People’s perception of time is subjective and based not only on their emotional state but also on heartbeat and heart rate (HR), two new studies suggest.
Researchers studied young adults with an electrocardiogram (ECG), measuring electrical activity at millisecond resolution while participants listened to tones that varied in duration. Participants were asked to report whether certain tones were longer or shorter, in relation to others.
The researchers found that the momentary perception of time was not continuous but rather expanded or contracted with each heartbeat. When the heartbeat preceding a tone was shorter, participants regarded the tone as longer in duration; but when the preceding heartbeat was longer, the participants experienced the tone as shorter.
“Our findings suggest that there is a unique role that cardiac dynamics play in the momentary experience of time,” lead author Saeedah Sadeghi, MSc, a doctoral candidate in the department of psychology at Cornell University, Ithaca, N.Y., said in an interview.
The study was published online in Psychophysiology.
In a second study, published in the journal Current Biology, a separate team of researchers asked participants to judge whether a brief event – the presentation of a tone or an image – was shorter or longer than a reference duration. ECG was used to track systole and diastole when participants were presented with these events.
The researchers found that the durations were underestimated during systole and overestimated during diastole, suggesting that time seemed to “speed up” or “slow down,” based on cardiac contraction and relaxation. When participants rated the events as more arousing, their perceived durations contracted, even during diastole.
“In our new paper, we show that our heart shapes the perceived duration of events, so time passes quicker when the heart contracts but slower when the heart relaxes,” lead author Irena Arslanova, PhD, postdoctoral researcher in cognitive neuroscience, Royal Holloway University of London, told this news organization.
Temporal ‘wrinkles’
“Subjective time is malleable,” observed Ms. Sadeghi and colleagues in their report. “Rather than being a uniform dimension, perceived duration has ‘wrinkles,’ with certain intervals appearing to dilate or contract relative to objective time” – a phenomenon sometimes referred to as “distortion.”
“We have known that people aren’t always consistent in how they perceive time, and objective duration doesn’t always explain subjective perception of time,” Ms. Sadeghi said.
Although the potential role of the heart in the experience of time has been hypothesized, research into the heart-time connection has been limited, with previous studies focusing primarily on estimating the average cardiac measures on longer time scales over seconds to minutes.
The current study sought to investigate “the beat-by-beat fluctuations of the heart period on the experience of brief moments in time” because, compared with longer time scales, subsecond temporal perception “has different underlying mechanisms” and a subsecond stimulus can be a “small fraction of a heartbeat.”
To home in on this small fraction, the researchers studied 45 participants (aged 18-21), who listened to 210 tones ranging in duration from 80 ms (short) to 188 ms (long). The tones were linearly spaced at 18-ms increments (80, 98, 116, 134, 152, 170, 188).
Participants were asked to categorize each tone as “short” or “long.” All tones were randomly assigned to be synchronized either with the systolic or diastolic phase of the cardiac cycle (50% each). The tones were triggered by participants’ heartbeats.
In addition, participants engaged in a heartbeat-counting activity, in which they were asked not to touch their pulse but to count their heartbeats by tuning in to their bodily sensations at intervals of 25, 35, and 45 seconds.