Dissecting emotional and cardiac contributions to duration perception: Evidence from two EEG experiments.

Time perception is inherently malleable, influenced by both emotional and bodily states. Past research suggests that transient heartbeat-linked interoceptive signals can modulate time perception, with some studies reporting that brief stimuli presented during cardiac systole are perceived as shorter than those during diastole. Here, we used electroencephalography (EEG) across two experiments to examine how such cardiac-phase effects are neurally instantiated, and how they interact with emotional content of the stimuli. In Experiment 1, participants judged the duration of brief neutral visual stimuli (Gabor patches) presented during systole or diastole. We did not observe a reliable group-level behavioural cardiac-phase effect. Despite that, EEG revealed systolic modulation of late visual activity. Crucially, exploratory analyses showed that more negative late cortical activity predicted temporal underestimation only during systole, not diastole. In Experiment 2, we extended this design to emotionally salient stimuli (neutral vs fearful faces). Fearful faces were perceived as shorter in duration and accompanied by enhanced N170-like negativity compared to neutral faces. But this effect was not modulated by cardiac phase, suggesting that emotional salience is a much more powerful driver of duration perception than subtle cardiac fluctuations. Yet, even for faces, enhanced EEG negativity predicted temporal contraction only during systole. Together, these findings reveal that while group-level behavioural cardiac-phase effects are variable, the systole-specific neural mechanism, whereby reduced cortical activity predicts temporal contraction, replicated across both experiments. This suggests that cardiac signals can shape duration perception through transient modulation of cortical processing.