The size illusion in children from five years of age and adults.

First it was established that the size illusion occurs not only when complex patterns are presented kinaesthetically but even with simple stimuli such as straight lines and circles. Thus it was established that information overload is not the underlying cause of the illusion. The size illusion was investigated in children aged from five to twelve years and in adults. The stimulus circle was presented in passive kinaesthetic, sequential visual, in combined kinaesthetic and sequential visual, in static visual, and in combined kinaesthetic and static visual conditions either at fast or at slow speeds. A between-subjects design was used. In all conditions where the stimulus presentation included the kinaesthetic modality alone or in combination with visual or sequential visual conditions, size overestimation was found, while in the sequential visual and static visual conditions overestimation of the size of the stimulus was absent. Further, the kinaesthetic illusion was stable across the age range tested, indicating that the illusion is a property of the kinaesthetic system and is not influenced by learning, ie is hard wired.