Is the face-perception system human-specific at birth?

The present study investigates the human-specificity of the orienting system that allows neonates to look preferentially at faces. Three experiments were carried out to determine whether the face-perception system that is present at birth is broad enough to include both human and nonhuman primate faces. The results demonstrate that the newborns did not show any spontaneous visual preference for the human face when presented simultaneously with a monkey face that shared the same features, configuration, and low-level perceptual properties (Experiment 1). The newborns were, however, able to discriminate between the 2 faces belonging to the 2 different species (Experiment 2). In Experiment 3, the newborns were found to prefer looking at an upright, compared with an inverted, monkey face, as they do for human faces. Overall, the results demonstrate that newborns perceive monkey and human faces in a similar way. These findings are consistent with the hypothesis that the system underlying face preference at birth is broad enough to bias newborns' attention toward both human and nonhuman primate faces.     

The effect of inversion on the encoding of normal and “thatcherized” faces

In the “Thatcher illusion” a face, in which the eyes and mouth are inverted relative to the rest of the face, looks grotesque when shown upright but not when inverted. In four experiments we investigated the contribution of local and global processing to this illusion in normal observers. We examined inversion effects (i.e., better performance for upright than for inverted faces) in a task requiring discrimination of whether faces were or were not “thatcherized”. Observers made same/different judgements to isolated face parts (Experiments 1-2) and to whole faces (Experiments 3-4). Face pairs had the same or different identity, allowing for different process- ing strategies using feature-based or configural information, respectively. In Experiment 1, feature-based matching of same-person face parts yielded only a small inversion effect for normal face parts. However, when feature-based matching was prevented by using the face parts of different people on all trials (Experiment 2) an inversion effect occurred for normal but not for thatcherized parts. In Experiments 3 and 4, inversion effects occurred with normal but not with thatcherized whole faces, on both same- and different-person matching tasks. This suggests that a common configural strategy was used with whole (normal) faces. Face context facilitated attention to misoriented parts in same-person but not in different-person matching. The results indicate that (1) face inversion disrupts local configural processing, but not the processing of image features, and (2) thatcherization disrupts local configural processing in upright faces.     

The recognition and categorization of upright and inverted emotional expressions by 7-month-old infants

Upright and inverted faces were used to determine whether 7-month-old infants discriminate emotional expressions on the basis of affectively relevant information. In Experiment 1, infants recognized the similarity of happy faces over changing identities and discriminated this expression from fear and anger when the stimuli were presented upright, but not when they were inverted. In Experiment 2, infants were able to discriminate happiness from fear and anger posed by a single model, regardless of the orientation of the stimuli. From these studies it was suggested that categorizing emotional expressions depends upon attending to affectively relevant, orientation-specific information, whereas the discrimination of emotional expressions can be done on a featural basis, something that remains invariant regardless of the orientation of the stimuli. In Experiment 3, infants discriminated toothy happiness posed by several models from nontoothy happiness and nontoothy anger when the stimuli were presented upright and inverted. Thus, when salient features were available, the infants based their discriminations on perceptual aspects rather than on conceptual aspects such as categories of emotions.     

Faces are special for newly hatched chicks: evidence for inborn domain‐specific mechanisms underlying spontaneous preferences for face‐like stimuli

It is currently being debated whether human newborns’ preference for faces is due to an unlearned, domain‐specific and configural representation of the appearance of a face, or to general mechanisms, such as an up‐down bias (favouring top‐heavy stimuli, which have more elements in their upper part). Here we show that 2‐day‐old domestic chicks, visually naïve for the arrangement of inner facial features, spontaneously prefer face‐like, schematic, stimuli. This preference is maintained when the up‐down bias is controlled for (Experiment1) or when put in direct conflict with facedness (Experiment 4). In contrast, we found no evidence for the presence of an up‐down bias in chicks (Experiment 2). Moreover, our results indicate that the eye region of stimuli is crucial in determining the expression of spontaneous preferences for faces (Experiments 3 and 4).     

An inversion effect modified by expertise in capuchin monkeys

The face inversion effect may be defined as the general impairment in recognition that occurs when faces are rotated 180°. This phenomenon seems particularly strong for faces as opposed to other objects and is often used as a marker of a specialized face-processing mechanism. Four brown capuchin monkeys (Cebus apella) were tested on their ability to discriminate several classes of facial and non-facial stimuli presented in both their upright and inverted orientations in an oddity task. Results revealed significantly better performance on upright than inverted presentations of capuchin and human face stimuli, but not on chimpanzee faces or automobiles. These data support previous studies in humans and other primates suggesting that the inversion effect occurs for stimuli for which subjects have developed an expertise.     

Perceptual learning and acquired face familiarity: Evidence from inversion,use of internal features,and generalization between viewpoints

Pairs of similar faces were created from photographs of different people using morphing software. The ability of participants to discriminate between novel pairs of faces and between those to which they had received brief, unsupervised, exposure (5×2 s each) was assessed. In all experiments exposure improved discrimination performance. Overall, discrimination was better when the faces were upright, but exposure produced improved discrimination for both upright and inverted faces (Experiment 1). The improvement produced by exposure was selective to internal face features (Experiment 2) and was evident when there was a change in orientation (three-quarter to full face or vice versa) between exposure and test (Experiment 3). These findings indicate that perceptual learning observed following brief exposure to faces exhibit well-established hallmarks of familiar face processing (i.e., internal feature advantage and insensitivity to a change of viewpoint). Considered in combination with previous studies using the same type of stimuli (Mundy, Honey, & Dwyer, 2007), the current results imply that general perceptual learning mechanisms contribute to the acquisition of face familiarity.     

Newborns' recognition of changing and unchanging aspects of schematic faces

The present study investigated newborns' ability to discriminate, recognize, and learn visual information embedded in the schematic face-like patterns preferred at birth. Four experiments were carried out using the visual-paired comparison paradigm. Results indicated that newborns discriminated face-like stimuli relying on their internal features (Experiments 1 and 4) and recognized a perceptual invariance between face-like configurations in conditions of low (Experiment 2) and high-perceptual variability (Experiment 3) of their inner elements. Altogether, data show that the presence of the preferred structure that schematically defines a face, displaying a triplet of elements in the correct locations for eyes and mouth, does not constitute a limit that constrains newborns' face learning processes.     

Visual cues of motion that trigger animacy perception at birth: the case of self‐propulsion

Self‐propelled motion is a powerful cue that conveys information that an object is animate. In this case, animate refers to an entity's capacity to initiate motion without an applied external force. Sensitivity to this motion cue is present in infants that are a few months old, but whether this sensitivity is experience‐dependent or is already present at birth is unknown. Here, we tested newborns to examine whether predispositions to process self‐produced motion cues underlying animacy perception were present soon after birth. We systematically manipulated the onset of motion by self‐propulsion (Experiment 1) and the change in trajectory direction in the presence or absence of direct contact with an external object (Experiments 2 and 3) to investigate how these motion cues determine preference in newborns. Overall, data demonstrated that, at least at birth, the self‐propelled onset of motion is a crucial visual cue that allowed newborns to differentiate between self‐ and non‐self‐propelled objects (Experiment 1) because when this cue was removed, newborns did not manifest any visual preference (Experiment 2), even if they were able to discriminate between the stimuli (Experiment 3). To our knowledge, this is the first study aimed at identifying sensitivity in human newborns to the most basic and rudimentary motion cues that reliably trigger perceptions of animacy in adults. Our findings are compatible with the hypothesis of the existence of inborn predispositions to visual cues of motion that trigger animacy perception in adults.     

Impaired face recognition does not preclude intact whole face perception

We studied intact and impaired processes in a prosopagnosic patient (RP). In Experiment 1, RP showed an inversion superiority effect with both faces and objects, with better performance when stimuli were presented upside down than in normal upright orientation. In Experiment 2, we studied the effect of face configuration directly by comparing matching performance with normal vs. scrambled faces. RP was worse with normal than with scrambled faces, whereas normal controls showed an advantage of a good face context. In Experiment 3, RP showed interference from external face features on the evaluation of internal face features. These results indicate, first, that although RP is impaired in face recognition and face matching, he does still encode the whole face rather than relying completely on parts-based procedures. Second, RP has a deficit at the level of the configural processes involved in finding subtle differences between individual faces, as his performance is worse when presented with a normal face configuration than with scrambled or inverted faces.     

Search asymmetries with real faces: testing the anger-superiority effect

The anger-superiority hypothesis states that angry faces are detected more efficiently than friendly faces. Previously research used schematized stimuli, which minimizes perceptual confounds, but violates ecological validity. The authors argue that a confounding of appearance and meaning is unavoidable and even unproblematic if real faces are presented. Four experiments tested carefully controlled photos in a search-asymmetry design. Experiments 1 and 2 revealed more efficient detection of an angry face among happy faces than vice versa. Experiment 3 indicated that the advantage was due to the mouth, but not to the eyes, and Experiment 4, using upright and inverted thatcherized faces, suggests a perceptual basis. The results are in line with a sensory-bias hypothesis that facial expressions evolved to exploit extant capabilities of the visual system.     

Sensitivity to auditory‐tactile colocation in early infancy

An ability to detect the common location of multisensory stimulation is essential for us to perceive a coherent environment, to represent the interface between the body and the external world, and to act on sensory information. Regarding the tactile environment “at hand”, we need to represent somatosensory stimuli impinging on the skin surface in the same spatial reference frame as distal stimuli, such as those transduced by vision and audition. Across two experiments we investigated whether 6‐ (n = 14; Experiment 1) and 4‐month‐old (n = 14; Experiment 2) infants were sensitive to the colocation of tactile and auditory signals delivered to the hands. We recorded infants’ visual preferences for spatially congruent and incongruent auditory‐tactile events delivered to their hands. At 6 months, infants looked longer toward incongruent stimuli, whilst at 4 months infants looked longer toward congruent stimuli. Thus, even from 4 months of age, infants are sensitive to the colocation of simultaneously presented auditory and tactile stimuli. We conclude that 4‐ and 6‐month‐old infants can represent auditory and tactile stimuli in a common spatial frame of reference. We explain the age‐wise shift in infants’ preferences from congruent to incongruent in terms of an increased preference for novel crossmodal spatial relations based on the accumulation of experience. A comparison of looking preferences across the congruent and incongruent conditions with a unisensory control condition indicates that the ability to perceive auditory‐tactile colocation is based on a crossmodal rather than a supramodal spatial code by 6 months of age at least.     

Newborns’ attention is driven by the translational movement

The present study investigated whether 2-day-old newborns are able to discriminate two translating meaningless Point-Light Displays (PLD) videos, in which the shape of one of them changes compared to that of the other along the trajectory, independently from movement kinematics, and if this ability is present both when stimuli differed at the end or at the beginning of the movement. To manipulate the instant in which along the movement the difference between stimuli was evident, and to maintain every unspecific dissimilarity possibly determining the preference, videos were played in a loop either forward or backwards. In Experiment 1, PLD stimuli moved with natural accelerated-decelerated kinematics; in Experiment 2 they moved at constant velocity. Four groups of newborns were submitted to the preferential looking technique experiments. Results showed that newborns looked longer at natural kinematics and that, irrespective of the type of kinematics, they discriminated the two stimuli only when videos were played forward, that is, only when stimuli differed at the end of the movement. These data suggest that, independently from kinematics, movement translational components induce newborns to allocate attention at the end of the observed movement. Given the strict link between attention and eye movements, we suggest that this effect may bootstrap the system and give rise to proactive gaze, the typical gaze behaviour present during executed and observed goal-directed actions.     

Sensitivity to spacing changes in faces and nonface objects in preschool-aged children and adults

Sensitivity to variations in the spacing of features in faces and a class of nonface objects (i.e., frontal images of cars) was tested in 3- and 4-year-old children and adults using a delayed or simultaneous two-alternative forced choice matching-to-sample task. In the adults, detection of spacing information was robust against exemplar differences for faces but varied across exemplars for cars (Experiment 1A). The 4-year-olds performed above chance in both face and car discrimination even when differences in spacing were very small (within ±1.6 standard deviations [SDs]) and the task involved memory components (Experiment 1B), and the same was true for the 3-year-olds when tested with larger spacing changes (within ±2.5 SDs) in a task that posed no memory demands (Experiment 2). An advantage in the discrimination of faces over cars was found at 4 years of age, but only when spacing cues were made more readily available (within ±2.5 SDs). Results demonstrate that the ability to discriminate objects based on feature spacing (i.e., sensitivity to second-order information) is present at 3 years of age and becomes more pronounced for faces than cars by 4 years of age.     

Bimodal emotion congruency is critical to preverbal infants’ abstract rule learning

Extracting general rules from specific examples is important, as we must face the same challenge displayed in various formats. Previous studies have found that bimodal presentation of grammar‐like rules (e.g. ABA) enhanced 5‐month‐olds’ capacity to acquire a rule that infants failed to learn when the rule was presented with visual presentation of the shapes alone (circle‐triangle‐circle) or auditory presentation of the syllables (la‐ba‐la) alone. However, the mechanisms and constraints for this bimodal learning facilitation are still unknown. In this study, we used audio‐visual relation congruency between bimodal stimulation to disentangle possible facilitation sources. We exposed 8‐ to 10‐month‐old infants to an AAB sequence consisting of visual faces with affective expressions and/or auditory voices conveying emotions. Our results showed that infants were able to distinguish the learned AAB rule from other novel rules under bimodal stimulation when the affects in audio and visual stimuli were congruently paired (Experiments 1A and 2A). Infants failed to acquire the same rule when audio‐visual stimuli were incongruently matched (Experiment 2B) and when only the visual (Experiment 1B) or the audio (Experiment 1C) stimuli were presented. Our results highlight that bimodal facilitation in infant rule learning is not only dependent on better statistical probability and redundant sensory information, but also the relational congruency of audio‐visual information. A video abstract of this article can be viewed at https://m.youtube.com/watch?v=KYTyjH1k9RQ     

The influence of head contour and nose angle on the perception of eye-gaze direction

We report seven experiments that investigate the influence that head orientation exerts on the perception of eye-gaze direction. In each of these experiments, participants were asked to decide whether the eyes in a brief and masked presentation were looking directly at them or were averted. In each case, the eyes could be presented alone, or in the context of congruent or incongruent stimuli In Experiment 1A, the congruent and incongruent stimuli were provided by the orientation of face features and head outline. Discrimination of gaze direction was found to be better when face and gaze were congruent than in both of the other conditions, an effect that was not eliminated by inversion of the stimuli (Experiment 1B). In Experiment 2A, the internal face features were removed, but the outline of the head profile was found to produce an identical pattern of effects on gaze discrimination, effects that were again insensitive to inversion (Experiment 2B) and which persisted when lateral displacement of the eyes was controlled (Experiment 2C). Finally, in Experiment 3A, nose angle was also found to influence participants' ability to discriminate direct gaze from averted gaze, but here the effect was eliminated by inversion of the stimuli (Experiment 3B). We concluded that an image-based mechanism is responsible for the influence of head profile on gaze perception, whereas the analysis of nose angle involves the configural processing of face features.     

Suprasegmental information affects processing of talking faces at birth

From birth, newborns show a preference for faces talking a native language compared to silent faces. The present study addresses two questions that remained unanswered by previous research: (a) Does the familiarity with the language play a role in this process and (b) Are all the linguistic and paralinguistic cues necessary in this case? Experiment 1 extended newborns’ preference for native speakers to non-native ones. Given that fetuses and newborns are sensitive to the prosodic characteristics of speech, Experiments 2 and 3 presented faces talking native and nonnative languages with the speech stream being low-pass filtered. Results showed that newborns preferred looking at a person who talked to them even when only the prosodic cues were provided for both languages. Nonetheless, a familiarity preference for the previously talking face is observed in the “normal speech” condition (i.e., Experiment 1) and a novelty preference in the “filtered speech” condition (Experiments 2 and 3). This asymmetry reveals that newborns process these two types of stimuli differently and that they may already be sensitive to a mismatch between the articulatory movements of the face and the corresponding speech sounds.     

Peak shift but not range effects in recognition of faces

University students were trained to discriminate between two gray-scale images of faces that varied along a continuum from a unique face to an average face created by morphing. Following training, participants were tested without feedback for their ability to recognize the positive face (S+) within a range of faces along the continuum. In Experiments 1 and 4, the range of stimuli presented during testing was manipulated. In Experiment 2, participants viewed different ranges of faces during an adaptation period that followed training and preceded testing. In all experiments, generalization functions revealed peak shifts or area shifts (fewer “yes” responses to novel faces on the negative side of the S+), but no systematic effects of the test or adaptation range. Peak shift was found both for upright and inverted faces and occurred even if the orientation of the face was reversed between training and test. Using similar methods, either an area shift or range effect (but not both together) was demonstrated for line tilt stimuli (Experiment 3), and the appearance of these effects depended on instructions. It appears that peak shift and area shift are robust across many different kinds of stimuli, but range effects may not readily occur with complex multidimensional stimuli.     

Effects of gaze‐aversion on visual‐spatial imagination

Research suggests that averting gaze from an interlocutor can improve both children's and adults' performance in a range of cognitive tasks. With the present experiments, we investigated the effect of gaze aversion on adults' visual‐spatial imagination, using a methodology adapted from Kerr (1987). Participants mentally kept track of a pathway through an imaginary matrix, while either maintaining eye‐contact with the experimenter, closing their eyes, gazing at a static or a dynamic visual stimulus (in Experiment 1), or fixating an upright or inverted image of the experimenter's face (in Experiment 2). The results show that whereas maintaining eye‐contact with another person disrupts accurate imagination of this pathway, averting gaze or looking at other visual stimuli does not. We conclude that gaze aversion benefits cognitive performance, not just by disengaging visual attention from irrelevant visual information, but also by interrupting social interaction processes involved in face‐to‐face communication.     

The perception of identity by 6 1/2-month-old infants.

In Study 1, sixteen 6 1/2-month-olds were habituated to a Reversible stimulus (an upright face that could be perceived as an entirely different upright face when it was rotated 180 degrees) and to a Nonreversible stimulus (a face that could be perceived as upright in only one orientation). Following habituation for each type of stimulus, test trials paired the habituated face with a novel stimulus (an inversion of the same face). For both Reversible and Nonreversible stimuli, the physical difference between the old and new test stimuli was the same (a 180 degrees rotation); however, infants devoted more visual attention to the 180 degrees rotation only when it was a Reversible face, suggesting that the identity change was detected. Experiment 2 ruled out the explanation that infants might have failed to dishabituate to the inversion of the Nonreversible stimulus because they could not remember it. Results are interpreted as evidence that 6 1/2-month-old infants are not limited to face recognition based on similarity in pattern arrangement alone, but are capable of processing faces at a representational level.     

The role of eyes in early face processing: a rapid adaptation study of the inversion effect

The current study employed a rapid adaptation procedure to test the neuronal mechanisms of the face inversion effect (FIE) on the early face-sensitive event-related potential (ERP) component N170. Five categories of face-related stimuli (isolated eyes, isolated mouths, eyeless faces, mouthless faces, and full faces) and houses were presented in upright and inverted orientations as adaptors for inverted full face test stimuli. Strong adaptation was found for all face-related stimuli except mouths. The adaptation effect was larger for inverted than upright stimuli, but only when eyes were present. These results underline an important role of eyes in early face processing. A mechanism of eye-dependent orientation sensitivity during the structural encoding stage of faces is proposed.