Two groups of mentally retarded children (MA: 4 to 8 years) were pretrained using two different methods. It was predicted that shift performance of the two groups trained to use different strategies would resemble those of two different developmental levels. (MP)

The optional shift performance of 52 reflective and 50 impulsive second-grade girls was assessed under two response-consequence conditions: (1) reward for correct responses only, and (2) reward for correct responses and a penalty for incorrect responses. (Author/MP)