Variability and its sources in infant categorization

Variability of infants’ categorization performance and potential sources of this variability were investigated. Using data from 13 categorization studies employing a habituation-of-looking paradigm with infants 3, 5, 6, and 9 months of age, a method for establishing a categorization criterion was developed and then used to classify individual infants as “categorizers” for particular tasks. Logistic regression analyses were then used to identify demographic and information-processing variables that predicted “categorizer” classification. Variables that increased the odds of being classified as a categorizer were gender, number of habituation trials, and duration of peak look during habituation; total looking time during habituation decreased the odds of categorizer classification. These findings are discussed in the context of individual differences in information processing.     

Individual differences in infant fearfulness and cognitive performance: a testing,performance, or competence effect?

The author conducted 2 studies to examine the relations between infant fear and cognitive testing performance in 12-month-old infants. In Study 1, fear was assessed by using 2 standard temperament questionnaires and a laboratory-based, standardized stranger approach. Individual differences in cognitive development were assessed using the Object Permanence Scale of the Infant Psychological Development Scales (I. C. Uzgiris & J. M. Hunt, 1975). All 3 assessments of fear significantly predicted object permanence performance, with correlations ranging from -.32 to -.35. In Study 2, fear was assessed via a maternal report questionnaire, and habituation performance was assessed via a basic-level categorization task. Familiarity with the examiner and with the testing environment was manipulated to test for a familiarity influence on performance. Testing revealed individual differences in both fear and habituation. Results suggest that highly fearful infants required more trials to habituate and were less likely to meet the habituation criterion than infants who were less fearful. Methodological and conceptual implications of these results are discussed.     

Examining individual differences in infants’ habituation patterns using objective quantitative techniques

The assessment of individual differences in infant habituation patterns is important for answering basic questions about continuity in cognitive development. Nevertheless, there are flaws with existing methods for determining relevant parameters of the cognitive processes associated with habituation. In this paper, a more rigorous, model-based alternative approach is illustrated. The approach demonstrates how the habituation data of individual infants may be fit by specific functions, how habituation may be distinguished from random responding, and how the parameter estimates of individual infants’ habituation functions might be analyzed for meaningful subgroups or clusters. The model-based approach provides novel insights about individual subgroups when applied to a real habituation data set and thereby demonstrates the feasibility and utility of the techniques advocated.     

Visual habituation in human infants: development and rearing circumstances

Summary Habituation is a type of learning that reflects changing responsiveness to repeated information. In two longitudinal studies, we examined individual differences, stability, and developmental change in the ontogeny of visual habituation in human infants across the middle of the first year of life. To study this phenomenon in breadth, we tested infants from two social classes within the same culture and infants from two different cultures. Infants demonstrated significant, but comparable, individual differences in habituation across socioeconomic and cultural variations in rearing circumstances; they showed significant, if moderate, stability in habituation; and they habituated significantly more quickly with age. These results are interpreted in terms of developing human beings' increasing efficiency in processing visual information near the beginning of extrauterine life.     

Biracial and monoracial infant own‐race face perception: an eye tracking study

We know that early experience plays a crucial role in the development of face processing, but we know little about how infants learn to distinguish faces from different races, especially for non‐Caucasian populations. Moreover, it is unknown whether differential processing of different race faces observed in typically studied monoracial infants extends to biracial infants as well. Thus, we investigated 3‐month‐old Caucasian, Asian and biracial (Caucasian‐Asian) infants’ ability to distinguish Caucasian and Asian faces. Infants completed two within‐subject, infant‐controlled habituation sequences and test trials as an eye tracker recorded looking times and scanning patterns. Examination of individual differences revealed significant positive correlations between own‐race novelty preference and scanning frequency between eye and mouth regions of own‐race habituation stimuli for Caucasian and Asian infants, suggesting that facility in own‐race face discrimination stems from active inspection of internal facial features in these groups. Biracial infants, however, showed the opposite effect: An ‘own‐race’ novelty preference was associated with reduced scanning between eye and mouth regions of ‘own‐race’ habituation stimuli, suggesting that biracial infants use a distinct approach to processing frequently encountered faces. Future directions for investigating face processing development in biracial populations are discussed. A video abstract of this article can be viewed at http://youtu.be/a_dDXfFuEfY     

Infant information-processing performance and maternal education

Relations between maternal education and indices of infant information-processing performance were examined. A sample of 93 3-month olds whose mothers' completed education level was adequately distributed were seen in an infant control habituation procedure. Eighteen infants failed to complete the procedure, and 76 reached a conventional habituation criterion. No significant differences in habituation performance by maternal education level emerged. This finding suggests that information-processing indices obtained in the first 6 months are useful as predictive measures of mental development that are uncorrelated with important markers of infants' environmental rearing conditions.     

Newborn habituation to visual stimuli: a sex difference in novelty detection

Thirty-six newborn human infants were repeatedly exposed to one of two visual stimuli, a four-square or 144-square black and white checkerboard target, until a set criterion of habituation was demonstrated, as measured by a decrement in visual fixation time. When the habituation criterion was reached, independent groups of Ss were either presented with the same target or with a target of either moderate or large discrepancy from the standard habituation stimulus. Results indicated that (1) there was habituation of visual attention, which replicated previous findings, and suggests that some infants soon after birth are capable of storing simple visual information, and (2) following habituation female infants displayed greater recovery of attention than male infants when the moderate stimulus change was introduced.     

Infant information processing and family history of specific language impairment: converging evidence for RAP deficits from two paradigms

An infant's ability to process auditory signals presented in rapid succession (i.e. rapid auditory processing abilities [RAP]) has been shown to predict differences in language outcomes in toddlers and preschool children. Early deficits in RAP abilities may serve as a behavioral marker for language-based learning disabilities. The purpose of this study is to determine if performance on infant information processing measures designed to tap RAP and global processing skills differ as a function of family history of specific language impairment (SLI) and/or the particular demand characteristics of the paradigm used. Seventeen 6- to 9-month-old infants from families with a history of specific language impairment (FH+) and 29 control infants (FH-) participated in this study. Infants' performance on two different RAP paradigms (head-turn procedure [HT] and auditory-visual habituation/recognition memory [AVH/RM]) and on a global processing task (visual habituation/recognition memory [VH/RM]) was assessed at 6 and 9 months. Toddler language and cognitive skills were evaluated at 12 and 16 months. A number of significant group differences were seen: FH+ infants showed significantly poorer discrimination of fast rate stimuli on both RAP tasks, took longer to habituate on both habituation/recognition memory measures, and had lower novelty preference scores on the visual habituation/recognition memory task. Infants' performance on the two RAP measures provided independent but converging contributions to outcome. Thus, different mechanisms appear to underlie performance on operantly conditioned tasks as compared to habituation/recognition memory paradigms. Further, infant RAP processing abilities predicted to 12- and 16-month language scores above and beyond family history of SLI. The results of this study provide additional support for the validity of infant RAP abilities as a behavioral marker for later language outcome. Finally, this is the first study to use a battery of infant tasks to demonstrate multi-modal processing deficits in infants at risk for SLI.     

Comparison of infant and adult P300 from auditory stimuli.

Event-related brain potentials (ERPs) using auditory stimuli were recorded from 5- to 10-month-old infants and normal young adults with a passive tone sequence paradigm. A P3 (P300) component was obtained which demonstrated the same central-parietal maximum scalp distribution for both subject groups. P3 amplitude was smaller and its peak latency longer for infants compared to those of the adults across all electrode sites. P3 measures remained stable across stimulus trials indicating that ERP habituation was not occurring. Evaluation of individual subjects suggests that the P3 can be elicited from infants with auditory stimuli in a manner similar to that from adults and may serve as a useful index for the assessment of cognitive function in infants.     

Habituation in high‐risk infants: reliability and patterns of responding

We examined both the reliability of infant‐controlled habituation and patterns of responding in a group of high‐risk infants (mean age 16 mos). Good test–retest reliability was found for mean, total, and baseline looking time for one of the stimuli. Classification of infants' pattern of performance yielded two groups: linear (57%) and non‐linear (29%) responders; 14% of cases could not be classified because of cross‐session inconsistencies in performance. Linear responders had shorter total looking times, fewer trials to criterion, and showed more habituation than non‐linear responders, thus validating the linear/non‐linear distinction. Our findings indicate that the infant‐controlled habituation task can be used reliably with infants who are at high risk for developmental disorders. Indeed, we provide evidence that this task is not only reliable, but may also provide meaningful distinctions between infants within the high‐risk population. Discussion focuses on the role of attention in distinguishing between short (linear) and long (non‐linear) lookers. Copyright © 2003 John Wiley & Sons, Ltd.     

Cardiac orienting responses of 6- and 16-week-old infants

Since previous data suggested that the magnitude of orienting evidenced by cardiac deceleration increased over the first 16 weeks of life, 6- and 16-week-old infants were compared on various characteristics of orienting: habituation, dishabituation, and magnitude of deceleration to stimulus offset as well as to stimulus onset. Neither the change in stimulus following habituation trials nor the stimulus offset produced a large enough response to confidently evaluate age differences suggested by the data. Stimulus onset elicited a pronounced deceleration which for the two age groups was of equivalent magnitude on initial trials and declined similarly with stimulus repetition. It was suggested that similarity of the two age groups on these parameters was due to control of state within a narrow alert range, and that, in general, younger infants are less likely than older infants to show orienting when conditions for orienting are marginal.     

Infant ability to tell voices apart rests on language experience

A visual fixation study tested whether 7-month-olds can discriminate between different talkers. The infants were first habituated to talkers producing sentences in either a familiar or unfamiliar language, then heard test sentences from previously unheard speakers, either in the language used for habituation, or in another language. When the language at test mismatched that in habituation, infants always noticed the change. When language remained constant and only talker altered, however, infants detected the change only if the language was the native tongue. Adult listeners with a different native tongue from the infants did not reproduce the discriminability patterns shown by the infants, and infants detected neither voice nor language changes in reversed speech; both these results argue against explanation of the native-language voice discrimination in terms of acoustic properties of the stimuli. The ability to identify talkers is, like many other perceptual abilities, strongly influenced by early life experience.     

Infants' discrimination of happy and sad music

Infants can detect information specifying affect in infant- and adult-directed speech, familiar and unfamiliar facial expressions, and in point-light displays of facial expressions. We examined 3-, 5-, 7-, and 9-month-olds' discrimination of musical excerpts judged by adults and preschoolers as happy and sad. In Experiment 1, using an infant-controlled habituation procedure, 3-, 5-, 7-, and 9-month-olds heard three musical excerpts that were rated as either happy or sad. Following habituation, infants were presented with two new musical excerpts from the other affect group. Nine-month-olds discriminated the musical excerpts rated as affectively different. Five- and seven-month-olds discriminated the happy and sad excerpts when they were habituated to sad excerpts but not when they were habituated to happy excerpts. Three-month-olds showed no evidence of discriminating the sad and happy excerpts. In Experiment 2, 5-, 7-, and 9-month-olds were presented with two new musical excerpts from the same affective group as the habituation excerpts. At no age did infants discriminate these novel, yet affectively similar, musical excerpts. In Experiment 3, we examined 5-, 7-, and 9-month-olds' discrimination of individual excerpts rated as affectively similar. Only the 9-month-olds discriminated the affectively similar individual excerpts. Results are discussed in terms of infants' ability to discriminate affect across a variety of events and its relevance for later social-communicative development.     

Infants track action goals within and across agents

The ability to understand that goals and other intentional relations are attributes of individual people is of fundamental importance to social life. It enables us to predict and interpret actions on-line by relating a person's prior and current behaviors, and distinguishing them from the behaviors of other persons. In this paper, we consider the origins of the ability to mark goals as attributes of individual people. Using a visual habituation paradigm to assess infants' tracking of goals, we tested whether infants represented goals are specific to particular agents. Thirteen-month-old infants restricted reaching goals to particular agents, but generalized a conventional linguistic action, labeling, across agents. Nine-month-old showed the former pattern but not the latter. We discuss these findings in the context of developing understandings of person specific and person general action knowledge.     

Young infants' reasoning about hidden objects: evidence from violation-of-expectation tasks with test trials only

The present research examined alternative accounts of prior violation-of-expectation (VOE) reports that young infants can represent and reason about hidden objects. According to these accounts, young infants' apparent success in these VOE tasks reflects only novelty and familiarity preferences induced by the habituation or familiarization trials in the tasks. In two experiments, 4-month-old infants were tested in VOE tasks with test trials only. The infants still gave evidence that they could represent and reason about hidden objects: they were surprised, as indicated by greater attention, when a wide object became fully hidden behind a narrow occluder (Experiment 1) or inside a narrow container (Experiment 2). These and control results demonstrate that young infants can succeed at VOE tasks involving hidden objects even when given no habituation or familiarization trials. The present research thus provides additional support for the conclusion that young infants possess expectations about hidden objects. Methodological issues concerning the use of habituation or familiarization trials in VOE tasks are also discussed.     

The ratio principle holds over a million-to-one range of illumination

Infant sensitivity to kinetic information specifying three-dimensional object shape was assessed using computer-generated random-dot displays. Four-month-old infants were habituated to displays of an object oscillating about two different axes on alternating trials. Following habituation, the infants were tested for recovery from habituation to a display of the same object and a novel object. Both test displays employed a new axis of rotation. The infants generalized habituation to the same object and increased their looking to the new object. These results provide evidence that infants are sensitive to motion-carried information specifying three-dimensional object shape, since the random-dot displays minimized static information that differentiated the two objects. These findings suggest that, at least by 4 months of age, infants can detect subtle differences in shape from purely kinetic information.     

Pattern perception in infants: effects of structure and transformation

Four experiments on pattern perception in 4-month-old infants are reported. The first two experiments examined the perception of pattern structure as defined by Garner (1974). Although the infants did not show an immediate preference for well-structured patterns (Experiment 1), during habituation they showed a reliable decrement in looking only to well-structured patterns (Experiment 2). On recovery trials in Experiment 2 infants were presented with two types of pattern change: a new configuration of the habituation pattern and a change in the orientation of the habituation pattern. The infants recovered looking to the orientation change, but generally not to the changes in configuration. It is argued that the results of Experiment 2 highlight the role of symmetry, especially vertical symmetry, in infant pattern perception. Recovery of looking to changes in the orientation, size, and position of the habituation pattern was examined in Experiments 3 and 4 where it was demonstrated that such changes are salient to the infant, arguably because of the presence of a surrounding, external frame.     

Influences of information processing and disengagement in infants' looking behaviour

The present study considers the joint influences of information processing and disengagement in looking behaviour within a habituation paradigm. Six‐month‐old infants were habituated, during which their heart rate (HR) was measured. A parametric model of habituation yielded for each infant parameter estimates of their habituation performance. These parameters were interpreted as assessing information processing and disengagement. Corresponding measures were obtained from the HR data. The HR measures and habituation model parameter estimates were significantly correlated, as predicted. In addition, an attention getter, presented prior to each habituation trial, influenced indicators of information processing, but not of disengagement. Results confirmed the advantages of a modelling approach. In addition, and more importantly, findings led to the conclusion that both information processing as well as disengagement are involved in infants' looking behaviour in visual habituation. Copyright © 2009 John Wiley & Sons, Ltd.     

婴儿识别面部表情的能力及其发展模式

采用婴儿控制的习惯化－去习惯化实验设计,测查了４２名８－１２个月的婴儿对愉快（Ｈ）、愤怒（Ａ）和惧怕（Ｆ）三种表情（照片）的习惯化速率及在六种表情配对顺序下（Ｈ－Ａ,Ａ－Ｈ,Ｈ－Ｆ,Ｆ－Ｈ,Ａ－Ｆ,Ｆ－Ａ）的识别能力。实验结果表明：（１）多数婴儿的注视高峰出现在习惯化过程早期;（２）不同年龄的婴儿对三种表情的习惯化速率相同;（３）在三种表情的六种配对情况下,不同年龄的婴儿对任一对表情中的第一个习惯化后,均可对第二个表情去习惯化,即在识别过程中不存在顺序效应。