Infant temperament and subject loss due to crying during operant conditioning.

Infants who failed to complete a 2-day operant-conditioning task were compared with a stratified random sample of those who did on measures of infant temperament and several demographic characteristics. A discriminant-function analysis revealed that female infants who cried differed from female infants who did not cry on measures of duration of orienting and latency to approach sudden or novel stimuli. Reliable prediction of crying and noncrying could not, however, be made for males. No sex differences emerged in the incidence of crying or in the number of sessions completed. Partially successful females (i.e., those completing 1 of the 2 sessions) could reliably be discriminated from those who cried during the first session on measures of age at testing and maternal ratings of smiling behavior. The results of this study suggest that, as with habituation studies, subject loss in operant-conditioning studies is influenced by individual differences among the infants which may or may not adversely affect external validity.

The effect of crying on long-term memory in infancy.

The influence of crying on infants' long-term memory for a learned response was investigated in 3 experiments. In each, infants were trained to move a crib mobile containing 10 identical objects by means of kicking and were then exposed to a reinforcer containing only 2 of these components. This shift in component numerosity produced crying in 53% of the infants. Infants who cried in response to the reward shift evidenced no retention of the contingency 1 week later (Experiment 1) but did have excellent retention at 1 day (Experiment 2). In Experiment 3, a brief reactivation treatment alleviated forgetting at 3 weeks regardless of the presence of crying in response to the change in mobiles. An unexpected recency effect characterized the efficacy of the reactivation treatment. The results indicate that crying in response to the violation of a reward-expectation habit functions as an amnesic agent to produce accelerated forgetting.