====== 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 :[[content/life_sciences/human_body/core_clock]] ).

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 : [[https://www.sciencedirect.com/science/article/pii/S0042698913000412?via%3Dihub#b0140|Spatio-temporal topography of saccadic overestimation of time]] {{:oa_padlock_grn.png?16}}//Vision Research//, Volume 83, 3 May 2013, Pages 56-65