Infants' sensitivity to accretion and deletion of texture as information for depth at an edge

Based on Gibson's hypothesis that accretion and deletion of texture in the optic array provides unambiguous information for the spatial layout of surfaces, we sought evidence of early responsiveness to this information with infant subjects. 5- and 7-month-olds viewed computer-generated random-dot displays in which accretion and deletion of texture provided the only information for contours, specifying either a foreground surface moving in front of and occluding a moving background surface or 2 partially overlapping surfaces. The infants in both age groups showed significant preferences to reach for the apparently nearer regions in the displays. Since previous research has shown that infants reach more frequently for the nearer of 2 surfaces, these results indicate that 5- and 7-month-olds are sensitive to accretion and deletion of texture as information for the spatial layout of surfaces.     

Perception of kinetic illusory contours by two-month-old infants

Perception of kinetic illusory contours by 2-month-old infants was explored with sparse random-dot displays depicting an illusory shape against a background. In Experiment 1, 24 infants were habituated to a shape specified by accretion and deletion of background texture and relative motion, and exhibited a novelty preference when presented with luminance-defined familiar and novel shapes. Subsequent experiments explored kinetic cues in isolation. In Experiment 2 (n = 24), relative motion information was removed, leaving accretion and deletion of texture and luminance cues, and in Experiment 3 (n = 24), only relative motion information was available. In both these experiments the novelty preference obtained in Experiment 1 was replicated. Results from a control condition (n = 12) mitigated against the likelihood of an inherent preference for either of the test shapes. These findings reveal an early capacity to perceive shape solely from kinetic information, and suggest a mechanism geared toward spatiotemporal boundary formation that is functional shortly after birth. Theories of development of edge and motion discrimination are discussed.     

Four-month-old infants' sensitivity to binocular and kinetic information for three-dimensional-object shape

4-month-old infants were tested for sensitivity to kinetic and binocular information for 3-dimensional-object shape. The study included 2 tests: a test for sensitivity to binocular disparity and a shape perception test. The disparity sensitivity test used a preferential looking procedure developed by Held, Birch, and Gwiazda. On the basis of the results of this test, infants were assigned to disparity-sensitive and disparity-insensitive groups. In the shape perception test, a "transfer-across-depth-cues" method was employed. Infants were habituated to a rotating object whose shape was specified by kinetic information and were then presented with stationary stereograms specifying the same object and a novel-shaped object. The disparity-sensitive infants looked significantly longer at the novel object than at the familiar object, whereas the disparity-insensitive infants showed no difference in looking time to the novel and the familiar objects. The results indicate that disparity-sensitive 4-month-old infants can perceive 3-dimensional-object shape from kinetic and binocular depth information.     

Effective Action by Infants to Contact Objects by Reaching and Leaning

The ability of infants aged 8–12 months to coordinate their arm and trunk movements to contact an object located in different positions was investigated in 2 experiments. In the first, 8- and 10-month-old infants reached for near objects but both reached and leaned for more distant ones indicating that they perceived that forward leaning extends the range of contact beyond that of reaching alone. In addition, arm and trunk movements were initiated simultaneously; visual information concerning object distance was sufficient to activate an integrated reaching-and-leaning response. Object distances were increased and a mechanical aid was provided on half the trials in the second experiment with 10- and 12-month-old infants. For both age groups the degree of leaning was reduced for objects that were out of reach without the aid. Only older infants were able to use the aid to extend partially their range of contact. Overall the results support the conclusions that, by at least 8 months, infants perceive that leaning extends their effective reaching space; by 10 months they perceive the limits within which reaching together with leaning is likely to be effective; and by 12 months they begin to perceive how this space may be extended by a mechanical aid.     

Perceiving the Affordance of Contact in Fourand Five-Month-Old Infants

The focus of this study was on the ability of infants to perceive whether an object is positioned at a distance that would make contact possible. As a toy was presented, sometimes within and sometimes beyond reach, the initiation of reaching and leaning forward was scored. Infants were divided into leaning and nonleaning groups. Both leaning and nonleaning 5-month-olds changed their behavior dramatically when the object was placed beyond, as opposed to within, reach. The nonleaners showed a decline in reaching when this boundary for contact was crossed. The "leaners" did not; rather, they began to lean forward. These results suggest that 5-month-olds use information for the affordance of contact. 4-month-olds provided less evidence that arm length regulates reaching. 5-month-old infants acted as if they not only had some sensitivity to the absolute distance of an object but also to the effect that leaning forward has on their ability to make contact with a distant object.     

Kinetic contours in infants' visual perception

3-month-old infants' perception of "camouflaged" forms that are only visible when moving was studied. Displays were used in which figure and ground had an identical random dot texture, and no edge indicated the form of the figure. The form was invisible when stationary. Discrimination of 2 different forms was tested (a) when the forms were visible only through motion, and (b) when the forms appeared as stationary white figures on black ground. The babies discriminated the forms in both conditions. Furthermore, when infants were habituated to one of the moving forms and subsequently presented with the same and a new static form, they looked longer at the new form. This indicates that they recognized the static form as either the same or different from the moving form seen before, although the optical sources of information were completely different. At 3 months, infants can therefore effectively use kinetic information to organize the visual input in higher-order structures.     

Auditory-visual perception of changing distance by human infants

2 studies examined 5-month-old infants' sensitivity to auditory-visual specification of distance and direction of movement. In 1 experiment, infants were presented successively with 2 filmed events--1 of an automobile approaching, and the other of the same automobile driving away. A soundtrack that increased or decreased in amplitude was played along with each film, either in a match or mismatch condition. Infants did not show differential looking patterns related to the match or mismatch of auditory and visual information. In a second experiment, infants were tested using a paired preference technique. The films were shown side-by-side along with a single soundtrack appropriate to 1 of them. Looking time was monitored as before. These infants demonstrated visual preferences for the sound-matched films, evidently detecting the relationship between auditory and visual information when this procedure was used.     

Object Permanence in Young Infants: Further Evidence

Recent evidence suggests that 4.5- and even 3.5-month-old infants realize that objects continue to exist when hidden. The goal of the present experiments was to obtain converging evidence of object permanence in young infants. Experiments were conducted using paradigms previously used to demonstrate object permanence in 5.5-month-old infants and 6.5-month-old infants. In one experiment, 3.5-month-old infants watched a short or a tall carrot slide along a track. The track's center was hidden by a screen with a large window in its upper half. The short carrot was shorter than the window's lower edge and so did not appear in the window when passing behind the screen; the tall carrot was taller than the window's lower edge and hence should have appeared in the window but did not. The infants looked reliably longer at the tall than at the short carrot event, suggesting that they (a) represented the existence, height, and trajectory of each carrot behind the screen and (b) expected the tall carrot to appear in the screen window and were surprised that it did not. Control trials supported this interpretation. In another experiment, 4.0-month-old infants saw a toy car roll along a track that was partly hidden by a screen. A large toy mouse was placed behind the screen, either on top or in back of the track. The female infants looked reliably longer when the mouse stood on top as opposed to in back of the track, suggesting that they (a) represented the existence and trajectory of the car behind the screen, (b) represented the existence and location of the mouse behind the screen, and (c) were surprised to see the car reappear from behind the screen when the mouse stood in its path. A second experiment supported this interpretation. The results of these experiments provide further evidence that infants aged 3.5 months and older are able to represent and to reason about hidden objects.     

Infant perception of object unity from translatory motion in depth and vertical translation

Previous research indicated that 4-month-old infants perceive the unity of a center-occluded object when its visible ends share a common lateral translation in space. The present work investigated the class of motion relationships that can specify object unity to infants, specifically, asking whether it includes all rigid translations. 3 experiments tested the informativeness of 2 axes of translation not previously studied: translation in depth and vertical translation. These motions also allowed assessment of certain interpretations of previous results that invoke specific sensory consequences of lateral movement, rather than perceived motion, as underlying perceived unity. Experiment 1 provided evidence that a small extent of translation in depth specified the unity of an object, but only to the subgroup of infants who detected the motion. Experiment 2 used a greater displacement in depth and found clear evidence for perception of object unity. Experiment 3 indicated that vertical translation, in which the 2 visible areas of the partly hidden object undergo dissimilar changes, also specifies object unity to infants. These results suggest that infants' perception of object unity depends on perceived coherence of motion, no matter how specified, and that the class of informative motions includes all rigid translations.     

Infants parse dynamic action

As observers of human behavior, infants are faced with a complex flow of motion in which pauses are rare and only occasionally coincide with boundaries between intentional actions. Two studies investigated whether, despite such complexity, 10- to 11-month-old infants (N = 16 for each study) possess skills for parsing ongoing behavior along boundaries correlated with the initiation and completion of intentions. After being familiarized with digitized sequences of continuous everyday action, infants showed renewed interest in test versions in which motion paused in the midst of an actor's pursuit of intentions (interrupting test videos). In contrast, pauses that suspended motion at intention boundary points (completing test videos) sparked no such renewed interest on infants' part. Moreover, basic salience differences between the two types of test videos were not the source of infants' increased interest when intentions were interrupted (Study 2). These findings demonstrate that infants readily detect disruptions of the structure inherent in intentional action, and hence parse ongoing behavior with respect to such structure. Such parsing skill is likely a prerequisite to the development of genuine intentional understanding.     

Inability of five-month-old infants to retrieve a contiguous object: a failure of conceptual understanding or of control of action?

Infants of 5 to 6 months of age can retrieve a free-standing object, but fail to retrieve the same object from atop a slightly larger object. The accepted explanation has been that the infants do not understand that an object continues to exist independently when placed upon another. Predictions based on that explanation were tested against the hypothesis that infants' problem consists of lack of precision in visually guided reaching and lack of ability to inhibit reflexive reactions to touch. Twelve infants each at 5 and 7 months of age were tested on 16 trials. More 5-month-olds succeeded, in less time, and with fewer touches to an edge of the base, on trials more forgiving of an imprecise reach than on less forgiving trials. Success in retrieving objects close in size and fully contiguous with their bases was seen even at 5 months when the demands on skill in reaching were reduced. It is proposed that when 5-month-old infants fail to retrieve one object placed upon another, it is not because of a lack of conceptual understanding, but because they lack the skill to reach to the top object without accidentally touching an edge of the base en route.     

Developmental Change in Infant Categorization: The Perception of Correlations among Facial Features

Previous studies indicated that the ability to detect correlations among attributes emerges between 7 and 10 months of age. In the present study, the generality of this developmental transition was examined. Using an infant-control habituation procedure, 48 7- and 10-month-old infants were tested for the perception of correlations among basic facial features. The developmental effects were replicated. Only the 10-month-old infants demonstrated their sensitivity to the pattern of correlation by generalizing to a novel face that preserved the experienced pattern of correlation, while showing increased attention to a face in which the pattern of correlation was violated. 7-month-old infants generalized to both test stimuli containing familiar features, regardless of the status of the correlation. Implications for face perception and the processing of categorical information are discussed.     

Infant emotional and cortisol responses to goal blockage

This study examined the relation of infant emotional responses of anger and sadness to cortisol response in 2 goal blockage situations. One goal blockage with 4-month-old infants (N = 56) involved a contingency learning procedure where infants' learned response was no longer effective in reinstating an event. The other goal blockage with 6-month-old infants (N = 84) involved the still face procedure where infants' reactions to their mothers' lack of responsivity were not effective in reestablishing interaction. For both blockages, sadness was related to cortisol response, though anger was not--the greater the sadness, the higher the cortisol response. This differential relation is consistent with other evidence indicating the more positive role of anger as opposed to sadness in overcoming an obstacle.     

Joint Attention and Conversation in Mother-Infant-Sibling Triads

The current study investigated the general nature of joint attentional and conversational interaction in mother-infant-sibling triads. 9 19-month-old infants and 9 24-month-old infants were videotaped during 20 min of free play with their mothers and preschool-aged siblings around a common activity. Analyses revealed that even 19-month-old infants were capable of participating in triadic interactions and conversations, and that the proportional frequency of both these measures increased with age. Triadic conversations were nearly 3 times longer and elicited nearly twice as many infant turns per conversation as dyadic conversations. Infants were more likely to join into an ongoing conversational topic than to initiate one themselves, and they were more likely to take a turn in those conversations if they were in a joint attentional state with the speaker. Infants were just as likely to respond to a comment or request directed to another person as they were to one directed to themselves, indicating reliable comprehension of language not addressed to them. These results suggest that the mother-infant-sibling interactive context differs in important ways from the mother-infant dyadic context and that it is a richer language learning environment than previously supposed.     

Perceiving "outside the box" occurs early in development: evidence for boundary extension in three- to seven-month-old infants

This investigation examined whether infants display boundary extension-a tendency to remember more of a visual scene than was presented. Three- to 7-month-olds were familiarized with a photograph of a visual scene, and tested with wide-angle versus close-up views of the scene. Infants preferred the close-up, indicating that they perceived the wide angle (the one consistent with boundary extension) as more familiar. Converging experiments showed that: (a) infants did not spontaneously prefer the close-up, (b) adults did not judge the wide angle to be more similar to the familiarization stimulus, and (c) infants spontaneously preferred the close-up when the photographs depicted outline objects without backgrounds. The findings suggest that infants anticipate information that lies beyond the borders of a scene view.     

Infants' cross-modal transfer from solid objects to their graphic representations

12-month-old infants were familiarized either tactually or visually with objects and then tested for visual recognition memory using either (1) the familiar and a novel object, (2) colored pictures of the objects, or (3) outline drawings of them. In Study 1, infants showed recognition memory on all 3 visual intramodal problems but showed cross-modal transfer only when objects were used as test stimuli. With increased familiarization times in Study 2, transfer from tactually presented samples to both pictorial displays was achieved, indicating that after feeling an object the infants were able to recognize it visually solely on the basis of its contour. With reduced familiarization times in Study 3, there was no evidence for transfer from visually presented samples to the 2 pictorial displays, replicating the pattern of results observed cross-modally in Study 1 and suggesting that, at least in certain respects, cross-modal and intramodal perception follow similar principles.     

The rhythmic structure of mother-infant interaction in term and preterm infants

The purpose of this study was to quantify social interaction rhythms in 3- and 5-month-old term and preterm infants and their mothers. Infant-mother dyads were videotaped in a 3-min face-to-face paradigm. For each second of the interaction, separate scores were assigned to infant and mother indicating levels of affective involvement, creating 2 180-sec time series. Spectral and cross-spectral techniques were used to quantify periodicities in each member of the dyad and to estimate the synchrony or coherence of interactional rhythms between each infant and mother. Results showed the existence of periodicities in the behavior of each infant and mother at 3 and 5 months, with most subjects showing spectral peaks between .022 and .10 Hz. Increases from 3 to 5 months in behavioral periodicities were found for infants and mothers as well as for the coherence between infant-mother dyads. Term dyads showed higher coherence than preterm dyads at both 3 and 5 months. Term infants more often led the interaction at both ages. These results were taken as evidence that behavioral periodicities, which may be biologically based, underlie early mother-infant interaction and provide a temporal structure for the organization of cognitive and affective experience. Differences in synchrony between term and preterm infants may explain later reported differences in language between these groups.     

The Development of a Linkage between Count Nouns and Object Categories: Evidence from Fifteen- to Twenty-One-Month-Old Infants

Recent research suggests that, although young children appreciate many different kinds of conceptual relations among objects, they focus specifically on taxonomic relations in the context of word learning. However, because the evidence for children's appreciation of this linkage between words and object categories has come primarily from children who have made substantial linguistic and conceptual advances, it offers limited information concerning the development of this linkage. In the experiments reported here, we employ a match-to-sample task to focus specifically on the development of an appreciation of the linkage between words (here, count nouns) and object categories in infants in the period just prior to and just subsequent to the naming explosion. The results demonstrate that, for 21-month-old infants, most of whom have recently entered the vocabulary explosion (Experiment 1), and for 16-month-old infants, most of whom have yet to commence the vocabulary explosion (Experiment 2), novel nouns focus attention on taxonomic relations among objects. This is important because it reveals a nascent appreciation of a linkage between words and object categories in infants who are at the very onset of language production. Results are interpreted within a developmental account of infants' emerging appreciation of a specific linkage between count nouns and object categories.     

Intermodal Perception of Happy and Angry Expressive Behaviors by Seven-Month-Old Infants

2 studies were conducted to examine the roles of facial motion and temporal correspondences in the intermodal perception of happy and angry expressive events. 7-month-old infants saw 2 video facial expressions and heard a single vocal expression characteristic of one of the facial expressions. Infants saw either a normally lighted face (fully illuminated condition) or a moving dot display of a face (point light condition). In Study 1, one woman expressed the affects vocally, another woman expressed the affects facially, and what they said also differed. Infants in the point light condition showed a reliable preference for the affectively concordant displays, while infants in the fully illuminated condition showed no preference for the affectively concordant display. In a second study, the visual and vocal displays were produced by a single individual on one occasion and were presented to infants 5 sec out of synchrony. Infants in both conditions looked longer at the affectively concordant displays. The results of the 2 studies indicate that infants can discriminate happy and angry affective expressions on the basis of motion information, and that the temporal correspondences unifying these affective events may be affect-specific rhythms.     

Long-Term Memory for Context-Specific Category Information at Six Months

The ability of 6-month-old infants to remember a functional category acquired in a specific context was assessed in 3 experiments via an operant procedure in which infants learned to perform a specific action (a footkick) to activate an object suspended before them. In Experiment 1, infants trained with different exemplars in the same context transferred responding to a novel exemplar in the same but not a different context 24 hours later. Experiment 2 revealed that infants' reactivated memory of category training remained intact and context-specific after 3 weeks. In Experiment 3, a novel category exemplar was able to reactivate the forgotten memory of category training only in the encoding context. At 6 months, information about the place where categories are constructed is prerequisite for retrieval of a category concept from long-term memory. This requirement insures that early category concepts remain stable over relatively long periods.