A new research has found that humans use their senses to help keep track of short intervals of time, and this suggests that our perception of time is not maintained by an internal body clock alone.
Scientists from University College London (UCL) set out to answer the question "Where does our sense of time come from?" Their results show that it comes partly from observing how much the world changes, as we have learnt to expect our sensory inputs to change at a particular 'average' rate.
Comparing the change we see to this average value helps us judge how much time has passed, and refines our internal timekeeping.
The study includes two key experiments. In one experiment 20 participants watched small circles of light appear on a screen twice in a row, and were asked to say which appearance lasted longer.
When the circles were accompanied by a mottled pattern programmed to change randomly, but with a regular average rate, participants' judgments were better - suggesting that they used the rate of change in the patterns to judge the passing of time.
In another experiment the authors asked participants to judge how long the mottled patterns themselves lasted, but varied the rates at which those patterns changed. When the patterns changed faster, participants judged them to have lasted longer - again showing that sensory change shapes our sense of time.
"Our sense of time is affected by outside stimuli, and is therefore highly mutable, which is something that resonates with people's feeling about the passing of time," said Maneesh Sahani, an author of the paper.
The study has been published online in Current Biology.