Perceptual learning in flavor-aversion learning:: Alternating and blocked exposure to a compound of flavors and to an element of that compound

Rats received different schedules of pre-exposure to a compound flavor (AX) and to one element of that compound (X). In Group ALT, exposure consisted of alternating trials with AX and X; Group BLK received a block with all AX trials before a separate block with all X trials (or vice versa). Discrimination between AX and X was assessed then by establishing an aversion to X and measuring the generalization of this aversion to AX In Experiments 1A and 1B, generalization was less in Group ALT than in Group BLK. In Experiment 2, this latter result was confirmed and furthermore only Group ALT, and not Group BLK, showed less generalization than a group that received exposure to X alone. These results are discussed in terms of their implications for theories of perceptual learning. (C) 2004 Elsevier Inc. All rights reserved.