Sensing between heartbeats
The length of time humans feel an object depends on the phase of their heartbeat when they first touch it.
Most of what is known about human senses comes from experiments under laboratory conditions where participants stay still and stimuli are presented to them by the scientists. However, this approach does not reflect what happens in real life as we move around, changing the position of our eyes, heads and hands, to actively sense the world.
Our perception also changes depending on what is going on inside our bodies and minds at any one time. For instance, our sensitivity to touch varies during the two phases of our heartbeat: people are less perceptive to being touched during systole (when the heart ejects blood), compared to when they are touched during diastole (when the heart refills with blood). But it was unclear if this relationship influences how we actively touch and sense objects. For instance, do people seek touch in a particular phase of their heartbeat, and how does this change their response to the object?
To investigate, Galvez-Pol et al. traced people’s heartbeats while they actively touched different objects. Without looking, the participants had to work out whether the objects had vertical or horizontal grooves. Although they did not start their touches in a specific phase of the heartbeat, their hearts did influence their behaviour. If they started the touch during systole, they held their fingers over the object for longer. The effect was especially noticeable when it was difficult to discriminate the objects’ grooves.
Galvez-Pol et al. reasoned that this was down to participants having to compensate for the loss in touch sensitivity during the systole phase of their heartbeat. This suggests that people actively adjust how they acquire sensory information, such as touch, based on how their bodily functions alter their senses.
These findings provide a starting point for future studies investigating how internal bodily fluctuations impact how we sense and respond to things in real world scenarios. This could potentially shed light on the differences between the way neurotypical and neurodivergent individuals sense the world.
Originally published at https://elifesciences.org/digests/78126.
