Organicity and mental retardation: analysis of eye and head movements

Eye and head movements of ten mentally retarded (MR) children and ten normal school children were recorded. Each was directed to look to one side or the other in response to verbal commands, to gestural directions, or to the appearance of illuminated fixation targets. Under these conditions: 1. Large gaze movements of MR subjects were accompanied by head movements more frequently than those of the normal subjects. Furthermore, for similar gaze deviations, head movement of MR subjects tended to be larger than those of normal subjects. 2. Head movements of normal subjects rarely began before eye movement, but those of MR subjects often did so. This "abnormal" MR eye-head movement pattern was more frequent in response to verbal or gestural commands than in response elicited by illumination of fixation targets.