Infants aged 5–12 weeks were shown a silent colour film whose clarity/focus was contingent on their sucking on a dummy nipple. In the ‘suck-for-clear’ condition the mean rate of sucking increased significantly over baseline level, and decreased when the contingency shifted to ‘suck-for-blur’. When the initial condition was suck-for-blur, sucking rate remained close to baseline level (even after the shift to suck-for-clear). Time spent looking at the clear film increased in both conditions, but there was little change in looking at the blurred pictures. With the introduction of the contingency conditions patterns of looking at the clearing and cleared pictures changed, and looking at the cleared picture increased in the suck-for-clear but not the suck-for-blur condition. Asymmetry of the results indicates that infants are better able to use an active response for instrumental means than to inhibit a response to achieve instrumental control. Implications for the development of voluntary control of action are explored.
Negative induction in instrumental behavior reinforced by central stimulation
