Low body temperature affects associative processes in long-trace conditioned flavor aversion

A series of experiments examined the effect of low body temperature on the associative process in long-trace conditioned flavor aversion. Experiment 1 demonstrated that maintaining a low body temperature between conditioned stimulus (CS) and unconditioned stimulus (US) administration facilitates the associative process and allows a flavor aversion to be conditioned in young rats over an interval that would normally not support conditioning. Experiments 2 and 3 demonstrated that this was due neither to lingering systemic saccharin serving as a CS nor to a cold induced enhancement of US intensity. Experiment 4 demonstrated that inducing hypothermia at various times during a 3-h CS-US interval results in an apparent delay of reinforcement gradient. We propose that a cold induced decrease in metabolic rate slows the internal clock that governs the perception of time and that the CS-US association depends upon perceived contiguity rather than upon an external clock-referenced contiguity.