While you’re reading this, your heart is beating. It’s pumping blood through your body, carrying vital oxygen and nutrients to help keep you alive.
We are hardly aware of this relentless, life-affirming pounding underneath our skin, even though it happens over 100,000 times every single day.
While our heartbeat escapes our notice most of the time, though, that doesn’t mean it has zero effect on our powers of attention.
Quite the contrary, in fact, as researchers from the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) explain in a new study.
“Even though humans are mostly not aware of their heartbeats, several heartbeat-related effects have been reported to influence conscious perception,” the authors write in their paper.
Last year, some of the same team explored how fluctuations in heart activity can modulate our ability to consciously perceive external stimuli.
In experiments, they found that volunteers were less likely to detect subtle electrical pulses during one phase of the heartbeat cycle, called systole.
During systole, the heart muscle contracts, pumping blood into arteries. After this happens, diastole occurs; the heart relaxes after contracting, and its chambers fills up with blood once more.
What this showed from a scientific point of view was that humans exhibit less somatosensory perception – the sensation of things throughout the body – during systole than during diastole.
In other words, we seem to perceive things less at the moment that the heart clenches and pumps blood through the body.
Directly after, though, when the heart relaxes before the next heartbeat, we can register sensations more clearly.
Why does this happen? Arguably, it’s possible humans adapted this trait so that we aren’t constantly disturbed by our own pulse.