Stimulus control of eye orientations: Shaping S+ only versus shaping S- only

To determine how stimulus control of eye orientation was established and how that process affected learning, an analysis of normal preschool children's eye orientations and pointing responses to each of two simultaneously presented stimuli (S+ and S-) was conducted. Using a probe design to test for acquisition, each subject was trained on two tasks. In one task, S+ (selections of this stimulus produced reinforcement) was held constant at the final criterion level while S- (selections of this stimulus never produced reinforcement) was manipulated using stimulus shaping procedures. The second task was programmed with the opposite method (S+ shaped while S- held constant). Results showed that more pointing response errors, more occurences of eye orientations, and longer durations of eye orientations characterized conditions where S+ was held constant and S- was shaped. The individual analysis of the eye orientation data indicated that differences in eye orientation to stimuli under the two programs were largely due to relatively higher frequency of orientation to the S- stimulus under program condtions that shaped S- and held S+ constant.