Reports results of an experiment involving a hydranencephalic infant lacking cerebral hemispheres and a normal twin in testing for associative learning. Cardiac orienting responses to stimulus omission indicated that learning had taken place in both infants. (CS)

Describes how a behavioral system in Aplysia (marine snail) can be used to examine mechanisms of several forms of learning at different levels of analysis: behavioral, cell-physiological, ultrastructural, and molecular. Focusing on short-term sensitization, suggests how molecular mechanisms can be extended to explain long-term memory and classical…