A simple method of improving leverpress avoidance by rats

Abstract

In three experiments, rats were trained to avoid electric shock in a free-operant leverpress procedure.After stable performance was obtained, sessions were suspended for periods of 1 to 4 weeks. In 24 of 28 Ss, shock rates were lower, some by as much as 75%, when avoidance sessions were resumed. This improvement extended throughout the entire 60-100-min session. and occurred despite variations in apparatus, strain of rat, length or efficacy of prevacation training, lesions in the amygdala, and unshocked exposure to the apparatus during "vacation."Reliable production of efficient leverpress shock avoidance by rats has long been a nettlesome problem. Bolles (1970) considers this an inevitable consequence of selecting for reinforcement a behavior which is not a "species-specific defense reaction." Nevertheless, a number of suggestions have been offered as partial remedies to the often noted propensities of rats for leverholding and/or pressing only in short postshock bursts. For example , Biederman , D'Amato, and Keller (1964) recommend locating visual stimuli on the wall of the chamber opposite that holding the lever. Giulian and Schmaltz (1973) opt for appetitive preconditioning, Forgione (1970), for disabling the lever during and shortly after shock, and Cahoon and Crosby (1969), for reducing the size of the chamber to dimensions just big enough to accommodate the S.We offer in this paper still another technique for improving leverpress avoidance performance by rats. Discovered quite by accident in the course of research on the effects of restricted amygdaloid lesions on shock avoidance, it is the ultimate in simplicity and ease of application, requiring no equipment or skills whatsoever. No guarantee is extended by the authors, but our inability to undermine the technique by a wide variety of systematic and unsystematic variations suggests it is extremely robust. EXPERIMENT IThis experiment was designed to investigate the effects of amygdaloid lesions on the acquisition and retention of free-operant avoidance. Such lesions disrupt acquisition of both active and passive avoidance with discrete trials (Goddard, 1964). No such disruption was noted in the present experiment, but 12 of 14 rats, experimental and control alike, did show a remarkable *Now at Department of Psychology. University of Utah. In conducting the research described in this report, the investigators adhered to the "Guide for Laboratory Animal Facilities and Care," as promulgated by the Committee on Revision of the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, National Academy of Sc ience-National Research Council. 5 improvement in shock avoidance over a 3-week "recupera tion" from surgery. MethodSubjects. Fourteen naive Long-Evans hooded rats were used. All were male, and weighed between 200 and 300 g. Three rat s had received bilateral lesions within the amygdaloid complex 3 weeks prior to the beginning of the experiment. Seven othe rs underw ent similar surgery in the course of the experimen...

Discriminated and nondiscriminated avoidance conditioning of the rearing response in rats

“…The number of USs received in Sessions 1 and 24 for each rat were 126-23, 178-28, 13-103, 245-35, and 146-15, for Rats 1, 2, 3,4, and 5, respectively. (3) There was a remarkable "vacation" effect (Manning, Jackson, & McDonough, 1974); i.e., the number of USs decreased markedly in an unpublished study by the present authors (Shirnai, Yamazaki, Shishirni, & Imada, Note 1) in which a discriminated avoidance paradigm was used, rats that received exactly the same amount of shock as the avoidance rats, but in which avoidance was made impossible by the use of a yoked design, developed marked freezing following an initial jumping tendency. The second line of evidence is that in the present experiment there was clear evidence of temporal discrimination, which is frequently observed in leverpress Sidman avoidance experiments with rats (e.g., Anger, 1963).…”

WARMUP IN AVOIDANCE AS A FUNCTION OF TIME SINCE PRIOR TRAINING1

“…However, her data presentation used response rates and shock rates based on entire sessions, so one cannot determine whether warmup effects were affected in that experiment. Manning, Jackson, and McDonough (1974) carried out a set of manipulations similar to those of Clay-Findley, using vacation lengths of 19, 15, and 7 days, and found improved performances when training was resumed. However, they did examine warmup effects by means of shock rates in successive 10-min periods, as in the present experiments, and found that the postvacation shock rates were lower over the entire sessions.…”