Brain controls time perception

Research by a University of Queensland scientist has shown that our own brain activity can influence our sense of timing.

Work by Dr Derek Arnold of the UQ School of Psychology goes against a widely held belief that activity in the cortex of the human brain does not influence how we perceive time.

Dr Arnold's examined sensory changes by analysing activity in the cortex of the human brain.

He has found that large changes were detected more rapidly than smaller changes. He also found that large changes seemed to occur earlier than did smaller changes.

“The size of the change had a greater impact on timing than it did on the ability to detect the change,” he said.

“So, it seems that perceived timing is more closely related to when observers become confident of change detection, rather than with the point at which changes can actually first be detected," said Dr Arnold.

He said that the results had some surprising implications. The most obvious was that our sense of timing was shaped by activity in the cortex of the human brain. The other concerned the existence of free will.

“It is believed by many scientists and philosophers that our actions are instigated by unconscious processes over which we have no control. However, our results suggest that we are responsible for our own actions,” said Dr Arnold.

Dr Arnold said a timing experiment had previously been used to question the existence of free will.

“In the 1980s, a US-based physiologist, Benjamin Libet, had observers instigate a movement at a random time of their own choosing while he recorded activity from their brains,” he said.

“The observers reported when they had decided to instigate movement. Surprisingly, brain activity related to the instigation of movement could be detected before observers reported that they had decided to move.

“Scientists and philosophers have used these results to question the existence of free will, the idea being that our decisions are just an explanation we use to make sense of actions that have already been instigated by unconscious processes over which we have no control.

“However, this idea is based on the premise that observers have an accurate sense of timing. Our more recent results suggest that this is unlikely.”

Dr Arnold said his research data suggested that observers were conservative – that timing judgments reflected when observers became confident of detection, but not of when changes could first be detected.

“The apparent delay of decisions to instigate movement, relative to the brain activity involved in implementing that movement, probably involved the same type of inaccurate and conservative sense of timing,” he said.

“Accordingly, we would be responsible for our own decisions – we just wouldn't have a very accurate sense of when we made them.”  

Editor's Note: Original news release can be found here.