Age effects in dynamic vision based on orientation identification.

Dynamic vision considers the time domain of visual processing, presumably a function of the magnocellular system. The temporal visual component is not completely developed at the beginning of school age. The effects of age on a certain aspect of dynamic visual perception are reported in this study of 286 subjects in the age range of 7-68 years. Three simple orientation identification tasks were used: a fixation, a saccade, and an anti task. In each case the subjects had to identify the last of a series of fast changing orientations of a T-symbol before it disappeared after a random time period. The percentage of correct identifications in 50-100 trials was measured for each of the three tasks. In the age range of about 14 to about 28 years the subjects could perform the tasks at 90% correct or better. At younger and at older ages the mean values of the scores are considerably lower due to a higher percentage of subjects with difficulties in the performance of the tasks. It is discussed whether it is the magnocellular system which mediates the dynamic orientation identification in these tasks and which begins to decline relatively early in life in parallel with a relative loss of saccade control.