A developmental study of choice reaction time: the effect of two forms of stimulus degradation on encoding.

To assess the effects of environmental enrichment, 156 normal, full-term institutionalized infants were randomly assigned to Group I (30 min per day of supplementary vestibular stimulation), Group II (30 min per day of supplementary vestibular-plus-verbal stimulation), or Group III (untreated controls). Stimulation began at about the age of 12 days and continued until the children were adopted, approximately 6 weeks later. Children were assessed at regular intervals on the Gesell Developmental Schedules, until the age of 27 months. Group comparisons revealed no significant treatment effects.