Journal of Comparative and Physiological Psychology 1969, Vol. 68, No. 2, 193-198 CLASSICAL CONDITIONING, PSEUDOCONDITIONING, AND SENSITIZATION IN "NORMAL" AND FOREBRAINLESS GOLDFISH' J. BRUCE OVERMIER 2 AND PAUL F. CURNOW University of Minnesota Forebrain-ablated and sham-operated goldfish received 10 classical condi- tioning trials a day for 10 days. Both groups showed acquisition when com- pared to pseudoconditioning and sensitization controls. However, there were no differences between the classical conditioning of forebrainless and sham- operated Ss, suggesting that the failure of forebrainless fish to learn an ac- tive instrumental avoidance response is not due to impairment of associa- tive functions. Furthermore, lack of response magnitude differences between forebrainless and sham-operated Sa within the classical-conditioning, pseudo- conditioning, and sensitization procedures suggests that these groups did not differ in arousal even following exposure to shock. However, Sa subjected to neither shocks nor forebrain ablation showed more spontaneous ac- tivity than Ss subjected to either or both. Research concerning the function of the forebrain (telencephalon) in fish (teleosts) has typically failed to uncover any easily discernible motor or sensory deficits fol- lowing forebrain ablation other than the expected loss of olfaction (Healey, 1957). However, some recent investigations into the function of the fish forebrain found that its complete removal resulted in (a) a marked impairment in the acquisition of an instrumental avoidance response, (6) a complete loss of a previously learned avoidance response, but (c) no impairment in escape responding (Hainsworth, Over- mier, & Snowden, 1967; Kaplan & Aron- son, 1967; Savage, 1968a). That respond- ing during the conditioned stimulus was impaired while responding to the uncon- ditioned stimulus was unimpaired is inter- preted to imply that the deficits in avoid- 1 This research was supported by grants from the National Institute of Health (MH-1304S) and the Graduate School, University of Minnesota, to J. Bruce Overmier and from the National Science Foundation, National Institute of Child Health and Human Development, and the Graduate School, University of Minnesota, to the Center for Research in Human Learning, University of Minnesota. Thanks are due Anna Geyer and Karl Schwarzkopf for their aid in the conduct of this experiment. 2 Requests for reprints should be sent to J. Bruce Overmier, Department of Psychology, Uni- versity of Minnesota, Minneapolis, Minnesota 55455. ance behavior following forebrain ablation were specific to responding to the signal for shock (the conditioned fear signal). Currently popular theories of avoidance hypothesize that avoidance behavior in- volves (a) the acquisition by the signal (CS) of arousing motivational and cue properties through classical conditioning, then (6) the CS cues the initiation of the instrumental avoidance response, which (c) is then reinforced by reduction of acquired motivation. Forebrain ablation could selec- tively impair any of these elements. Be- cause neuroanatomical homologies exist between the fish forebrain and the mam- malian limbic system (Droogleever Fortuyn, 1961) and because limbic struc- tures have often been implicated in the acquisition of emotional reactions (Mc- Cleary & Moore, 1965), a likely hypothe- sis is that the observed avoidance deficit results from an interference with the ac- quisition of motivational proterties (fear) by the CS. Karamyan (1962) has reported that con- ditioned responses can be elicited from nor- mal and forebrainless fish (carp) with equal ease. However, the brevity of this report and its lack of control comparisons leave us unsure of this equality. The present experiment tests this interference- with - the - acquisition - of - arousing - motiva - tional-properties-by-the-CS hypothesis by 193