Influences of learned verbal labels and sleep on temporal event memory

Conceptual knowledge is known to modulate episodic memory, but it remains unclear whether and how verbal labels shape event learning and recollection over time. To investigate this issue, we asked participants to study and memorise unfamiliar animations and their titles. The titles conveyed fast or slow motion speed (e.g., a bus vs ambulance travelling). Event memory was assessed at different time points—soon after learning and after 12 h of sleep or wakefulness—using a timed mental event reproduction task and verbal recall. Unlike previous findings with these stimuli, we found that intentional title study elicited title-related biases on reproduced durations soon after learning. Post-sleep but not post-wakefulness recollection also showed title-related biases and systematically longer reproduced durations. Nevertheless, reproduced durations correlated with stimulus segments, stimulus durations and verbal recall, indicating that event memories combined episodic and verbal conceptual features. Results suggest that intentional verbal learning promoted conceptual influences at encoding and that sleep-dependent consolidation enhanced these influences. We argue that the degree of integration between conceptual and episodic features determines the extent of conceptual influences and, more generally, the role of verbal labels in event learning and memory.