During early ontogeny, the rapid and cumulative acquisition of world knowledge contrasts with slower improvements in the ability to lay down detailed and long-lasting episodic memories. This emphasis on generalization at the expense of specificity persists well into middle childhood and possibly into adolescence. During this period, recognizing regularities, forming stable representations of recurring episodes, predicting the structure of future events, and building up semantic knowledge may be prioritized over remembering specific episodes. We highlight recent behavioral and neuroimaging evidence suggesting that maturational differences among subfields within the hippocampus contribute to the developmental lead-lag relation between generalization and specificity, and lay out future research directions.

Episodic memory relies on memory for the relations among multiple elements of an event and the ability to discriminate among similar elements of episodes. The latter phenomenon, termed pattern separation, has been studied mainly in young and older adults with relatively little research on children. Building on prior work with young children, we created an engaging computer-administered relational memory task assessing what-where relations. We also modified the Mnemonic Similarity Task used to assess pattern discrimination in young and older adults for use with preschool children. Results showed that 4 year-olds performed significantly worse than 6 year-olds and adults on both tasks, whereas 6 year-olds and adults performed comparably, even though there were no ceiling effects. However, performance on the two tasks did not correlate, suggesting that two distinct mnemonic processes with different developmental trajectories may contribute to age-related changes in episodic memory.

The ability to keep similar experiences separate in memory is critical for forming unique and lasting memories, as many events share overlapping features (e.g., birthday parties, holidays). Research on memory in young children suggests their memories often lack high-resolution details, i.e., show impoverished pattern separation (PS). Recently developed assessments of PS suitable for children allow us to relate the formation of distinct, detailed memories for the development of the hippocampus, a neural structure critical for this ability in adults. The hippocampus displays a protracted developmental profile and underlies the ability to form detailed memories. This study examined age-related differences in hippocampal subfield volumes in 4- to 8-year-old children and relations with performance on a mnemonic similarity task (MST) designed to index memory specificity. Results revealed age-moderated associations between MST performance and cornu ammonis 2-4/dentate gyrus subfields. Specifically, age-related differences in the ability to form detailed memories tracked with normative patterns of volume increases followed by reductions over this age range. That is, greater volume correlated with better performance in younger children, whereas smaller volume correlated with better performance in older children. These findings support the hypothesis that developmental differences in hippocampal circuitry contribute to age-related improvements in detailed memory formation during this period.

Episodic memory binds the diverse elements of an event into a coherent representation. This coherence allows for the reconstruction of different aspects of an experience when triggered by a cue related to a past event—a process of pattern completion. Previous work has shown that such holistic recollection is evident in young adults, as revealed by dependency in retrieval success for various associations from the same event. In addition, episodic memory shows clear quantitative increases during early childhood. However, the ontogeny of holistic recollection is uncharted. Using dependency analyses, we found here that 4-year-olds ( n = 32), 6-year-olds ( n = 30), and young adults ( n = 31) all retrieved complex events in a holistic manner; specifically, retrieval accuracy for one aspect of an event predicted accuracy for other aspects of the same event. However, the degree of holistic retrieval increased from the age 4 to adulthood. Thus, extended refinement of multiway binding may be one aspect of episodic memory development.

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