Newborns’ preference for face-relevant stimuli:
Effects of contrast polarity
Teresa Farroni*†, Mark H. Johnson*, Enrica Menon†, Luisa Zulian†, Dino Faraguna‡, and Gergely Csibra*§
*Centre for Brain and Cognitive Development, School of Psychology, Birkbeck, University of London, Malet Street, London WC1E 7HX, United Kingdom;
†Dipartimento di Psicologia dello Sviluppo e della Socializzazione, University of Padua, Via Venezia 8, 35131 Padua, Italy; and‡Unita ´ Pediatrica,
Ospedale di Monfalcone, Via Galvani 1, 34074 Monfalcone Gorizia, Italy
Edited by Michael I. Posner, University of Oregon, Eugene, OR, and approved October 10, 2005 (received for review March 17, 2005)
There is currently no agreement as to how specific or general are
the mechanisms underlying newborns’ face preferences. We ad-
dress this issue by manipulating the contrast polarity of schematic
and naturalistic face-related images and assessing the preferences
of newborns. We find that for both schematic and naturalistic face
images, the contrast polarity is important. Newborns did not show
a preference for an upright face-related image unless it was
composed of darker areas around the eyes and mouth. This result
is consistent with either sensitivity to the shadowed areas of a face
eye contact ? face processing
2). However, controversy remains as to whether this prefer-
ence is based on one or more nonspecific biases in the
newborn’s visual system that happen to maximally respond to
faces or whether the underlying mechanisms are stimulus-
specific (1, 3). This issue is important to debates in several
fields, including developmental psychology and cognitive neu-
roscience. For example, in adult cognitive neuroscience some
have argued that cortical regions are dedicated for face
processing, whereas others have proposed that these regions
are activated by a level of perceptual expertise most commonly
achieved with faces (4).
A number of authors have hypothesized that face processing
in newborns is relatively well developed and does not differ
significantly from that seen in adults (for review, see ref. 5).
Evidence in support of this view includes experiments with
naturalistic stimuli showing a preference for attractive faces (6,
7). Johnson and Morton (8, 9) argued that newborns’ responses
to faces are not attributable to adult-like processing but rather
are subserved by a primitive and subcortical mechanism they
termed ‘‘Conspec.’’ Conspec was initially defined as being a
mechanism that ‘‘contains structural information concerning the
visual characteristics possessed by conspecifics’’ (ref. 9, p. 85),
but it has become more generally used to refer to an ‘‘infant’s
disposition to direct their attention and sense of belonging to
other human beings.’’¶Although Morton and Johnson argued
that the general configuration that composes a face may be
important, they did not consider that there was sufficient
evidence at the time to commit to a specific underlying repre-
sentation. Nevertheless, their empirical observation from the
early experiments with newborns, and evidence from other
species, indicated that a stimulus with three high-contrast blobs
corresponding to the approximate location of the eyes and
mouth (a stimulus that they referred to as ‘‘Config’’) might be
Another view of the mechanisms underlying face preferences
in newborns is that the preference is the result of one or more
nonspecific biases, including a bias to look at the greater number
of elements or features in the upper visual field (10). This
so-called ‘‘top-heavy’’ bias has been used to account for several
ost researchers agree that in their natural environment
human newborns preferentially orient toward faces (1,
experiments using schematic face-like patterns, although it has
been less successful in accounting for the full range of results
obtained with naturalistic face stimuli (11). It is important to
note about the top-heavy bias account that the arrangement of
elements or features depends on the shape and size of a
high-contrast border surrounding them (12). Preference for
top-heavy configurations has not been observed without this
border (13), showing that the bias is more specific than just for
elements in the upper visual field. The hypothesized bias appears
to be sensitive to a greater number of elements of features in the
upper portion of a surface or object within a high-contrast
When considering the different viewpoints advanced to ac-
count for newborns’ visual preferences, it is useful to distinguish
between functional accounts and the exact mechanisms that
fulfill these functions. Both the top-heavy bias and the Config
representations are assumed to have the same function: the
detection of faces in the natural environment of the newborn.
The debate between these opposing views cannot be resolved by
comparing the stimuli with varying attractiveness to newborns,
because there are no independent criteria to decide whether a
certain stimulus forms a better face than another. Relying on our
adult intuitions may be misleading when we assess newborns’
visual biases. Whether or not a visual mechanism acts as a
an ideal face template but on its efficiency in drawing infants’
attention to faces in a natural environment. If a bias toward
top-heavy stimuli successfully selects faces in the species-typical
environment of a human newborn without generating too many
false alarms, then it is as domain-relevant as a preference for
stimuli matching the Config representation, and they share a
The functional approach to newborns’ visual preferences also
can be extended to allow us to draw further predictions about the
representations that underlie certain functions. We have pre-
dicted that newborns’ bias toward face-like stimuli would be
influenced by the contrast polarity of those stimuli. This pre-
diction follows from two related functions that one could ascribe
to newborns’ face preferences.
If the mechanisms that bias newborns’ orientation to stimuli
has been selected to find faces in a natural environment under
natural (top-down) illumination (i.e., the function is face
detection), it should also be sensitive to the light?shadow
pattern generated on faces by such conditions. In particular,
the eye and mouth regions are recessed on a face and therefore
appear to be darker than other parts of the face that are
directly illuminated. By chance, or perhaps necessity, all
previous studies of newborns’ face preference used darker
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
§To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
¶See the Conspec entry at www.psybox.com?web?dictionary?dictionaryWebindex.htm.
© 2005 by The National Academy of Sciences of the USA
November 22, 2005 ?
vol. 102 ?
no. 47 ?
blobs on white background as schematic face stimuli. If the
newborns’ visual biases evolved to help them locate faces in a
natural environment, infants should show no preference for
face-like patterns where the elements within the face are
lighter than the background, because those elements would
indicate protrusions rather than recesses for their visual
system. In contrast, theories that explain newborns’ face
preference in terms of non-face-specific underlying mecha-
nisms that bias toward larger number of enumerable features
in the upper half of a surface should predict the same, or even
stronger, preference for light elements on a dark background,
because these elements may appear to be closer to the observer
in relation to a background surface.
A more extended function that one can ascribe to newborns’
preferential orientation to certain stimuli is that it reflects a
bias toward potential communicative partners, in particular to
an upright face in which the eyes are directed toward the
observer (11, 14). Evidence that motivates this view includes
findings that newborns preferentially orient toward faces with
open, as opposed to closed, eyes (15) and faces with direct
gaze, as opposed to faces with averted gaze (11, 16). If
newborns’ preference is directed to eye-contact stimuli, it must
be sensitive to the contrast polarity of the elements, because
human gaze perception is known to depend on direction of
contrast (17). In particular, perceived gaze seems to be defined
for a human observer on the basis of a darker spot (the
iris?pupil) within a lighter background (the sclera), as it is
demonstrated by the Bogart illusion (18). If this is the case, a
stimulus that does not include darker blobs on lighter ground
could not be identified as an eye-contact stimulus even if it
otherwise resembles the structure of a face, because gaze
would not be defined in this stimulus. This scenario predicts
that if newborns were seeking eye-contact stimuli, they would
not be attracted by face-like configurations of white elements
on a black background.
The first of the present studies tested the prediction that the
well established preference for upright schematic face-like con-
figurations would disappear if they were composed of light
elements on a dark background. Accounts such as the top-heavy
bias should predict that the preference for face-like (or top-
heavy) pattern would be preserved, or possibly become stronger,
with contrast-reversed stimuli. The second study addressed the
question of whether the contrast polarity sensitivity of newborns’
preference is extended to real faces and across different lighting
Full-term newborns were selected to participate in the study
from the maternity ward of the Pediatric Clinic of the University
of Padua and of the Pediatric Unit of the Hospital of Monfal-
cone. All of them met the screening criteria of normal delivery,
had a birth weight between 2,596 and 3,960 g, and had an Apgar
score of at least 8 at 5 min. Their postnatal age was between 13
and 168 h. Parents were informed about the procedure and gave
their consent to their child’s participation. A total of 105
number of participants in each study). A further 44 newborns
were excluded from the analysis because of failure to complete
the test (12 newborns), strong side bias (20 newborns), or
technical errors (12 newborns).
The stimuli were presented on two adjacent 21-inch computer
covered the area around monitors to prevent other visual stimuli
from attracting the infants’ attention. In between the monitors,
a flickering red light-emitting diode (LED) (subtending 2° from
the 30-cm viewing distance) was used to attract the infants’
a video camera recorded the participants’ eye movement to
monitor their looking behavior on-line and to allow off-line
coding of their fixations.
The newborn sat on an experimenter’s lap in front of the two
monitors. The experimenter holding the infant was not aware
of the hypotheses under test. Each trial began with flickering
the LED in the center. As soon as the infant fixated on the
light, another experimenter, who monitored the infant’s eye
through the video camera, started the sequence of the trial by
pressing a key on the computer keyboard. This action auto-
matically turned off the LED, and the two stimuli appeared
simultaneously on each monitor. The stimuli remained on as
long as the infant fixated one of them. When the infant shifted
his?her gaze away from the display for more than 10 seconds,
the stimuli were removed and the center light was turned on.
This procedure, called ‘‘infant-control preferential looking
technique,’’ has previously been used in many studies (2, 11).
All of the newborns were presented with two trials in which the
position of the stimuli was reversed. The initial side of the two
stimuli (left or right) was counterbalanced across subjects.
differences are indicated by asterisks (*, P ? 0.05;**, P ? 0.01;***, P ? 0.001). The numbers below the columns represent the number of newborns tested in
the corresponding condition.
www.pnas.org?cgi?doi?10.1073?pnas.0502205102Farroni et al.
Videotapes of the baby’s eye movements throughout the trial
were subsequently analyzed by two coders, who were unaware
of the stimuli presented. The coders recorded, separately for
each stimulus and each trial, the number of orienting responses
and the total fixation time. Interrater reliability was calculated
for 10% of the participants with high intercoder reliability
(Cohen’s kappa ? 0.85 for the duration of fixation and 0.98 for
the number of orientations).
We analyzed two dependent variables of newborns’ behavior
(number of orientations and total looking time) against the
independent variables of face orientation (upright vs. inverted)
or direction of illumination (above vs. below) and the between-
subject factor of polarity (positive vs. negative) when it was
Experiment 1. The stimuli in Experiment 1a were two head-
shaped, head-sized, two-dimensional images with three square
features inside (Fig. 1). One of the stimuli had the squares in the
appropriate locations for eyes and mouth (i.e., an upright
face-like configuration), whereas in the other stimulus the
position of the squares was vertically reversed, with two squares
located below one square (i.e., an inverted face-like configura-
tion). The stimuli were presented in 14.5 ? 23 cm size on the two
monitors (one stimulus per monitor) at a distance of ?30 cm
from a central fixation point. Each square blob within the
contours measured 2 ? 2 cm. At a viewing distance of ?30 cm,
the center of the head-shaped contours was 45° right and left
In Experiment 1a the stimuli in the two conditions differed
only in contrast polarity: in the positive polarity condition, the
head shape was white against a black background and the
internal squares were black (i.e., the Config stimulus of ref. 9);
in the negative polarity condition, the head shape was black
against a white background and the internal squares were
A 2 ? 2 (face orientation ? polarity) ANOVA on the total
looking time in Experiment 1 resulted in no main effects but a
significant interaction (F1,31? 5.231; P ? 0.05). According to
post hoc tests, this interaction was attributable to the fact that
infants spent significantly more time looking at the upright face
in the positive polarity condition (t16? 2.180; P ? 0.05), whereas
no such difference occurred in the negative polarity condition
(t16? ?1.008; n.s.) (see Fig. 1). This pattern of results also was
confirmed by nonparametric Wilcoxon tests. Although infants in
the positive polarity condition looked longer at the upright face
(z ? 2.012; P ?0.05), they did not do so in the negative polarity
condition (z ? 1.068; n.s.). Similar analyses on the number of
orientations toward the two stimuli did not show any significant
Thus, the positive polarity condition of Experiment 1a
replicated the findings of earlier studies (2): newborns in this
condition looked longer at the upright than the inverted face
configuration. However, no such preference was observed in
newborns who saw the same figures in negative face polarity.
This finding indicates that contrast polarity direction did
influence newborns’ orientation responses, which were not
based solely on the number of high-contrast bounded elements
in the upper and lower parts of the stimuli.
Before drawing firm conclusions from this result, we have to
consider other possible causes of the absence of preference in
the negative polarity condition. In particular, although the
average luminance of the stimuli was lower in the positive than
in the negative polarity condition (see Fig. 1), it is possible that
the dark objects in the negative polarity condition were less
salient for, and drew less attention from, the newborns than
were the positive polarity stimuli, which could potentially
explain why they failed to show a preference between the
stimuli in the negative polarity condition. This account would
predict stronger attention and a longer looking time in the
positive than in the negative polarity condition. However, our
statistical analysis did not reveal such a main effect (F1,31?
2.899; n.s.) in the two-way ANOVA above, allowing us to rule
out this account of our findings.
Alternatively, reversing the contrast polarity of the stimuli
changed not only the face and its inner elements, but it also
enhanced the luminosity of the background. It is possible that
the white background behind the black head-outline attracted
the babies’ attention, and so they failed to explore the inner
features of the stimuli, which prevented them from detecting
any differences between upright and inverted configurations.
Experiment 1b was designed to investigate this possibility. In
this experiment the same stimuli were presented as in the
negative polarity condition of Experiment 1a with the ex-
ception that the stimuli appeared on a mid-gray (50%)
The total fixation time in Experiment 1b to the upright vs.
inverted face stimuli did not differ significantly (t16? ?1.321;
n.s.) nor did the number of orientations toward them (t16 ?
?1.474; n.s.) (see Fig. 1). In fact, comparing these dependent
measures to the negative polarity faces across Experiments 1a
and 1b did not reveal any significant difference. Changing the
white background to gray, thus making the contrast around the
not bring back the preference for upright over inverted face
configuration in inverted polarity.
Another possible objection to our contrast polarity result is
that the low luminance content of the negative polarity images
the details of these stimuli. Fortunately, one of the hypotheses
that predicted the contrast polarity sensitivity of newborns’
preferences for face-like patterns also generates predictions for
the conditions that would make the preference reemerge within
a dark head-outline. Specifically, if the function of newborns’
orientation bias is to establish eye contact, and human eyes are
identified as dark spots within lighter areas (19), placing dark
‘‘irises’’ within the white squares in the negative polarity images
should bring the preference for upright images back. In Exper-
iment 1c, we changed the stimuli in Experiment 1b slightly by
inserting small black squares into the white ones (see Fig. 1). The
size of the black squares was 1 ? 1 cm.
A Student t test on the total looking time in Experiment 1c
yielded a significant effect of face orientation (t11? 2.212; P ?
0.05), indicating longer looking time at the upright than at the
of looking times (skewness ? 1.665; z ? 2.613), we repeated this
analysis on logarithmically transformed data, which resulted in
a stronger effect (t11 ? 2.484; P ? 0.03). The number of
orientations toward the two stimuli also differed significantly
(t11? 2.634; P ? 0.05), because the newborns looked more times
at the upright (17.3) than at the inverted (12.1) configuration.
We also compared the dependent measurements between
Experiments 1c and 1b to check whether inserting the black
squares into the white ones made any difference. A 2 ? 2 (face
orientation ? experiment) ANOVA on the looking times re-
vealed a significant interaction (F1,27? 7.391; P ? 0.01). An even
stronger interaction was found in a similar ANOVA on the
number of orientations toward the stimuli (F1,27 ? 11.463;
P ? 0.002).
These results confirmed that the lack of preference for the
upright configuration in the negative polarity condition of
Experiments 1a and 1b was not simply caused by lack of scanning
of lower luminance surfaces. In fact, the stimuli in Experiment
Despite this difference, newborns showed a clear preference for
the upright configuration, which therefore was attributable to
Farroni et al. PNAS ?
November 22, 2005 ?
vol. 102 ?
no. 47 ?
the small black elements that now appeared on the white
The results of Experiment 1 contradict the prediction drawn
from the account that explains newborns’ face preference only
by a nonspecific bias toward top-heavy stimuli (3). Although all
conditions in Experiment 1 contrasted an ‘‘upright’’ and an
‘‘inverted’’ configuration, the newborns displayed selective
preference only in two of these contrasts. Neither the lumi-
nance of the background nor the luminance of the bordered
surface determined whether infants would show a bias toward
one of he stimuli. One factor that is common in the two upright
patterns that preferentially attracted newborns’ attention is the
presence of dark elements on light background within a
Experiment 2. Experiment 2 was designed to test whether the
contrast polarity sensitivity of newborns’ visual preferences
applies not only to schematic but also to real faces, where
contrast relations change in a more continuous fashion. These
experiments were based on the previous finding of a preference
for an upright face in realistic face images (20). Stimuli in
Experiment 2 measured 17 cm wide and 25.5 cm tall.
In the positive polarity condition of Experiment 2a, infants
were presented with two high-quality black-and-white photo-
graphs of a woman’s face that was digitally modified to create an
upright and an inverted version of it (Fig. 1). The two stimuli
were identical except for the inner region of the face, which was
preserved in its canonical orientation in the upright face but was
rotated by 180° in the inverted face. This is the same manipu-
lation that was applied in previous studies with schematic and
real faces (20). The model was photographed in a frontal pose
with a neutral expression. In the negative polarity condition, we
used the same two pictures, but this time with the contrast
polarity reversed, while keeping the background black (Fig. 1).
The positive and negative polarity stimuli did not differ in
A 2 ? 2 (face orientation ? polarity) ANOVA on the total
looking time in Experiment 2a resulted in a significant main
interaction (F1,29 ? 6.455; P ? 0.02), and no main effect of
polarity (F1,29 ? 0.720; n.s.). To analyze the interaction, we
compared looking times to the two face orientations within the
two conditions. In the positive polarity condition, the newborns
looked much longer at the upright than at the inverted face (t15
? 4.887; P ? 0.001), whereas no such significant difference was
found in the negative polarity condition (t14? 1.039; n.s.) (see
Fig. 1). This pattern of result was confirmed by nonparametric
tests. In the positive polarity condition, 15 of 16 infants looked
longer at the upright than at the inverted faces (P ? 0.001 by sign
test), and a Wilcoxon test also showed significantly longer
looking at the upright face (z ? 3.361; P ? 0.001). In contrast,
only 9 of 15 newborns looked longer at the upright face in the
negative polarity condition (P ? 0.5 by sign test), and a rank test
yielded no significant result either (Wilcoxon z ? 0.966, n.s.).
Similar tests on the number of orientations resulted in no
Experiment 2a essentially replicated the findings of Experi-
ment 1a. Although there was no significant preference for either
stimulus in the negative polarity condition, we found a strong
bias in looking time toward the upright face in the positive
polarity condition. However, we also found a main effect of face
orientation, suggesting that the newborns tended to prefer the
upright face in both conditions. This result can be explained by
the nonsignificant bias toward the upright faces in the negative
polarity condition, a trend not observed in Experiment 1. This
finding is not surprising if infants tend to prefer stimuli that
contain darker spots on lighter background in their upper part,
as the ‘‘eye-contact hypothesis’’ suggests. Note that the polarity-
inverted sclera on the negative image represent precisely such
elements, as they appear to form ‘‘pseudopupils’’ on lighter
backgrounds. Whether this illusion made newborns look slightly
longer at the upright than at the inverted configuration in the
negative polarity condition, the interaction between face orien-
tation and polarity confirmed that their bias toward the upright
configuration was much stronger in the positive polarity condi-
tion, where the larger dark elements appeared on a light
background, making them more easily detectable by newborns’
eyes. Note also that the absence of main effect of contrast
polarity makes it unlikely that differential effects in the two
conditions were attributable to generally higher attention to the
positive polarity images.
The sensitivity to larger dark elements in face-like patterns
may be a byproduct of the newborns’ visual system, but it may
also reflect the fact that this preference is tuned to the particular
distribution of dark and light patches characteristic of a face
illuminated from above. Specifically, when the light comes from
above, it creates large dark areas in the sockets around the eyes,
whereas other directions of illumination tend to generate pat-
terns containing higher spatial frequencies. Experiment 2b
tested directly whether newborns could discriminate between,
and are biased toward one of, two faces, which are illuminated
either from above or from below.
We presented newborns with the same female face photo-
graphed with two different directions of illumination: from
stimuli was the same, whereas the distribution of the darker and
lighter patches was markedly different. The face showed a
The direction of illumination had a strong effect on newborns’
preference: they looked longer (t11? 4.076; P ? 0.01) and more
times (t11 ? 2.620; P ? 0.05) at the top-lit face than at the
bottom-lit face. Nonparametric Wilcoxon tests also confirmed
these results, showing that the newborns tended to prefer the
face illuminated from above both in terms of looking times (z ?
2.667; P ? 0.01) and in terms of number of orientations (z ?
2.323; P ? 0.05).
Experiment 2 demonstrated that the sensitivity to contrast
polarity in newborns’ preferences is not restricted to schematic
face-like stimuli but is also present in their orientation toward
photographic images. We also have shown that preference for a
face stimulus depends not only on the contrast polarity but also
on the shading pattern created by lighting conditions. It is
reasonable to assume that these two aspects of the orientation
bias reflect the functioning of a single mechanism, which favors
face-like configurations in which the elements in the upper parts
are darker than their background.
These experiments demonstrate that the contrast polarity of
schematic and realistic face stimuli influences the degree of
preference shown by newborns for an upright face configuration.
The pattern of data that we have obtained over the experiments
makes it unlikely that our results can be explained by differences
in the overall luminance of our stimuli (see Fig. 1 and Experi-
ment 1c) or by differences in general within-object luminance.
The latter possibility predicts that newborns will generally look
longer at stimuli in which the figure or object has greater
luminance. By this account, preferences for an upright config-
uration are shown only with pairs of stimuli that have a relatively
high intraobject luminance. However, in both Experiments 1a
and 2a there was no significant difference in the overall looking
time to positive and negative contrast stimuli. Further, in
Experiment 1c newborns showed a preference between stimuli
with less intraobject luminance than in Experiment 1b in which
no preference was shown. Finally, a preference also was ob-
served in Experiment 2b in which luminance was generally lower
www.pnas.org?cgi?doi?10.1073?pnas.0502205102 Farroni et al.
than in all of the other experiments. The absence of statistical
effects of contrast polarity on looking times indicated that the
contrast polarity exerted its impact by modulating the perceptual
preference of newborns rather than by facilitating or reducing
their overall attention.
Most hypotheses about the nature of newborns’ preferences
either no effect of contrast polarity or a stronger preference for
the negative contrast polarity. Conversely, a mechanism that is
sensitive to the unique form of a human face under natural
lighting conditions (daylight or overhead illumination) may be
sensitive to the darker shadowed areas around the eyes and
mouth. Similarly, a mechanism that attempts to identify eye
contact within the context of an upright face also will be biased
toward stimuli that potentially contain appropriate contrast
polarity. Our results are consistent with the view that the
mechanism(s) underlying newborn preference for upright con-
figurations requires the contrast polarity characteristic of faces
and?or eyes in which one or more dark areas are surrounded by
a lighter surface.
Our observations thus suggest that these mechanisms are, in
some respects, more face-related than previously supposed.
Whether the configuration of elements is required to be those
of facial features or not (Config or top-heavy bias), these
elements must occur within a border that defines an overall
object or surface and must be set against a background that is
lighter than the elements themselves, consistent with cavities
or recessed shadowed areas. It is plausible to assume that
evolutionary selection on newborns’ visual preferences would
have relied on these characteristics of human faces, which in
natural lighting conditions are as invariant aspects of them as
the geometric arrangements of the elements within faces. Few,
if any, naturally occurring objects share the patterns of shadow
and reflected light characteristic of faces. Thus, the ‘‘positive’’
and ‘‘negative’’ polarities investigated in this article are de-
fined relative to the unique structure of faces. From this
perspective, artificially generated stimuli, such as a banded
head-shaped surface with more shadowed indentations in the
upper half, may be sufficient to activate preferences in new-
borns but are unlikely to be encountered within their natural
environment. Note that newborns do not need the ability to
extract the direction of illumination from patterned stimuli to
show such a preference. A mechanism that biases their orien-
tation toward visual patterns that are consistent with faces
being illuminated from above would be sufficient to fulfill the
function of finding conspecifics in a natural environment.
Alternatively, several characteristics of newborns’ visual pref-
erences suggest that they may have been selected for a more
specific function than the detection of conspecific faces: the
detection of communicative partners. The first piece of evidence
that supports this view is that newborns prefer upright to
inverted face configurations (1, 2), even though they are likely to
see faces in noncanonical orientations. A face in any orientation
could be a sign of the presence of a human, but only an upright
face indicates a potential communicative partner because nor-
mal human face-to-face communication occurs only in the
canonical face orientation. Importantly, caregivers always make
sure that their baby’s head is aligned with their own head when
they initiate an interaction with their offspring (21). Second,
human newborns prefer faces with direct gaze to faces with
averted gaze (11), even with schematic faces (16). This prefer-
ence disappears if the faces are inverted (our unpublished data).
Third, as the results of the present studies suggest, infants’
preferences are restricted to stimuli composed of darker ele-
ments on lighter background, the same contrast relation that is
used in identifying gaze direction in humans (17–19). Taken
together, these aspects of newborns’ preferences imply that
human babies at birth are most attracted to stimuli appropriate
for social interaction.
Eye contact is one of the strongest communicative signals in
humans, and it is plausible to assume that evolutionary selec-
tion has made human newborns sensitive to such a signal.
Recognizing this, Baron-Cohen (22, 23) proposed that an
innate eye-direction detection module assists infants in eval-
uating the gaze direction of social partners. Our hypothesis is
less ambitious here in that it simply involves sensitivity to, and
a bias to attend toward, stimuli that would most likely indicate
a face with gaze directed to the viewer. For such a bias,
newborns do not need a mechanism to identify the exact gaze
direction of a face; it is sufficient if they orient toward visual
patterns that are consistent with a human being looking at
them. Similar preferences also may be found in the auditory
domain. Newborns prefer not only human voices to other
sounds (24), and speech to nonspeech stimuli (25), but they are
also biased toward the specific intonation patterns (i.e., infant-
directed speech) that indicate that they are the ones who are
addressed by an utterance (26).
We offered two different functional accounts (top-lit faces or
eye-contact stimuli) for the contrast polarity sensitivity of new-
borns’ visual biases. It remains a question for further research,
and beyond the scope of the present article, to decide which of
these accounts provides a better explanation for newborns’
preferences to face-like stimuli. Both accounts predicted the lack
of preference for upright patterns when contrasting images with
negative face polarity (Experiments 1a and 2a). Additionally,
and beyond this prediction, both accounts generated novel
positive predictions for the kind of stimuli that newborns would
prefer, and both predictions were confirmed (Experiments 1c
and 2b). It is important to note that these accounts are not
mutually exclusive. It is possible that the same mechanism that
also would help them to locate and fixate eyes at close proximity.
In both cases, the approximate size of the retinal image of darker
elements on light background could be similar (27). Future
research will investigate this possibility.
We thank the parents and infants who participated in the study,
Stefano Massaccesi for the help with the software, and Sara Benetti,
Monica Volpato, and Silvia Rigato for the help with testing participants.
This work was supported by Medical Research Council Program Grant
G97 15587 (to M.H.J. and G.C.) and by ‘‘Progetto Giovani Ricercatori’’
2002 and the Wellcome Trust (073985?Z?03?Z to T.F.).
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