Conditioned head-turning in human newborns

Three experiments demonstrated learning in human newborns with techniques involving the strengthening of a head-turning response through reinforcement contingencies. The first study demonstrated that administration of a dextrose-water solution contingent upon an ipsilateral response to tactile stimulation of the cheek increases the frequency of such responding. A second study presented the tactile stimulus on the opposite cheeks on alternate trials, right- and left-sided stimulation being paired with differential auditory stimuli. Reinforcement was given differentially for ipsilateral responding to the two “eliciting” stimuli, and learning was revealed through increased occurrence of the reinforced response, in contrast to habituation of the nonreinforced response. In the final experiment, involving tactile stimulation on only one side, the two auditory stimuli served as positive and negative cues. Ipsilateral turns to right-sided stimulation in the presence of one cue were reinforced, while such turns in the presence of the other cue were not. Infants acquired the discrimination and demonstrated reversal behavior when the cue-reinforcement contingencies were reversed. All subjects in these studies were under 4 days of age, and all experimental treatments were given in one session lasting no longer than 1 hour. No major effect of age was obtained, nor did amount of time since previous feeding within the range studied exert any effect. Since the demonstrated acquisition of discriminative behavior resulted from experimental procedures in which arousal level and sensitization were controlled, the effect of reinforcing circumstances on the head-turning behavior must be ascribed to learning.