Abstract
180 rats aged 3 or 300 days were either handled for 20 consecutive days or were unhandled. 40 days after treatment, rats learned a discriminated avoidance task, with 1 of 3 UCS (shock) intensities. Handling improved avoidance performance of both 3- and 300-day-old Ss with mild (0.5-ma.) and moderate (1.0-ma.) shock intensities. Avoidance performance of infantile-handled rats was superior to performance of other Ss at lower shock levels but was inferior to other groups with a stronger shock level (2.0 ma.). Performance of older unhandled Ss was very poor with low shock but improved consistently with increases in shock intensity. These findings are interpreted in terms of handling and age effects on responsiveness to painful stimulation.
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