How long is a second?

A paper by doctoral researcher Ninja K. Horr, Dr Massimiliano Di Luca, and Dr Maria Wimber, recently accepted for publication in NeuroImage, investigates the brain's ability to keep track of time.

From everyday experience, we know that physical and perceived duration are not equivalent.  “Time flies when you’re having fun,” but “a watched pot never boils.” Distortions in subjective duration can also be observed in intervals lasting one second or less. Quantifying such distortions allows us to understand mechanisms underlying the brain’s ability to keep track of time.

The authors found that a one-second regular or predictable rhythmic sound sequence is perceived to last longer than an irregular sequence. At a neural level, regular sequences are special as they make oscillations of brain activity sync up to the regularly presented stimuli. This phenomenon is called neural entrainment. The present research paper shows a connection between neural entrainment and perceived duration. Physically identical regular sequences are perceived as longer when they show stronger entrainment and the size of this effect is related to participants’ individual tendency to overestimate regularity. Given the brain responds more vigorously to each stimulus in the entrained sequence, the connection between perceived duration and entrainment supports the idea that a period of time with high neural activity appears to last longer. This further hints at the intrinsic connection between perceptual processing and the estimation of event duration, and opens up a new avenue of research on how temporal structure influences both of these.