The development of social referencing

The development of social referencing in 40 infants aged 6-9, 10-13, and 14-22 months was investigated in this study. Social referencing was defined broadly to include children's looks toward parents, their instrumental toy behaviors, affective expressions, and other behaviors toward parents. Children's looks at parents were more selective with increasing age, with older infants preferring to look directly at their parents' faces and younger infants showing no preference for looks to faces over looks elsewhere at the parent. Younger infants looked most often when their parents expressed positive affect, whereas older infants looked most often when parents displayed fearful reactions toward a stimulus. Evidence of a behavioral regulatory effect on instrumental toy behaviors was found only among infants 10-13 months of age. However, only infants older than 14 months of age inhibited touching the toy until after referencing the parent. On some measures these older infants showed a preference for toys associated with fearful messages. Affective expressions were in line with positive and negative behavior toward toys. No support for mood modification or simple imitation as explanations for the effects was found. Results indicated that the looking behavior of younger children may function differently than that of older children, and that social referencing involves a number of component skills that develop during the end of the first year and throughout the second year of life.     

In Defense of Qualitative Changes in Development

The balance between the preservation of early cognitive functions and serious transformations on these functions shifts across time. Piaget’s writings, which favored transformations, are being replaced by writings that emphasize continuities between select cognitive functions of infants and older children. The claim that young infants possess elements present in the older child’s concepts of number, physical impossibility, and object permanence is vulnerable to criticism because the inferences are based primarily on the single measure of change in looking time. It is suggested that investigators use unique constructs to describe phenomena observed in young infants that appear, on the surface, to resemble the psychological competences observed during later developmental stages.     

The development of visual expectations in the first year

The development of expectations was investigated by using the Visual Expectations Procedure. In Experiment 1, 128 infants aged 6-, 9-, and 12-months-old saw two 40-trial sequences of a videotaped mechanical toy appearing in various locations. The sequences represented an alternation pattern (i.e., ABAB) or a complex pivot pattern (i.e., ABCBABCB). In Experiment 2, 76 infants aged 4-, 8-, and 12-months-old saw either a left-right alternation or a top-bottom alternation. Reaction time improved and the percentage of anticipations increased between 6 and 9 months in Experiment 1 and between 4 and 8 months in Experiment 2 but not thereafter. Anticipations for the pivot sequence and for younger infants on both sequences were often incorrect (i.e., gaze shifts occurred before stimulus onset but were not directed toward the upcoming stimulus). We conclude that young infants have expectations that reflect some degree of general or procedural knowledge, but it is not clear that this behavior implies specific, articulated expectations about upcoming events.     

Infant visual sustained attention and respiratory sinus arrhythmia

Infants were studied cross-sectionally at 14, 20, and 26 weeks of age. They were presented with varying and complex patterns on a TV screen. Two-thirds of the presentations were accompanied by an "interrupting stimulus" in the periphery delayed in time from the onset of fixation on the central stimulus. The infants were not easily distracted from looking at the central stimulus when the presentation of the interrupting stimulus occurred at the point of maximal heart rate (HR) deceleration. However, if the presentation occurred at the end of the HR response, the infants were easily distracted. Infants with large amounts of respiratory sinus arrhythmia (RSA; i.e., HR variability) in a baseline recording were less distractible during the deceleration-defined trials than were infants with low amounts of RSA. High-RSA infants also showed larger HR deceleration on these trials than did the low-RSA infants. These results are consistent with a model positing that sustained HR lowering during visual fixation is an index of active attention and that RSA is an index of voluntary, sustained attention in infants.     

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.     

The development of visual short-term memory capacity in infants

Four experiments assessed visual short-term memory capacity in 4- to 13-month-old infants by comparing their looking to changing and nonchanging stimulus streams presented side by side. In each stream, 1 to 6 colored squares repeatedly appeared and disappeared. In changing streams, the color of a different randomly chosen square changed each time the display reappeared; the colors remained the same in nonchanging streams. Infants should look longer at changing streams, but only if they can remember the colors of the squares. The youngest infants preferred changing streams only when the displays contained one object, whereas older infants preferred changing streams when the displays contained up to 4 objects. Thus, visual short-term memory capacity increases significantly across the first year of life.     

The CS− effect in simple conditioning and stimulus selection during development

Changes in affect toward a particular stimulus can take place very rapidly through Pavlovian conditioning, if presentation of the conditioned stimulus (CS+) paired with the unconditioned stimulus (US) is accompanied by presentation of a “CS?,” another value of the same dimension as the CS+ but not paired with a US. This effect has considerable generality. It has been observed in terms of both olfactory and visual CSs, in terms of appetitive as well as aversive conditioning, and for adult as well as infant rats. The CS? effect has seemed especially important for infants, which may be related to the general tendency for infants to exhibit less stimulus selection than older animals. Finally, the CS? effect has enabled the development of a simple test of short-term retention that can quite effectively assess memory for either incidental or target events. These tests so far have indicated a clear ontogenetic decrease in rate of forgetting over short intervals, corresponding to the well-known development-related decrease in forgetting over long intervals (infantile amnesia). The tests also have shown that short-term forgetting of intentional and target events is surprisingly similar, with some indication of more rapid forgetting for the incidental events. Alternative interpretations of the CS? effect and some preliminary tests of these interpretations are discussed.     

Approval and Disapproval: Infant Responsiveness to Vocal Affect in Familiar and Unfamiliar Languages

In a series of 5 auditory preference experiments, 120 5-month-old infants were presented with Approval and Prohibition vocalizations in infant-directed (ID) and adult-directed (AD) English, and in ID speech in nonsense English and 3 unfamiliar languages, German, Italian, and Japanese. Dependent measures were looking-time to the side of stimulus presentation, and positive and negative facial affect. No consistent differences in looking-time were found. However, infants showed small but significant differences in facial affect in response to ID vocalizations in every language except Japanese. Infants smiled more to Approvals, and when they showed negative affect, it was more likely to occur in response to Prohibitions. Infants did not show differential affect in response to Approvals and Prohibitions in AD speech. The results indicate that young infants can discriminate affective vocal expressions in ID speech in several languages and that ID speech is more effective than AD speech in eliciting infant affect.     

Ontogenetic forgetting of stimulus attributes

The effects of age on the forgetting of stimulus attributes in a differential fear-conditioning paradigm were examined with 18- and 70-day-old rats tested in either the original conditions or shifted stimulating conditions at one of three retention intervals (1, 48, and 120 h). Adults displayed significant shifts at each retention interval, with those tested in the original context displaying greater fear than those tested in the shifted conditions. By contrast, by 48 h the 18-day-olds had forgotten the specific attributes of the training situation and began treating the two stimulating conditions as functionally equivalent (Experiment 1). In Experiment 2, we tracked the ontogenetic emergence of adult-like memory for stimulus attributes and found a dramatic increase in memory capability by 25 days of age. Experiment 3 illustrated that the forgotten memory attributes of infants may be retrieved by administering a 90-sec cuing treatment 10 min prior to the 48-h test. Implications for the phenomenon of infantile amnesia are discussed.     

Preference for Infant-directed Speech in the First Month after Birth

2 experiments examined behavioral preferences for infant-directed (ID) speech over adult-directed (AD) speech in young infants. Using a modification of the visual-fixation-based auditory-preference procedure, Experiments 1 and 2 examined whether 12 1-month-old and 16 2-day-old infants looked longer at a visual stimulus when looking produced ID as opposed to AD speech. The results showed that both 1-month-olds and newborns preferred ID over AD speech. Although the absolute magnitude of the ID speech preference was significantly greater, with the older infants showing longer looking durations than the younger infants, subsequent analyses showed no significant difference in the relative magnitude of this effect. Differences in overall looking times between the 2 groups apparently reflect task variables rather than differences in speech processing. These results suggest that infants' preference for the exaggerated prosodic features of ID speech is present from birth and may not depend on any specific postnatal experience. However, the possible role of prenatal auditory experience with speech is considered.     

Visual and verbal processes involved in the development of picture-recognition skills

4-5-year-old, 6-7-year-old, and 8-9-year-old children were given picture-recognition tasks in which recognition stimuli were systematically varied with respect to familiarization stimuli. Subjects were required either to verbalize or remain silent during familiarization and to identify either central figure only or whole picture recognition. Results suggested that (a) young children base recognition primarily on central figure whereas older children are more likely to utilize the entire stimulus array, and (b) younger children are more likely than older children to use spoken labels as a basis for recognition when they verbalize during familiarization.     

Toys and social interaction between infant peers

Claims that young infants fail to react in a social manner to one another and that toys preempt attention to peers were assessed by comparing the interactions observed between infant peers when they met in the presence of toys versus in their absence. 44 pairs of unacquainted infants (either 10--12 or 22--24 months of age) came with their mothers to an unfamiliar room. Without toys available in the room, infants of both ages more often contacted one another, smiled at and gestured to one another, and duplicated each other's actions. With toys, they showed and exchanged toys and spent more time synchronously manipulating similar play material. The results document that infants as young as 10 months of age are responsive to the person and behavior of an unfamiliar peer and that they are no less responsive than older infants to the social versus nonsocial aspects of a novel setting.     

Adults'' Responses to Infants Varying in Appearance of Age and Attractiveness

The relations among age appearance, facial attractiveness, and adult expectations of the developmental maturity of infants were examined in 3 studies. In Study 1, a relation was demonstrated between ratings of the attractiveness (77 judges) and age appearance (53 judges) of 6-month-olds: less attractive infants were judged to be older than their attractive age-mates. In Study 2, 75 parents judged the specific developmental abilities of 6-month-old infants and estimated the age of the babies. Parents overestimated both the age and the developmental abilities of the unattractive infants. Furthermore, ability estimates for the unattractive infants were significantly higher than judgments of the typical abilities of 6-month-olds made by another group of 35 parents. Finally, the results of Study 2 were replicated in Study 3 conducted with 348 mothers. It was also demonstrated in Study 3 that, although mothers expected unattractive infants to be capable of more specific developmental skills, they nevertheless rated the general competence of the unattractive infants to be lower than that of attractive infants. Specious contradictions in the attractiveness and age appearance literatures are resolved by these results: age appearance seems to function as an informational cue with respect to specific age-appropriate abilities, whereas attractiveness elicits evaluative attributions of general competence. Both types of information conveyed in faces may have important implications for adult evaluations of infants and older children.     

Individual Differences in Infant Visual Attention: Four-Month-Olds' Discrimination and Generalization of Global and Local Stimulus Properties

Cognitive performance and development is negatively correlated with fixation duration patterns during infancy, and evidence suggests that long-looking infants may process visual information more slowly than short-looking infants. 3 experiments described here tested the possibility that these differences may be due to differential sensitivity to global and local visual information. Infants were administered discrimination and generalization tasks involving global and local information at varying levels of familiarization time. Results indicated that 4-month-olds process visual information in a global-to-local sequence. Both long- and short-looking infants were sensitive to both types of information, although long lookers required additional familiarization time to match the performance of short lookers. Finally, apparent "generalization" of global information at brief familiarization levels was traced to insensitivity to local stimulus properties. The results do not support the hypothesis that long- and short-looking infants are differentially sensitive to global versus local visual information at 4 months of age.     

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.     

Human postdiscrimination gradients: The effects of three-stimulus discrimination training

Young adult subjects were trained in a discrimination involving three pure tones varying in pitch, with two positive stimuli and a negative stimulus located midway between the two. Subjects in the control conditions were trained only with the two positive stimuli. Generalization gradients were bimodal in all cases, but for the control subjects, the modes were at the positive stimulus values, while postdiscrimination gradients were displaced away from the negative stimulus toward the extremes of the continuum. Since, with this procedure, the training and test adaptation levels were the same, the observed displacements are difficult to explain in terms of an adaptation-level account of peak shifts. The observed shifts are more consistent with the conditioning-extinction model which assumes interactions between inhibitory and excitatory gradients. However, overall response rates did not reflect the action of summation processes.     

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.     

Predicting shifts in generalization gradients with perceptrons

Perceptron models have been used extensively to model perceptual learning and the effects of discrimination training on generalization, as well as to explore natural classification mechanisms. Here, we assess the ability of existing models to account for the time course of generalization shifts that occur when individuals learn to distinguish sounds. A set of simulations demonstrates that commonly used single-layer and multilayer perceptron networks do not predict transitory shifts in generalization over the course of training but that such dynamics can be accounted for when the output functions of these networks are modified to mimic the properties of cortical tuning curves. The simulations further suggest that prudent selection of stimuli and training criteria can allow for more precise predictions of learning-related shifts in generalization gradients in behavioral experiments. In particular, the simulations predict that individuals will show maximal peak shift after different numbers of trials, that easier contrasts will lead to slower development of shifted peaks, and that whether generalization shifts persist or dissipate will depend on which stimulus dimensions individuals use to distinguish stimuli and how those dimensions are neurally encoded.     

Expectation and anticipation of dynamic visual events by 3.5-month-old babies

We report an investigation of the development of visual expectancies in 3.5-month-old infants. One of the infant's eyes was videorecorded as the infant watched a series of slides that were presented noncontingent on behavior. Babies were presented an alternating and an irregular series of 30 slides with a 700-msec onset duration separated by an interstimulus interval (ISI). The ISI for the alternating series was 1,100 msec, whereas the slides for the irregular series were separated by 900, 1,100, or 1,300 msec, randomly ordered. One-half of the babies saw the irregular series first, and one-half saw the regular series first. Babies in both groups provided evidence that they developed expectations for the visual events in the alternating series. Their reaction times (RTs) declined significantly from 3-5 "baseline" presentations, and their RTs were reliably faster during the alternating than the irregular series. Additionally, babies in the alternating-late group had significantly more stimulus anticipations during the alternating than during the irregular series. These findings indicate that 3.5-month-olds can detect regularity in a spatiotemporal series, will develop expectancies for events in the series, and will act on the basis of those expectancies even when those actions have no effect on the stimulus events. We believe that infants are motivated to develop expectations for noncontrollable spatiotemporal events, because these expectations permit them to bring their visual behavior under partial internal control.     

Infant Auditory Temporal Acuity: Gap Detection

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, or variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listener, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.