Infants' perception of subjective contours from apparent motion

We examined infants' perception of subjective contours in Subjective-Contour-from-Apparent-Motion (SCAM) stimuli [e.g., Cicerone, C. M., Hoffman, D. D., Gowdy, P. D., & Kim, J. S. (1995). The perception of color from motion. Perception & Psychophysics, 57, 761-777] using the preferential looking technique. The SCAM stimulus is composed of random dots which are assigned two different colors. Circular region assigned one color moved apparently, keeping all dots' location unchanged. In the SCAM stimulus, adults can perceive subjective color spreading and subjective contours in apparent motion (http://c-faculty.chuo-u.ac.jp/ approximately ymasa/okamura/ibd_demo.html). In the present study, we conducted two experiments by using this type of SCAM stimulus. A total of thirty-six 3-8-month-olds participated. In experiment 1, we presented two stimuli to the infants side by side: a SCAM stimulus consisting of different luminance, and a non-SCAM stimulus consisting of isoluminance dots. The results indicated that the 5-8-month-olds showed preference for the SCAM stimuli. In experiments 2 and 3, we confirmed that the infants' preference for the SCAM stimulus was not generated by the local difference and local change made by luminance of dots but by the subjective contours. These results suggest that 5-8-month-olds were able to perceive subjective contours in the SCAM stimuli.     

Perceptual transparency in 3- to 4-month-old infants

We examined perceptual transparency in infants. In a previous study, Johnson and Aslin (2000 Developmental Psychology 36 808 - 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.     

Anisotropic motion coherence sensitivities to expansion/contraction motion in early infancy

We investigated 2- and 3-month-olds' motion coherence sensitivities to radial expansion/contraction by using the preferential looking method. The infants were tested with a stimulus composed of two dynamic random dot patterns placed side by side: an expansion (or a contraction) pattern and a random directional pattern. The results showed that the 3-month-old infants tested with both a contraction and random directional pattern could discriminate between those two motions significantly, even when the contraction motion coherence was relatively low (50%). On the other hand, the 3-month-old infants who were tested with both expansion and random directional pattern could not discriminate between those two motions. None of the 2-month-old infants showed significant discrimination between the expansion/contraction and random motion patterns. Results of the present study suggest that anisotropic motion coherence sensitivities to radial expansion/contraction emerge at around 3 months of age.     

Do infants recognize the Arcimboldo images as faces? Behavioral and near-infrared spectroscopic study

Arcimboldo images induce the perception of faces when shown upright despite the fact that only nonfacial objects such as vegetables and fruits are painted. In the current study, we examined whether infants recognize a face in the Arcimboldo images by using the preferential looking technique and near-infrared spectroscopy (NIRS). In the first experiment, we measured looking preference between upright and inverted Arcimboldo images among 5- and 6-month-olds and 7- and 8-month-olds. We hypothesized that if infants perceive the Arcimboldo images as faces, they would prefer the upright images to the inverted ones. We found that only 7- and 8-month-olds significantly preferred upright images, suggesting that they could perceive the Arcimboldo images as faces. In the second experiment, we measured hemodynamic responses using NIRS. Based on the behavioral data, we hypothesized that 7- and 8-month-olds would show different neural activity for upright and inverted Arcimboldo images, as do adults. Therefore, we measured hemodynamic responses in 7- and 8-month-olds while they were looking at upright and inverted Arcimboldo images. Their responses were then compared with the baseline activation during the presentation of individual vegetables. We found that the concentration of oxyhemoglobin increased in the left temporal area during the presentation of the upright images compared with the baseline during the presentation of vegetables. The results of the two experiments suggest that (a) the ability to recognize the upright Arcimboldo images as faces develops at around 7 or 8 months of age and (b) processing of the upright Arcimboldo images is related to the left temporal area of the brain.     

Discrimination learning during the first year: stimulus and positional cues

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.     

Infants’ perception of depth from cast shadows

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocularviewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.     

Infants' perception of depth from cast shadows

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocular-viewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.     

Movement contributes to infants’ recognition of the human form

Three experiments demonstrate that biological movement facilitates young infants’ recognition of the whole human form. A body discrimination task was used in which 6-, 9-, and 12-month-old infants were habituated to typical human bodies and then shown scrambled human bodies at the test. Recovery of interest to the scrambled bodies was observed in 9- and 12-month-old infants in Experiment 1, but only when the body images were animated to move in a biologically possible way. In Experiment 2, nonbiological movement was incorporated into the typical and scrambled body images, but this did not facilitate body recognition in 9- and 12-month-olds. A preferential looking paradigm was used in Experiment 3 to determine if infants had a spontaneous preference for the scrambled versus typical body stimuli when these were both animated. The results showed that 12-month-olds preferred the scrambled body stimuli, 9-month-olds preferred the typical body stimuli and the 6-month-olds showed no preference for either type of body stimuli. These findings suggest that human body recognition involves integrating form and movement, possibly in the superior temporal sulcus, from as early as 9 months of life.     

Do infants possess an evolved spider-detection mechanism?

Previous studies with various non-human animals have revealed that they possess an evolved predator recognition mechanism that specifies the appearance of recurring threats. We used the preferential looking and habituation paradigms in three experiments to investigate whether 5-month-old human infants have a perceptual template for spiders that generalizes to real-world images of spiders. A fourth experiment assessed whether 5-month-olds have a perceptual template for a non-threatening biological stimulus (i.e., a flower). The results supported the hypothesis that humans, like other species, may possess a cognitive mechanism for detecting specific animals that were potentially harmful throughout evolutionary history.     

Changes in infants' ability to switch visual attention in the first three months of life.

The abilities of 1-month-old and 3-month-old infants to shift their gaze from a central target to a peripheral target were compared in four experiments. In experiment 1 targets matched in mean luminance to the background were presented to infants in the periphery at varying levels of contrast. The contrast thresholds for target detection were found to be significantly different for 1-month-olds compared with 3-month-olds. With targets set close to these contrast thresholds, correct refixations and the latency for shifting attention were examined in experiment 2. Two conditions were used: a peripheral target was presented against a homogeneous background (noncompetition); and in the second condition, the patterned target appeared at one of two lighter peripheral windows set against a darker background (competition). Although there was no difference between the two age groups in the latency for shifting visual attention, 1-month-olds were found to make more directional errors in the competition condition. The competition effect of two potential targets on latencies was examined in experiment 3. In the competition condition, two identical peripheral patterned targets were presented to the infants. The 3-month-olds refixated more quickly to one of the double targets in the competition condition than to a single peripheral target, whereas 1-month-olds were slowed down by a double target display. Finally, in experiment 4 the ability of the infants to process and disengage from a central stimulus and to refixate towards a similar peripheral target was examined. This type of competition disrupted both the direction of the first eye movement and the latency to shift attention in both age groups. However, the effect was significantly greater for the 1-month-olds. Taken together, the results of these experiments demonstrate the greater disruption of fixation-shift behaviour in 1-month-olds compared with 3-month-olds when competing visual stimuli are used. This developmental change is explained in terms of maturation of executive cortical orienting systems over the first months of life.     

Infants’ perception of curved illusory contour with motion

Recently, Masuda et al. (submitted for publication) showed that adults perceive moving rigid or nonrigid motion from illusory contour with neon color spreading in which the inducer has pendular motion with or without phase difference. In Experiment 1, we used the preferential looking method to investigate whether 3–8-month-old infants can discriminate illusory and non-illusory contour figures, and found that the 7–8-month-old, but not the 3–6-month-old, infants showed significant preference for illusory contour with phase difference. In Experiment 2, we tested the validity of the visual stimuli in the present study, and whether infants could detect illusory contour from the current neon color spreading figures. The results showed that all infants might detect illusory contour figure with neon color spreading figures. The results of Experiments 1 and 2 suggest that 7–8-month-old infants potentially perceive illusory contour from the visual stimulus with phase-different movement of inducers, which elicits the perception of nonrigid dynamic subjective contour in adults.     

Evidence of a shift from featural to configural face processing in infancy

Two experiments examined whether 4-, 6-, and 10-month-old infants process natural looking faces by feature, i.e. processing internal facial features independently of the facial context or holistically by processing the features in conjunction with the facial context. Infants were habituated to two faces and looking time was measured. After habituation they were tested with a habituation face, a switch-face, or a novel face. In the switch-faces, the eyes and mouth of the habituation faces were switched. The results showed that the 4-month-olds processed eyes and mouth by feature, whereas the 10-month-olds processed both features holistically. The 6-month-olds were in a transitional stage where they processed the mouth holistically but the eyes still as a feature. Thus, the results demonstrated a shift from featural to holistic processing in the age range of 4 to 10 months.     

Evidence for mental subdivision of space by infants: 3- to 4-month-olds spontaneously bisect a small-scale area into left and right categories

Young infants have been shown to represent the left versus right spatial category relations of a target object and a vertical referent bar. In the present study, we examined whether infants would represent left versus right when the vertical bar was removed from the stimulus display. In Experiment 1, 3- to 4-month-olds who had been familiarized with stimuli depicting a diamond appearing in different locations to the left or right of the vertical midline displayed a mean novel category preference for a stimulus depicting the diamond on the opposite side of the midline. In Experiment 2, another group of 3- to 4-month-olds discriminated the within-category position changes of the diamond as it appeared to the left or right of the vertical midline. The results indicate that young infants can mentally bisect small-scale space into left versus right categories.     

Infants’ recognition of objects using canonical color

We explored infants’ ability to recognize the canonical colors of daily objects, including two color-specific objects (human face and fruit) and a non-color-specific object (flower), by using a preferential looking technique. A total of 58 infants between 5 and 8 months of age were tested with a stimulus composed of two color pictures of an object placed side by side: a correctly colored picture (e.g., red strawberry) and an inappropriately colored picture (e.g., green-blue strawberry). The results showed that, overall, the 6- to 8-month-olds showed preference for the correctly colored pictures for color-specific objects, whereas they did not show preference for the correctly colored pictures for the non-color-specific object. The 5-month-olds showed no significant preference for the correctly colored pictures for all object conditions. These findings imply that the recognition of canonical color for objects emerges at 6 months of age.     

Development of preferences for the human body shape in infancy

Two studies investigated the development of infants' visual preferences for the human body shape. In Study 1, infants of 12, 15 and 18 months were tested in a standard preferential looking experiment, in which they were shown paired line drawings of typical and scrambled bodies. Results indicated that the 18-month-olds had a reliable preference for the scrambled body shapes over typical body shapes, while the younger infants did not show differential responding. In Study 2, 12- and 18-month-olds were tested with the same procedure, except that the typical and scrambled body stimuli were photographic images. The results of Study 2 again indicated that only the 18-month-olds had a reliable preference for the scrambled body shapes. This finding contrasts sharply with infants' precocious preferences for human faces, suggesting that infants' learning about human faces and human bodies follow different developmental trajectories.     

Visual tracking in young infants: Evidence for object identity or object permanence?

Previous research has shown that 5-month-old infants visually anticipate a moving object's appearance after it disappears behind a screen. This experiment assesses the underlying basis for such anticipatory tracking. Three tracking tasks were presented to 5- and 9-month-old infants. In the Permanence task, the object's continuous existence was apparently violated while it was behind a screen. In the Feature and Trajectory tasks, the object's features or trajectory changed while behind the screen. Disruptions in the infant's smooth visual pursuit of the object were recorded. Five-mont-olds showed disruptions of visual tracking in the Feature and Trajectory tasks, but not in the Permanence task. The tracking of the 9-month-olds was disrupted in all three tasks. We conclude that both 5- and 9-month-olds possess rules specifying the identity of a moving object which is occluded. For 5-month-olds these rules are based upon the object's features and trajectory, but not upon a concept of object permanence. For 9-month-olds all three rules—feature, trajectory, and permanence—are utilized in visual tracking.     

Rapid acquisition of phonological alternations by infants

We explore whether infants can learn novel phonological alternations on the basis of distributional information. In Experiment 1, two groups of 12-month-old infants were familiarized with artificial languages whose distributional properties exhibited either stop or fricative voicing alternations. At test, infants in the two exposure groups had different preferences for novel sequences involving voiced and voiceless stops and fricatives, suggesting that each group had internalized a different familiarization alternation. In Experiment 2, 8.5-month-olds exhibited the same patterns of preference. In Experiments 3 and 4, we investigated whether infants' preferences were driven solely by preferences for sequences of high transitional probability. Although 8.5-month-olds in Experiment 3 were sensitive to the relative probabilities of sequences in the familiarization stimuli, only 12-month-olds in Experiment 4 showed evidence of having grouped alternating segments into a single functional category. Taken together, these results suggest a developmental trajectory for the acquisition of phonological alternations using distributional cues in the input.     

Developmental changes in infants' processing of happy and angry facial expressions: a neurobehavioral study

Event-related brain potentials were measured in 7- and 12-month-old infants to examine the development of processing happy and angry facial expressions. In 7-month-olds a larger negativity to happy faces was observed at frontal, central, temporal and parietal sites (Experiment 1), whereas 12-month-olds showed a larger negativity to angry faces at occipital sites (Experiment 2). These data suggest that processing of these facial expressions undergoes development between 7 and 12 months: while 7-month-olds exhibit heightened sensitivity to happy faces, 12-month-olds resemble adults in their heightened sensitivity to angry faces. In Experiment 3 infants' visual preference was assessed behaviorally, revealing that the differences in ERPs observed at 7 and 12 months do not simply reflect differences in visual preference.     

Infant sensitivity to shadow motions

Preferential looking experiments investigated 5- and 8-month-old infants' perception and understanding of the motions of a shadow that appeared to be cast by a ball upon a box. When all the surfaces within the display were stationary, infants looked reliably longer when the shadow moved than when the shadow was stationary, indicating that they detected the shadow and its motion. In further experiments, however, infants' looking was not consistent with a sensitivity to the shadow's natural motion: They looked longer at natural events in which the shadow moved with the ball or remained at rest under the moving box than at unnatural events in which the shadow moved with the box or remained at rest under the moving ball. These findings suggest that infants overextend to shadows a principle that applies to material objects: Objects move together if and only if they are in contact. In a final experiment, infants were habituated to a moving shadow that repeatedly violated one aspect of the contact principle. In a subsequent test they failed to infer that the shadow would violate another aspect of the contact principle. Instead, they appeared to suspend all predictions concerning the behavior of the shadow.     

Effects of multimodal presentation and stimulus familiarity on auditory and visual processing

Two experiments examined the effects of multimodal presentation and stimulus familiarity on auditory and visual processing. In Experiment 1, 10-month-olds were habituated to either an auditory stimulus, a visual stimulus, or an auditory-visual multimodal stimulus. Processing time was assessed during the habituation phase, and discrimination of auditory and visual stimuli was assessed during a subsequent testing phase. In Experiment 2, the familiarity of the auditory or visual stimulus was systematically manipulated by prefamiliarizing infants to either the auditory or visual stimulus prior to the experiment proper. With the exception of the prefamiliarized auditory condition in Experiment 2, infants in the multimodal conditions failed to increase looking when the visual component changed at test. This finding is noteworthy given that infants discriminated the same visual stimuli when presented unimodally, and there was no evidence that multimodal presentation attenuated auditory processing. Possible factors underlying these effects are discussed.