Perception of figure orientation by nonambulatory children with profound mental retardation.

An habituation-dishabituation procedure was used to study perception of changes in figure orientation by nonambulatory children with profound mental retardation. On each of 3 days, 16 participants were given familiarization trials with either a vertical or an horizontal pattern, followed by test trials with the familiarized stimulus and one of three novel stimuli--a 90 degree or 45 degree rotation of the pattern, or a rearrangement of the pattern elements into a square. Visual fixation times decreased over familiarization trials. Fixation times on test trials were longer for novel than for familiar stimuli, indicating that these children discriminated changes in form and orientation.