Acquisition and retention of conditioned fear during different stages in the development of mice.

Abstract

No difference was found in acquisition of a conditioned fear response in mice 14-59 days of age; older Ss showed only slightly superior performance on a retention test at 10 weeks. Despite this, a curvilinear relationship occurred between age at treatment and subsequent emotionality in an open field. The data from this and a previous study suggest that although classical and instrumental conditioning may be factors involved in early treatment-later behavior studies, their effects are approximately constant from the end of the 2nd week of life to maturity. This would imply that the "critical-period effect" is due to a differential effect on general arousal caused by treatment at different ages, rather than to differences in conditioning.