Infants’ understanding of auditory events

Infants’ reaching‐in‐the‐dark was studied in a sample of normal 7.5–11‐month‐olds to determine whether infants can use sound cues to localize and recognize the action and objects of complex events. Infants were shown an event in which a moving, sounding object rotated clockwise through the infant's reaching space in the light and dark. Infrared recorded videotapes were later coded for reaching behaviour. Results showed that infants were able to localize the object on most trials in the dark but were slower and less efficient than in the light. Infants grasped the object at first contact and contacted the object near its salient feature in the dark, suggesting recognition of the object. Further, contact time was 1.7 s less when infants grasped the object at first contact in the dark (recognition) than when they touched the object, suggesting that recognition of the object improves reaching efficiency. There were no age and gender differences. In sum, the results support the use of the reaching‐in‐the‐dark method to demonstrate auditory localization of moving sounds and to reveal infants capacity to use represented information to guide subsequent action. Copyright © 1999 John Wiley & Sons, Ltd.     

Infants’ coding of location in continuous space

The ability to code location in continuous space is fundamental to spatial behavior. Existing evidence indicates a robust ability for such coding by 12 months, but systematic evidence on earlier origins is lacking. A series of studies investigated 5-month-olds’ ability to code the location of an object hidden in a sandbox, using a looking-time paradigm. In Experiment 1, after familiarization with a hiding-and-finding sequence at one location, infants looked longer at an object being disclosed from a location 12 inches (30 cm) away than at an object emerging from the hiding location, showing they were able to code location in continuous space. In Experiment 2, infants reacted with greater looking when objects emerged from locations 8 inches (20 cm) away from the hiding location, showing that location coding was more finely grained than could be inferred based on the first study. In Experiment 3, infants were familiarized with an object shown in hiding-and-finding sequences at two different locations. Infants looked longer at objects emerging 12 inches (30 cm) away from the most recent hiding location than to emergence from the other location, showing that infants could code location even when events had previously occurred at each location. In Experiment 4, after familiarization with two objects with different shapes, colors, and sounding characteristics, shown in hiding-and-finding sequences in two locations, infants reacted to location violations as they had in Experiment 3. However, they did not react to object violations, that is, events in which the wrong object emerged from a hiding location. Experiment 5 also found no effect of object violation, even when the infants initially saw the two objects side by side. Spatiotemporal characteristics may play a more central role in early object individuation than they do later, although further study is required.     

Infants’ perception of object–surface interplays

Twelve‐ and 18‐month‐old infants participated in a study designed to investigate the quality of their manual action when relating an object to the surface on which it is explored. Specifically, infants’ perception‐action routines were observed when they were presented with multiple objects (wooden scoop, Velcro block, and crayon) on surfaces of varying properties (paper, sand, and Velcro) to determine if sensory feedback or perceptual awareness steered their exploration of the available materials. Infants were observed to selectively tailor their manual actions across conditions, apparently guided by a perceived awareness of the fit between their manual dexterity and the environmental arrangement.     

Infants’ unprovoked acts of force toward others

Infants harm others at higher rates than older children and adults. A common explanation is that infants fail to regulate their frustration, becoming aggressive when they do not get what they want. The present research investigated whether infants also use force against others without provocation, for instance because they seek to explore the consequences of hitting or try to pet someone using too much force. Two studies with infants aged 11 to 24 months investigated infants’ use of force against others in everyday life using maternal report (Study 1) and direct observation (Study 2). In both studies, a large proportion of infants’ acts of force were unprovoked and occurred without signs of infant distress. Unlike provoked acts, unprovoked acts showed a decrease late in the second year and were positively associated with reports of infant pleasure‐proneness. The presence of unprovoked acts of harm may reflect that infants’ actions are not reliably guided by an aversion for harming others and may provide unique opportunities for early moral development.     

Infants’ responsiveness to maternal speech and singing

Infants who were 6 months of age were presented with extended audiovisual episodes of their mother's infant-directed speech or singing. Cumulative visual fixation and initial fixation of the mother's image were longer for maternal singing than for maternal speech. Moreover, movement reduction, which may signal intense engagement, accompanied visual fixation more frequently for maternal singing than for maternal speech. The stereotypy and repetitiveness of maternal singing may promote moderate arousal levels, which sustain infant attention, in contrast to the greater variability of speech, which may result in cycles of heightened arousal, gaze aversion, and re-engagement. The regular pulse of music may also enhance emotional coordination between mother and infant.     

Infants’ developing understanding of the link between looker and object

Three studies investigated infants’ understanding that gaze involves a relation between a person and the object of his or her gaze. Infants were habituated to an event in which an actor turned and looked at one of two toys. Then, infants saw test events in which (1) the actor turned to the same side as during habituation to look at a different toy, or (2) the actor turned to the other side to look at the same toy as during habituation. The first of these involved a change in the relation between actor and object. The second involved a new physical motion on the part of the actor but no change in the relation between actor and object. Seven‐ and 9‐month‐old infants did not respond to the change in relation between actor and object, although infants at both ages followed the actor's gaze to the toys. In contrast, 12‐month‐old infants responded to the change in the actor–object relation. Control conditions verified that the paradigm was a sensitive index of the younger infants’ representations of action: 7‐ and 9‐month‐olds responded to a change in the actor–object relation when the actor's gaze was accompanied by a grasp. Taken together, these findings indicate that gaze‐following does not initially go hand in hand with understanding the relation between a person who looks and the object of his or her gaze, and that infants begin to understand this relation between 9 and 12 months.     

Infants’ ability to track and reach for temporarily occluded objects

Six‐month‐old infants were presented with a moving object that temporarily became invisible. The object moved on a horizontal path and was made invisible for either 400, 800 or 1,200 ms before being within reach. Two kinds of events were used to make the object invisible: blackout of the room lights and occlusion behind a screen. First, infants saw 6 trials of the fully visible motion, then 12 trials of a temporarily invisible motion and finally 6 trials of the fully visible motion again. Each infant was presented with only one of the 6 experimental conditions. The results show that reaching is much more severely affected by a period of temporary non‐visibility than tracking. The effects of the two modes of non‐visibility were rather different. In general, blackout deteriorated tracking and made the gaze lag at reappearance. It inhibited reaching but this effect attenuated with experience. Longer periods of blackout deteriorated tracking and reaching more. Compared to blackout, occlusion had both a facilitating and an inhibiting effect on infants’ actions. Tracking had less tendency to lag but reaching showed more severe inhibition. The results are discussed in terms of graded representations. Furthermore, it is argued that an occluder facilitates tracking by providing information of where the moving object becomes visible again and it inhibits reaching by interfering with the representation of the object behind the occluder.     

Infants’ responsiveness to pictorial depth cues in preferential-reaching studies: A meta-analysis

The findings of numerous preferential-reaching studies suggest that infants first respond to pictorial depth cues between 5 and 7 months of age. However, three recent preferential-reaching studies have found evidence of responsiveness to pictorial depth cues in 5-month-olds. We investigated these apparently contradictory results by conducting meta-analyses of the data from 5-month-olds who participated in preferential-reaching studies. The data from 16 samples, comprising 475 infants 5–5.5 months of age, were integrated. The results showed that the infants responded more consistently to depth relationships specified by pictorial cues under monocular than under binocular viewing conditions (p < .001), indicating that 5-month-old infants respond to pictorial depth cues. This effect remained significant (p < .001) when the individual experiments that had found significant results were omitted from the analysis. Although the majority of experiments were unable to find evidence of pictorial depth perception individually, this ability was clearly revealed when their results were combined.     

Infants’ responses to objects representing levels of word knowledge and categorical information

The effects of differing levels of word knowledge on infants’ sequential touching behaviors were investigated in two studies. In both, parent report was used to assess three levels of word knowledge: known, frontier, and unknown. In the first study, 14-month-old infants sequentially touched objects consistent with parents’ reports of their word knowledge. In the second study, 20-month-old infants sequentially touched objects by both conceptual category and reported level of word knowledge. It appears that even infants, like adults, can make distinctions among objects on the basis of their knowledge about the objects’ labels.     

Infants’ grip strength predicts mu rhythm attenuation during observation of lifting actions with weighted blocks

Research has established that the body is fundamentally involved in perception: bodily experience influences activation of the shared neural system underlying action perception and production during action observation, and bodily characteristics influence perception of the spatial environment. However, whether bodily characteristics influence action perception and its underlying neural system is unknown, particularly in early ontogeny. We measured grip strength in 12‐month‐old infants and investigated relations with mu rhythm attenuation, an electroencephalographic correlate of the neural system underlying action perception, during observation of lifting actions performed with differently weighted blocks. We found that infants with higher grip strength exhibited significant mu attenuation during observation of lifting actions, whereas infants with lower grip strength did not. Moreover, a progressively strong relation between grip strength and mu attenuation during observation of lifts was found with increased block weight. We propose that this relation is attributable to differences in infants’ ability to recognize the effort associated with lifting objects of different weights, as a consequence of their developing strength. Together, our results extend the body's role in perception by demonstrating that bodily characteristics influence action perception by shaping the activation of its underlying neural system.     

Infants’ developing expectations of possible and impossible tool-use events between ages 8 and 12 months

Infants’ developing causal expectations for the outcome of a simple tool-use event from ages 8 to 12 months were investigated. Causal expectations were studied by comparing infants’ developing tool-use actions (i.e. as tool-use agents) with their developing perceptual reactions (i.e. as tool-use observers) to possible and impossible tool-use events. In Experiment 1, tool-use actions were studied by presenting infants, ages 8 and 12 months, with tool-use object-retrieval problems. In Experiment 2, a second age-matched sample of infants watched a comparable series of possible and impossible tool-use events in which a tool was used to retrieve a goal-object. Two core related findings were made. First, infants’ causal action and causal perception develop in parallel. In both action and perception, supporting tool-use develops before surrounding tool-use. Second, infants’ tool-use action develops before their causal perception of comparable tool-use events. The findings support the constructivist hypothesis that infants’ causal actions may develop before and inform their causal perceptions.     

Sing that tune: Infants’ perception of melody and lyrics and the facilitation of phonetic recognition in songs

To better understand how infants process complex auditory input, this study investigated whether 11-month-old infants perceive the pitch (melodic) or the phonetic (lyric) components within songs as more salient, and whether melody facilitates phonetic recognition. Using a preferential looking paradigm, uni-dimensional and multi-dimensional songs were tested; either the pitch or syllable order of the stimuli varied. As a group, infants detected a change in pitch order in a 4-note sequence when the syllables were redundant (experiment 1), but did not detect the identical pitch change with variegated syllables (experiment 2). Infants were better able to detect a change in syllable order in a sung sequence (experiment 2) than the identical syllable change in a spoken sequence (experiment 1). These results suggest that by 11 months, infants cannot “ignore” phonetic information in the context of perceptually salient pitch variation. Moreover, the increased phonetic recognition in song contexts mirrors findings that demonstrate advantages of infant-directed speech. Findings are discussed in terms of how stimulus complexity interacts with the perception of sung speech in infancy.     

Infants’ expressive behaviors to mothers and unfamiliar partners during face-to-face interactions from 4 to 10 months

Changes in the organization of infant looking, facial expressions, and vocalizations were examined over age (4, 7, and 10 months) and with different social partners. Although infants at all ages accompanied smiling with looking at both mothers and unfamiliar partners, 7- and 10-month infants accompanied vocalization with looking only when they were with mothers. Seven- and 10-month-olds vocalized with unfamiliar partners only when they were smiling at the same time. When mothers stopped talking, infants reduced smiling significantly at all ages, yet vocalized more at 10 months. In the second half of the first year, there are fundamental changes in the coordination of infant expressive behaviors that reveal a keen attunement to variations in maternal behavior and the familiarity of social partners.     

Categorization,categorical perception,and asymmetry in infants’ representation of face race

The present study examined whether 6‐ and 9‐month‐old Caucasian infants could categorize faces according to race. In Experiment 1, infants were familiarized with different female faces from a common ethnic background (i.e. either Caucasian or Asian) and then tested with female faces from a novel race category. Nine‐month‐olds were able to form discrete categories of Caucasian and Asian faces. However, 6‐month‐olds did not form discrete categories of faces based on race. In Experiment 2, a second group of 6‐ and 9‐month‐olds was tested to determine whether they could discriminate between different faces from the same race category. Results showed that both age groups could only discriminate between different faces from the own‐race category of Caucasian faces. The findings of the two experiments taken together suggest that 9‐month‐olds formed a category of Caucasian faces that are further differentiated at the individual level. In contrast, although they could form a category of Asian faces, they could not discriminate between such other‐race faces. This asymmetry in category formation at 9 months (i.e. categorization of own‐race faces vs. categorical perception of other‐race faces) suggests that differential experience with own‐ and other‐race faces plays an important role in infants’ acquisition of face processing abilities.     

Infants’ statistical word segmentation in an artificial language is linked to both parental speech input and reported production abilities

Individual variability in infant's language processing is partly explained by environmental factors, like the quantity of parental speech input, as well as by infant‐specific factors, like speech production. Here, we explore how these factors affect infant word segmentation. We used an artificial language to ensure that only statistical regularities (like transitional probabilities between syllables) could cue word boundaries, and then asked how the quantity of parental speech input and infants’ babbling repertoire predict infants’ abilities to use these statistical cues. We replicated prior reports showing that 8‐month‐old infants use statistical cues to segment words, with a preference for part‐words over words (a novelty effect). Crucially, 8‐month‐olds with larger novelty effects had received more speech input at 4 months and had greater production abilities at 8 months. These findings establish for the first time that the ability to extract statistical information from speech correlates with individual factors in infancy, like early speech experience and language production. Implications of these findings for understanding individual variability in early language acquisition are discussed.     

Social Categorization in Intergroup Contexts: Three Kinds of Self‐Categorization

In reviewing self‐categorization theory and the literature upon which it is based, we conclude that individuals' attempts to form social categories could lead to three kinds of self‐categorization. We label them intergroup categorization, ingroup categorization, and outgroup categorization. We review literature supporting these three types and argue that they can help to explain and organize the existing evidence. Moreover, we conclude that distinguishing these three kinds of self‐categorization lead to novel predictions regarding social identity, social cognition, and groups. We offer some of those predictions by discussing their potential causes (building from optimal distinctiveness and security seeking literatures) and implications (on topics including prototype complexity, self‐stereotyping, stereotype formation, intergroup behavior, dual identity, conformity, and the psychological implications of perceiving uncategorized collections of people). This paper offers a platform from which to build theoretical and empirical advances in social identity, social cognition, and intergroup relations.     

Gender Differences in Supervisors’ Use of Performance Feedback1

This study examined whether male and female supervisors differed in their delivery of performance feedback to subordinates. Male and female subjects supervised 2 confederate subordinates whose performance was stable and either above or below average. Supervisors regularly checked each subordinate's performance and could deliver one of several feedback messages. A MANOVA was performed on frequency of specific negative, general negative, specific positive, general positive, and neutral feedback messages, followed by step down analyses to isolate which dependent variables contributed uniquely. Male and female supervisors were distinguished by their use of specific negative feedback. Males were more likely to provide such messages to poorly performing subordinates, a result consistent with suggestions that males are characterized by a more directive leadership style.     

Infants’ intentionally communicative vocalizations elicit responses from caregivers and are the best predictors of the transition to language: A longitudinal investigation of infants’ vocalizations,gestures and word production

What aspects of infants’ prelinguistic communication are most valuable for learning to speak, and why? We test whether early vocalizations and gestures drive the transition to word use because, in addition to indicating motoric readiness, they (a) are early instances of intentional communication and (b) elicit verbal responses from caregivers. In study 1, 11 month olds (N = 134) were observed to coordinate vocalizations and gestures with gaze to their caregiver's face at above chance rates, indicating that they are plausibly intentionally communicative. Study 2 tested whether those infant communicative acts that were gaze‐coordinated best predicted later expressive vocabulary. We report a novel procedure for predicting vocabulary via multi‐model inference over a comprehensive set of infant behaviours produced at 11 and 12 months (n = 58). This makes it possible to establish the relative predictive value of different behaviours that are hierarchically organized by level of granularity. Gaze‐coordinated vocalizations were the most valuable predictors of expressive vocabulary size up to 24 months. Study 3 established that caregivers were more likely to respond to gaze‐coordinated behaviours. Moreover, the dyadic combination of infant gaze‐coordinated vocalization and caregiver response was by far the best predictor of later vocabulary size. We conclude that practice with prelinguistic intentional communication facilitates the leap to symbol use. Learning is optimized when caregivers respond to intentional vocalizations with appropriate language.