Ontogenetic comparison of memory for Pavlovian conditioned aversions to temperature, vibration, odor, or brightness

Ontogenetic differences in forgetting of Pavlovian conditioning were tested in four experiments with 550 rats of ages 12, 18, or 60 days postpartum. The experiments had in common the same unconditioned stimulus (US; footshock) and procedures for conditioning and testing, but the conditioned stimulus (CS) differed. The CS was a particular vibrotactile stimulus (Experiment 1), ambient temperature (Experiment 2), odorant (Experiment 3), or brightness (Experiment 4). The intent of this study was to assess, in more comparable circumstances than previously tested, the possibility of substantial differences in infantile amnesia for different sensory modalities. Particular attention was given those modalities that mature early and had not been tested in previous studies of infantile amnesia. The results verified some degree of infantile amnesia for even those sensory modalities used adaptively from birth.