The autokinetic effect is a phenomenon of human visual perception in which a stationary, small point of light in an otherwise dark or featureless environment appears to move. It was first recorded by a Russian officer keeping watch who observed illusory movement of a star near the horizon. It presumably occurs because motion perception is always relative to some reference point. In darkness or in a featureless environment there is no reference point, so the movement of the single point is undefined. The direction of the movements does not appear to be correlated with the involuntary movements of the eyes, but may be determined by errors between eye position and that specified by efference copy of the movement signals sent to the extraocular muscles .
The amplitude of the movements is also undefined. Individual observers set their own frames of reference to judge amplitude (and possibly direction). Because the phenomenon is labile, it has been used to show the effects of social influence or suggestion on judgements. For example, if an observer who would otherwise say the light is moving one foot overhears another observer say the light is moving one yard then the first observer will report that the light moved one yard. Discovery of the influence of suggestion on the autokinetic effect is often attributed to Sherif (1935), but it was recorded by Adams (1912), if not others.
Many sightings of UFOs have also been attributed to the autokinetic effect's action on stars or planets.
In literature
An evocative passage appears in H. G. Wells' novel The War of the Worlds. Although Wells ascribes the apparent "swimming" of the planet to telescope vibration and eye fatigue, it is likely that the autokinetic effect is also being described:
- Looking through the telescope, one saw a circle of deep blue and the little round planet swimming in the field. It seemed such a little thing, so bright and small and still, faintly marked with transverse stripes, and slightly flattened from the perfect round. But so little it was, so silvery warm--a pin's-head of light! It was as if it quivered, but really this was the telescope vibrating with the activity of the clockwork that kept the planet in view.
- As I watched, the planet seemed to grow larger and smaller and to advance and recede, but that was simply that my eye was tired. Forty millions of miles it was from us--more than forty millions of miles of void. Few people realise the immensity of vacancy in which the dust of the material universe swims.
See also
References
Adams, H. F. (1912). Autokinetic sensations. Psychological Monographs, 14, 1-45.
Sherif, M. (1935). A study of some social factors in perception. Archives of Psychology, 27(187) .