Increased inhibition and decreased facilitation effect during a lexical decision task in children

Widespread theories propose that implicit memory is established in the early stages of development, while explicit memory continues to develop until later stages. However, recent studies have argued that implicit memory changes developmentally. In order to elucidate the differences of implicit memory and semantic memory structures between children and adults, a single-word presentation method was developed using lexical decision tasks in which repeated real words, related real words, unrelated real words and pseudowords were presented in a list. Semantic priming and repetition priming using a single-word presentation method were employed in 25 children and 18 adults. Reaction time (RT) and correct rate for real words following pseudowords served as the base. Inhibition effect was defined as an increase in RT between a real word preceded by an unrelated real word and a real word preceded by a pseudoword. Facilitation effect was defined as a decrease in RT between a real word preceded by a related real word and a real word preceded by a pseudoword. Although the effect sizes of semantic priming did not differ between children and adults, the inhibition effect was larger and the facilitation effect was smaller in children. Repetition priming in children did not differ from that in adults. These findings challenge the idea of developmental invariance in implicit memory, suggesting that the strength of links between nodes in the semantic network increases and the range of spreading activation expands developmentally.