Learning processes in the human newborn. Sensitization, habituation, and classical conditioning.

Data have been presented to document that the human newborn is a conditionable organism. Babies in the first days of life possess sensitivity to stimulation in all sensory modalities, an unconditioned repertoire of responses to some of these sensory stimuli, and a capacity for associating simultaneously presented stimuli. Thus a perceived but previously neutral stimulus with respect to the elicitation of some particular behavior can itself become an effective stimulus through paired associations with an effective stimulus, and may now produce a response similar to the initially effective stimulus. For such a phenomenon to occur, the organism must be capable of remembering. The duration of memory is empirically demonstrable through probes or tests with the neutral stimulus, at various time intervals following the last experience of the pairing. Besides engaging in classical conditioning involving transfer of elicitability from an effective stimulus to a previously ineffective stimulus (or its converse, as in extinction), demonstrating that human newborns do learn, babies are also demonstrably capable habituators. They exhibit diminution of response intensity or frequency to repetitively presented, and particularly closely spaced and essentially innocuous, stimuli. Newborns also exhibit generalized sensitization to stimulation such that, when neonates are aroused, stimuli will nondiscriminatively elicit behaviors. It is thus important that appropriate controls for nonconditioning processes, which may also involve change in behavior through experience, be included in any demonstrations that purport to show the conditionability of the newborn.