The number of trials of compound conditioning: its effect on latent inhibition in rats

Two experiments interspersed nonreinforced tests for the strength of the preexposed and nonpreexposed elements of a compound CS throughout conditioning. The nonreinforced exposures and the conditioning trials were superimposed on an appetitive operant baseline, and conditioned suppression of the rats' bar pressing was the dependent variable. In both experiments, the preexposed element failed to suppress responding and failed to gain strength over trials. The nonpreexposed element at first suppressed responding completely but gradually lost control of responding, even while the compound continued to suppress responding asymptotically. The results are discussed in terms of 'loss of salience' and 'discrimination' hypotheses.