Infant Differences in Rate of Visual Encoding

To clarify the basis for infant differences in rate of visual encoding, the eye movements of a sample of 9 12-week-old infants were recorded throughout an encoding experiment. Results showed that the more slowly encoding infants scanned less extensively over the stimulus, often spent extended intervals in the continuous inspection of one part of the figure, and frequently engaged in prolonged fixations. A second experiment provided comparable scanning data from a sample of 9 2-week-old infants. There were significant age differences in the manner of visual scanning, and the scanning style of the more slowly encoding 12-week-old infants proved to be more like that of the younger infants. Possible explanations for both the between-age and within-age differences are proposed.     

Integration of Sequential Information for Shape Perception by Infants: A Developmental Study

Perception of form by spatiotemporal integration was investigated in 3 experiments. In the first, infants aged 8, 10, and 12 months were tested using a novelty-preference procedure to determine the earliest age at which recognition of rectilinear and curvilinear form occurred. Infants were shown a light-point tracing of the outline of a figure, followed by simultaneous presentation of 2 test objects, one of the same shape as the tracing and one of a different shape. The tracing was double the size of the test objects. Only infants in the oldest group responded selectively by looking longer at the object of different shape. In the second experiment with 12-month-old infants only, it was shown that recognition of rectilinear, but not curvilinear, form occurred despite a difference in the orientation and size of tracing and object. Computer-generated tracings were used in the final experiment to compare form recognition for 2D and 3D stimuli. Selective responding occurred only for the latter. These findings show that by 12 months infants perceive the correspondence between the figural properties of a tracing and its extended form, but that this perception is dependent on the provision of depth cues.     

Imitation or Exploration? Young Infants' Matching of Adults' Oral Gestures

The claim that very young infants can imitate rests largely on reports that infants match adult displays of mouth opening (MO) and tongue protrusion (TP). Recent reviews suggest that only tongue protruding is reliably matched by young infants. This study tests the proposal that infants' "imitation" of tongue protruding reflects a coincidental match between a sight that infants find interesting and a behavior by which infants express interest. In Study 1, 4-week-old infants who looked longer at a nonsocial light display also produced TPs at higher rates than infants showing less interest. In Study 2, 4-week-old infants showed more interest in (looked longer at) a tongue-protruding adult face than a mouth-opening face. Study 3 tracked 2 infants' responses to interesting objects for several weeks before and after the onset of manual reaching. Both infants produced tongue protrusions in response to objects within reach before but not after reaching developed. Together, the results of the 3 studies suggest that infants' tongue protrusions in response to a tongue-protruding adult reflect very early attempts at oral exploration of interesting objects.     

The development of infant sensitivity to biomechanical motions

3 experiments were conducted to examine infant sensitivity at 20, 30, and 36 weeks of age to the 3-dimensional structure of a human form specified through biomechanical motions. All 3 experiments manipulated occlusion information in computer-generated arrays of point-lights moving as if attached to the major joints and head of a person walking. These displays are readily recognized as persons by adults when occlusion information is present, but not when it is absent or inconsistent with the implicit structure of the human body. Converging findings from Experiments 1 and 2 suggested that 36-week-old infants were sensitive to the presence of occlusion information in point-light walker displays; neither 20- nor 30-week-old infants showed any sensitivity to this information. The results of Experiment 3 revealed further that 36-week-old infants were sensitive to whether or not the pattern of occlusion was consistent with the implicit form of the human body, but only when the displays were presented in an upright orientation. These findings are interpreted as suggesting that infants, by 36 weeks of age, are extracting fundamental properties necessary for interpreting a point-light display as a person.     

Concept acquisition in the human infant.

The ability of 18-, 24-, and 30-week-old infants to learn conceptual categories regarding adult female faces was examined using a habituation paradigm. Little evidence for conceptual categorization occurred at 18 or 24 weeks, but at 30 weeks infants learned to respond to "a specific female face regardless of orientation" and to "female faces in general."     

Infant visual scanning of two- and three-dimensional forms

2- and 3-dimensional forms affected 4- and 8-week-old infant visual behavior differently, 4-week-old infants fixated a recessed 3-dimensional form more than a 2-dimensional form but did not scan it differently. 8-week-old infants did not look more at 1 stimulus than another but scanned a raised 3-dimensional form differently than a 2-dimensional equivalent. For all stimuli and both age groups, there was a relation between attractiveness of stimuli and how they were scanned; babies who were most attracted to stimuli inspected them with the smallest eye movements.     

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.     

Intermanual transfer of shapes in preterm human infants from 33 to 34 + 6 weeks postconceptional age

This study investigated the ability of preterm infants to learn an object shape with one hand and discriminate a new shape in the opposite hand (without visual control). Twenty-four preterm infants between 33 and 34 + 6 gestational weeks received a tactile habituation task with either their right or left hand followed by a tactile discrimination task in the opposite hand. The results confirmed that habituation occurred for both shapes and both hands. Infants subsequently held the novel shape longer in the opposite hand. The results reveal that preterm infants are capable of intermanual transfer of shape information. In spite of the immaturity of the corpus callosum in preterm infants, its development seems to be sufficient to allow some transfer of information between both hands.     

Continuous vowel discrimination in normal and at risk infants.

The present study investigated vowel discrimination in 2-week-old infants using a nonnutritive, high-amplitude sucking measure in a habituation-dishabituation paradigm. Infants were presented with pairs of vowel stimuli differing in equal logarithmic steps along the /i/ to /I/ continuum. Stimulus pairs of equal acoustic differences were selected to be either within or between the adult phonetic categories. Infants were divided into 3 experimental stimulus shift conditions: within category, between category, and control. Using a scoring system to asses perinatal events, half the infants in each condition were categorized as being at "higher risk" for developmental (p less than .05) were found between the control and both the within and between phonetic category conditions. No effects due to risk score population differences proved to be significant. These results indicate that 8-week-old infants discriminate the vowels /i/ and /I/ in a continuous as opposed to a categorical manner. Some differences were noted in response patterns between high- and low-risk score infants.     

Heart Rate and Behavioral measures of Attention in Six-, Nine-, and Twelve-Month-Old Infants during Object Exploration

In this study we examined the effect of heart rate and behavioral measures of attention on distractibility of 6-, 9-, and 12-month-old infants. The infants were presented with a toy, and a distractor was presented while they attended to the toy. The distractor was presented during heart rate changes indicating sustained attention or attention termination, or during periods of time when behavioral ratings indicated the infant was in focused or casual attention. There were longer distraction latencies during attentional engagement as defined by heart rate changes or behavioral ratings than for periods of inattention. Infants had the longest distraction latencies when heart rate and behavior measures were congruent with respect to attention engagement (heart rate deceleration and focused attention). Conversely, latencies were shortes for congruent values of inattention (heart rate acceleration and casual attention). Infant information processing may be greatest when a heart rate deceleration occurs simultaneously with an episode of focused attention.     

Individual differences in infant-mother attachment at twelve and eighteen months: stability and change in families under stress

100 economically disadvantaged mothers and their infants were observed in the Ainsworth and Wittig "strange situation" at 12 and 18 months. Infants were classified as secure, anxiously attached/avoidant, or anxiously attached/resistant. In addition, mothers reported occurrence of stressful events related to the stability of the caretaking environment during the 12--18 month period by completing a 44-item checklist concerning work, finances, family, neighbors, health, etc. 62 infants were assigned to the same attachment classification at both 12 and 18 months (p less than .01). Despite this stability, significantly more infants changes classification than in a recent study of stable middle-class families. With the present sample, anxious attachment was associated with less stable caretaking environments than secure attachment; change from secure to anxious attachment was associated with higher stressful-event scores than stable secure attachment.     

Thirteen-month-olds rely on shared labels and shape similarity for inductive inferences

This study examined the influence of shape similarity and labels on 13-month-olds' inductive inferences. In 3 experiments, 123 infants were presented with novel target objects with or without a nonvisible property, followed by test objects that varied in shape similarity. When objects were not labeled, infants generalized the nonvisible property to high-similarity objects (Experiment 1). When objects were labeled with the same noun, infants generalized the nonvisible property to high- and low-similarity objects (Experiment 2). Finally, when objects were labeled with different nouns, infants generalized the nonvisible property to high-similarity objects (Experiment 3). Thus, infants who are beginning to acquire productive language rely on shared shape similarity and shared names to guide their inductive inferences.     

Effects of motion and figural goodness on haptic object perception in infancy

4-month-old infants held 2 rings, 1 in each hand, out of view. The rings moved rigidly together and were either the same (Experiment 1) or different (Experiment 2) in substance, weight, texture, and shape. After haptic habituation to a ring display, patterns of preferential looking to visibly connected vs. separated rings provided evidence that the infants perceived the rings in both experiments as parts of one connected object. This perception was no weaker when the rings differed in shape and substance, even though infants were shown (Experiment 3) to detect that difference. In the haptic mode, as in the visual mode, infants appear to perceive object unity by analyzing motion but not by analyzing figural goodness. The findings suggest that an amodal mechanism underlies object perception.     

The Influence of Shape Similarity and Shared Labels on Infants'' Inductive Inferences about Nonobvious Object Properties

This study examined the influence of object labels and shape similarity on 16- to 21-month-old infants' inductive inferences. In three experiments, a total of 144 infants were presented with novel target objects with or without a nonobvious property, followed by test objects that varied in shape similarity to the target. When objects were not labeled, infants generalized the nonobvious property to test objects that were highly similar in shape (Experiment 1). When objects were labeled with novel nouns, infants relied both on shape similarity and shared labels to generalize properties (Experiment 2). Finally, when objects were labeled with familiar nouns, infants generalized the properties to those objects that shared the same label, regardless of shape similarity (Experiment 3). The results of these experiments delineate the role of perceptual similarity and conceptual information in guiding infants' inductive inferences.     

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.     

Differential rates of visual information processing in full-term and preterm infants

This study investigated the effect of increasing familiarization time on the visual recognition memory of 6- and 12-month-old full-term and preterm infants. Infants were given trials in which they viewed a shape for either 10-, 15-, 20-, or 30-sec familiarization and were then tested for visual recognition memory using the paired comparison technique. While the older infants showed evidence of recognition memory after less familiarization time than the younger ones, at both ages preterms required considerably longer familiarization than full-terms. The pattern of performance replicates our earlier finding of developmental lags in the visual information processing of 6-month-old preterms and extends these findings to 12-month-olds. These results suggest that there are persistent differences between preterm and full-term infants throughout at least the first year of life in this very fundamental aspect of cognition.     

The Robustness of Infant Haptic Memory: Testing Its Capacity to Withstand Delay and Haptic Interference

The robustness of infant haptic memory was assessed in terms of its capacity to withstand either a brief delay or potential retroactive "interference" from other haptic input. 48 infants (mean age 8 months) were familiarized haptically to a small cube or sphere with smooth or rough surface texture and subsequently tested for recognition of the shape and texture of this stimulus in terms of the relative level of haptic response to 3 test stimuli, comprising the familiar stimulus, a new-shape stimulus, and a new-texture stimulus. The test stimuli were presented ( a ) immediately, ( b ) after a 5-min delay, or ( c ) after a second familiarization or "interference" phase involving another haptic stimulus different in shape and texture to the first. The infants demonstrated recognition of shape and texture in the No Delay condition, of shape and (marginally) of texture in the Delay condition, but only of texture in the Interference condition. The greater susceptibility of shape to interference was considered in terms of the degree of similarity among the shapes employed in the study.     

Attractiveness of lactating females' breast odors to neonates

A series of experiments investigated the responses of human infants to olfactory cues produced by lactating females. 2-week-old bottle-feeding girls oriented preferentially to the breast odor (odorized pad) of a nursing woman when paired with such odors from either a nonparturient female or axillary odors from the same lactating female. Responses to axillary odor from a lactating female did not differ from those to a clean (nonodorized) pad. These data indicate that breast odors from lactating females are especially attractive to female infants who are unfamiliar with the stimulus woman and who have had no prior breast-feeding experience.     

Effects of maternal absence due to employment on the quality of infant-mother attachment in a low-risk sample

Recent reports have suggested that day-care experience initiated prior to 12 months of age is associated with increased proportions of infants whose attachment to mother is classified as "insecure-avoidant." However, reviewers have questioned the generality of these findings, noting that samples in which associations between early day-care experience and avoidant attachment patterns have been reported come from high-risk populations, and/or that the infants' day-care settings may not have been of high quality. In the present study, effects of maternal absences on infant-mother attachment quality were assessed in a low-risk, middle-class sample (N = 110). In all instances, substitute care had been initiated at least 4 months prior to the infant's first birthday and was provided in the infant's home by a person unrelated to the baby. Infants were assessed using the Ainsworth Strange Situation when they were 12-13 months of age. Analyses indicated that a significantly greater proportion of infants whose mothers worked outside the home (N = 54) were assigned to the category "insecure-avoidant" as compared to infants whose mothers remained in the home (N = 56) throughout the first year of life. Analyses of demographic and psychological data available for the sample indicated that this relation is dependent upon maternal parity (primi- vs. multiparous mother). The association between attachment quality and work status was significant only for firstborn children of full-time working mothers. The results are interpreted as evidence that the repeated daily separations experienced by infants whose mothers are working full-time constitute a "risk" factor for the development of "insecure-avoidant" infant-mother attachments.     

Infant response to stimuli of similar hue and dissimilar shape: tracing the origins of the categorization of objects by hue

This study confirms that infants, like older children, are capable of responding "categorically" to stimuli of different shape if these are similar in hue. 24 infants (mean age 20.0 weeks) were familiarized to a stimulus in 1 hue (dominant wavelength 515 nm) and in either of 2 different shapes (face of a bear or a rabbit) and then presented with 4 main test comparisons in which the familiar stimulus was paired with a novel stimulus in either the familiar or the alternate (novel) shape and in a novel hue from the same or a different category (dominant wavelengths being 548 and 482 nm, respectively, and equally different from the familiar hue). Infants displayed a preference for the novel stimuli only in the new-category hue. Control tasks with a further 40 infants (same mean age as experimental group) eliminated alternative explanations of this pattern of response in terms of differential brightness of the hues, hue preferences, or inability to discriminate the shapes.