Infant Discrimination Research Articles

Electrophysiological correlates of number discrimination in infants

Electrophysiological correlates of number discrimination in infants

Visual evoked potential measure of texture discrimination in infants: A longitudinal study

A surface comprising spatially coherent columnar nanostructures is expected to retain intercolumnar liquid during a quartz crystal microbalance measurement due to the surface structure. Part of the liquid retained by the nanostructures may then be displaced by adsorbate.Slanted columnar nanostructure thin films were designed to vary in height but remain structurally similar, fabricated by glancing angle deposition, and characterized by generalized ellipsometry. A frequency overtone analysis, introduced here, was applied to analyze quartz crystal microbalance data for the exchange of isotope liquids over the nanostructured surfaces and determine the areal inertial mass of structure-retained liquid. The adsorption of cetyltrimethylammonium bromide onto nanostructures was investigated by simultaneous quartz crystal microbalance and generalized ellipsometry measurements.The areal inertial mass of structure-retained liquid varies linearly with nanostructure height. The proportionality constant is a function of the surface topography and agrees with the generalized ellipsometry-determined nanostructure film porosity, implying that nearly all intercolumnar liquid is retained. We report that for adsorption processes within porous nanostructured films, the quartz crystal microbalance is sensitive not to the combined areal inertial mass of adsorbate and retained liquid but rather to the density difference between adsorbate and liquid due to the volume exchange within the nanostructure film.

Three- and six-month-old infants' haptic processing and discrimination of texture

Three- and six-month-old infants' haptic processing and discrimination of texture

Tempo discrimination in infants

An habituation/dishabituation paradigm demonstrates that 2- and 4-month-old infants are able to discriminate auditory sequences that vary slightly in tempo. Discriminations were only observed for intermediate tempi (600 ms but not 100, 300, 1500 ms IOI), suggesting that infants have the same optimal tempo range as adults.

Auditory discrimination in infants as revealed by the mismatch negativity of the event‐related brain potential

In adults, deviant sounds occurring among repetitive standard sounds elicit the mismatch negativity (MMN) component of auditory event‐related brain potential (ERP) even when these sounds are not attended to. MMN appears to be generated in the auditory cortex by a comparison process between deviant auditory input and a neuronal sensory‐memory trace that is formed by the repetitive standard stimuli and which represents their physical features. Recent ERP studies have shown that MMN is also elicited in newborns and in older infants by physical changes in simple tones, as well as by changes in phonemes. Thus, MMN might provide a new tool for objective assessment of normal and deficient development of auditory discrimination, sensory memory, and speech perception in infants.

Speed and cerebral correlates of syllable discrimination in infants.

The remarkable linguistic abilities of human neonates are well documented. Young infants can discriminate phonemes even if they are not used in their native language, an ability which regresses during the first year of life. This ability to discriminate is often studied by repeating a stimulus for several minutes until some behavioural response of the infant habituates, and later examining whether the response recovers when the stimulus is changed. This method, however, does not reveal how fast infants can detect phonetic changes, nor what brain mechanisms are involved. We describe here high-density recordings of event-related potentials in three-month-old infants listening to syllables whose first consonants differed in place of articulation. Two processing stages, corresponding to an increasingly refined analysis of the auditory input, were identified and localised to the temporal lobes. A late frontal response to novelty was also observed. The infant brain recognizes a phonetic change in less than 400 ms.

Young infants’ sensitivity to formant transitions.

Infant discrimination of pairs of vowels, CV and VC syllables was studied with Swedish subjects whose mean age was about 100 days. The data were obtained using the high-amplitude sucking paradigm. Eighty-seven subjects were tested in four different sessions, during which the following contrasts were studied: [ɑ ] vs [a], [bɑ ] vs [dɑ ], [ba] vs [bɑ ], and [ɑ b] vs [ɑ d]. The contrasts were obtained by a 2-Bark shift of the F2 frequency. When applied to the vowel’s F2, this shift resulted in two distinct vowels. When applied to the onset (or offset) of F2 transitions, it generates a /b/ vs /d/ contrast. To control for learning effects due to the repeated measures procedure, the overall experiment is counterbalanced. Each subject was randomly assigned to one of the possible 24 permutations of the four experimental conditions. The results indicate a more reliable discrimination for stimuli in which the relevant information was carried by initial or final formant transitions.

Infant Discrimination of Gestural Classes: Perceptual Precursors of ASL Acquisition

This research investigates the ability of 3.5-month-old hearing infants to discriminate between classes of gestures in American Sign Language (ASL). Perceptually, the classes differ in underlying movement dimensions, as reflected in adult similarity judgments (Poizner 1981 1983). Linguistically, the classes are used to mark different inflectional categories in ASL. Using a habituation-recovery paradigm, 36 infants were habituated to three tokens from one class. After reaching criterion, infants were presented with two new tokens: one a new member of the habituation set, the other a member of the previously unseen gestural class. Infants showed greater recovery to the new token from the unfamiliar class than they did to the new token from the familiar class. These results demonstrate that infant abilities to distinguish between classes of gestures parallel adult perceptual abilities as reflected in similarity ratings. They also indicate that, at four months, infants possess the prerequisite ability to classify gestures based on variations in movement in ways that correspond to inflectional distinctions in ASL.

Cerebral palsy in very low birthweight infants.

Eighty one very low birthweight survivors with cerebral palsy were matched with controls by sex, gestational age, and place of birth. Using discriminant analysis, the perinatal profiles for infants with cerebral palsy and their controls were shown to differ significantly. When infants with various types of cerebral palsy were analysed with their controls the discriminating variables differed. Diplegic infants could be differentiated from controls on antenatal variables alone, but significant discrimination of hemiplegic and quadriplegic infants required the addition of postnatal variables. Cranial ultrasound appearances differed appreciably between types of cerebral palsy. Future studies should differentiate between types of cerebral palsy and include ultrasound data. Cerebral palsy in very low birthweight infants is unlikely to prove a useful outcome indicator for neonatal intensive care.

Temporal rate as a determinant of orientation discrimination in infants

Temporal rate as a determinant of orientation discrimination in infants

Could temporal order differences underlie 2-month-olds' discrimination of English voicing contrasts?

Previous studies have shown that infants discriminate voice onset time (VOT) differences for certain speech contrasts categorically. In addition, investigations of nonspeech processing by infants also yield evidence of categorical discrimination of temporal-order differences. These findings have led some researchers to argue that common auditory mechanisms underlie the infant's discrimination of timing differences in speech and nonspeech contrasts [e.g., Jusczyk et al., J. Acoust. Soc. Am. 67, 262-270 (1980)]. Nevertheless, some discrepancies in the location of the infant's category boundaries for different kinds of contrasts have been noted [e.g., Eilers et al. (1980)]. Because different procedures were used to study the different kinds of contrasts, interpretation of the discrepancies between the studies has been difficult. In the present study, three different continua were examined: [ba]-[pa] stimuli, which differed in VOT; [du]-[tu] stimuli, which differed in VOT but which lacked format transitions; nonspeech formant onset time (FOT) stimuli that varied in the time that lower harmonics increased in amplitude. An experiment with adults indicated a close match between the perceptual boundaries for the three series. Similarly, tests with 2-month-old infants using high amplitude sucking procedure yielded estimates of perceptual category boundaries at between 20 and 40 ms for all three stimulus series.

Infant Discrimination of Naturalistic Emotional Expressions: The Role of Face and Voice

The ability of infants to discriminate dynamic, multimodal expressions of emotion was assessed in a series of 5 experiments. In Experiment 1, 48 infants of 4 and 5 months (total N = 96) were habituated to color/sound videotapes of 6 women speaking the same script sadly or happily. Following habituation, 2 new women were presented, each speaking once in the familiarized emotion and once in the novel emotion. Order of stimulus presentation (Sad----Happy, Happy----Sad) was counterbalanced. 5-month-olds were able to discriminate the expressions in both directions, whereas 4-month-olds could discriminate them only in the Sad----Happy direction. In Experiment 2, the ability of 5- and 7-month-olds to discriminate happy and angry expressions was examined using the Happy----Angry stimulus order alone. Only the 7-month-olds could differentiate these stimuli. In Experiment 3, it was shown that 7-month-olds could not distinguish these same Happy----Angry stimuli without vocal accompaniment. The purpose of the fourth experiment was to determine whether the voice played an equally important role in the Sad----Happy discrimination of Experiment 1. Surprisingly, a 5-month group tested without voice readily discriminated these stimuli. Finally, the fifth experiment sought to determine whether an Angry----Happy comparison might also be discriminable without voice. A 7-month group tested in this manner could not discriminate these expressions, while a group tested with voice could. The results indicate that infants can differentiate dynamic, multimodal expressions as early as 5 months, that they distinguish dynamically distinct expressions earlier than more similarly animated expressions, and that they seem to rely more on the voice than the face in making these discriminations.

Infant Discrimination of Naturalistic Emotional Expressions: The Role of Face and Voice

The ability of infants to discriminate dynamic, multimodal expressions of emotion was assessed in a series of 5 experiments. In Experiment 1, 48 infants of 4 and 5 months (total N = 96) were habituated to color/sound videotapes of 6 women speaking the same script sadly or happily. Following habituation, 2 new women were presented, each speaking once in the familiarized emotion and once in the novel emotion. Order of stimulus presentation (Sad----Happy, Happy----Sad) was counterbalanced. 5-month-olds were able to discriminate the expressions in both directions, whereas 4-month-olds could discriminate them only in the Sad----Happy direction. In Experiment 2, the ability of 5- and 7-month-olds to discriminate happy and angry expressions was examined using the Happy----Angry stimulus order alone. Only the 7-month-olds could differentiate these stimuli. In Experiment 3, it was shown that 7-month-olds could not distinguish these same Happy----Angry stimuli without vocal accompaniment. The purpose of the fourth experiment was to determine whether the voice played an equally important role in the Sad----Happy discrimination of Experiment 1. Surprisingly, a 5-month group tested without voice readily discriminated these stimuli. Finally, the fifth experiment sought to determine whether an Angry----Happy comparison might also be discriminable without voice. A 7-month group tested in this manner could not discriminate these expressions, while a group tested with voice could. The results indicate that infants can differentiate dynamic, multimodal expressions as early as 5 months, that they distinguish dynamically distinct expressions earlier than more similarly animated expressions, and that they seem to rely more on the voice than the face in making these discriminations.

Infant speech-sound discrimination testing: effects of stimulus intensity and procedural model on measures of performance.

Performance of infants in a speech-sound discrimination task (/ba/ vs /da/) was measured at three stimulus intensity levels (50, 60, and 70 dB SPL) using the operant head-turn procedure. The procedure was modified so that data could be treated as though from a single-interval (yes-no) procedure, as is commonly done, as well as if from a sustained attention (vigilance) task. Discrimination performance changed significantly with increase in intensity, suggesting caution in the interpretation of results from infant discrimination studies in which only single stimulus intensity levels within this range are used. The assumptions made about the underlying methodological model did not change the performance-intensity relationships. However, infants demonstrated response decrement, typical of vigilance tasks, which supports the notion that the head-turn procedure is represented best by the vigilance model. Analysis then was done according to a method designed for tasks with undefined observation intervals [C. S. Watson and T. L. Nichols, J. Acoust. Soc. Am. 59, 655-668 (1976)]. Results reveal that, while group data are reasonably well represented across levels of difficulty by the fixed-interval model, there is a variation in performance as a function of time following trial onset that could lead to underestimation of performance in some cases.

Contrast discrimination in human infants.

Contrast discrimination in human infants.

Contrast discrimination in human infants.

The ability to detect differences in spatial contrast is crucial to object recognition and identification. This ability is generally examined by measuring the contrast discrimination function. This function represents, for a variety of conditions, the smallest contrast difference required to discriminate otherwise identical patterns. We examined human infants' ability to discriminate patterns on the basis of differences in spatial contrast. The forced-choice preferential looking procedure was used to estimate contrast increment thresholds at a number of background contrasts. The Weber fractions of 6- and 12-week-old infants were about 1 log unit higher than adult values for background contrasts ranging from 0.14 to 0.55. Furthermore, the slopes of infants' discrimination functions were much shallower than those of adults. These age differences in contrast discrimination imply certain changes in the neural mechanisms that underlie contrast encoding. They also aid our understanding of the anomalies observed in early pattern vision.

The Perception of Smiling and Its Experiential Correlates in Three-Month-Old Infants

We studied individual differences in 3-month-olds' perceptions of smiling and the experiential correlates of those differences. In the laboratory, infants saw a graduated series of smiles that grew in intensity of expression. As a group, 3-month-olds preferred increasingly intense expressions of smiling, but individually they showed different growth rates of preference across the smiling series. Further, infants' preferences related to their home experiences: Infants who showed greater sensitivity to smiling had mothers who more frequently encouraged attention to themselves when they were smiling and their infants were looking at them. Infant discrimination within and between categories of facial expression and the relative strengths of association between different kinds of naturally occurring experiences and infant perceptual sensitivity are discussed.

Sensory primacy in the infant's discrimination of the mother

Sensory primacy in the infant's discrimination of the mother

Phonetic discrimination and perceptual reorganization in human infants

Phonetic discrimination and perceptual reorganization in human infants

Infant discrimination of dynamic emotional expressions

This study examines 7- and 9-month-olds’ ability to categorize cats as separate from dogs, and dogs as separate from cats in an object examination task. In Experiment 1, 7- and 9-month-olds (N=30) familiarized with toy cat replicas were found to form a category of cat that included novel cats but excluded a dog and an eagle. In Experiment 2, 7- and 9-month-olds (N=30) familiarized with toy dog replicas were found to form a category of dog that included a novel dogs and a novel cat but excluded an eagle. These results mirror those of 3- to 4-month-olds tested with visual preference methods and stand in contrast to previously reported object examination results. Analyses of the distribution of features in the exemplars used to familiarize infants suggest that, like the 3- to 4-month-olds, the 7- and 9-month-olds in these studies form categories within the task, and on the basis of feature distributions.