A note on depression of instrumental responding after one trial of outcome devaluation

After a response has been rewarded with an outcome, subsequent devaluation of that outcome by the toxin LiCl reduces responding. Balleine and Dickinson (1991) argued that this effect depends on incentive learning, which requires reexposure to the outcome after its pairing with the toxin. However, Rescorla (1992) reported that a single pairing of the outcome with LiCl was sufficient to depress responding even without reexposure. This result has been attributed by Balleine and Dickinson (1992) to the use of a hypertonic solution. Two experiments are reported here which replicate the prior single trial effect using an equivalent level of toxin in an isotonic solution.