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We examined the sensitivity of 2- and 3-month-old infants to radial expansion/contraction at various speeds. The stimuli comprised one radial motion pattern (expansion or contraction) and one translational motion pattern (up, down, left or right; counterbalanced across infants) placed side by side. The two patterns in each stimulus had the same speed. Three-month-old infants could discriminate between radiation and translation, even under relatively low speeds (5.31 and 2.66 degrees /s), whereas discrimination between the two patterns by 2-month-old infants was very limited. Thus, the range of speeds at which infants can detect radial expansion/contraction changes extensively between 2 and 3 months of age. This change in radial motion sensitivity may reflect the development of cortical motion mechanisms in the dorsal pathway, which is specialised to detect radial motion.

We investigated the perceptual development of motion transparency in 3- to 5-month-old infants. In two experiments we tested a total of 55 infants and examined their preferential looking behaviour. In experiment 1, we presented transparent motion as a target, and uniform motion as a non-target consisting of random-dot motions. We measured the time during which infants looked at the target and non-target stimuli. In experiment 2, we used paired-dot motions (Qian et al, 1994 Journal of Neuroscience14 7357 – 7366) as non-targets and also measured target looking time. We calculated the ratio of the target looking time to the total target and no-target looking time. In both experiments we controlled the dot size, speed, the horizontal travel distance of the dots, and the motion pattern of the dots. The results demonstrated that 5-month-old infants showed a statistically significant preference for motion transparency in almost all stimulus conditions, whereas the preference in 3- and 4-month-old infants depended on stimulus conditions. These results suggest that the sensitivity to motion transparency was robust in 5-month-olds, but not in 3- and 4-month-olds.

We examined perceptual transparency in infants. In a previous study, Johnson and Aslin (2000 Developmental Psychology36 808 – 816) found that 4-month-olds could perceive transparency in a moving chromatic display, but not in an achromatic display. In this study, we further examined perceptual transparency in infants using a static achromatic display. Considering the development of figural organisation and contrast sensitivity, we assumed that 3- to 4-month-olds would perceive transparency even in a static achromatic display. We created a transparency and a non-transparent display composed of a partially overlapping circle and square, by switching the colours. Infants aged 3 to 4 months ( n = 24) were familiarised with the transparency display (experiment 1) or with the non-transparent display (experiment 2). Then, they were confronted with a uniform colour and a two-colour figure. Infants showed novelty preference for the two-colour figure after they had been familiarised with the transparency display (experiment 1), but not after they had been familiarised with the non-transparent display (experiment 2). These results suggest that 3- to 4-month-old infants can perceive transparency in a static achromatic display.

Visual completion has been divided into two types: modal and amodal. While psychophysical studies with adults provided several common properties between modal and amodal completion, studies with infants showed differential trends in the development of these perceptual abilities. In the present study, we further examined the development of these two kinds of visual completion in infants aged 3 to 6 months. We created a display composed of a partially overlapping circle and square. The display induced either modal or amodal completion depending on the colour. Infants were familiarised with either the modal or the amodal display. After this familiarisation, the infants were tested on their discrimination between the complete figure and the broken figure. If the infants could perceptually complete the figures in the familiarisation display, they were expected to show a novelty preference for the broken figure. A total of thirty-two infants participated in the present study. Our results suggest that modal completion develops by 3 – 4 months of age, whereas amodal completion develops by 5 – 6 months of age.

We conducted four experiments on the development of motion perception in a total of 109 3- to 5-month-old infants using motion stimuli consisting of opposite-moving dots. A psychophysical study showed that adult subjects perceived two global planes with opposite-moving dots, but this global perception collapsed when paired opposite-moving dots were located within 0.4deg of one another (Qian, Andersen, & Adelson, 1994). We used this paired-dot stimulus as a non-target and the opponent motion stimulus as a target and examined target preference using methods based on forced-choice-preferential looking (Teller, 1979). In Experiment 1, we used 90 moving dots as stimuli. The results showed that 5-month-old infants had a significant preference for the targets but 4- and 3-month-olds did not. In Experiment 2, we used a small number of dots, and the results showed that 5-month-old infants did not prefer the target significantly. These results suggest that the preference for a target decreases according to the number of dots. In Experiment 3, we used opponent motion with long traveling length of the dots, and the results showed that all age groups, including 3-month-olds, had a preference for the moving targets. We showed that the preference observed in Experiment 3 was dependent not on local traveling length but on the global opponency. These results suggest that the perception of motion opponency based on a global motion cue emerges at 5 months of age (Experiments 1 and 2) and that the traveling length of the dots promote this perception (Experiments 3 and 4).

The purpose of this study was to examine 5-month-old infant's sensitivity to a shading cue with radial motion. Our stimuli were radially expanding or contracting circles with vertical or horizontal shadings. We tested infants’ preference for vertical (top- and bottom-lit) and horizontal (left- and right-lit) shadings. The results indicate that infants tested with the vertical shading showed significant preference for the top-lit shading, whereas infants tested with the horizontal shading did not show any significant preference. The fact that the significant preference was observed only in the vertical shading condition suggests that 5-month-old infants might use shading information on the basis of the “light-from-above assumption.” We revealed that even 5-month-old infants are sensitive to shading information when they are exposed to shading stimuli with radial motion.

In this paper, we assessed the developmental changes in face recognition by three infant chimpanzees aged 1–18 weeks, using preferential-looking procedures that measured the infants’ eye- and head-tracking of moving stimuli. In Experiment 1, we prepared photographs of the mother of each infant and an “average” chimpanzee face using computer-graphics technology. Prior to 4 weeks of age, the infants showed few tracking responses and no differential responses. Between 4 and 8 weeks of age, they paid greater attention to their mother's face. From 8 weeks onward, they again showed no differences, but exhibited frequent tracking responses. Experiment 2 investigated the infants’ tracking responses between a familiar human's and an “average” human face. The infants did not show any evidence of recognizing the human faces. We discuss the development of face recognition in relation to the effects of other species’ faces and postnatal visual experience.

We examined the developmental process of the sensitivity to expansion and contraction with two separate experiments. In the present study, 121 2–8-month-old-infants were participated. In the expansion search condition, 58 infants were exposed to a display consisted of an expansion (target) and 11 contractions (distractors). In the contraction search condition, the other 63 infants were exposed to a display consisted of a contraction (target) and 11 expansions (distractors). The results showed that in the expansion search condition the infants except for 2-month-olds show significant preference for the target. The sensitivity (or insensitivity) to expansion (or contraction) over 3 months of age observed in the present study is similar to the asymmetry for the perception of expansion/contraction [T. Takeuchi, Visual search of expansion and contraction, Vision Res. 37 (1997) 2083–2090]. The relation between the development of the asymmetric perception of expansion/contraction and that of the cortical pathway was discussed.

In this paper, we summarize a series of studies on the developmental changes in social cognition in mother-raised infant chimpanzees from birth to around 2 years old. The infants preferentially tracked a photograph of their mother's face at 1 month but showed indifferent preferences to faces at 2 months old. This change in facial recognition was correlated with a decrease in neonatal spontaneous smiling, increase in social smiling and a decline in neonatal imitation of facial expressions. Also at around 2 months, the infants began to show preferences for directed-gaze faces over averted gazes, and the amount of mutual gaze time between mother and infant chimpanzees increased. Thus, by 2 months of age, abilities required for dyadic interactions are already developed in chimpanzees as is the case in humans. The development of triadic interactions, however, is rather different between these two species. The infant chimpanzee can follow another's pointing or gaze at around 1 year, but even by 2 years old, does not “share” attention with the others.

In the present study, we examined whether infant Japanese macaques categorize objects without any training, using a similar technique also used with human infants (the paired-preference method). During the familiarization phase, subjects were presented twice with two pairs of different objects from one global-level category. During the test phase, they were presented twice with a pair consisting of a novel familiar-category object and a novel global-level category object. The subjects were tested with three global-level categories (animal, furniture, and vehicle). It was found that they showed significant novelty preferences as a whole, indicating that they processed similarities between familiarization objects and novel familiar-category objects. These results suggest that subjects responded distinctively to objects without training, indicating the possibility that infant macaques possess the capacity for categorization.

Emotional facial expressions are considered adaptive universal signals that emerged through phylogenetic evolution because of their crucial role for the survival of social species. From infancy humans develop dedicated neural circuits to exhibit and recognize a variety of facial expressions. However increasing evidence has shown instead that culture not only specifies when and how certain emotions can be expressed – i.e. social norms – but the mature perceptual mechanisms used to transmit and decode the visual information from emotional signals also differ between Western and Eastern adults. Specifically the mouth is more informative for transmitting emotional signals in Westerners and the eye region for Easterners engendering culture specific fixation biases towards these features. During development it is recognized that cultural differences can be observed at the level of emotional reactivity and regulation and to the culturally dominant modes of attention. Nonetheless no study has ever explored whether culture shapes the processing of facial emotional signals early in development. Our data show that by 7 months infants from both cultures visually discriminate facial expressions of emotion by relying on culturally distinct fixation strategies resembling those used by the adults from the environment in which they develop.

We investigated 3-8-month-olds' (N=62) perception of illusory contours in a Kanizsa figure by using a preferential looking technique. Previous studies suggest that this ability develops around 8 months of age. However, we hypothesized that even 3-4-month-olds could perceive illusory contours in a moving figure. To check our hypothesis, we created an illusory contour figure in which the illusory square underwent lateral movement. By rotating the elements of this figure, we created non-illusory contour figures. We found that: (1) infants preferred moving illusory contours to non-illusory contours by 3-4 months of age, and (2) only 7-8-month-olds preferred static illusory contours. Our findings demonstrate that motion information promotes infants' perception of illusory contours. Our results parallel those reported in the study of partly occluded objects ().

Orienting visual attention allows us to properly select relevant visual information from a noisy environment. Despite extensive investigation of the orienting of visual attention in infancy, it is unknown whether and how stimulus characteristics modulate the deployment of attention from birth to 4 months of age, a period in which the efficiency in orienting of attention improves dramatically. The aim of the present study was to compare 4-month-old infants’ and newborns’ ability to orient attention from central to peripheral stimuli that have the same or different attributes. In Experiment 1, all the stimuli were dynamic and the only attribute of the central and peripheral stimuli to be manipulated was face orientation. In Experiment 2, both face orientation and motion of the central and peripheral stimuli were contrasted. The number of valid trials and saccadic latency were measured at both ages. Our results demonstrated that the deployment of attention is mainly influenced by motion at birth, while it is also influenced by face orientation at 4-month of age. These findings provide insight into the development of the orienting visual attention in the first few months of life and suggest that maturation may be not the only factor that determines the developmental change in orienting visual attention from birth to 4 months.

Humans have the tendency to perceive a face even in a non-living object. Previous studies report that people perceive facial features and even interpret a personality in a car front. Following these findings, we investigated whether the perception of a face in a face-like object is mediated by human face processing, which involves both featural and configural processing. In our experiment, participants were presented with 30 face-like objects and were asked about the existence of facial features, the intensity of typicality/distinctiveness, and the intensity of facial expression. Using multiple regression analysis, which predicts the perception of a face in a face-like object, we found that the existence of eyes was a significant predictor of variance in perceiving a face in a face-like object.

A cast shadow occurs when an object blocks the light from an illumination and projects a dark region onto a surface. Previous studies have reported that adults are slower to identify an object when the object has an incongruent cast shadow than when it has a congruent cast shadow ( Castiello, 2001 ). Here, we used the familiarization-novelty preference procedure to examine whether 5- to 8-month-old infants could detect the relationship between object shapes and cast shadows. In Experiment 1, we examined the infants' ability to detect incongruency between objects and cast shadows. Results showed that 7- to 8-month olds could detect incongruence between the object shapes and the cast shadows, whereas 5- to 6-month olds did not. Yet, our control experiment showed that infants could not detect this incongruence from stimuli in which a white outline had been added to the original cast shadow to decrease the possibility of it being perceived as a cast shadow (Experiment 2). The results of these experiments demonstrate that 7- to 8-month olds responded to the congruence of cast shadows and to consistent contrast polarity between the cast shadow and its background.

The goal of this study was to ascertain at what age infants could discriminate male and female faces using only the internal features of the face. The habituation-dishabituation technique was used to estimate infants' discrimination between male and female faces. Analysis showed that 8-mo.-old infants discriminated female and male faces, whereas 6-mo.-old infants did not, but showed an asymmetry in discrimination. 6-mo.-old infants who were habituated to the female face fixated consistently longer on the novel male face in test trials, so sex discrimination was complete but not observed after habituation to male faces. Data are discussed in relation to the role of experience in face discrimination.

In this study, we transformed the real front view of facial images by cardioidal strain change. Subjects then made relative and actual age estimations of the facial images. The results were as follows. First, the transformed facial images were successfully judged in terms of the degree of transformation (cardioidal strain degree). Second, from the subjects' estimation of actual age, the effect of the transformation degree differed between female and male facial images. The effect was weaker for the male facial images than for the female. Additionally, for the male facial images the effect of the transformation differed according to face type; there was a significant effect for childlike faces. © 1999 Scripta Technica, Electron Comm Jpn Pt 3, 82(5): 39–48, 1999

The current study examined the temporal dynamics of coarse and fine spatial information processing in 7- to 8-month-old infants. The ability to discriminate between spatially filtered images was assessed by measuring infants' spontaneous preference for a changing over no-changing image sequences. In Experiments 1 and 2, we found that infants were able to discriminate between low spatial frequency (LSF) image sequences at shorter durations (150 ms) than was the case with high spatial frequency (HSF) images (300 ms). When the LSF and HSF changes were pitted against each other in hybrid images containing both spatial frequencies (Experiment 3), the 7- to 8-month-old infants showed a preference for the LSF change across all tested durations (150 ms to 600 ms). However, infants' processing of hybrid image sequences was modulated both by changes in the relative contrast energy between LSFs and HSFs (Experiment 4), and image duration (Experiment 5). Finally, we found that in 12- to 13-month-old infants, the shift toward HSF dominance occurred at shorter duration than in 7- to 8-month-old infants (Experiment 6). Our findings are among the first to provide a temporal characterization of coarse-to-fine processing in infants' perception. Possible links to the development of specialized visual pathways are discussed.

We examined whether the homogeneity of the two profiles of Rubin's goblet affects figure/ground perception in infants. We modified the two profiles of Rubin's goblet in order to compare figure/ground perception under four test patterns: (1) two profiles painted with horizontal lines (horizontal-line condition), (2) two profiles painted middle gray (uni-color condition), (3) one profile painted light gray and the other dark gray (two-color condition), and (4) a goblet painted with concentric circles (concentric-circles condition). In the horizontal-line condition the homogeneity of the profile was strengthened, and in the two-color condition the homogeneity of the profile was weakened compared to the uni-color condition, which was an original Rubin's goblet. In the concentric-circles condition the homogeneity of the reversed areas of the horizontal-line were strengthened. After infants were familiarized with each Rubin's goblet, the infants were tested on their discrimination between the two profiles and the goblet in the post-familiarization test. In horizontal-line condition, uni-color condition and concentric-circles condition infants showed a novelty preference for the two profiles in the post-familiarization test. On the other hand, in the two-color condition no preference was observed in the post-familiarization test. This means that infants perceived the goblet as figure and the two profiles as ground in the horizontal-line condition, the uni-color condition and the concentric-circles condition. We found that infants could not perceive the goblet area as figure when the homogeneity of the two profiles was weakened. It can be said that figure/ground perception in infancy is not affected by strengthened homogeneity, but is affected by weakened homogeneity.

This article presents two studies investigating the relationships between physical measurements and psychological judgments of human faces. The first study is concerned with gender and age classification, the second with femininity-masculinity and childlike-adultlike judgments of Japanese faces. The results indicate that (1) faces can be accurately classified into age categories based on physical measurements, (2) whereas age classification depends on the global information of a face, gender classification depends on its local information and (3) the femininity-masculinity judgment of male faces tends to be made on the basis of age information. The authors relate these results to the processing of KANSEI-information of, or subjective feelings about, a biological stimulus.

There is a large literature focused on the color perception of matte surface. However, recent research showed that the component of surface specular reflection, such as glossiness, also affects categorical color perception. For instance, the color term "gold" was used to name high specular stimuli within a specific range of chromaticity, which overlaps with those of yellow and orange for low specular stimuli. In the present study, we investigated whether the component of surface specular reflectance affects the color perception of 5- to 8-month-old infants by using the preferential looking technique. In the first experiment, we conducted a simple test to determine whether infants perceive yellow and gold as the same color by comparing their preference for these colors over green. If the infants perceive yellow and gold as the same color, they would show similar preference scores over green. On the other hand, if infants show different preference scores over green, it indicates that infants do not perceive yellow and gold as the same color. Only the 7-8 month-old infants showed different preference scores for gold and yellow over green. This result indicates that the 7-8 month-old infants perceive gold and yellow as different colors. In Experiment 2, we eliminated the component of specular reflectance on the gold surface and presented it against green to infants. A similar preference score of yellow over green was obtained. This result suggests that the difference between the preference scores for gold and yellow over green in Experiment 1 was based on representations of glossiness.

BackgroundIt is known that subjective contours are perceived even when a figure involves motion. However, whether this includes the perception of rigidity or deformation of an illusory surface remains unknown. In particular, since most visual stimuli used in previous studies were generated in order to induce illusory rigid objects, the potential perception of material properties such as rigidity or elasticity in these illusory surfaces has not been examined. Here, we elucidate whether the magnitude of phase difference in oscillation influences the visual impressions of an object's elasticity (Experiment 1) and identify whether such elasticity perceptions are accompanied by the shape of the subjective contours, which can be assumed to be strongly correlated with the perception of rigidity (Experiment 2).Methodology/principal findingsIn Experiment 1, the phase differences in the oscillating motion of inducers were controlled to investigate whether they influenced the visual impression of an illusory object's elasticity. The results demonstrated that the impression of the elasticity of an illusory surface with subjective contours was systematically flipped with the degree of phase difference. In Experiment 2, we examined whether the subjective contours of a perceived object appeared linear or curved using multi-dimensional scaling analysis. The results indicated that the contours of a moving illusory object were perceived as more curved than linear in all phase-difference conditions.Conclusions/significanceThese findings suggest that the phase difference in an object's motion is a significant factor in the material perception of motion-related elasticity.

A radially expanding flow with a linear positive speed gradient is perceived as a rigid object approaching the observer, whereas such a flow having no or a reduced speed gradient is perceived as a non-rigid, two-dimensionally deforming object (De Bruyn & Orban, 1990). We tested elementary school-aged children (younger children, 6–9 years, and older children, 9–11 years) and adults (20–22 years) to examine the development of the perception of rigidity. The results suggest that the perception of rigidity in response to a radial flow pattern with a speed gradient is similar in older (but not younger) children and adults. The development of rigidity perception from a radial flow pattern may be related to the maturation of the dorsal and ventral visual pathways during the elementary school years. Copyright © 2016 John Wiley & Sons, Ltd.

The current study examined infants' sensitivity to Wollaston's effect: When identical eyes are placed in differently angled faces, the perceived gaze direction shifts toward the orientation of the face such that physically, the direct gaze is perceived as averted toward the orientation of the face. Consistent with Wollaston's effect, we found that looking toward direct and averted gaze by 4- to 5- and 7- to 8-month-olds (n = 40) was affected by the head orientation context. These results demonstrate that infants aged 4 to 5 and 7 to 8 months integrate eye and head information to perceive another's gaze direction. In light of recent psychophysical findings, the current results suggest that the visual function supporting constant gaze perception across head rotation is already at work by 4 to 5 months of age.

We studied whether 5-month-old to 8-month-old infants process faces in a size-invariant manner by applying the fNIRS-adaptation paradigm used in our previous study. We used near-infrared spectroscopy to measure hemodynamic responses in the temporal regions of infants' brains during the repeated presentation of an identical face and different faces while changing the size of the faces. As a result, we found that (a) the hemodynamic responses in the channels around the T5 and T6 positions increased significantly during the presentation of different faces and (b) the hemodynamic responses in these channels showed attenuation to the presentation of the same face compared with the presentation of different faces even when the size of the faces altered. Our findings indicated that infants could show adaptation to the same face despite size alterations and that this processing occurred in the bilateral temporal areas.

In three-dimensional face recognition studies, it is well known that viewing rotating faces enhance face recognition. For infants, our previous study indicated that 8-month-old infants showed recognition of three-dimensional rotating faces with a direct gaze, and they did not learn with an averted gaze. This suggests that gaze direction may affect three-dimensional face recognition in infants. In this experiment, we used near-infrared spectroscopy to measure infants' hemodynamic responses to averted gaze and direct gaze. We hypothesized that infants would show different neural activity for averted and direct gazes. The responses were compared with the baseline activation during the presentation of non-face objects. We found that the concentration of oxyhemoglobin increased in the temporal cortex on both sides only during the presentation of averted gaze compared with that of the baseline period. This is the first study to show that infants' brain activity in three-dimensional face processing is different between averted gaze and direct gaze.

The current study examined color constancy in infants using a familiarization paradigm. We first obtained isoluminance in each infant as defined by the minimum motion paradigm and used these data to control the luminance of stimuli in the main experiments. In the familiarization phase of the main experiment, two identical smiling face patterns were presented side by side in surrounding patches of various colors, presented on a computer-controlled display. The colors in the stimuli simulated the chromaticity of color chips (OSA uniform color scale) under a certain illuminant. The chromaticity of the whole pattern was changed to simulate illuminant color changes in the test phase except for one of the smiling face patterns that preserved its chromaticity and luminance. If infants had color constancy, they would perceive the face without any change in the chromaticity and luminance as a novel object surface and would show preference for it. Two types of illuminant changes were applied, from 6500 to 10,000 K and from 6500 to 4500 K, in correlated color temperature. The luminance contrast between the background and the face patterns remained constant across the illuminant changes. Our results showed that 4.5-month-old infants preferred the pattern that did not change its chromaticity under both types of illuminant color changes. This finding suggests that 4.5-month-olds may have color constancy under the strict control of luminance contrast.

We explored the ability of infants to recognize the smell of daily foods, including strawberries and tomatoes, by using a preferential-looking-technique. Experiment 1 was conducted while strawberries were in season (from March to June) in order to enhance the frequency of participant exposure to strawberries outside of the laboratory. Thirty-seven infants aged 6–8 months were tested with a stimulus composed of a pair of photos of strawberries and tomatoes placed side by side and accompanied by a strawberry odor, a tomato odor, or no odors. Infants showed a preference for the strawberry picture when they smelled the congruent odor, but no such preference for the tomato picture. These results suggest that even young infants can recognize olfactory–visual congruency. We conducted Experiment 2 while strawberries were out of season (from July to September) to reduce participant exposure to strawberries in their daily life. Twenty-six infants aged 6–8 months were tested with a stimulus composed of a pair of photos of strawberries and tomatoes placed side by side and accompanied by a strawberry odor, or no odors. In Experiment 2, the olfactory–visual binding effect disappeared. This implies that visual–olfactory binding is triggered by an observer’s experience.

Recent adult functional magnetic resonance imaging (fMRI) studies reported that face-sensitive cortical areas showed attenuated responses to the repeated presentation of an identical facial image compared to the presentation of different facial images (fMRI-adaptation effects: e.g., Andrews and Ewbank, 2004). Building upon this finding, the current study, employing the adaptation paradigm, used near-infrared spectroscopy (NIRS) to explore the neural basis of face processing in infants. In Experiment 1, we compared hemodynamic responses in the bilateral temporal regions during the repeated presentation of the same face (the same-face condition) and the sequential presentation of different faces (the different-face condition). We found that (1) hemodynamic responses in the channels around the T5 and T6 regions increased during the presentation of different faces compared to those during the presentation of different objects; and that (2) these channels showed significantly lower response in the same-face condition than in the different-face condition, demonstrating the neural adaptation effect in 5- to 8-month-olds as measured by NIRS. In Experiment 2, when faces in both the same-face and different-face conditions were changed in viewpoint, lower hemodynamic responses in the same-face condition were found in 7- to 8-month-olds but not in 5- to 6-month-olds. Our results suggest that faces are represented in a viewpoint-invariant manner in 7- and 8-month-old infants.

Eye gaze is an important tool for social contact. In this study, we investigated whether direct gaze facilitates the recognition of three-dimensional face images in infants. We presented artificially produced face images in rotation to 6–8 month-old infants. The eye gaze of the face images was either direct or averted. Sixty-one sequential images of each face were created by rotating the vertical axis of the face from frontal view to ±30°. The recognition performances of the infants were then compared between faces with direct gaze and faces with averted gaze. Infants showed evidence that they were able to discriminate the novel from familiarized face by 8 months of age and only when gaze is direct. These results suggest that gaze direction may affect three-dimensional face recognition in infants.

This study investigated infants' ability to learn artificially produced three-dimensional faces and non-face objects by using the three-dimensional graphic software. We created three-dimensional faces and non-face objects that contained no texture or fixed light source and used a familiarization-novelty preference procedure to familiarize infants with multiple views of a face or a shoe (non-face object). We set two familiarization presentations: one of sequentially rotating images of a single object (rotating presentation) and another of 6 different static view images (static presentation). After familiarization, we checked infants' recognition of the learning objects between these conditions. In Experiment 1, we examined the infants' ability to learn face and non-face objects in static and rotating presentations. Results showed that 6- to 8-month-old infants could learn the non-face objects in both presentations, while they could not learn the faces in the rotating presentation. In Experiments 2 and 3, we modified the rotating presentation for face learning. In Experiment 2, we used three-quarter views at test. In Experiment 3, we set a slower speed rotation. However, the infants still could not learn the faces. These results showed that infants' ability to learn faces differs from their ability to learn non-face objects.

A "transfer-across-depth-cues" method was used to explore the development of the ability to generate and use spatial representations of an object as specified by static pictorial depth cues. Infants were habituated to an object with depth specified by one cue and then presented with the same shape with depth specified by a different cue. Only if an abstract representation of that object had been formed could transfer across cues occur. Shading and line junctions uniquely determined the 3D shapes in these displays so that they appeared to be either a slice of cake with a flat top or a rocket. Without these cues, both line drawings were identical. Infants aged 6 to 7 months showed significant evidence of transfer, while infants aged 4 to 5 months did not. A control experiment demonstrated that the younger infants could discriminate between the objects when a single depth cue specified the shapes. These results are similar to our previous findings, which indicated that 6- to 7-month-old infants show transfer across shading and surface-contour cues, specifying convex and concave surfaces (A. Tsuruhara, T. Sawada, S. Kanazawa, M. K. Yamaguchi, & A. Yonas, 2009). This work supports the hypothesis that the ability to form 3D spatial representations from pictorial depth cues develops at about 6 months of age.

Adult observers can quickly identify specific actions performed by an invisible actor from the points of lights attached to the actor's head and major joints. Infants are also sensitive to biological motion and prefer to see it depicted by a dynamic point-light display. In detecting biological motion such as whole body and facial movements, neuroimaging studies have demonstrated the involvement of the occipitotemporal cortex, including the superior temporal sulcus (STS). In the present study, we used the point-light display technique and near-infrared spectroscopy (NIRS) to examine infant brain activity while viewing facial biological motion depicted in a point-light display. Dynamic facial point-light displays (PLD) were made from video recordings of three actors making a facial expression of surprise in a dark room. As in Bassili's study, about 80 luminous markers were scattered over the surface of the actor's faces. In the experiment, we measured infant's hemodynamic responses to these displays using NIRS. We hypothesized that infants would show different neural activity for upright and inverted PLD. The responses were compared to the baseline activation during the presentation of individual still images, which were frames extracted from the dynamic PLD. We found that the concentration of oxy-Hb increased in the right temporal area during the presentation of the upright PLD compared to that of the baseline period. This is the first study to demonstrate that infant's brain activity in face processing is induced only by the motion cue of facial movement depicted by dynamic PLD.

Background Perceived spatial intervals between successive flashes can be distorted by varying the temporal intervals between them (the “tau effect”). A previous study showed that a tau effect for visual flashes could be induced when they were accompanied by auditory beeps with varied temporal intervals (an audiovisual tau effect). Methodology/Principal Findings We conducted two experiments to investigate whether the audiovisual tau effect occurs in infancy. Forty-eight infants aged 5–8 months took part in this study. In Experiment 1, infants were familiarized with audiovisual stimuli consisting of three pairs of two flashes and three beeps. The onsets of the first and third pairs of flashes were respectively matched to those of the first and third beeps. The onset of the second pair of flashes was separated from that of the second beep by 150 ms. Following the familiarization phase, infants were exposed to a test stimulus composed of two vertical arrays of three static flashes with different spatial intervals. We hypothesized that if the audiovisual tau effect occurred in infancy then infants would preferentially look at the flash array with spatial intervals that would be expected to be different from the perceived spatial intervals between flashes they were exposed to in the familiarization phase. The results of Experiment 1 supported this hypothesis. In Experiment 2, the first and third beeps were removed from the familiarization stimuli, resulting in the disappearance of the audiovisual tau effect. This indicates that the modulation of temporal intervals among flashes by beeps was essential for the audiovisual tau effect to occur (Experiment 2). Conclusions/Significance These results suggest that the cross-modal processing that underlies the audiovisual tau effect occurs even in early infancy. In particular, the results indicate that audiovisual modulation of temporal intervals emerges by 5–8 months of age.

Previously, we used near-infrared spectroscopy (NIRS) to measure infant's brain activity during face processing by detecting changes in hemodynamic responses, oxy-Hb, deoxy-Hb, and total-Hb concentrations [1,2]. We found that the right temporal cortex of the brain was activated when infants looked at upright frontal faces rather than inverted faces, and at the frontal view as well as the profile view on 8-month-olds. In the present study, we investigated 7- and 8-month-olds' brain activity related to the perception of mother's and stranger's faces by NIRS. The finding was that oxy-Hb and total-Hb concentrations in the right temporal cortex increased against the baseline during presentation of the mother's face. For strangers' faces, the total-Hb concentration in the right temporal cortex was greater than the baseline. By contrast, oxy- and total-Hb concentrations in the left temporal cortex increased only in the presentation of mother's face. The great activity in the right temporal region for faces irrespective of familiarity was consistent with a predominance of the right temporal cortex found previously in infants [1,2] as well as functional magnetic resonance imaging (fMRI) studies in adults [3,4]. In contrast to the activity in the right temporal cortex, the greater hemodynamic response in the left temporal cortex was observed only in the mother's face condition. These findings suggest that the processing of the mother's face enhances activity in bilateral temporal cortex. This is the first study to clarify the location of brain activity in infants related to the perception of their mother's face.

We report asymmetrical cortical responses (steady-state visual evoked potentials) to radial expansion and contraction in human infants and adults. Forty-four infants (22 3-month-olds and 22 4-month-olds) and nine adults viewed dynamic dot patterns which cyclically (2.1 Hz) alternate between radial expansion (or contraction) and random directional motion. The first harmonic (F1) response in the steady-state VEP response must arise from mechanisms sensitive to the global radial motion structure. We compared F1 amplitudes between expansion-random and contraction-random motion alternations. F1 amplitudes for contraction were significantly larger than those for expansion for the older infants and adults but not for the younger infants. These results suggest that the human cortical motion mechanisms have asymmetrical sensitivity for radial expansion vs. contraction, which develops at around 4 months of age. The relation between development of sensitivity to radial motion and cortical motion mechanisms is discussed.

There have been numerous studies of the Munker-White illusion, but few have focused on the perceptual development of it in human infants. Therefore, this study explores the perceptual development of the Munker-White illusion in infants. In this study, we created two kinds of Munker-White illusion patterns that had different subjective saturation, and investigated infants' preference for these two kinds of patterns. Previous studies have shown that infants had a preference for high colorimetric saturation stimuli. Therefore, if infants could perceive the Munker-White illusion, we postulated that they would show a preference for stimuli that have high subjective saturation. In experiment 1, 4-8-month-old infants showed a preference for the stimuli that had a higher subjective saturation. In experiment 2, we confirmed that the preference shown in experiment 1 was not dependent on the difference of the 'color area ratio' that existed in the stimuli of experiment 1. Our results suggest that 4-8-month-old infants can perceive Munker-White illusion.

The purpose of this study was to explore the infants' ability to perceive 3D shape from pictorial depth cues. While several previous studies showed that infants discriminate between displays which differ in pictorial information for depth and can use this information to direct reaching, it is not clear that infants form a common representation of an object's shape from different pictorial depth cues. To clarify the infants' ability for pictorial depth cues, we employed a "transfer-across-depth-cues" method with four-to-five-month-old and six-to-seven-month-old infants. Using this method, we examined the transfer between two pictorial depth cues: shading and surface contours. Infants were habituated to a 3D shape specified by one cue and were then presented with the same shape and a novel shape, both specified by the other depth cue. In this situation the familiar shape could be detected only if one perceived the 3D shape from the pictorial depth cues. Our results indicated that older infants showed a significant novelty preference while the younger group did not. We found that, at least by six-to-seven-months old, infants develop a common representation over different pictorial depth cues.

Previous psychophysical studies have shown that the adult human visual system makes use of form information such as occlusion to determine whether to integrate or segregate local motion signals (J. McDermott, Y. Weiss, & E. H. Adelson, 2001). Using the displays developed by McDermott et al., these experiments examined whether occlusion and amodal completion affect motion integration in infants. After familiarizing infants with the displays, infants were tested for preference between coherent motion and local motion displays. The results indicate that 5- to 8-month-olds, but not 3-month-olds, showed a significantly greater preference for the local motion display under occlusion conditions. These results suggest that 5- to 8-month-olds perceive motion to be coherent under occlusion conditions. The results are compatible with previous data showing that amodal completion of static information emerges at around 5-6 months of age (Y. Otsuka et al., 2006a), adding that infants use amodal completion for motion integration at this same time.

Although lots of studies about neon color spreading have been reported, few of these studies have focused on the perceptual development of it in human infants. Therefore, this study explores the perceptual development of neon color spreading in infants. In experiment 1, we examined 3-6-month-olds' perception of neon color spreading in static conditions. In experiment 2, we examined 3-6-month-olds' perception of neon color spreading in moving conditions. Our results suggest that while only 5-6-month-old infants show a preference for neon color spreading in the static condition, 3-4-month-old infants also prefer neon color spreading if motion information is available.