The present paper is a preliminary report of our work exploring skill learning and repetition priming in parallel studies of mirror symmetry detection in humans and network models. The memory mechanisms supporting the acquisition of skill and repetition priming in humans have been the subject of much speculation. On one account, drawing on the distinction between procedural and declarative learning, these learning phenomena grow out of experience-based tuning and reorganization of processing modules engaged by performance in a given domain, in a manner that is intimately tied to the operation of those modules. Such learning appears similar to that suggested by the Incremental learning algorithms currently being explored in massively-parallel connectionist models (e.g., the Boltzmann machine). In the present work, both learning phenomena were observed in the behavioral data from human subjects and the simulation data from the network models. The network models showed priming effects from the start of de novo learning despite being designed to handle generalization to new materials - the essence of skill learning - and without additional mechanisms designed to provide a temporary advantage for recently presented material. Priming occurred for the human subjects despite the use of novel materials for which pre-existing representations cannot already be present in memory. These findings support the notion that skill learning and repetition priming are linked to basic incremental learning mechanisms that serve to configure and reorganize processing modules engaged by experience.

Relational memory improves during middle childhood and adolescence, yet the neural correlates underlying those improvements are debated. Although memory for spatial, temporal, and other associative relations requires the hippocampus, it is not established whether within-individual changes in hippocampal structure contribute to memory improvements from middle childhood into adolescence. Here, we investigated how structural changes in hippocampal head, body, and tail subregions predict improvements in the capacity to remember item-space, item-time, and item-item relations. Memory for each relation and volumes of hippocampal subregions were assessed longitudinally in 171 participants across 3 time points (M_age at T1 = 9.45 years; M_age at T2 = 10.86 years, M_age at T3 = 12.12 years; comprising 393 behavioral assessments and 362 structural scans). Among older children, volumetric growth in: (a) head and body predicted improvements in item-time memory, (b) head predicted improvements in item-item memory; and (c) right tail predicted improvements in item-space memory. The present research establishes that changes in hippocampal structure are related to improvements in relational memory, and that sub-regional changes in hippocampal volume differentially predict changes in different aspects of relational memory. These findings underscore a division of labor along the anterior-posterior axis of the hippocampus during child development.