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. Participants who did not encode semantically structured sequences did not show the semantic congruence effect and performed worse than those who encoded semantically structured sequences on congruent trials. Across conditions, the temporal distance between items at encoding positively predicted correct temporal proximity judgements. Overall, these findings demonstrate that semantic relatedness between encoded items can facilitate immediate temporal order memory depending on the encoding of semantically structured item sets. We discuss these results regarding the role and potential benefits of semantic and temporal context processing for constructive episodic memory.