Tested whether unreinforced preexposure to one element of a compound CS would prevent that element from overshadowing the other element, using 64 male hooded COBS rats. Groups of Ss were given 20 preexposure trials to a light prior to conditioned emotional response (CER) conditioning or were given no pre-exposure. In CER conditioning, Ss received either a noise plus light or a noise followed by shock. In Ss given no pre-exposure, the presence of the light significantly attenuated conditioned suppression to the noise CS. However, in the pre-exposed compound-cue group no reduction in suppression to the noise CS was observed after 4 CER trials. After 8 CER trials, suppression to the noise CS was significantly attenuated. Latent inhibition temporarily reduced the extent to which the light CS overshadowed the noise CS. Overshadowing of the noise in the pre-exposed compound-cue group after 8 CER trials was not accompanied by any increase in suppression to the light CS. (PsycINFO Database Record (c) 2006 APA, all rights reserved)