Wiley & Sons, Ltd.
Inf. Child Dev. 10: 39 – 45 (2001)
Recognition of Faces of Different Species
41
was obtained were tested. None had personal experience of individual macaque
monkeys, nor of sheep. There were 18 (nine boys, nine girls) 6–7-year-old
children (mean age=6.9; range= 6.3 – 7.5), and 19 (12 boys, seven girls) 8-yearold children (mean age=8.4; range=8 – 8.11).
Stimuli
The stimuli were presented on a video monitor. They were 60 halftone images
of faces from three categories: human (Caucasians), monkey (rhesus macaque
and tonkeanas macaque) and sheep (examples displayed on Figure 1). The pose
was always full-face, top-lit. The face outline was masked to ensure that no neck
or background information was seen. All faces were captured with a neutral
expression (closed mouth, open eyes, normal muscle tone). In addition, for HF,
individuals had no jewellery, glasses or obvious make up. The size of the image
was 10 × 6 cm, presented at a 30 cm viewing distance. Brightness and contrast
levels for all images were computationally manipulated to be uniform across
pictures in the three categories.
Figure 1.
Examples of the MF, HF and SF used in the experiments.
Copyright © 2001 John Wiley & Sons, Ltd.
Inf. Child Dev. 10: 39 – 45 (2001)
42
O. Pascalis et al.
Procedure
A two-alternative forced choice task was used. Participants were tested
individually, seated 30 cm in front of a computer screen in a quiet room. Each
participant was instructed that one picture would appear on the screen for a 1-s
familiarization period, and that they would then be asked to recognize it from
a pair of two images. Following the 1-s display of the target image, there was a
3-s unfilled interval, then two pictures (the familiar one and a novel from the
same category) were simultaneously presented until the participant had pointed
to the picture he/she felt they had seen before. They were asked to be as
accurate as possible. The left– right position of the novel stimulus was counterbalanced across trials. A prior training period with geometric patterns was
carried out and repeated until subjects reached 100% correct responses. Then all
the participants were tested first with the upright HF. The other five conditions
were also blocked, but presented in a random order: these five conditions were
HF inverted, MF upright, MF inverted, SF upright, and SF inverted. There were
ten trials for each condition. A criterion of five errors for the upright HF was
used to reject subjects. If they were unable to do the task with HF, it was
evidence of misunderstanding of the instructions; however, no subjects were
rejected from Experiment I.
Results
The number of errors was scored for each participant for each condition. A
three-way within-subjects analysis of variance (ANOVA) (2 age×3 species× 2
orientation) showed a significant effect for age (F(1,35)= 29.35, pB 0.01). Overall, accuracy for faces increased significantly with age (a mean of 3.49 errors for
the youngest and 2.11 for the oldest groups). There was a significant effect of
species (F(2,70)=18.09, p B 0.01). Recognition was better for the HF (mean=
2.15 errors), than for MF (mean= 2.77 errors) than for SF (mean= 3.49 errors).
There was a significant effect of orientation (F(1,35)= 21.94, p B 0.01). Upright
faces (mean=2.44 errors) were better recognized than inverted faces (mean=
3.17 errors).
The only significant interaction was between orientation and species
(F(2,70)= 4.37, pB 0.05). Table 1 shows the nature of the species differences:
only primate faces induced an inversion-effect, while accuracy for upright and
inverted SF did not differ. The responses were, however, better than chance for
all the categories.
Discussion
Accuracy improved with age for this face recognition task. However, the
qualitative pattern was similar across the age groups. Like adults, both younger
and older children showed an inversion-effect, which was specific to primate
faces.
Table 1.
Experiment I: errors (mean (S.D.)) in face recognition for HF, MF and SF
Age
Human
upright
Human
inverted
Monkey
upright
Monkey
inverted
Sheep
upright
Sheep
inverted
6–7
8
2.11 (1.6)
1.15 (1)
3.44 (1.2)
1.89 (1.4)
3.05 (1)
1.42 (0.8)
3.72 (1.4)
2.89 (1.6)
4.4 (1.5)
2.52 (1.5)
4.2 (1.5)
2.8 (1.47)
Copyright © 2001 John Wiley & Sons, Ltd.
Inf. Child Dev. 10: 39 – 45 (2001)
Recognition of Faces of Different Species
43
Thus, Flin’s finding that an inversion-effect can be found in children before 10
years of age can be extended to younger children, and the effect also generalizes
to faces of other primates. One way in which this could happen is if the
representational template for recognizing HF can also be used for judging MF
(see Campbell et al., 1997).
EXPERIMENT II
A second experiment was designed to investigate if younger children with less
experience with faces would behave similarly to 6– 8-year-olds.
Method
Participants
Fifty-seven children from the Ziegleau School in Strasbourg, who had volunteered to take part in the study, and for whom written parents’ consent was
obtained were tested. None had personal experience of individual macaque
monkeys, nor of sheep. Only five 5-year-old children did not reach the criterion
of less than five errors for upright faces and were rejected from the final sample.
There were 20 (10 boys, 10 girls) 5-year-old children, (mean age= 5.4; range=
5 –5.8); 17 (nine boys, eight girls) 6– 7-year-old children (mean age= 6.8;
range = 6.3–7.5); and 20 (10 boys, 10 girls) 8-year-old children (mean age= 8.5;
range = 8.1–8.11).
Procedure
The procedure was the same as for Experiment I, except that the familiarization period was increased from 1 to 5 s to ensure a sufficient encoding of the
stimulus by the younger group. Indeed, Pascalis and de Haan (in press) showed
that the younger the child is, the more familiarization time is needed for the
stimulus to be fully encoded. The stimuli were the same as those used in
Experiment I.
Results
The number of errors was scored for each participant for each condition. A
three-way within-subjects ANOVA (3 age× 3 species× 2 orientation) showed a
significant effect for age (F(2,55) = 4.95, p B 0.01), the overall accuracy for HF
and other species faces increases significantly with age (2.42 errors at 5 years of
age, 2.05 errors at 6– 7 years of age and 1.7 errors at 8 years of age). There was
a significant effect of species (F(2,110) = 49.49, pB 0.01). Recognition accuracy
was better for HF (mean=1.39 errors) than for MF (mean= 1.81 errors), and
than for SH (mean= 2.98 errors). There was a significant effect of orientation
(F(1,55)=15.44, p B0.01), with upright faces being better recognized than inverted faces (mean=1.18 errors for upright, and 2.34 for inverted faces).
Table 2.
Experiment II: errors (mean (S.D.)) in face recognition for HF, MF and SF
Age
Human
upright
Human
inverted
Monkey
upright
Monkey
inverted
Sheep
upright
Sheep
inverted
5
6–7
8
0.95 (0.74)
1.23 (0.93)
0.85 (0.67)
2.6 (1.2)
1.35 (1.2)
1.8 (1.08)
1.8 (1.33)
0.82 (0.95)
1.22 (0.80)
3 (1.87)
2.47 (1.8)
2.4 (1.56)
3.1 (1.06)
3.2 (1.74)
3.1 (2)
3.1 (1.64)
3.3 (1.26)
2.8 (1.47)
Copyright © 2001 John Wiley & Sons, Ltd.
Inf. Child Dev. 10: 39 – 45 (2001)
44
O. Pascalis et al.
The only significant interaction was between orientation and species
(F(2,110)= 11.24, p B0.01). Table 2 shows the nature of the species differences:
only primate faces induce an inversion-effect, the number of errors for upright
and inverted sheep is equivalent for each age group. As in Experiment I, the
responses were better than chance for all the categories.
Discussion
This experiment showed that 5-year-old children’s face recognition is not as
accurate as that one observed in older children, but it is more adult-like than
expected, because the human and primate inversion-effect was clearly present.
Like adults and older children, the 5-year-olds gave an inversion-effect for both
HF and MF, but not for SF.
GENERAL DISCUSSION
The hypothesis that guided this study was that sensitivity to inversion should
develop throughout childhood and that it may be selective for HF. MF were
predicted to show inversion sensitivity in older children. Our results failed to
show any developmental changes, other than in general accuracy, in the
processing of faces of own- and other-species. The average number of errors
decreases from 5 to 8 years of age.
This may be the first demonstration of an inversion-effect for face recognition
in 5-year-old children. The finding of a better ability to process upright faces
than inverted faces is consistent with Tanaka et al. (1998), who showed that
6-year-old children can process faces holistically.
If sensitivity to inversion is taken as an index of face-processing selectivity
(Yin, 1969), then it would seem to be accomplished by the age of 5 years. It is
more likely, however, that there are a number of performance measures of
face-expertise, and that these may follow different developmental trajectories,
with relatively different levels of reliance on configural (or low spatial frequency) processing. Familiar or known faces may behave differently than
unknown faces in this regard. With respect to unknown faces, however, forced
choice recognition can be achieved in an adult-like fashion, both in terms of
species and of orientation specificity, by the age of 5 years. In terms of Nelson’s
model (this volume), the face module has become tuned to the characteristics of
the primate face by this age.
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Copyright © 2001 John Wiley & Sons, Ltd.
Inf. Child Dev. 10: 39 – 45 (2001)