Heartbeats Modify Time Perception

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New research reveals that the timing of our heartbeats relative to external events distorts our perception of how much time has passed.

The study provides evidence that cardiac signals directly impact time perception on a moment-to-moment basis.

Key Facts:

  • Time perception was shown to contract during heart systole (when the heart contracts) and expand during diastole (when the heart relaxes between beats).
  • This effect occurred for both auditory and visual stimuli, suggesting a modality-general cardiac influence on time perception.
  • The distortion was present for non-arousing stimuli but disappeared as the subjective arousal to emotional stimuli increased.
  • The findings support the idea that time perception relies on integrating external sensory information with internal bodily signals.

Source: Current Biology. 2023 Apr 10;33(7):1389-1395.e4.

Manipulating the Cardiac Cycle

The study, published in Current Biology, used an ingenious method to investigate how the cardiac cycle impacts time perception.

Researchers manipulated when visual shapes or auditory tones were presented relative to participants’ heartbeats.

Stimuli were timed to occur either during heart systole or diastole.

Systole is when the heart contracts to pump blood, triggering increased firing of baroreceptors that signal cardiac info to the brain.

Diastole is the relaxation phase between beats when baroreceptor firing stops.

By locking stimulus timing to different cardiac phases, the study could examine how our perception of duration is shaped by phasic bodily signals generated with each heartbeat.

Time Dilation and Contraction Within Each Cardiac Cycle

The results revealed that identical stimuli were perceived to last longer when presented during diastole compared to systole.

This suggests that time subjectively dilates during diastole but contracts during systole.

The effect occurred both for visual and auditory stimuli, pointing to a supramodal influence of cardiac phase on duration perception.

The time distortion was around 10 milliseconds on average.

This finding accords with prior work showing cardiac activity shapes perception and brain function.

But it provides more direct evidence that our perception of time is continuously modulated by signals from each heartbeat.

The Role of Arousal in Cardiac-Driven Time Distortions

In a second experiment, the cardiac timing manipulation was combined with emotional stimuli – images of happy and fearful facial expressions.

After rating their arousal to each face, an interesting interaction emerged.

The opposing time contraction and dilation effects were present for low and medium arousal stimuli.

But as subjective arousal increased, the cardiac-led temporal distortion disappeared.

Duration perception was biased toward contraction across both systole and diastole.

This highlights arousal as a key factor mediating cardiac influences on time perception.

The balance of cardiac effects breaks down under heightened arousal.

Potential Mechanisms Underlying Cardiac-Led Time Distortions

What mechanisms might explain how cardiac phase distorts time perception? The researchers proposed two possibilities:

  1. Sensory modulation – Baroreceptor firing during systole may attenuate sensory processing. Diminished sensory encoding could cause temporal contraction, counteracted by time expansion during diastole.
  2. Temporal accumulation – Interoceptive signals at each phase may directly impact accumulation of temporal information. Systole may simulate heightened arousal, accelerating the pacemaker. Diastole may have the opposite effect.

Future studies combining the cardiac timing manipulation with EEG/MEG can distinguish between these accounts.

Overall, the findings illuminate how time perception arises from integrating exteroceptive sensory information with phasic interoceptive bodily signals.

Wider Implications for Understanding Embodied Cognition

These results have broader implications for embodied cognition theories which emphasize deep interplay between body and brain.

Interoceptive influences from the heart and other visceral systems are receiving growing recognition for shaping perception, cognition and emotion.

But much remains unknown about how bodily signals impact moment-to-moment information processing.

By showing cardiac phase regularly distorts duration judgments, this study provides compelling evidence that neural encoding of each heartbeat causally impacts perception.

Our subjective experience does not passively represent the external world but is continually constructed from dynamic integration of external sensory inputs with the body’s internal milieu.

In this way, the beating heart helps shape not only our bodies but also our minds, down to our very perception of time.

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