Two pigeons were trained on a simultaneous split-field single-key stimulus-matching procedure. The decline of keypecking during nonmatching stimuli was examined. Observations during nonmatching conditions indicated that as keypecking declined discrete overt patterns of behavior emerged to each of the two nonmatching compounds. The decline in keypecking and the emergence of discrete overt patterns of behavior was observed to occur first to one nonmatching compound and then to the second combination.