Perceived time & heartbeat

This blog entry about the Current Biology article “Perceived time expands and contracts within each heartbeat” relates perfectly to my previous blog on “cardiac activity: its role in perception and action

Perception of passing time can be distorted. Emotional experiences, particularly arousal, can contract or expand experienced duration via their interactions with attentional and sensory processing mechanisms. Current models suggest that perceived duration can be encoded from accumulation processes and from temporally evolving neural dynamics. Yet all neural dynamics and information processing ensue at the backdrop of continuous interoceptive signals originating from within the body. Indeed, phasic fluctuations within the cardiac cycle impact neural and information processing.
This article shows that these momentary cardiac fluctuations distort experienced time and that their effect interacts with subjectively experienced arousal. In a temporal bisection task, durations (200–400 ms) of an emotionally neutral visual shape or auditory tone or of an image displaying happy or fearful facial expressions were categorized as short or long.

Across both experiments, stimulus presentation was time-locked to systole, when the heart contracts and baroreceptors fire signals to the brain, and to diastole, when the heart relaxes, and baroreceptors are quiescent. When participants judged the duration of emotionally neural stimuli, systole led to temporal contraction, whereas diastole led to temporal expansion. Such cardiac-led distortions were further modulated by the arousal ratings of the perceived facial expressions. At low arousal, systole contracted while diastole expanded time, but as arousal increased, this cardiac-led time distortion disappeared, shifting duration perception toward contraction. Thus, experienced time contracts and expands within each heartbeat—a balance that is disrupted under heightened arousal.

Across two experiments, participants first learned to discriminate a short (200 ms) from a long (400 ms) reference duration and were then asked to judge whether intermediate test durations (200, 250, 300, 350, and 400 ms) were more like the short or the long reference. Across both experiments, stimulus presentation was time-locked to either the systolic (R + 100 ms) or the diastolic (R + 500 ms) cardiac phase (B).
In experiment 1, participants performed the task for visual and auditory stimuli in separate blocks, judging the duration of emotionally neutral visual images or auditory tones.
In experiment 2, a new group of participants judged the duration of images depicting happy or fearful facial expressions presented in a random order. In experiment 2, after the temporal bisection task, participants were presented with each face again for 300 ms and were asked to rate how aroused it made them feel on an adapted 5-point self-assessment mannequin (SAM) scale from calm (1) to aroused (5).
  • Time-locking identical stimuli to distinct cardiac phases distorts perceived duration
  • The cardiac-led time distortion is modulated by experienced arousal
  • At low arousal, systolic time contraction is counteracted by diastolic time expansion
  • At high arousal, diastolic time expansion shifts toward time contraction
Simple slopes analysis breaking down the cardiac phase by subjective arousal interaction on PSE (point of subjective equality) values in experiment 2. A linear mixed model was run on the PSE values modeling the effects of the cardiac phase (systole, diastole), subjective arousal, and changes in heart rate. The cardiac effect on PSEs was concentrated at low and mean levels of arousal but disappeared at high arousal levels. Arousal ratings were mean-centered. 

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