Encoding of semantic structure shapes temporal order memory for visual object stimuli.

Episodic memory does not perfectly reproduce past experiences but combines encoded episode-specific information and semantic knowledge in a constructive way. Previous research has shown that semantic category knowledge can bias location memory for individual items, suggesting that similar mechanisms may affect other key dimensions of episodic memory. Here, we investigated whether immediate temporal order memory is influenced by semantic relatedness between encoded items and whether this effect is modulated by semantic structure at encoding, episodic association strength and semantic typicality. Across two experiments, participants completed a temporal order memory task in which they encoded sequences of object images and subsequently judged the relative temporal proximity between items. Results showed that participants who encoded semantically structured sequences performed significantly better on congruent retrieval trials where the correct choice (the temporally closer item) was semantically related to the cue versus on incongruent trials where the incorrect choice was semantically related to the cue. This semantic congruence effect was stronger with shorter temporal distance between the cue and target item at encoding. Participants who did not encode semantically structured sequences did not show the semantic congruence effect. Overall, these findings demonstrate that semantic relatedness between encoded items can bias immediate temporal order memory depending on the presence of semantic structure within encoded item sets. We discuss these results as evidence that semantic knowledge influences temporal order memory through encoding of structured context, highlighting the alignment between semantic and temporal associations as an important modulating factor for this interaction.