Moments of transfer of stimulus control in practical assembly tasks by mentally retarded adults

Twenty vocational rehabilitation clients, divided into two aptitude groups, were trained to assemble three different 10-part apparatuses (lawn mower engine, electric drill, and bicycle brake) using three progressive prompt delay intervals (1, 3, and 5 seconds). The experimenter modeled selection and placement of each part on Trial 1 (0-second delay). On Trial 2, the modeling prompt was delayed 1, 3, or 5 seconds. On subsequent trials, a correct response increased the delay interval while an incorrect response shortened the delay interval. The 1-second delay condition produced fewest errors, most trials with no errors, and earliest acquisition. The patterns of the "moments of transfer" (shift from prompt dependent to independent responding) were similar for the high- and low-aptitude groups.