The effects of partial reinforcement on the acquisition and extinction of avoidance behavior in gerbils

Abstract

Separate groups of gerbils received 100%, 50%, or 0% reinforcement during avoidance acquisition. A reinforced trial was one in wh ich the avoidance contingency was in effect, while a nonreinforced trial was a CS-US pairing. Groups trained under either partial or continuous reinforcement were subdivided into two extinction conditions, 100% c1assical CS-US trials or regular avoidance extinction. In acquisition, CR frequency and percent reinforcement were positively related. Significantly more rapid extinction obtained under the CS-US pairing procedure relative to regular avoidance extinction, and animals trained under partial reinforcement were more resistant to extinction than animals trained under continuous reinforcement. These results were interpreted in terms of the effects of delayed punishment on nonreinforced trials in acquisition and extinction. The traditional discrirninative avoidance extinction procedure is one in wh ich the CS is presented alone and the US omitted, although the avoidance response remains effective in terminating the CS. Recently, Davenport & Olson (1968) have redefined extinction of avoidance so that the operations are more symmetrical with respect to those employed following appetitive instrumental training, Le., the reinforcement contingency for the instrumental response is eliminated. The redefined extinction trial is essentially a classical conditioning trial in which the CS is inevitably followed by the US irrespective of the S's behavior, although the US must then be response terminated_ This procedure effectively elirninates reinforcement via CS termination and/or US omission while maintaining motivation via the US presentations. When the traditionaI avoidance extinction procedure is employed, extreme persistence of the avoidance response is often observed (e.g., Solomon & Wynne, 1954). Davenport & Olson (1968), however, employing the redefined extinction procedure, found rather abrupt extinction of the leverpress avoidance response in rats. Unfortunately, these investigators did not include groups extinguished under traditional procedures for comparison. Gilbert (1970), on the other hand, found that wheel-turning avoidance in rabbits was much more persistent in a

Effects of percentage of shock avoidance on avoidance behavior in gerbils

“…Although these animals experienced a 50% US These acquisition results clearly reveal the importance of the shock avoidance contingency in determining shuttlebox avoidance performance in the Mongolian gerbil. The results further suggest that the decremental effects of intermittent reinforcement previously observed in studies of gerbil avoidance learning (Galvani, 1971(Galvani, , 1973a(Galvani, , b, 1975 were principally related to the failure to avoid the US on a nonreinforced trial, rather than being attributable to a lack of CS termination or feedback, as suggested in Galvani (1973a). Thus, in spite of receiving 100% reinforcement with respect to the CS termination and feedback contingencies, Groups AV100, PRI00, and CCI00, exposed to 100%, 50%, and 0% US avoidance, respectively, differed considerably in acquisition performance.…”

“…Both PR groups, therefore, had a 50% reinforcement schedule with respect to US avoidance. The PR50 group, however, received nonreinforced trials of the classical type, as in previous studies (e.g., Galvani, 1971) . Finally, Group CC100 gerbils experienced CS termination after every CR, but on all trials CS onset was inevitably followed by shock (hence 0% reinforcement).…”

“…The apparatus consisted of two Scientific Prototype Model AIOOS toggle-floor shuttleboxes (13.5 x 13 x 40 cm) described in detail in Galvani (1971). Each shuttlebox was enclosed in a ventilated, sound-attenuated chamber illuminated by a 7.5-W incandescent lamp.…”

“…As many as four sources-US escape, US avoidance, CS termination, and feedback-might be regarded as potential facilitators of avoidance response strength. Previous studies of intermittent reinforcement in the author 's laboratory (Galvani, 1971(Galvani, , 1973aGalvani, Twitty, & Foster, 1975) have employed a "classical trial" to define nonreinforcement. Procedurally classical trials eliminate, or at least attenuate, all of the above noted sources of reinforcement for the avoidance response.…”

Effects of feedback on discriminative avoidance acquisition and extinction in the gerbil (Meriones unguiculatus)

“…Two identical toggle-floor shuttleboxes (13.5 x 13 x 40 em) made by Scientific Prototype (Model AI00S) were employed (see Galvani, 1971, for more detailed description). Each shuttlebox was enclosed in a ventilated sound-attenuated chamber illuminated by a 7.5-W incandescent lamp.…”