The 'stopped clock illusion'

When quickly glancing at an analogue clock with a second-hand, it often seems that the second-hand is 'stuck' for the first second - in other words the first tick of the hand appears to take longer than it should. In many cases the hand can even seem to step backwards one second.

This well-known and highly repeatable illusion has been recognised for many centuries - presumably dating back to the invention of the analogue clock.

The technical term for the illusion is Chronostasis (static time).

It has not yet been fully explained.

Although the illusion is seemingly trivial, it does have important implications for any human activities which involve important split-second decisions based on visual cues.

The consensus among perceptual psychologists is that it could be related to a 'mismatch' between eye-movements (called saccades) and the visual interpretation areas of the brain. Possibly involving references to some kind of inbuilt 'mental clock' ( see : Core Clockplugin-autotooltip__plain plugin-autotooltip_bigCore Clock

In humans, mammals, fish, insects, and very many other organisms, the 'Core Clock' which regulates variations in body functions is set to (approximately) 24 hours. This is the so-called Circadian Rhythm. - which in many organisms, is synchronised via daylight. ).

Recent research, however, is suggesting that it may not be related to eye saccades :

Chronostasis is not a saccade-specific mechanism, limited to occur at the location of the saccade target. It rather reflects a global mechanism for duration estimation of visual stimuli. The overestimation of durations could be caused by an active compensation in conditions where the exact time of a stimulus onset is not clearly perceived, but it appears possible that it is a passive result of how the time of a stimulus onset is predicted by the visual system in general."

Source : Spatio-temporal topography of saccadic overestimation of time Vision Research, Volume 83, Pages 56-65