Facilitation of discriminated avoidance learning by dissociation of CS and manipulandum

Abstract

Many studies have reported inordinate difficulty in obtaining avoidance learning in discriminated bar-press and related situations, particularly with visual cues (illumination changes) serving as the CS. It is shown that avoidance learning can be substantially increased by dissociating the CS from the manipulandum, which usually occur in close physical proximity. In verification of earlier work, discontinuous shock was again shown to enhance avoidance learning markedly. ProblemA curious fact of discriminated avoidance learning is that, even under seemingly favorable conditions, it often does not occur. Rats given the simple task of pressing a bar (or turning a wheel) in the presenge of a visual CS (change in illumination level) frequently fail to achieve even a modest level of avoidance learning despite extensive training (e. g., D ' Amato & Schiff, 1964; Meyer et aI., 1960). Previous research aimed at uncovering the variables responsible for such failures has shown that discriminated avoidance learning can be greatly facilitated by the use of discontinuous shock, i. e., shock having brief on-periods and longer offperiods (D' Amato et aI., in press). In the present study the contribution of another variable, location of the CS, was investigated. In virtually all bar-press avoidance studies employing a visual cue as the CS the stimulus source is located on the same wall as the bar, requiring S to approach the CS-a secondary aversive stimulusin order to make the instrumental response. Conceivably this is one of the factors which inhibits discriminated avoidance learning in the bar-press and related situations. A second purpose of the study was to determine whether discontinuous shock would continue to enhance avoidance learning when this presumably disrupting factor was 'removed. MethodThe Ss were 34; naive albino rats (13 males), 4-8 mos. of age! drawn from litters bred in our laboratory. Two standard Grason-Stadler Skinner boxes were modified by placing 3 identical I-in. pilot lights on both the front and rear walls of the boxes, making it possible to program the CS (illumination of the pilot lights) to appear on either wall.Group FC (N, 10) was trained with the CS located on the front wall and with conventional continuous shock as the US. Group RC (N, 14) was also trained with continuous shock, but the CS appeared on the rear wall. For Psycho,," &i., 1964, Vol. 1.Group RD (N, 10) the CS was located on the rear wall, while the US was a discontinuous shock.On Day 1 all Ss received 40 avoidance training trials, during which S was shaped on the escape response until a reasonable instrumental response appeared. Group RD received continuous shock during these trials. The CS-US interval was 5 sec.; shock was maintained between .6 and .8 ma; the intertrial interval, programmed by a film tape, averaged about 40 sec. When S failed to avoid, CS and US remained on until terminated by an escape response.On Day 2, 500 training trials were given, the shock level being increased to .8-1.0 mao During these trials Group...

Discriminated avoidance conditioning: Stimulus function in shaping and training

“…What is not at all clear is the cause of the low general level of performance of Ss in this and the preceding study. Every Significant training and handling routine as well as the equipment employed are virtually identical with D 'Amato et al (1964'Amato et al ( , 1965 and Biederman et al (1964). The role of S strain is probably important but cannot serve as the complete explanation since the Sprague-Dawley strain used in some of the earlier experiments was also used in Biederman (1967) without improving the overall level of avoidance.…”

“…Experiments devoted to the program of determining the experimental variables controlling discriminated avoidance learning (D 'Amato, Keller, & DiCara, 1964;Biederman, D'Amato, & Keller, 1964;D'Amato, Keller, & Biederman, 1965) have had considerable success in obtaining a high degree of discriminated avoidance conditioning by the manipulation of the nature of the UCS (continuous or discontinuous shock) and the discriminanda (light and/or white nOise).…”

Is there sign-tracking in aversive conditioning?

“…While the results of Biederman, D'Amato, and Keller (1964), McAdam (1964), and Whittleton, Kostanek, and Sawrey (1965) are consistent with aversive sign-tracking, the interpretation of these results is complicated by the existence of an instrumental avoidance contingency. In the absence of instrumental contingencies , will rats withdraw from a signal for shock and approach a signal for no shock?…”

Timing behavior in squirrel monkeys as a function of positive vs. negative reinforcement

“…(This may relate to the finding of Biederman et al (1964) that pulsating shock was more effective than continuous shock in converting an escape response to an avoidance response J in rats.) The final schedule used only pulsating noise as the negative reinforcer.…”