A neural network model of hippocampal contributions to category learning.

In addition to its critical role in encoding individual episodes, the hippocampus is capable of extracting regularities across experiences. This ability is central to category learning, and a growing literature indicates that the hippocampus indeed makes important contributions to this form of learning. Using a neural network model that mirrors the anatomy of the hippocampus, we investigated the mechanisms by which the hippocampus may support novel category learning. We simulated three category learning paradigms and evaluated the network's ability to categorize and recognize specific exemplars in each. We found that the trisynaptic pathway within the hippocampus-connecting entorhinal cortex to dentate gyrus, CA3, and CA1-was critical for remembering exemplar-specific information, reflecting the rapid binding and pattern separation capabilities of this circuit. The monosynaptic pathway from entorhinal cortex to CA1, in contrast, specialized in detecting the regularities that define category structure across exemplars, supported by the use of distributed representations and a relatively slower learning rate. Together, the simulations provide an account of how the hippocampus and its constituent pathways support novel category learning.

Discovering category boundaries: The role of comparison in infants' novel category learning.

A key question in categorization is how infants extract regularities from the exemplars they encounter. Detecting similarities and dissimilarities across items is vital in order to determine category-relevant features. Previous research found evidence that infants acquire a single category more easily with paired presentations in comparison with single presentations (Oakes & Ribar, 2005, Infancy, 7, 85; Oakes & Kovack-Lesh, 2007, Cogniție, Creier, Comportament / Cognition, Brain, Behavior, XI, 661). Here, we focus on infants' acquisition of a category contrast, that is, when they are exposed to two categories. In an eye-tracking study, we examined 10-month-old infants' ability to learn two novel visual categories when presented with one item at a time and with items in pairs. Infants were familiarized with pairs of items from the same category or with pairs of items from different categories (cross-category pairs). Using a linear model with a priori contrasts, we show that infants' learning is directly related to the opportunity for category comparison: There is no evidence of category learning in the single-item condition, improved performance when familiarized with same-category pairs, and finally robust category learning when familiarized with cross-category pairs. We conclude that comparison which involves items from different categories promotes category formation, by highlighting differences and promoting a discovery of category boundaries.

The role of labels and motions in infant category learning.

We investigated the impact of two highly salient transient features, labels and motions, on novel visual category learning in 10-month-old infants. In three eye-tracking experiments, infants were presented with exemplars from two novel categories either accompanied by category-specific labels, accompanied by category-specific motions, or in silence. Labels (Experiment 1) and motions (Experiment 2) were presented using a gaze-contingent design in which these transient features were triggered by infants' fixations. Gaze-contingent transient features, despite being redundant, had a strong impact on categorization. The results revealed that both labels and motions support infants' category formation. Furthermore, both labels and motions promoted similarity-focused exploration, whereas no such pattern was found when infants learned the categories in silence. Analyses of visual exploration patterns revealed that infants readily form expectations about motion properties of categories and that these expectations drive their looking behavior.

Let's talk action: Infant-directed speech facilitates infants' action learning.

Parents modulate their speech and their actions during infant-directed interactions, and these modulations facilitate infants' language and action learning, respectively. But do these behaviors and their benefits cross these modality boundaries? We investigated mothers' infant-directed speech and actions while they demonstrated the action-effects of 4 novel objects to their 14-month-old infants. Mothers (N = 35) spent the majority of the time either speaking or demonstrating the to-be-learned actions to their infant while hardly talking and acting at the same time. Moreover, mothers' infant-directed speech predicted infants' action learning success beyond the effect of infant-directed actions. Thus, mothers' speech modulations during naturalistic interactions do more than support infants' language learning; they also facilitate infants' action learning, presumably by directing and maintaining infants' attention toward the to-be learned actions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

To call a cloud 'cirrus': sound symbolism in names for categories or items.

The aim of the present paper is to experimentally test whether sound symbolism has selective effects on labels with different ranges-of-reference within a simple noun-hierarchy. In two experiments, adult participants learned the make up of two categories of unfamiliar objects ('alien life forms'), and were passively exposed to either category-labels or item-labels, in a learning-by-guessing categorization task. Following category training, participants were tested on their visual discrimination of object pairs. For different groups of participants, the labels were either congruent or incongruent with the objects. In Experiment 1, when trained on items with individual labels, participants were worse (made more errors) at detecting visual object mismatches when trained labels were incongruent. In Experiment 2, when participants were trained on items in labelled categories, participants were faster at detecting a match if the trained labels were congruent, and faster at detecting a mismatch if the trained labels were incongruent. This pattern of results suggests that sound symbolism in category labels facilitates later similarity judgments when congruent, and discrimination when incongruent, whereas for item labels incongruence generates error in judgements of visual object differences. These findings reveal that sound symbolic congruence has a different outcome at different levels of labelling within a noun hierarchy. These effects emerged in the absence of the label itself, indicating subtle but pervasive effects on visual object processing.

Balloons and bavoons versus spikes and shikes: ERPs reveal shared neural processes for shape-sound-meaning congruence in words, and shape-sound congruence in pseudowords.

There is something about the sound of a pseudoword like takete that goes better with a spiky, than a curvy shape (Köhler, 1929:1947). Yet despite decades of research into sound symbolism, the role of this effect on real words in the lexicons of natural languages remains controversial. We report one behavioural and one ERP study investigating whether sound symbolism is active during normal language processing for real words in a speaker's native language, in the same way as for novel word forms. The results indicate that sound-symbolic congruence has a number of influences on natural language processing: Written forms presented in a congruent visual context generate more errors during lexical access, as well as a chain of differences in the ERP. These effects have a very early onset (40-80 ms, 100-160 ms, 280-320 ms) and are later overshadowed by familiar types of semantic processing, indicating that sound symbolism represents an early sensory-co-activation effect.