摘要
The present study investigated how snapping behavior toward familiar and unfamiliar prey is modified by reward omission and aversive conditioning in the f^re-bellied toad Bombina orientalis. Toads were trained to snap at cricket images by rewarding them with live crickets. The task was learned, and the learning criterion （10 snapping responses within 2 minutes） was reached in all individuals investigated. Subsequent reward omission did not alter the frequency of snapping to the familiar cricket stimulus. Snapping decreased only in some individuals, when a mild foot shock was applied at snapping. However, at presenta- tion of images of hitherto unfamiliar meal worms and foot-shock application at snapping to the stimulus, the majority of toads diminished snapping significantly. Snapping responses decreased more rapidly, when snapping at meal worms was not rewarded or a footshock was applied uncorrelated to the presentation of or snapping at meal worms. These results demonstrate that in toads familiarity and unfamiliarity of prey stimuli are important factors in aversive learning, because well-trained responses to familiar stimuli become immune against reward omission. Furthermore, at presentation of unfamiliar stimuli, omission of reward and un- correlated footshock had a stronger aversive effect than correlated footshock [Current Zoology 57 （6）： 709-716, 2011 ].
