Search

Time is central to any understanding of the world. In adults, estimation errors grow linearly with the length of the interval, much faster than would be expected of a clock-like mechanism. Here we present the first direct demonstration that this is also true in human infants. Using an eye-tracking paradigm, we examined 4-, 6-, 10-, and 14-month-olds' responses to the omission of a recurring target, on either a 3- or 5-s cycle. At all ages (a) both fixation and pupil dilation measures were time locked to the periodicity of the test interval, and (b) estimation errors grew linearly with the length of the interval, suggesting that trademark interval timing is in place from 4 months.

With many features competing for attention in their visual environment, infants must learn to deploy attention toward informative cues while ignoring distractions. Three eye tracking experiments were conducted to investigate whether 6- and 8-month-olds (total N = 102) would shift attention away from a distractor stimulus to learn a cue-reward relation. While 8-month-olds showed evidence of increasingly selective attention toward the predictive cues, even when the distractors were highly salient, 6-month-olds shifted attention toward the predictive cues only when the distractors were equally (not more) engaging. These experiments suggest that attention in infancy is highly dependent on the relative weightings of predictiveness and visual salience, which may differ across development and context.

Two experiments demonstrate that 5-month-olds are sensitive to local redundancy in visual-temporal sequences. In Experiment 1, 20 infants saw 2 separate sequences of looming colored shapes that possessed the same elements but contrasting transitional probabilities. One sequence was random whereas the other was based on bigrams. Without any prior exposure, infants looked longer at the random sequence. In Experiment 2, 17 infants looked equally long at bigram- and trigram-based sequences. However, an analysis of local redundancy revealed that in both experiments disengagement from the sequences was governed by local repetitions rather than by global sequence statistics. This finding suggests that a spontaneous sensitivity to stimulus complexity helps orient infants to sequences they can learn from. (Contains 6 figures.)

Computational models are tools for testing mechanistic theories of learning and development. Formal models allow us to instantiate theories of cognitive development in computer simulations. Model behavior can then be compared to real performance. Connectionist models, loosely based on neural information processing, have been successful in capturing a range of developmental phenomena, in particular on-line within-task category learning by young infants. Here we describe two new models. One demonstrates how age dependent changes in neural receptive field sizes can explain observed changes in on-line category learning between 3 and 10 months of age. The other aims to reconcile two conflicting views of infant categorization by focusing on the different task requirements of preferential looking and manual exploration studies. A dual-memory hypothesis posits that within-task category learning that drives looking time behaviors is based on a fast-learning memory system, whereas categorization based on background experience and assessed by paradigms requiring complex motor behavior relies on a second, slow-learning system. The models demonstrate how emphasizing the mechanistic causes of behaviors leads to discovery of deeper, more explanatory accounts of learning and development. (Contains 6 figures.)

This article presents an eye-tracking study using a novel combination of visual saliency maps and "area-of-interest" analyses to explore online feature extraction during category learning in infants. Category learning in 12-month-olds (N = 22) involved a transition from looking at high-saliency image regions to looking at more informative, highly variable object parts. In contrast, 4-month-olds (N = 27) exhibited a different pattern displaying a similar decreasing impact of saliency accompanied by a steady focus on the object's center, indicating that targeted feature extraction during category learning develops across the 1st year of life. These results illustrate how the effects of lower and higher level processes may be disentangled using a combined saliency map and area-of-interest analysis. (Contains 4 figures.)

Individuals of all ages extract structure from the sequences of patterns they encounter in their environment, an ability that is at the very heart of cognition. Exactly what underlies this ability has been the subject of much debate over the years. A novel mechanism, implicit chunk recognition (ICR), is proposed for sequence segmentation and chunk extraction. The mechanism relies on the recognition of previously encountered subsequences (chunks) in the input rather than on the prediction of upcoming items in the input sequence. A connectionist autoassociator model of ICR, truncated recursive autoassociative chunk extractor (TRACX), is presented in which chunks are extracted by means of truncated recursion. The performance and robustness of the model is demonstrated in a series of 9 simulations of empirical data, covering a wide range of phenomena from the infant statistical learning and adult implicit learning literatures, as well as 2 simulations demonstrating the model's ability to generalize to new input and to develop internal representations whose structure reflects that of the items in the input sequence. TRACX outperforms PARSER (Perruchet & Vintner, 1998) and the simple recurrent network (SRN, Cleeremans & McClelland, 1991) in matching human sequence segmentation on existing data. A new study is presented exploring 8-month-olds' use of backward transitional probabilities to segment auditory sequences. (Contains 10 footnotes, 3 tables, and 7 figures.)

It is well established that 2-year-olds attribute a novel label to an object's global shape rather than local features (i.e., parts). Although recent studies have found that younger infants also attend to global rather than local features when given a label, the test stimuli in these experiments confounded parts and shape by varying both or neither. With infants (16- and 24-month-olds) and adults, this experiment disentangled shape and parts with appropriate test objects. Results showed a clear development of a strategy incorporating multiple cues. Across three age groups, there was an increase in generalizing labels to objects matching the exemplar's local and global features (parts, base, and shape), and a decrease to objects matching in only one local feature. We discuss these results in terms of a learned flexibility in using multiple cues to predict lexical categories. (Contains 2 figures and 1 footnote.)

Using a sequential touching procedure, we examined whether 18-month-olds could use different categorization strategies adaptively as a function of context. Infants were presented with test toys of land animals (quadrupeds), cars, and hybrids made by recombining car parts with animal parts. Infants who experienced a context emphasizing a taxonomic divide were subsequently more likely to form categories that reflected a taxonomic divide, whereas infants who experienced a context emphasizing a partonomic divide were subsequently more likely to form categories based on functional parts. These results suggest that 18-month-olds can adapt their categorization strategies flexibly in accordance with ambient contextual cues. This adds to the growing body of evidence that early categorization is flexible and not rigidly tied to characteristic features in the environment. (Contains 1 figure and 3 tables.)

Two experiments investigated infants' ability to localize tactile sensations in peripersonal space. Infants aged 10 months (Experiment 1) and 6.5 months (Experiment 2) were presented with vibrotactile stimuli unpredictably to either hand while they adopted either a crossed- or uncrossed-hands posture. At 6.5 months, infants' responses were predominantly manual, whereas at 10 months, visual orienting behavior was more evident. Analyses of the direction of the responses indicated that (a) both age groups were able to locate tactile stimuli, (b) the ability to remap visual and manual responses to tactile stimuli across postural changes develops between 6.5 and 10 months of age, and (c) the 6.5-month-olds were biased to respond manually in the direction appropriate to the more familiar uncrossed-hands posture across both postures. The authors argue that there is an early visual influence on tactile spatial perception and suggest that the ability to remap visual and manual directional responses across changes in posture develops between 6.5 and 10 months, most likely because of the experience of crossing the midline gained during this period.

One hundred 18-month-olds were tested using sequential touching and following 4 different priming contexts using sets of toys that could be simultaneously categorized at either the basic or global level. An exact expression of the expected mean sequence length for arbitrary categories was derived as a function of the number of touches made, and a finite mixture model analytic method was also used to explore individual variability in categorization. Toddlers could categorize flexibly and spontaneously selected the level of categorization as a function of the prior prime. Perceptual Variability emerged as a predictor of the level at which infants subsequently categorized. The infants were also able to classify objects as members of both basic- and global-level categories simultaneously.

Young infants are very sensitive to feature distribution information in the environment. However, existing work suggests that they do not make use of correlation information to form certain perceptual categories until at least 7 months of age. We suggest that the failure to use correlation information is a by-product of familiarization procedures that encourage infants to over encode individual exemplars rather than relations across exemplars. By changing the exemplar presentation regime to one in which exemplars are rapidly (2 s durations) and repeatedly presented we find that 4-month-olds can form perceptual categories on the basis of feature correlation information. In addition, this ability emerges rapidly between 114 and 134 days. We argue that the ability to process correlation information is present very early on but that the demonstration of that ability in categorization tasks is mediated by the demands of the task the infant is tested with. (Contains 3 figures, 1 table, and 2 notes.)

Disentangling bottom-up and top-down processing in adult category learning is notoriously difficult. Studying category learning in infancy provides a simple way of exploring category learning while minimizing the contribution of top-down information. Three- to 4-month-old infants presented with cat or dog images will form a perceptual category representation for cat that excludes dogs and for dog that includes cats. The authors argue that an inclusion relationship in the distribution of features in the images explains the asymmetry. Using computational modeling and behavioral testing, the authors show that the asymmetry can be reversed or removed by using stimulus images that reverse or remove the inclusion relationship. The findings suggest that categorization of nonhuman animal images by young infants is essentially a bottom-up process.

Visual object processing in infancy is often described as proceeding from an early stage in which object features are processed independently to a later stage in which relations between features are taken into account (e.g., Cohen, 1998). Here we present the Representational Acuity Hypothesis, which argues that this behavioral shift can be explained by a developmental decrease in the size of neural receptive fields in the cortical areas responsible for object representation, together with a tuning to specific object features. We evaluate this hypothesis with a connectionist model of infant perceptual categorization. The model shows a behavioral shift in featural to relational processing consistent with similar results observed in the infant categorization experiments of Younger (1985) and Younger and Cohen (1986). (Contains 7 figures and 2 footnotes.)

Tested 4-month-olds' memory for surface feature and location information following brief occlusions. Found that when target objects were images of female faces or monochromatic asterisks, infants increased looking times following changes in identity or color but not changes in location or combinations of feature and location. When objects were images of manipulable toys, infants increased looking time following location change but not identity change or location and identity information. (Author/KB)

Examined 7- and 9-month-olds' ability to categorize cats and dogs as separate from one another. Found that both groups formed a cat category that included novel cats but excluded a dog and an eagle, and formed a dog category that included novel dogs and a novel cat but excluded an eagle. Results mirrored those of 3- to 4-month-olds with visual preference methods and contrasted with previously-reported object examination results. (Author/KB)

Describes connectionist model showing exclusivity asymmetries when categorizing visual stimuli, similar to pattern shown by infants. Examines asymmetries in terms of an associative learning mechanism, distributed internal representations, and statistics of feature distributions in the stimuli. Details test of model with infants, finding that asymmetry persisted when a category was acquired in the presence of mixed category exemplars. (Author/KB)

• New contextual learning paradigm tailored to toddlers and young children. • Development of contextual regularity learning between 3 and 5 years of age. • Sensitivity to spatial regularities persists from infancy to childhood. • At five years of age children integrate colour and spatial cues to guide behaviour. The ability to acquire contextual regularities is fundamental in everyday life because it helps us to navigate the environment, directing our attention where relevant events are more likely to occur. Sensitivity to spatial regularities has been largely reported from infancy. Nevertheless, it is currently unclear when children can use this rapidly acquired contextual knowledge to guide their behavior. Evidence of this ability is indeed mixed in school-aged children and, to date, it has never been explored in younger children and toddlers. The current study investigated the development of contextual regularity learning in children aged 3 to 5 years. To this aim, we designed a new contextual learning paradigm in which young children were presented with recurring configurations of bushes and were asked to guess behind which bush a cartoon monkey was hiding. In a series of two experiments, we manipulated the relevance of color and visuospatial cues for the underlying task goal and tested how this affected young children's behavior. Our results bridge the gap between the infant and adult literatures, showing that sensitivity to spatial configurations persists from infancy to childhood, but it is only around the fifth year of life that children naturally start to integrate multiple cues to guide their behavior. [ABSTRACT FROM AUTHOR]

Spontaneous Motor Tempo (SMT) is influenced by individual differences in age and body size. We present the first data documenting the SMT of infants from 5 to 37 months of age using a simple drumming task. As in late childhood and adulthood, we predicted that infant SMT would slow across the first years of life. However, we find that older infants drum more quickly than younger infants. Furthermore, studies of adults suggest larger bodies prefer slower rhythms. This relationship may be the product of biomechanical resonance, or effects may be driven by rhythmic experience, such as of locomotion. We used infants, whose body size is dissociated from their predominant experience of locomotion as their parent often carries them, to test this argument. We reveal that infant SMT is predicted by parent, but not own, body size, supporting a passive experience‐based argument, and propose that early rhythm may be set by repetitive vestibular stimulation when carried by the caregiver. [ABSTRACT FROM AUTHOR]

Multisensory information has been shown to modulate attention in infants and facilitate learning in adults, by enhancing the amodal properties of a stimulus. However, it remains unclear whether this translates to learning in a multisensory environment across middle childhood, and particularly in the case of incidental learning. One hundred and eighty-one children aged between 6 and 10 years participated in this study using a novel Multisensory Attention Learning Task (MALT). Participants were asked to respond to the presence of a target stimulus whilst ignoring distractors. Correct target selection resulted in the movement of the target exemplar to either the upper left or right screen quadrant, according to category membership. Category membership was defined either by visual-only, auditory-only or multisensory information. As early as 6 years of age, children demonstrated greater performance on the incidental categorization task following exposure to multisensory audiovisual cues compared to unisensory information. These findings provide important insight into the use of multisensory information in learning, and particularly on incidental category learning. Implications for the deployment of multisensory learning tasks within education across development will be discussed. [ABSTRACT FROM AUTHOR]

Even newborn infants are able to extract structure from a stream of sensory inputs; yet how this is achieved remains largely a mystery. We present a connectionist autoencoder model, TRACX2, that learns to extract sequence structure by gradually constructing chunks, storing these chunks in a distributed manner across its synaptic weights and recognizing these chunks when they re-occur in the input stream. Chunks are graded rather than all-or-nothing in nature. As chunks are learnt their component parts become more and more tightly bound together. TRACX2 successfully models the data fromfive experiments from the infant visual statistical learning literature, including tasks involving forward and backward transitional probabilities, low-salience embedded chunk items, part-sequences and illusory items. The model also captures performance differences across ages through the tuning of a singlelearning rate parameter. These results suggest that infant statistical learning is underpinned by the same domain-general learning mechanism that operates in auditory statistical learning and, potentially, in adult artificial grammar learning. This article is part of the themed issue 'Newfrontiers for statistical learning in the cognitive sciences'. [ABSTRACT FROM AUTHOR]

Gamma-band oscillatory activity (GBA) is an established neural signature of sustained occluded object representation in infants and adults. However, it is not yet known whether the magnitude of GBA in the infant brain reflects the quantity of occluded items held in memory. To examine this, we compared GBA of 6-8 month-old infants during occlusion periods after the representation of two objects vs. that of one object. We found that maintaining a representation of two objects during occlusion resulted in significantly greater GBA relative to maintaining a single object. Further, this enhancement was located in the right occipital region, which is consistent with previous object representation research in adults and infants. We conclude that enhanced GBA reflects neural processes underlying infants' representation of small numbers. [ABSTRACT FROM AUTHOR]

Very few experiments have studied the two item same/different relation in young human infants. This contrasts with an extensive animal literature. We tested young infants with two novel tasks designed specifically to provide convergent comparative measures. Each infant completed both tasks allowing an assessment of their understanding of the abstract concept rather than task-specific abilities. In a looking time task with photographic stimuli, we found that 8-month-olds are sensitive to the relation but 4-month-olds are not. The second task used an anticipatory eye movement paradigm with simple geometric stimuli. On each trial, two colored shapes appear and moved upwards behind an occluder. They reappeared on either the upper left or right depending on the relation between them. Infants at both ages learned and generalized the dependency but only for the different relation. These results show that human infants can learn the same/different concept but that, in strong continuity with animal results, their abilities are firmly grounded in perception. [ABSTRACT FROM AUTHOR]

We measured looking times and ERPs to examine the cognitive and brain bases of perceptual category learning in 6-month-old infants. In Experiment 1, we showed that categorization and exemplar discrimination rely on different cortical processes. Specifically, the repetition of individual exemplars resulted in differential cortical processing at posterior channels at an early stage during object processing (100-300 msec), whereas discriminating among members of different categories was reflected in ERP differences over anterior cortical regions occurring later in time (300-500 msec) than the repetition effects. In Experiment 2, replicating the findings of Study 1, we found that infants engage the same cortical processes to categorize visual objects into basic-level categories, regardless of whether a basic (bird vs. fish) or global level is crossed (birds vs. cars). This pattern of findings is consistent with perceptual accounts of infant categorization [Quinn, P. C., & Eimas, P. D. Perceptual organization and categorization in young infants. In C. Rovee-Collier & L. P. Lipsitt (Eds.), Advances in infancy research (Vol. 10, pp. 1-36). Norwood, NJ: Ablex, 1996] and accords with recent adult neural-level models of perceptual categorization. [ABSTRACT FROM AUTHOR]

While brain imaging studies of visual cognition have contributed extensively to our understanding of the different mechanisms involved in object processing and categorization, in adulthood, infancy studies have only started to employ these techniques. We identify in this paper a few of the methodological and theoretical reasons that hindered a more enthusiastic use of imaging methods. Focusing on three theoretical questions that stand out from the infant object categorization literature we show that, when the methodology is adapted to the study of young populations and the interpretations guided by equivalent results from the adult literature, brain imaging can help shed light on cognitive development. [ABSTRACT FROM AUTHOR]

In a series of experiments we tested 4- and 8-month-olds' ability to represent the spatial layout of an object across changes in its orientation with respect to egocentric spatial coordinates. A fixed-trial familiarization procedure based on visual habituation behaviour shows that both age groups are able to discriminate between different object-centred spatial configurations. Furthermore, both age groups demonstrate the ability to make discriminations of object-centred spatial coordinates that require simultaneous reference to at least two spatial axes of the object. We discuss these findings in relation to theories of the early development of object recognition and spatial reference skills. [ABSTRACT FROM AUTHOR]

This manuscript surveys computational modeling efforts by researchers in developmental psychology. Developmental psychology is ready to blossom into a modern science that focuses on causal mechanistic explanations of development rather than just describing and classifying behaviors. Computational modeling is the key to this process. However, to be effective, models must not only mimic observed data. They must also be transparent, grounded, and plausible to be accepted by the developmental psychology community. Connectionist model provides one such example. Many developmental features of typical and atypical perception, cognition, and language have been modeled using connectionist methods. Successful models are closely tied to the details of existing empirical studies and make concrete testable predictions. The success of such a project relies on the close collaboration of computational scientists with empirical psychologists. [ABSTRACT FROM AUTHOR]

Common-onset visual masking (COVM) occurs when a mask and a target have common onset but delayed offset, with the mask persisting beyond the duration of the target [Di Lollo, V., Enns, J. T., & Rensink, R. A. Competition for consciousness among visual events: The psychophysics of reentrant visual events. Journal of Experimental Psychology: General, 129, 481–507, 2000]. We report the first behavioral and electrophysiological evidence of COVM in infants. An initial behavioral study included a familiarization phase during which a visual pattern (the target) surrounded by four black dots (the mask) was f lashed 15 times to the infant. In the ‘unmasked’ condition, the mask disappeared with the target. In the ‘masked’ condition, the mask remained on the screen after deletion of the target for a further 93 msec. During the test phase, the familiar target pattern was paired with a new pattern. Infants in the unmasked condition showed a significant familiarity preference, suggesting that they had encoded the target during familiarization, whereas those in the masked condition showed no preference, suggesting that they had not encoded the target during familiarization. In the second experiment, high-density event-related potentials were used to investigate the electrophysiological pattern of activity that accompanies COVM. Six-month-old infants viewed both masked and unmasked conditions. Electrophysiological data indicated that over posterior channels the masked condition elicited a larger amplitude positive wave around 300 msec after stimulus onset than trials in the unmasked condition. [ABSTRACT FROM AUTHOR]

Habituation and related procedures are the primary behavioral tools used to assess perceptual and cognitive competence in early infancy. This article introduces a neurally constrained computational model of infant habituation. The model combines the two leading process theories of infant habituation into a single functional system that is grounded in functional brain circuitry. The HAB model (for Habituation, Autoassociation, and Brain) proposes that habituation behaviors emerge from the opponent, complementary processes of hippocampal selective inhibition and cortical long-term potentiation. Simulations of a seminal experiment by Fantz [Visual experience in infants: Decreased attention familiar patterns relative to novel ones. Science, 146, 668–670, 1964] are reported. The ability of the model to capture the fine detail of infant data (especially age-related changes in performance) underlines the useful contribution of neurocomputational models to our understanding of behavior in general, and of early cognition in particular. [ABSTRACT FROM AUTHOR]

This review pursues the idea that a dual visual system approach is fruitful for interpreting work on infant cognition. We provide examples from the visual perception and cognition literature demonstrating that the potential graspability of stimuli typically used in infant studies influence how these stimuli are processed by the infant brain. Specifically, we argue that small, local, familiar and moving stimuli are more likely to be processed by the dorsal (how or action) stream of visual processing. In contrast, larger, stationary objects are likely to be processed by the ventral (what or perception) stream. This analysis clarifies apparently conflicting results in the literature. [Copyright &y& Elsevier]

Research on infant cognition using habituation methods has sparked considerable controversy in recent years. At the core of the debates is the issue of whether infants have early (and possibly innate) conceptual understandings. This article reviews a range of computational models of habituation that might provide insights into such discussions. The models are assessed against key behavioral and neural features of habituation: temporal unfolding, exponential decrease, familiarity-to-novelty shift, habituation to repeated testing, discriminability of habitual items, selective inhibition and cortical–subcortical interactions. The review suggests that current models fail to offer comprehensive explanations of the behavioral phenomena. [ABSTRACT FROM AUTHOR]

To explore questions of how human infants begin to perceive partly occluded objects, we devised two connectionist models of perceptual development. The models were endowed with an existing ability to detect several kinds of visual information that have been found important in infants’ and adults’ perception of object unity (motion, co-motion, common motion, relatability, parallelism, texture and T-junctions). They were then presented with stimuli consisting of either one or two objects and an occluding screen. The models’ task was to determine whether the object or objects were joined when such a percept was ambiguous, after specified amounts of training with events in which a subset of possible visual information was provided. The model that was trained in an enriched environment achieved superior levels of performance and was able to generalize veridical percepts to a wide range of novel stimuli. Implications for perceptual development in humans, current theories of development and origins of knowledge are discussed. [ABSTRACT FROM AUTHOR]

Comments on the components of the mechanisms of development of unity perception in infants. Impact of computational modeling on cognitive development; Interactions of mediated response and environment; Factors contributing to visual system development.

Describes a connectionist autoencoder model of perceptual categorization that shows the same asymmetries as infants. Details of an experiment conducted with 3- to 4-month-old infants that verified the predicted pattern of looking time behaviors; Overview of the sequential category learning in autoencoder networks; Explanation of asymmetric categorization observed in infant behavior.

Abstract: An appreciation of object-centred spatial relations involves representing a ‘within-object’ spatial relation across changes in the object orientation. This representational ability is important in adult object recognition [Biederman, I. (1987). Recognition-by-components: A theory of human image understanding. Psychological Review, 94, 115–147; Marr, D., & Nishihara, H. K. (1978). Representation and recognition of the spatial organisation of three-dimensional structure. Proceedings of the Royal Society of London, Series B (Biological Sciences), 200, 269–294; Tarr, M. J., & Pinker, S. (1990). When does human object recognition use a viewer-centred reference frame? Psychological Science, 1, 253–256] and is also thought to be a fundamental component of the mature object concept [Piaget, J. (1954). The Construction of Reality in the Child. Routledge & Kegan-Paul: London, UK. (Originally published in French in 1937)]. An experiment is reported in which eighteen 4-month-old infants were familiarised to a specific spatial relation within an object, across six different orientations of the object. On subsequent test trials the object was presented to the infants in an entirely novel orientation. Between successive test trials the within-object spatial relation was alternated between novel and familiar. The infants demonstrated significant sensitivity of their looking to both the novelty of the stimuli and the order in which novel and familiar stimuli were presented. It is concluded that by 4 months of age infants are able to form object-centred spatial frames of reference. These findings are discussed in the light of our current understanding of the development of object representation during infancy. [Copyright &y& Elsevier]