The use of perspective as a depth cue with a 2D display in 4 and 5-month-old infants

Four experiments were conducted to study the use of perspective as a depth cue in infants, using an eye-tracking-system. In the first experiment, no significant difference was observed between the looks for the "normal" and the "strange" events on the complete display and at the target in 4-month-olds. In the second experiment, the results of 5-month-olds were similar to those obtained by 4-month-olds but they looked more at the test events when the "strange" event was presented first. In the third experiment, 5 month-olds were shown a repeated presentation adapted from the "Partial-Lag" design. Infants' exploration of the target indicated that they looked more at the "strange" event than at the "normal" event. In the fourth experiment, the same design was used with 4-month-olds but no difference between conditions was observed. Five-month-olds seem to be able to use the perspective cues alone. These different data are discussed.     

Infants’ scanning of dynamic faces during the first year

This research investigated infants’ scanning of a talking, socially engaging face. Three- to four-month-olds looked equally at the mouth and eyes whereas 9-month-olds attended more to the eyes than mouth. These findings shed light on information infants’ seek from dynamic face stimuli.     

Do 5-Month-Old Infants Possess an Evolved Detection Mechanism for Snakes,Sharks, and Rodents?

The 4 experiments reported here used the preferential looking and habituation paradigms to examine whether 5-month-olds possess a perceptual template for snakes, sharks, and rodents. It was predicted that if infants possess such a template, then they would attend preferentially to schematic images of these nonhuman animal stimuli relative to scrambled versions of the same stimuli. The results revealed that infants looked longer at a schematic snake than at 2 scrambled versions of the image and generalized from real snakes to the schematic image. The experiments also demonstrated that 5-month-olds showed no preferential looking for schematic sharks or schematic rodents relative to scrambled versions of those images. These data add to the growing support for the view that humans, like many nonhuman animals, possess an evolved fear mechanism for detecting threats that were recurrent across evolutionary time.     

Development of body emotion perception in infancy: From discrimination to recognition

Research suggests that infants progress from discrimination to recognition of emotions in faces during the first half year of life. It is unknown whether the perception of emotions from bodies develops in a similar manner. In the current study, when presented with happy and angry body videos and voices, 5-month-olds looked longer at the matching video when they were presented upright but not when they were inverted. In contrast, 3.5-month-olds failed to match even with upright videos. Thus, 5-month-olds but not 3.5-month-olds exhibited evidence of recognition of emotions from bodies by demonstrating intermodal matching. In a subsequent experiment, younger infants did discriminate between body emotion videos but failed to exhibit an inversion effect, suggesting that discrimination may be based on low-level stimulus features. These results document a developmental change from discrimination based on non-emotional information at 3.5 months to recognition of body emotions at 5 months. This pattern of development is similar to face emotion knowledge development and suggests that both the face and body emotion perception systems develop rapidly during the first half year of life.     

Emerging perception of causality in action-and-reaction sequences from 4 to 6 months of age: Is it domain-specific?

Two experiments (N=136) studied how 4- to 6-month-olds perceive a simple schematic event, seen as goal-directed action and reaction from 3 years of age. In our causal reaction event, a red square moved toward a blue square, stopping prior to contact. Blue began to move away before red stopped, so that both briefly moved simultaneously at a distance. Primarily, our study sought to determine from what age infants see the causal structure of this reaction event. In addition, we looked at whether this causal percept depends on an animate style of motion and whether it correlates with tasks assessing goal perception and goal-directed action. Infants saw either causal reactions or noncausal delayed control events in which blue started some time after red stopped. These events involved squares that moved either rigidly or nonrigidly in an apparently animate manner. After habituation to one of the four events, infants were tested on reversal of the habituation event. Spatiotemporal features reversed for all events, but causal roles changed only in reversed reactions. The 6-month-olds dishabituated significantly more to reversal of causal reaction events than to noncausal delay events, whereas younger infants reacted similarly to reversal of both. Thus, perceptual causality for reaction events emerges by 6 months of age, a younger age than previously reported but, crucially, the same age at which perceptual causality for launch events has emerged in prior research. On our second question, animate/inanimate motion had no effect at any age, nor did significant correlations emerge with our additional tasks assessing goal perception or goal-directed object retrieval. Available evidence, here and elsewhere, is as compatible with a view that infants initially see A affecting B, without differentiation into physical or psychological causality, as with the standard assumption of distinct physical/psychological causal perception.     

Stimulus energy does not account for 2-month-olds' face preferences

We examined the determinants of 2-month-olds' preferences among facelike and abstract patterns. Observed preferences were compared with the predictions of two preference models--one based on stimulus energy (as measured by the amplitude spectrum) and the other based on stimulus structure (as measured by the phase spectrum). It is known that the phase spectrum is the primary determinant of perceived identity to adults. Twenty-five 2-month-olds saw six pairings of four patterns: a schematic face, a lattice, a pattern composed of the amplitude spectrum of the lattice and the phase spectrum of the face, and a pattern composed of the amplitude spectrum of the face and the phase spectrum of the lattice. Only patterns with the face's phase spectrum look facelike to adults. Unlike the preferences of newborns (Kleiner, 1987), 2-month-olds' preferences could be predicted from the phase spectrum but not from the amplitude spectrum. In other words, the 2-month-olds preferred the patterns that looked facelike to adults. These results offer clear evidence that 2-month-olds' preferences for facelike patterns are not governed by stimulus energy.     

Visual dissociation: an illusory conjunction of pictures and forms

Undergraduates viewed rapidly presented series of color photographs (9/s) and were required to indicate which photograph appeared within a black outline rectangle (the "frame"). Experiment 1 demonstrated that subjects were often confident and wrong, reporting the immediately preceding or following picture in the sequence. Experiment 2 showed that migration of the frame to other pictures cannot be attributed to spatial separation, because the same effect occurred when a small frame was presented in the center of the picture itself. Experiment 3 ruled out masking of the "framed" picture as the cause of the illusion by showing that the framed picture is indeed identified on those trials where the frame appears to be elsewhere. Experiment 4 showed that when simpler, more familiar stimuli (numbers) were presented, a more rapid presentation rate (18/s) was required to obtain the effect. It is proposed that the illusion reflects the action of integrative processes in a very short-term buffer and that it may provide a new tool with which to study the integration of features within scenes.     

Three-month-olds' visual preference for faces and its underlying visual processing mechanisms

This study was aimed at investigating the face preference phenomenon and its underlying mechanisms at 3 months of age. Using an eye-tracker apparatus, Experiment 1 demonstrated that 3-month-olds prefer natural face images to unnatural ones, replicating and extending previous evidence obtained with schematic facelike stimuli. Experiments 2 and 3 showed that the general mechanisms that induce face preference in newborns could not explain the same phenomenon at 3 months of age, when infants are attracted by perceptual cues more specific to faces. This suggests that signs of a process of cognitive specialization are already present in 3-month-olds' visual behavior toward faces.     

Emergence of the ability to discriminate a blue from gray at one month of age

Two different methods which minimize achromatic cues were used to test the ability of 1-month-olds to discriminate gray from broadband blue (lambda peak = 475-480 nm). Unlike the newborns we tested previously, 1-month-olds demonstrated the discrimination with both methods. In Experiment 1 they showed preferences for each of four blue-and-gray checkerboards over gray squares of the same mean luminance, even though the luminance of the gray checks was varied in small steps over a wide range. In Experiment 2 they looked longer at a blue square than at a gray square, after they had been habituated to five other gray squares of varying luminance. Compared to previous results, these data imply an improvement between birth and 1 month of age in the discrimination of gray from broadband blue. Possible physiological changes underlying this improvement are discussed.     

When do infants expect hands to be connected to a person?

A violation-of-expectation paradigm was used to test whether infants infer a person based on the presence of hands alone. Infants were familiarized to a pair of hands that extended out from a curtain to play with a rattle, after which the curtain was opened to reveal either a real person or a mannequin. Infants’ looking at these outcomes was compared with baseline looking at the person and the mannequin. Experiment 1 showed that 9-month-olds looked significantly longer at the mannequin than at the person after familiarization to hands. Experiment 2 ruled out a low-level feature matching interpretation by showing the same looking pattern in 9-month-olds even when the hands were covered with silver gloves. In Experiment 3, 6-month-olds showed no differential looking at the mannequin and person after familiarization to hands. Taken together, these experiments suggest that infants acquire the expectation that hands are connected to a person between 6 and 9 months of age. This finding has implications for how infants’ attribute goals to manual actions.     

Out of Sight Is Not Out of Mind: Developmental Changes in Infants' Understanding of Visual Perception During the Second Year

Three experiments investigated 14-, 18-, and 24- month-old infants' understanding of visual perception. Infants viewed films in which a protagonist was either able to view the location of a hidden object (Visual Access condition) or was blindfolded when the object location was revealed (No Visual Access condition). When requested to find the object, the protagonist pointed either at the correct location or at the incorrect location. Across experiments, 18-month-olds looked longer at the unexpected action (e.g., person pointing at the incorrect location in the Visual Access condition). By 24 month of age, infants could infer the correct search behavior from gaze alone. These findings suggest that by the middle of the second year of life, infants understand the psychological relation between an observer and an object, even if the object is no longer visible.     

Examining the role of social cues in early word learning

Infants watched a video of an adult pointing towards two different objects while hearing novel labels. Analyses indicated that 14- and 18-month-olds looked longer at the target object, but only 18-month-olds showed word learning. The results suggest that different types of social cues are available at different ages.     

Effects of the height of the internal features of faces on adults' aesthetic ratings and 5-month-olds' looking times

We examined the influence of the height of the internal features of faces on adults' ratings of attractiveness and on 5-month-olds' looking times. Subjects viewed drawings or coloured photographs of faces presented in pairs that were identical except that the internal features were at a low height, with a large forehead and small chin; at a high height, with a small forehead and large chin; or at a medium height. Adults rated faces with their features at the medium and low heights as more attractive than faces with their features at the high height, and, at least for drawings, rated faces with medium features as more attractive than faces with low features. Babies looked equally long at faces with their features at various heights except for looking slightly longer at faces with high rather than low features. The results suggest that the influence of feature height on reactions to faces is different for adults and 5-month-olds, and hence that it may be shaped by cultural learning and/or experience with faces sometime after early infancy.     

Effects of gesture and target on 12- and 18-month-olds' joint visual attention to objects in front of or behind them

Factors affecting joint visual attention in 12- and 18-month-olds were investigated. In Experiment 1 infants responded to 1 of 3 parental gestures: looking, looking and pointing, or looking, pointing, and verbalizing. Target objects were either identical to or distinctive from distractor objects. Targets were in front of or behind the infant to test G. E. Butterworth's (1991b) hypothesis that 12-month-olds do not follow gaze to objects behind them. Pointing elicited more episodes of joint visual attention than looking alone. Distinctive targets elicited more episodes of joint visual attention than identical targets. Although infants most reliably followed gestures to targets in front of them, even 12-month-olds followed gestures to targets behind them. In Experiment 2 parents were rotated so that the magnitude of their head turns to fixate front and back targets was equivalent. Infants looked more at front than at back targets, but there was also an effect of magnitude of head turn. Infants' relative neglect of back targets is partly due to the "size" of adult's gesture.     

The inversion effect in infancy: the role of internal and external features

The present work examined the changing role of inner and outer facial features in the recognition of upright and inverted faces in 5-, 7-, and 9-month-olds. Study 1 established that the “inversion effect” (impaired recognition of an inverted face) was present in infants as young as 5 months. In Study 2, internal and external features were inverted separately. Disrupting the internal configuration by inversion impaired recognition at all ages; disrupting the external configuration impaired recognition only at 5-months. In Study 3, an upright familiar face was paired with one having either novel internal or novel external features. The results confirmed that the 5-month-olds used only the external features to recognize faces, whereas older infants were as adept at using internal features as external ones. These findings suggest a shift, after 5 months, away from dependence on external features for face recognition and toward greater reliance on internal ones.     

The effects of attention-directing training on recognition memory task performance of three-year-old children

Thirty-eight 3-year-old children served as subjects in an investigation of recognition memory in which schematic faces differing only in the orientation of the eyes were employed as stimuli. A pretest was administered to all children, after which the two experimental groups received training in either attention to the distinctive feature of the training stimuli (also schematic faces) by means of a matching task, or in labeling the faces according to how they looked (sleepy, happy, sad, mad) and in using the labels to perform a matching task. After the training session all children were given a posttest on recognition memory of the faces. The verbally trained group obtained significantly higher scores on the posttest than either the feature or control groups. These results indicate that although the children were able to discriminate the faces, evidenced in their ease of performance on the training tasks, they were not able to use this knowledge unless given training in attaching labels to the stimuli, which enabled them to store the information for later use. Results are discussed in light of Gibson's (1969) theory of the developmental interrelations of cognitive processes.     

Beyond U-Shaped Development in Infants' Processing of Faces: An Information-Processing Account

The development of the "inversion" effect in face processing was examined in infants 3 to 6 months of age by testing their integration of the internal and external features of upright and inverted faces using a variation of the "switch" visual habituation paradigm. When combined with previous findings showing that 7-month-olds use integrative processing of an upright face, but featural processing of an inverted face (Cohen & Cashon, 2001a), the present findings suggest that from 3 to 7 months, infants' ability to integrate facial features follows an N-shaped developmental pattern for upright faces and an inverted U-shaped pattern for inverted faces. We discuss these results in terms of a set of domain-general information-processing principles.     

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

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

Amplitude and phase spectra as indices of infants' pattern preferences

This study examined whether the linear systems model of infants' visual preferences (Banks & Salapatek, 1981) could predict neonates' preferences, among facelike and abstract patterns. To do so, the study assessed the relative importance of stimulus energy (as measured by the amplitude spectrum) and stimulus structure (as measured by the phase spectrum) in determining early preferences. Forty-eight neonates viewed six pairings of four stimuli: (a) a schematic face, (b) a lattice, (c) a pattern composed of the amplitude spectrum of the lattice and the phase spectrum of the face, and (d) a pattern composed of the amplitude spectrum of the face and the phase spectrum of the lattice. The linear systems model predicted the observed preferences quite accurately. That is, the infants' preferences could be predicted from knowledge of the amplitude spectrum but not the phase spectrum. These results are interpreted as showing that neonates' preferences for facelike patterns are governed primarily by simulus energy and not by the familiarity or social significance of such patterns.