Can heartbeats shape our perception of time?

It is a truism that time seems to expand or contract depending on our circumstances. In a state of terror, seconds can stretch. A day spent in solitude can drag. When we’re trying to meet a deadline, hours race by.

A study published this month in the journal Psychophysiology by psychologists at Cornell University found that, when observed at the level of microseconds, some of these distortions could be driven by heartbeats, whose length is variable from moment to moment.

Psychologists fitted undergraduates with electrocardiograms to measure the length of each heartbeat precisely, and then asked them to estimate the length of brief audio tones. The psychologists discovered that after a longer heartbeat interval, subjects tended to perceive the tone as longer; shorter intervals led subjects to assess the tone as shorter. After each tone, the subjects’ heartbeat intervals lengthened.

A lower heart rate appeared to assist with perception, said Saeedeh Sadeghi, a doctoral candidate at Cornell and the study’s lead author. “When we need to perceive things from the outside world, the beats of the heart are noise to the cortex,” she said. “You can sample the world more — it’s easier to get things in — when the heart is silent.”

The study provides more evidence, after an era of research focusing on the brain, that “there is no single part of the brain or body that keeps time — it’s all a network,” she said. “The brain controls the heart, and the heart, in turn, impacts the brain.”

Interest in the perception of time has exploded since the Covid pandemic, when activity outside the home came to an abrupt halt for many and people worldwide found themselves facing stretches of undifferentiated time.

A study of time perception conducted during the first year of the lockdown in Britain found that 80 per cent of participants reported distortions in time, in different directions. On average, older, more socially isolated people reported that time slowed, and younger, more active people reported that it sped up.

“Our experience of time is affected in ways which mirror, generally, our well-being,” said Ruth S Ogden, a psychology professor at Liverpool John Moores University and author of the lockdown study. “People with depression experience a slowing of time, and that slowing of time is experienced as being a worsening factor of the depression.”

(This article originally appeared in The New York Times)