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This study investigated the difference in the McGurk effect between own-race-face and other-race-face stimuli among Japanese infants from 5 to 9 months of age. The McGurk effect results from infants using information from a speaker’s face in audiovisual speech integration. We hypothesized that the McGurk effect varies with the speaker’s race because of the other-race effect, which indicates an advantage for own-race faces in our face processing system. Experiment 1 demonstrated the other-race effect on audiovisual speech integration such that the infants ages 5–6 months and 8–9 months are likely to perceive the McGurk effect when observing an own-race-face speaker, but not when observing an other-race-face speaker. Experiment 2 found the other-race effect on audiovisual speech integration regardless of irrelevant speech identity cues. Experiment 3 confirmed the infants’ ability to differentiate two auditory syllables. These results showed that infants are likely to integrate voice with an own-race-face, but not with an other-race-face. This implies the role of experiences with own-race-faces in the development of audiovisual speech integration. Our findings also contribute to the discussion of whether perceptual narrowing is a modality-general, pan-sensory process.

Previous functional neuroimaging studies imply a crucial role of the superior temporal regions (e.g., superior temporal sulcus: STS) for processing of dynamic faces and bodies. However, little is known about the cortical processing of moving faces and bodies in infancy. The current study used functional near-infrared spectroscopy (fNIRS) to directly compare cortical hemodynamic responses to dynamic faces (videos of approaching people with blurred bodies) and dynamic bodies (videos of approaching people with blurred faces) in infants' brain. We also examined the body-inversion effect in 5- to 8-month-old infants using hemodynamic responses as a measure. We found significant brain activity for the dynamic faces and bodies in the superior area of bilateral temporal cortices in both 5- to 6-month-old and 7- to 8-month-old infants. The hemodynamic responses to dynamic faces occurred across a broader area of cortex in 7- to 8-month-olds than in 5- to 6-month-olds, but we did not find a developmental change for dynamic bodies. There was no significant activation when the stimuli were presented upside down, indicating that these activation patterns did not result from the low-level visual properties of dynamic faces and bodies. Additionally, we found that the superior temporal regions showed a body inversion effect in infants aged over 5 months: the upright dynamic body stimuli induced stronger activation compared to the inverted stimuli. The most important contribution of the present study is that we identified cortical areas responsive to dynamic bodies and faces in two groups of infants (5-6-months and 7-8-months of age) and we found different developmental trends for the processing of bodies and faces.

Significance Recent studies in neuroscience suggest that visual perception is not processed by the purely feed-forward system but by the interaction of forward, horizontal, and feedback processing called recurrent loops. The present study examined the development of recurrent processing using visual backward masking, a perceptual phenomenon in which a visual stimulus is rendered invisible by a mask that follows the stimulus, possibly because of the disruption of recurrent processing. We showed that backward masking is ineffective for infants under 7 mo of age and that they can perceive masked objects that older infants cannot see because of masking. These results suggest that recurrent processing is immature in early infancy and that the mechanisms of visual perception drastically change around this age., Recurrent loops in the visual cortex play a critical role in visual perception, which is likely not mediated by purely feed-forward pathways. However, the development of recurrent loops is poorly understood. The role of recurrent processing has been studied using visual backward masking, a perceptual phenomenon in which a visual stimulus is rendered invisible by a following mask, possibly because of the disruption of recurrent processing. Anatomical studies have reported that recurrent pathways are immature in early infancy. This raises the possibility that younger infants process visual information mainly in a feed-forward manner, and thus, they might be able to perceive visual stimuli that adults cannot see because of backward masking. Here, we show that infants under 7 mo of age are immune to visual backward masking and that masked stimuli remain visible to younger infants while older infants cannot perceive them. These results suggest that recurrent processing is immature in infants under 7 mo and that they are able to perceive objects even without recurrent processing. Our findings indicate that the algorithm for visual perception drastically changes in the second half of the first year of life.

Little is known about the time of development of binocular suppression. In the present study, we evaluated the emergence of binocular suppression in infants by using continuous flash suppression (CFS, Tsuchiya and Koch, 2005). In our experiment, one eye of infants was presented with a static face image at one side of the screen, while another eye was presented with dynamic Mondrian patterns in full screen. Adult observers confirmed that the static face image was consciously repressed by the changing Mondrian patterns. If binocular suppression was functional, the infants would not perceive the face and thus would not show any preference in the experiment. However, if binocular suppression in the infants was not yet acquired, they would perceive the face and the Mondrian patterns at the same time and would thus show preference for the side where the face was presented. The results showed that infants aged 2-3 months, but not those aged 4-5 months, detected the position of the face. Furthermore, this detection was not due to weak contrast sensitivity to the dynamic Mondrian mask. These results indicated that the immature binocular visual system may perceive different images from different eyes simultaneously and that infants may lose this ability after establishing binocular suppression at 4-5 months of age.

Previous studies have revealed perceptual narrowing for the own-race-face in face discrimination, but this phenomenon is poorly understood in face and voice integration. We focused on infants’ brain responses to the McGurk effect to examine whether the other-race effect occurs in the activation patterns. In Experiment 1, we conducted fNIRS measurements to find the presence of a mapping of the McGurk effect in Japanese 8- to 9-month-old infants and to examine the difference between the activation patterns in response to own-race-face and other-race-face stimuli. We used two race-face conditions, own-race-face (East Asian) and other-race-face (Caucasian), each of which contained audiovisual-matched and McGurk-type stimuli. While the infants (N = 34) were observing each speech stimulus for each race, we measured cerebral hemoglobin concentrations in bilateral temporal brain regions. The results showed that in the own-race-face condition, audiovisual-matched stimuli induced the activation of the left temporal region, and the McGurk stimuli induced the activation of the bilateral temporal regions. No significant activations were found in the other-race-face condition. These results mean that the McGurk effect occurred only in the own-race-face condition. In Experiment 2, we used a familiarization/novelty preference procedure to confirm that the infants (N = 28) could perceive the McGurk effect in the own-race-face condition but not that of the other-race-face. The behavioral data supported the results of the fNIRS data, implying the presence of narrowing for the own-race face in the McGurk effect. These results suggest that narrowing of the McGurk effect may be involved in the development of relatively high-order processing, such as face-to-face communication with people surrounding the infant. We discuss the hypothesis that perceptual narrowing is a modality-general, pan-sensory process.

Sound symbolism, which is the systematic and non-arbitrary link between a word and its meaning, has been suggested to bootstrap language acquisition in infants. However, it is unclear how sound symbolism is processed in the infants’ brain. To address this issue, we investigated the cortical response in 11-month-old infants in relation to sound-symbolic correspondences using near-infrared spectroscopy (NIRS). Two types of stimuli were presented: a novel visual stimulus (e.g., a round shape) followed by a novel auditory stimulus that either sound-symbolically matched (moma) or mismatched (kipi) the shape. We found a significant hemodynamic increase in the right temporal area, when the sound and the referent sound were symbolically matched, but this effect was limited to the moma stimulus. The anatomical locus corresponds to the right posterior superior temporal sulcus (rSTS), which is thought to process sound symbolism in adults. These findings suggest that prelinguistic infants have the biological basis to detect cross-modal correspondences between word sounds and visual referents.

Summary Motion direction of a large high-contrast pattern is more difficult to perceive than that of a small one [ 1 ]. This counterintuitive perceptual phenomenon is considered to reflect surround suppression, a receptive field property observed in the visual cortex [ 2 , 3 , 4 , 5 ]. Here, we demonstrate that this phenomenon can be observed in human infants. Infants at 7 to 8 months of age showed higher sensitivity for a small motion stimulus than for a large one. However, infants under 6 months showed the opposite result; motion sensitivity was higher for a large stimulus. These results suggest that suppressive surround regions beyond classical receptive fields develop in the second half of the first year. Moreover, we examined the size of spatial summation in infants and found that the spatial summation area shrinks from 3 to 8 months of age. Our findings suggest that the summation area for motion is broad with no surround suppression in early infancy and that it narrows and acquires suppressive surround regions in the first year of life, which might reflect the developmental changes in the receptive field structure.

Infants less than 1 year old are known to preferentially look at pictures of motion illusion induced by luminance gradation. However, the mechanisms underlying infant’s perception of motion illusion remain unclear. The current study analyzed the eye movement patterns of infants perceiving a motion illusion induced by stationary luminance gradations (a derivative of the Fraser-Wilcox illusion). Infants produced the same movement patterns that increase the magnitude of illusory motion in adults. We conclude that infants and adults similarly perceive motion illusion.

Motion direction of a large high-contrast pattern is more difficult to perceive than that of a small one [1]. This counterintuitive perceptual phenomenon is considered to reflect surround suppression, a receptive field property observed in the visual cortex [2-5]. Here, we demonstrate that this phenomenon can be observed in human infants. Infants at 7-8 months of age showed higher sensitivity for a small motion stimulus than for a large one. However, infants under 6 months showed the opposite result; motion sensitivity was higher for a large stimulus. These results suggest that suppressive surround regions beyond classical receptive fields develop in the second half of the first year. Moreover, we examined the size of receptive fields in infants using this phenomenon and found that the center region of receptive fields shrinks from 3 months to 8 months. Our findings suggest that receptive fields related to motion processing are broad and do not have extra-classical receptive fields in early infancy, and that they become narrower and acquire suppressive surround regions in the first year of life.

Our visual system can rapidly process stimuli relevant to our current behavioral goal within various irrelevant stimuli in natural scenes. This ability to detect and identify target stimuli during non target stimuli has been mainly studied in adults, so that the development of this high-level visual function has been unknown among infants, although it has been shown that 15-month-olds' temporal thresholds of face visibility are close to those of adults. However, we demonstrate here that infants younger than 15 months can identify a target face among nontarget but meaningful scene images. In the current study, we investigated infants' ability to detect and identify a face in a rapid serial visual presentation. Experiment 1 examined whether 5- to 8-month-olds could discriminate the difference in the presentation duration of visual streams (100 vs. 11 ms). Results showed that 7- and 8-month olds successfully discriminated between the presentation durations. In Experiment 2, we examined whether 5- to 8-month-olds could detect the face presented for 100 ms and found that 7- and 8-month-olds could detect the face embedded in rapid serial visual streams. To further clarify the face processing at this age of infants, we tested whether infants could identify upright and inverted faces in rapid visual streams in Experiments 3a and 3b. The results showed that 7- and 8-month-olds identified upright faces, but not inverted faces, during the visual stream, which reflected face inversion effects. Overall, we suggest that the temporal speed of face processing at 7 and 8 months of age would be comparable to that of adults. (C) 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

View-invariant face processing emerges early in life. A previous study (Nakato et al., 2009) measured infant hemodynamic responses to faces from the frontal and profile views in the bilateral temporal areas, which have been reported to be involved in face processing using near-infrared spectroscopy. It was reported that 5-month-old infants showed increased oxyhemoglobin (oxy-Hb) responses to frontal faces, but not to profile faces. In contrast, 8-month-old infants displayed increased oxy-Hb responses to profile faces as well as to frontal faces. In this study, we used the experimental method developed in the previous study to investigate the development of view-invariant face processing, every month for 5 months (from the first 3–8 months of life). We longitudinally measured hemodynamic responses to faces from the frontal and profile views in 14 infants. The longitudinal measurements allowed us to investigate individual differences in each participant. We modeled each infant's hemodynamic oxy-Hb responses to frontal and profile faces using linear regression analysis. Processing of profile faces emerged later and underwent larger improvements than that of frontal faces. We also found an anticorrelation between the speed of improvement in face processing and the hemodynamic response to faces at the age of 3- months. Group analysis of the averaged hemodynamic data from the 14 infants using linear regression revealed that the processing of profile faces emerged between 5 and 6 months of age. Infant view-invariant face processing developed first for frontal faces. This was followed by the emergence of processing of profile faces.

The human perceptual system enables us to extract visual properties of an object’s material from auditory information. In monkeys, the neural basis underlying such multisensory association develops through experience of exposure to a material; material information could be processed in the posterior inferior temporal cortex, progressively from the high-order visual areas. In humans, however, the development of this neural representation remains poorly understood. Here, we demonstrated for the first time the presence of a mapping of the auditory material property with visual material (“Metal” and “Wood”) in the right temporal region in preverbal 4- to 8-month-old infants, using near-infrared spectroscopy (NIRS). Furthermore, we found that infants acquired the audio-visual mapping for a property of the “Metal” material later than for the “Wood” material, since infants form the visual property of “Metal” material after approximately 6 months of age. These findings indicate that multisensory processing of material information induces the activation of brain areas related to sound symbolism. Our findings also indicate that the material’s familiarity might facilitate the development of multisensory processing during the first year of life.

Perceptual color space is continuous; however, we tend to divide it into only a small number of categories. It is unclear whether categorical color perception is obtained solely through the development of the visual system or whether it is affected by language acquisition. To address this issue, we recruited prelinguistic infants (5- to 7-mo-olds) to measure changes in brain activity in relation to categorical color differences by using near-infrared spectroscopy (NIRS). We presented two sets of geometric figures to infants: One set altered in color between green and blue, and the other set altered between two different shades of green. We found a significant increase in hemodynamic responses during the between-category alternations, but not during the within-category alternations. These differences in hemodynamic response based on categorical relationship were observed only in the bilateral occipitotemporal regions, and not in the occipital region. We confirmed that categorical color differences yield behavioral differences in infants. We also observed comparable hemodynamic responses to categorical color differences in adults. The present study provided the first evidence, to our knowledge, that colors of different categories are represented differently in the visual cortex of prelinguistic infants, which implies that color categories may develop independently before language acquisition.

We examined whether infants aged 6-8 months show object-based attention using the preferential looking method. In object-based attention, which is a prerequisite function for efficient real-world processing of various stimuli, a target that appears at a cued object is detected and processed faster than a target appearing at an uncued object. We presented 6- to 8-month-old infants with the visual stimuli consisting of two white vertical rectangles side by side, in which a target appearing at 1) the cued location, 2) the end opposite to the cued location, and 3) another rectangle's end following the cue, using an established paradigm, and measured each infant's first saccade to the target. We found that (1) infants of all ages could make the first saccade to the target appearing at the cued location, (2) only 8-month-old infants made the first saccade to the target appearing at the opposite end to the cued location more accurately than to the target appearing at the other rectangle's end. These results indicate that object-based attention might be acquired around 8 months compared with the spatial cueing effect that appears at around 6 months. Our findings suggest that the objects play a role in visual attention in 8-month-old infants.

Objective: We aimed to clarify the validity of fNIRS measurement for assessing the methylphenidate (MPH) induced neuropharmacological effect in medication-naive children with attention deficit hyperactivity disorder (ADHD) with or without comorbid autism spectrum disorder (ASD), thereby providing the first evidence for differing neurofunctional pathology between the two groups. Methods: We monitored the effects of a single acute clinical dose of MPH on the cortical hemodynamics of 32 medication-naive ADHD children (ADHD with ASD n=11 and ADHD without ASD n=21) performing a go/no-go task before and 1.5 h after MPH or placebo administration, using a randomized, double-blind, placebo-controlled, crossover design. In addition, all subjects’ symptoms were monitored using the Japanese version of the ADHD Rating Scale-IV (ADHDRS- IV-J) before and one month after MPH administration. Results: Medication-naive ADHD children without ASD exhibited reduced right prefrontal activation. MPH medication elicited significant right prefrontal activation except in comparative conditions associated with the placebo effect. Medication-naive ADHD children with ASD exhibited marginal activation before the first day of medication and reduced activation after MPH medication in the right prefrontal area. While the neuropharmacological effects of MPH were different, ADHD-RS-IV-J scores were significantly improved one month after MPH administration in ADHD groups both with and without ASD. Conclusion: Taken together, these results suggest that ADHD with ASD is characterized by a different underlying neurofunctional pathology for inhibition control than that without ASD. To our knowledge, this is the first comparative neuroimaging study between ADHD patients with and without comorbid ASD.

Infants' ability to recognize uncanny human faces increases during the first year of life. In turn, their ability to recognize faces of other species declines at almost the same period (perceptual narrowing). In the current study, we aimed to clarify the relationship between the perception of uncanniness of faces and perceptual narrowing in infants and adults. We used the “uncanny valley task,” in which the participants were required to discriminate the faces of humans and monkeys by different eye size. Results showed that 3- to 5-month-old infants could not discriminate either monkey or human faces by eye size, whereas 6- to 8-month olds could. Adults showed higher discrimination performance for human than monkey faces and perceived the human faces with extremely large or small eyes as exceedingly eerie. Our results suggest that perception of uncanniness of faces is formed after perceptual narrowing.

Human can easily detect other's eyes and gaze from early in life. Such sensitivity is supported by the contrast polarity of human eyes, which have a white sclera contrasting with the darker colored iris (Kobayashi & Kohshima, (1997). Nature, 387, 767-768; Kobayashi & Kohshima, (2001). Journal of Human Evolution, 40, 419-435). Recent studies suggest that the contrast polarity around the eyes plays an important role in infants' face processing. Newborns preferred upright face images to inverted ones in contrast-preserved faces, but not in contrast-reversed faces (Farroni et al., (2005). Proceedings of National Academy of Sciences of the United States of America, 102, p. 17245-17250). Seven- to 8-month-old infants failed to discriminate between faces when the contrast polarity of eyes was reversed (Otsuka et al., (2013). Journal of Experimental Child Psychology, 115, 598-606). Neuroimaging study with adults revealed that full-negative faces induced less activation in the right fusiform gyrus than either full-positive faces or negative faces with contrast-preserved eyes (Gilad et al., (2009). Proceedings of National Academy of Sciences of the United States of America, 106, p. 5353-5358). In the present study, we investigated whether contrast-reversed eyes diminish infants' brain activity related to face processing. We measured hemodynamic responses in the bilateral temporal area of 5- to 6-month-old infants. Their hemodynamic responses to faces with positive eyes and those with negative eyes were compared against the baseline activation during the presentation of object images. We found that the presentation of faces with positive eyes increased the concentration of oxy-Hb in the right temporal area and those of total-Hb in the bilateral temporal areas. No such change occurred for faces with negative eyes. Our results suggest the importance of contrast polarity of the eyes in the face-selective neural responses from early development.

Just as faces share the same basic arrangement of features, with two eyes above a nose above a mouth, human eyes all share the same basic contrast polarity relations, with a sclera lighter than an iris and a pupil, and this is unique among primates. The current study examined whether this bright–dark relationship of sclera to iris plays a critical role in face recognition from early in development. Specifically, we tested face discrimination in 7- and 8-month-old infants while independently manipulating the contrast polarity of the eye region and of the rest of the face. This gave four face contrast polarity conditions: fully positive condition, fully negative condition, positive face with negated eyes (“negative eyes”) condition, and negated face with positive eyes (“positive eyes”) condition. In a familiarization and novelty preference procedure, we found that 7- and 8-month-olds could discriminate between faces only when the contrast polarity of the eyes was preserved (positive) and that this did not depend on the contrast polarity of the rest of the face. This demonstrates the critical role of eye contrast polarity for face recognition in 7- and 8-month-olds and is consistent with previous findings for adults.

Infants’ recognition of facial expressions develops during postnatal life. Previous studies have showed that infants learned to discriminate the facial expression of basic emotions such as happy or angry expressions by approximately 7 months of age. Although infants’ recognition of intense expressions has been demonstrated, their recognition of subtle expressions is unclear. The present study examined whether 6- to 7-month-old infants recognize the subtle anger expression. We presented the subtle expressions either as static or as dynamic displays. In static presentations, infants recognized the subtle anger expression. This result suggests that the infants have high sensitivity to angry expressions which signal a dangerous situation. In dynamic presentations, infants did not recognize the subtle anger expression. Infants around this age rarely see the dynamic anger expression in their daily lives. Their limited experience with dynamic expressions of anger might make it hard to recognize a dynamic subtle expression. Infants could learn to utilize facial motions in the development of recognition of facial expressions.

Both horizontal and vertical binocular disparities produce depth perception in adults. In developmental studies, infants aged around 4 to 6 months were shown to perceive depth from horizontal disparity. However, infants’ sensitivity to vertical disparity has not been shown clearly. To examine the sensitivity in infants, this study measured preferential looking behavior of infants aged 20 to 27 weeks. Results showed a significant preference for the stimulus with vertical disparity, providing the first evidence of infants’ sensitivity to vertical disparity. The infants in the same age group did not show preference for stimulus with horizontal disparity when the stimulus were comparable to the stimulus with vertical disparity, while their sensitivity to horizontal disparity was confirmed with the stimuli used in a previous study. Our results would suggest that properties in processing horizontal and vertical disparities are different in infancy, and that the sensitivity to horizontal disparity are still premature in 27 weeks after birth. Optical Review Optical Review Look Inside Share Share this content on Facebook Share this content on Twitter Share this content on LinkedIn Other actions Export citations Register for Journal Updates About This Journal Reprints and Permissions

To examine young infants' sensitivity to a pictorial depth cue, we compared monocular and binocular preferential looking to objects of which depth was specified by height-in-the-picture-plane. For adults, this cue generates the perception that a lower object is closer than a higher object. This study showed that 4- and 5-month-old infants fixated the lower, apparently closer, figure more often under the monocular than binocular presentation providing evidence of their sensitivity to the pictorial depth cue. Because the displays were identical in the two conditions except for binocular information for depth, the difference in looking-behavior indicated sensitivity to depth information, excluding a possibility that they responded to 2D characteristics. This study also confirmed the usefulness of the method, preferential looking with a monocular and binocular comparison, to examine sensitivity to a pictorial depth cue in young infants, who are too immature to reach reliably for the closer of two objects.

A visual pattern's orientation influences how adults amodally complete that pattern. We examined whether this is also the case with infants using Markovich's pattern, consisting of a black polygon partially occluded by a gray disc, which is completed as either a vertically symmetrical hexagon or as a pentagon, depending on the pattern's orientation. Our experiment consisted of two prefamiliarization test trials, six familiarization trials, and two postfamiliarization test trials. In the familiarization trials, two identical Markovich patterns, upright or slanted, were presented to 7–8-month-old infants (N = 28) side by side on a CRT monitor. In the pre- and postfamiliarization test trials, a pentagon and a hexagon were presented side by side. Infants looked longer at the hexagon than at the pentagon in the postfamiliarization test trials. This suggests that infants completed the pattern as a pentagon regardless of the pattern's orientation. This lack of an orientation effect suggests that infants do not use the figure's symmetry as a guiding principle for amodal completion.

A preference for static face patterns is observed in newborns and disappears around 3 months after birth. A previous study has demonstrated that 5-month-old infants prefer schematic faces only when the internal features are moving, suggesting that face-specific movement enhances infants' preference. The present study investigates the facilitative effect of the movement of internal facial features on infants' preference. To examine infants' preference, we used animated face patterns consisting of a head-shaped contour and three disk blobs. The inner blobs expanded and contracted to represent the opening and closing of the eyes and mouth, and were constrained to open and close only in a biologically possible vertical direction resembling the facial muscle structure. We compared infants' preferential looking time for this vertically moving (VM) face pattern with their looking time for a horizontally moving (HM) face pattern in which blobs transformed at the same speed in a biologically impossible, horizontal direction. In Experiment 1, 7 to 8-month-olds preferred the VM to the HM, but 5 to 6-month-olds did not. However, the preference was diminished in both cases when the moving face patterns were presented without contour (Experiment 2). Our results suggest that internal facial features with vertical movements promote face preference in 7 to 8-month-olds. Copyright © 2011 John Wiley & Sons, Ltd.

We examined glossiness perception in infants using a preferential looking paradigm. In experiment 1, the images of two doll-shaped objects with matte and glossy surfaces were presented to infants aged 5 to 6 and 7 to 8 months. The results showed that the 7 to 8 month olds, but not the 5 to 6 month olds, looked significantly longer at the glossy object than at the matte object. In experiment 2, we additionally employed an object that was matte and covered with textures of white paint splashes, whose luminance histogram was almost identical to that of the glossy object. The results showed that the 7 to 8 month old infants could discriminate between the glossy object and the textured object even though both had similar luminance histograms. Qualitatively similar results were obtained for simple spheres that did not contain facial features. Therefore, the results of experiments 1 and 2 were not due to differences in the visibility of the dolls' facial features. These findings suggest that 7 to 8 month old infants perceive difference between glossy objects and matte objects on the basis of surface representations.

Recognition of other people's facial expressions of emotion plays an important role in social communication in infants as well as adults. Evidence from behavioral studies has demonstrated that the ability to recognize facial expressions develops by 6 to 7 months of age. Although the regions of the infant brain involved in processing facial expressions have not been investigated, neuroimaging studies in adults have revealed that several areas including the superior temporal sulcus (STS) participate in the processing of facial expressions. To examine whether the temporal area overlying the STS is responsible for the processing of facial expressions in infants, near-infrared spectroscopy (NIRS) was used to measure the neural activity in the temporal area overlying the STS as infants looked at happy and angry faces. NIRS provides a non-invasive means of estimating cerebral blood flow in the human brain and does not require severe constraints of head-movement. According to the International 10-20 system for EEG electrode placement, the measurement area was located in the bilateral temporal area centered at positions T5 and T6, which correspond to the STS. The time-course of the average change in total-Hb concentration revealed a clear difference in the pattern of hemodynamic responses to happy and angry faces. The hemodynamic response increased gradually when infants looked at happy faces and was activated continuously even after the disappearance of the face. In contrast, the hemodynamic responses for angry faces increased during the presentation of angry faces, then decreased rapidly after the face disappeared. Moreover, the left temporal area was significantly activated relative to the baseline when infants looked at happy faces, while the right temporal area was significantly activated for angry faces. These findings suggest hemispheric differences in temporal areas during the processing of positive and negative facial expressions in infants.

Using near-infrared spectroscopy (NIRS), we recorded changes of oxy-Hb, deoxy-Hb, and total-Hb in 7- to 8-month-old infants' and adults' brains in response to canonical face and scrambled face stimuli. Using a newly developed probe for NIRS recording, which was light and soft enough to be tolerated by infants, we were able to acquire data from the very young even in the awake state. Total-Hb in response to a canonical face stimulus was greater than for scrambled face stimuli only in the right hemisphere in infants. This indicates the presence of right hemisphere dominance of brain activity in response to face images in 7- to 8-month-old infants. In adults, oxy-Hb and total-Hb were significantly increased from baseline only for the canonical face in the right hemisphere. There were greater numbers of channels showing significantly increased activity for the canonical face in the right than in the left hemisphere. These data indicate that the right hemisphere is more dominant for canonical face perception in both infants and adults. However, overall, the increase of total-Hb and oxy-Hb in adults was modest compared to infants. Although the reason for the difference between infants and adults is unclear, in addition to developmental changes influencing face perception, some methodological problems may be present. Thus, because we recorded NIRS signals in infants and adults using the same method, anatomical and physiological problems might affect the results to some degree. Although comparing the results between infants and adults is not simple, the present study is the first to indicate how 7- to 8-month-old infants perceive scrambled face stimuli and to compare such results with those of adults in order to understand developmental changes in face perception.

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.

We examined whether infants could visually discriminate the orientation of a grating surrounded by an oblique square (experiment 1) and a vertical square (experiment 2). A familiarisation–novelty preference procedure was used. In experiment 1, infants aged 4 to 6 months did not visually distinguish the orientation of a grating surrounded by an oblique square. However, in experiment 2, in which a vertical surrounding square was used, such infants visually distinguished the orientation of a grating. Our results suggest that the external visual frame can affect infants' perception of the orientation of a grating, as it does in adults. In experiment 1, a grating was within an oblique square. Here, the relative orientation with respect to the external visual frame differs from the orientation relative to the retinal/gravitational axes. Such discrepancy appears to cause confusion in infants' perception of orientation.

The perception of colour in an embedded field is affected by the surround colour. This phenomenon is known as chromatic induction. In the present study we investigated whether the colour perception by infants aged 5–7 months could be affected by the surround colour. In Experiments 1 and 2 each stimulus was composed of an array of six squares in tandem. The colour appearance of the array in the familiarization stimulus was established by chromatic induction. In Experiment 1 we used familiarization stimuli that were perceived as two-colour array with a two-colour surround. In Experiment 2 we used a familiarization stimulus that was perceived as a uniform-colour array with a two-colour surround. In the test phase, the uniform-colour array and the two-colour array were presented on a white uniform-colour surround in both experiments. The results showed that in Experiment 1 the 5- and 7-month-old infants had novelty preference for the uniform-colour test array. This suggested that the infants' colour perception could be affected by surround colour. The results of Experiment 2 showed that the 7-month-olds showed a novelty preference for the two-colour test array, but the 5-month-olds showed no novelty preference. This suggested that 7-month-olds' colour perception could be affected by surround colour, but that of 5-month-olds could not. We discuss the contradiction of the results between Experiments 1 and 2. Copyright © 2007 John Wiley & Sons, Ltd.

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.

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.

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.