Experience-based and on-line categorization of objects in early infancy

Intersensory redundancy impedes face recognition in 12-month-old infants

This study examined the role of intersensory redundancy on 12-month-old infants' attention to and processing of face stimuli. Two experiments were conducted. In Experiment 1, 72 12-month-olds were tested using an online platform called Lookit. Infants were familiarized with two videos of an actor reciting a children's story presented simultaneously. A soundtrack either matched one of the videos (experimental condition) or neither of the videos (control condition). Visual-paired comparison (VPC) trials were completed to measure looking preferences for the faces presented synchronously and asynchronously during familiarization and for novel faces. Neither group displayed looking preferences during the VPC trials. It is possible that the complexity of the familiarization phase made the modality-specific face properties (i.e., facial characteristics and configuration) difficult to process. In Experiment 2, 56 12-month-old infants were familiarized with the video of only one actor presented either synchronously or asynchronously with the soundtrack. Following familiarization, participants completed a VPC procedure including the familiar face and a novel face. Results from Experiment 2 showed that infants in the synchronous condition paid more attention during familiarization than infants in the asynchronous condition. Infants in the asynchronous condition demonstrated recognition of the familiar face. These findings suggest that the competing face stimuli in the Experiment 1 were too complex for the facial characteristics to be processed. The procedure in Experiment 2 led to increased processing of the face in the asynchronous presentation. These results indicate that intersensory redundancy in the presentation of synchronous audiovisual faces is very salient, discouraging the processing of modality-specific visual properties. This research contributes to the understanding of face processing in multimodal contexts, which have been understudied, although a great deal of naturalistic face exposure occurs multimodally.

The effects of bilingualism on children's cross-situational word learning under different variability conditions

In the current study, we examined the separate and combined effects of exemplar and speaker variability on monolingual and bilingual children's cross-situational word learning performance. Results revealed that children's word learning performance did not differ when the input varied in a single dimension (i.e., exemplars or speakers) compared with a condition with no variability independent of their linguistic background. However, when performance in conditions that varied in a single dimension (i.e., exemplars or speakers) was compared with a condition that varied in multiple dimensions (i.e., exemplars and speakers), bilingual word learning advantages were observed; bilinguals were more likely to learn word-referent associations than monolinguals. Together, results suggest that children can learn and generalize word-referent associations from input that varies in exemplars and speakers and that bilingualism may bolster learning under conditions of increased input variability.

Modelling concrete and abstract concepts using brain-constrained deep neural networks

A neurobiologically constrained deep neural network mimicking cortical areas relevant for sensorimotor, linguistic and conceptual processing was used to investigate the putative biological mechanisms underlying conceptual category formation and semantic feature extraction. Networks were trained to learn neural patterns representing specific objects and actions relevant to semantically 'ground' concrete and abstract concepts. Grounding sets consisted of three grounding patterns with neurons representing specific perceptual or action-related features; neurons were either unique to one pattern or shared between patterns of the same set. Concrete categories were modelled as pattern triplets overlapping in their 'shared neurons', thus implementing semantic feature sharing of all instances of a category. In contrast, abstract concepts had partially shared feature neurons common to only pairs of category instances, thus, exhibiting family resemblance, but lacking full feature overlap. Stimulation with concrete and abstract conceptual patterns and biologically realistic unsupervised learning caused formation of strongly connected cell assemblies (CAs) specific to individual grounding patterns, whose neurons were spread out across all areas of the deep network. After learning, the shared neurons of the instances of concrete concepts were more prominent in central areas when compared with peripheral sensorimotor ones, whereas for abstract concepts the converse pattern of results was observed, with central areas exhibiting relatively fewer neurons shared between pairs of category members. We interpret these results in light of the current knowledge about the relative difficulty children show when learning abstract words. Implications for future neurocomputational modelling experiments as well as neurobiological theories of semantic representation are discussed.

Eleven-Month-Olds Link Sound Properties With Animal Categories

We examined 11-month-olds' tendency to generalize properties to category members, an ability that may contribute to the inductive reasoning abilities observed in later developmental periods. Across three experiments, we tested 11-month-olds' (N = 113) generalization of properties within the cat and dog categories. In each experiment, infants were familiarized to animal-sound pairings (i.e., dog barking; cat meowing) and tested on this association and the generalization of the sound property to new members of the familiarized categories. After familiarization with a single exemplar, 11-month-olds generalized the sound to new category members that were both highly similar and less similar to the familiarized animal (Experiment 1). When familiarized with mismatched animal-sound pairings (Experiment 2; i.e., dog meowing; cat barking), 11-month-olds did not learn or generalize the sound properties, suggesting that infants have pre-existing expectations about the links between the characteristic sound properties and the animal categories. When familiarized with unfamiliar sound-animal pairings (Experiment 3; i.e., dog-unfamiliar sound), 11-month-olds linked the animals with the novel sounds but did not generalize to new category members. Taken together, these findings highlight the conditions under which young infants generalize properties from one exemplar to other category members.

The development of categorisation and conceptual thinking in early childhood: methods and limitations

We present a systematic and qualitative review of academic literature on early conceptual development (0–24 months of age), with an emphasis on methodological aspects. The final sample of our review included 281 studies reported in 115 articles. The main aims of the article were four: first, to organise studies into sets according to methodological similarities and differences; second, to elaborate on the methodological procedures that characterise each set; third, to circumscribe the empirical indicators that different sets of studies consider as proof of the existence of concepts in early childhood; last, to identify methodological limitations and to propose possible ways to overcome them. We grouped the studies into five sets: preference and habituation experiments, category extension tasks, object sorting tasks, sequential touching tasks and object examination tasks. In the “Results” section, we review the core features of each set of studies. In the “Discussion” and “Conclusions” sections, we describe, for one thing, the most relevant methodological shortcomings. We end by arguing that a situated, semiotic and pragmatic perspective that emphasises the importance of ecological validity could open up new avenues of research to better understand the development of concepts in early childhood.

Does category-training facilitate 11-month-olds' acquisition of unfamiliar category-property associations?

The ability to form category-property links allows infants to extend a property from one category member to another. In two experiments, we examined whether orienting infants to the demands of the task, through categorization training, would facilitate 11-month-old infants' category-property extensions when familiarized with a single exemplar of an unfamiliar animal category. In Experiment 1, 11-month-olds (N = 35) were trained with two familiar animal-sound pairings (i.e., dog-bark, cat-meow), familiarized with two unfamiliar animal-sound pairings and then tested on their learning and generalization of the unfamiliar animal-sound associations. Across two conditions, Experiment 2 familiarized 11-month-olds (N = 69) to one familiar (i.e., dog-bark) and one novel animal-sound pairing. Conditions differed in their presentation of familiarization trials (i.e., random or blocked). Infants were then tested on their learning and extension of the animal-sound associations. In both experiments, infants did not demonstrate learning of the original animal sound pairing, nor generalization of the sound property to new members of the animal categories. These results indicate that the two category training paradigms implemented in the current studies did not facilitate 11-month-olds' ability to learn or generalize an unfamiliar animal-sound association, when familiarized with a single exemplar.

Infants' Daily Experience With Pets and Their Scanning of Animal Faces

Very little is known about the effect of pet experience on cognitive development in infancy. In Experiment 1, we document in a large sample (N = 1270) that 63% of families with infants under 12 months have at least one household pet. The potential effect on development is significant as the first postnatal year is a critically important time for changes in the brain and cognition. Because research has revealed how experience shapes early development, it is likely that the presence of a companion dog or cat in the home influences infants' development. In Experiment 2, we assess differences between infants who do and do not have pets (N = 171) in one aspect of cognitive development: their processing of animal faces. We examined visual exploration of images of dog, cat, monkey, and sheep faces by 4-, 6-, and 10-month-old infants. Although at the youngest ages infants with and without pets exhibited the same patterns of visual inspection of these animals faces, by 10 months infants with pets spent proportionately more time looking at the region of faces that contained the eyes than did infants without pets. Thus, exposure to pets contributes to how infants look at and learn about animal faces.

Curiosity-based learning in infants: a neurocomputational approach

Infants are curious learners who drive their own cognitive development by imposing structure on their learning environment as they explore. Understanding the mechanisms by which infants structure their own learning is therefore critical to our understanding of development. Here we propose an explicit mechanism for intrinsically motivated information selection that maximizes learning. We first present a neurocomputational model of infant visual category learning, capturing existing empirical data on the role of environmental complexity on learning. Next we "set the model free", allowing it to select its own stimuli based on a formalization of curiosity and three alternative selection mechanisms. We demonstrate that maximal learning emerges when the model is able to maximize stimulus novelty relative to its internal states, depending on the interaction across learning between the structure of the environment and the plasticity in the learner itself. We discuss the implications of this new curiosity mechanism for both existing computational models of reinforcement learning and for our understanding of this fundamental mechanism in early development.

Tactile-to-Visual Cross-Modal Transfer of Texture Categorisation Following Training: An fMRI Study

We investigated the neural underpinnings of texture categorisation using exemplars that were previously learned either within modalities (visual training and visual test) or across modalities (tactile training and visual test). Previous models of learning suggest a decrease in activation in brain regions that are typically involved in cognitive control during task acquisition, but a concomitant increase in activation in brain regions associated with the representation of the acquired information. In our study, participants were required to learn to categorise fabrics of different textures as either natural or synthetic. Training occurred over several sessions, with each fabric presented either visually or through touch to a participant. Pre- and post-training tests, in which participants categorised visual images only of the fabrics, were conducted during a functional magnetic resonance imaging (fMRI) scan. Consistent with previous research on cognitive processes involved in task acquisition, we found that categorisation training was associated with a decrease in activation in brain regions associated with cognitive systems involved in learning, including the superior parietal cortex, dorsal anterior cingulate cortex (dACC), and the right dorsolateral prefrontal cortex (DLFC). Moreover, these decreases were independent of training modality. In contrast, we found greater activation to visual textures in a region within the left medial occipital cortex (MOC) following training. There was no overall evidence of an effect of training modality in the main analyses, with texture-specific regional changes associated with both within- (visual) and cross- (touch) modal training. However, further analyses suggested that, unlike categorisation performance following within-modal training, crossmodal training was associated with bilateral activation of the MOC. Our results support previous evidence for a multisensory representation of texture within early visual regions of the cortex and provide insight into how multisensory categories are formed in the brain.

Learned Labels Shape Pre-speech Infants' Object Representations

Infants rapidly learn both linguistic and nonlinguistic representations of their environment and begin to link these from around 6 months. While there is an increasing body of evidence for the effect of labels heard in-task on infants' online processing, whether infants' learned linguistic representations shape learned nonlinguistic representations is unclear. In this study 10-month-old infants were trained over the course of a week with two 3D objects, one labeled, and one unlabeled. Infants then took part in a looking time task in which 2D images of the objects were presented individually in a silent familiarization phase, followed by a preferential looking trial. During the critical familiarization phase, infants looked for longer at the previously labeled stimulus than the unlabeled stimulus, suggesting that learning a label for an object had shaped infants' representations as indexed by looking times. We interpret these results in terms of label activation and novelty response accounts and discuss implications for our understanding of early representational development.

Development of category formation for faces differing by age in 9- to 12-month-olds: An effect of experience with infant faces

We examined category formation for faces differing in age in 9- and 12-month-olds, and the influence of exposure to infant faces on such ability. Infants were familiarized with adult or infant faces, and then tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category (Experiment 1). Both age groups formed discrete categories of adult and infant faces, but exposure to infant faces in everyday life did not modulate performance. The same task was conducted with child versus infant faces (Experiment 2). Whereas 9-month-olds preferred infant faces after familiarization with child faces, but not child faces after familiarization with infant faces, 12-month-olds formed discrete categories of child and infant faces. Moreover, more exposure to infant faces correlated with higher novel category preference scores when infants were familiarized with infant faces in 12-month-olds, but not 9-month-olds. The 9-month-old asymmetry did not reflect spontaneous preference for infant over child faces (Experiment 3). These findings indicate that 9- and 12-month-olds can form age-based categories of faces. The ability of 12-month-olds to form separate child and infant categories suggests that they have a more exclusive representation of face age, one that may be influenced by prior experience with infant faces.

Experience and distribution of attention: Pet exposure and infants' scanning of animal images

Although infants' cognitions about the world must be influenced by experience, little research has directly assessed the relation between everyday experience and infants' visual cognition in the laboratory. Eye-tracking procedures were used to measure 4-month-old infants' eye-movements as they visually investigated a series of images. Infants with pet experience (N = 27) directed a greater proportion of their looking at the most informative region of animal stimuli-the head-than did infants without such experience (N = 21); the two groups of infants did not differ in their scanning of images of human faces or vehicles. Thus, infants' visual cognitions are influenced by everyday experience, and theories of cognitive development in infancy must account for the effect of experience on development.

Experience with malleable objects influences shape-based object individuation by infants

Infants' ability to accurately represent and later recognize previously viewed objects, and conversely, to discriminate novel objects from those previously seen improves remarkably over the first two years of life. During this time, infants acquire extensive experience viewing and manipulating objects and these experiences influence their physical reasoning. Here we posited that infants' observations of object feature stability (rigid versus malleable) can influence the use of those features to individuate two successively viewed objects. We showed 8.5-month-olds a series of objects that could or could not change shape, then assessed their use of shape as a basis for object individuation. Infants who explored rigid objects later used shape differences to individuate objects; however, infants who explored malleable objects did not. This outcome suggests that the latter infants did not take into account shape differences during the physical reasoning task and provides further evidence that infants' attention to object features can be readily modified based on recent experiences.

Categorization of two-dimensional and three-dimensional stimuli by 18-month-old infants

In two experiments, 18-month-old infants' categorization of 3D replicas and 2D photographs of the same animals and vehicles were compared to explore infants' flexibility in categorization across different object representations. Using a sequential touching procedure, infants completed one superordinate and two basic-level categorization tasks with 3D replicas, 2D cut out photographs, or 2D images on photo cubes ("2D cubes"). For superordinate sets, 3D replicas elicited longer mean run lengths than 2D cut outs, and 3D replicas elicited equivalent mean run lengths as 2D cubes. For basic-level sets, infants categorized high-contrast animal sets when presented with 3D replicas, but they failed to categorize any of the 2D photograph sets. Categorization processes appear to differ for 3D and 2D stimuli, and infants' discovery of object properties over time while manipulating objects may facilitate categorization, as least at the superordinate level. These findings are discussed in the context of infants' representation abilities and the integration of perception and action.

Context and repetition in word learning

Young children learn words from a variety of situations, including shared storybook reading. A recent study by Horst et al. (2011a) demonstrates that children learned more new words during shared storybook reading if they were read the same stories repeatedly than if they were read different stories that had the same number of target words. The current paper reviews this study and further examines the effect of contextual repetition on children's word learning in both shared storybook reading and other situations, including fast mapping by mutual exclusivity. The studies reviewed here suggest that the same cognitive mechanisms support word learning in a variety of situations. Both practical considerations for experimental design and directions for future research are discussed.

5-Month-Olds' Categorization of Novel Objects: Task and Measure Dependence

To examine key parameters of the initial conditions in early category learning, two studies compared 5-month-olds' object categorization between tasks involving previously unseen novel objects, and between measures within tasks. Infants in Experiment 1 participated in a visual familiarization / novelty preference (VFNP) task with 2D stimulus images. Infants provided no evidence of categorization by either their looking or their examining even though infants in previous research systematically categorized the same objects by examining when they handled them in 3D. Infants in Experiment 2 participated in a VFNP task with 3D stimulus objects that allowed visual examination of objects' 3D instantiation while denying manual contact with the objects. Under these conditions, infants demonstrated categorization by examining but not by looking. Focused examination appears to be a key component of young infants' ability to form category representations of novel objects, and 3D instantiation appears to better engage such examining.

Contributions of attentional style and previous experience to 4-month-old infants' categorization

We examined how infants' categorization is jointly influenced by previous experience and how much they shift their gaze back-and-forth between stimuli. Extending previous findings reported by Kovack-Lesh, Horst, and Oakes (2008), we found that 4-month-old infants' (N = 122) learning of the exclusive category of cats was related to whether they had cats at home and how much they shifted attention between two available stimuli during familiarization. Individual differences in attention assessed in an unrelated task were not related to their categorization. Thus, infants' learning is multiply influenced by past experience and on-line attentional style.

Get the story straight: contextual repetition promotes word learning from storybooks

Although shared storybook reading is a common activity believed to improve the language skills of preschool children, how children learn new vocabulary from such experiences has been largely neglected in the literature. The current study systematically explores the effects of repeatedly reading the same storybooks on both young children's fast and slow mapping abilities. Specially created storybooks were read to 3-year-old children three times during the course of 1 week. Each of the nine storybooks contained two novel name-object pairs. At each session, children either heard three different stories with the same two novel name-object pairs or the same story three times. Importantly, all children heard each novel name the same number of times. Both immediate recall and retention were tested with a four-alternative forced-choice task with pictures of the novel objects. Children who heard the same stories repeatedly were very accurate on both the immediate recall and retention tasks. In contrast, children who heard different stories were only accurate on immediate recall during the last two sessions and failed to learn any of the new words. Overall, then, we found a dramatic increase in children's ability to both recall and retain novel name-object associations encountered during shared storybook reading when they heard the same stories multiple times in succession. Results are discussed in terms of contextual cueing effects observed in other cognitive domains.

The development of object categorization in young children: hierarchical inclusiveness, age, perceptual attribute, and group versus individual analyses

Multiple levels of category inclusiveness in 4 object domains (animals, vehicles, fruit, and furniture) were examined using a sequential touching procedure and assessed in both individual and group analyses in eighty 12-, 18-, 24-, and 30-month-olds. The roles of stimulus discriminability and child motor development, fatigue, and actions were also investigated. More inclusive levels of categorization systematically emerged before less inclusive levels, and a consistent advantage for categorizing high versus low perceptual contrasts was found. Group and individual analyses generally converged, but individual analyses added information about child categorization over group analyses. The development of object categorization in young children is discussed in light of efficiency of processing and similarity-differentiation theories.