Unconditioned stimulus intensity and retention interval effects.

In single-element taste-aversion learning, retention interval effects are seen if taste aversions are paradoxically weak when they are tested 1 day after conditioning than when they are tested 3 or more days after conditioning. One explanation of this phenomenon is that weaker taste aversions may increase in strength across a retention interval. To test this possibility, rats were given saccharin followed by an unconditioned stimulus (US) of weak, medium, or high intensity; testing occurred after a 1-day or a 5-day retention interval. The results showed retention-interval effects only at medium and high dosage levels, but not following a weak-intensity US. Furthermore, at the 5-day retention interval, aversion strength increased as the intensity of the US increased. However, at the 1-day retention interval, there were no significant differences due to US intensity. In accordance with previous experiments, this outcome suggests that nonassociative factors, such as US novelty, and not associative factors (e.g., US intensity), modulate taste aversion performance on a 1-day test.