Inescapable shock and food-competition dominance in rats

Abstract

Inescapable electric shock disrupts escape-avoidance learning in another apparatus. This . study demonstrates a deficit in a nonlearning task in which no aversive stimulus occurs.In Experiment 1, inescapable shock lowered rats' dominance in a food-competition situation relative to restrained controls. In Experiment 2, inescapable shock lowered rats dominance in the same food-competition situation relative to a group that received the equivalent amount of escapable shock, demonstrating that the inescapability of the shock caused at least part of the decrement observed in Experiment 1. Experiment 3 does not find that inescapable shock caused a significant difference in food consumed or running time when the rats were tested alone, showing it unlikely that the dominance effects were caused by decreased hunger or reduced running following inescapable shock.Variations in the degree to which organisms can control electric shocks to which they are exposed has both behavioral and physiological consequences (see Maier & Seligman, 1976 for a review), although the behaviors that have been shown to be influenced by exposure to inescapable shock all involve learning, aversive stimuli, or both. The range of behaviors influenced by prior exposure to inescapable shock remains unknown. There should be boundary conditions so that not all behaviors would be affected, but these conditions have not been explored. The purpose of the present series of studies was to discover whether exposure to inescapable shock can produce deficits in psychological processes other than learning in situations in which aversive stimuli do not occur. This seemed a reasonable first step in attempting to delineate the behavioral boundary conditions of inescapable shock effects.We chose to study whether exposure to inescapable shock would reduce the organism's position in a dominance hierarchy established in a food-competition situation. This seemed a reasonable choice because no obvious aversive stimulus such as electric shock is involved and the behavior does not appear to be learned during testing. It could be argued that the encounter between two rats during dominance testing is aversive, but it should be noted that the rats do not fight. Thus, at a minimum, physical pain is not involved. The behavior involved does not appear to be learned during testing, because the hierarchy typically appears on the very first test and remains stable if tested again (Stewart & Palfai, 1967). Because ines-

Influence of shock controllability by dominant rats on subsequent attack and defensive behaviors toward colony intruders

“…The reduction in elicited aggression following inescapable shock could therefore be due to a variety of mechanisms (e.g., learned response-reinforcer independence, neurochemical depletions, learned competing responses, shock analgesia). Rapaport and Maier (1978) report what appears to be a more convincing …”

“…The reduction in elicited aggression following inescapable shock could therefore be due to a variety of mechanisms (e.g., learned response-reinforcer independence, neurochemical depletions, learned competing responses, shock analgesia). Rapaport and Maier (1978) report what appears to be a more convincing expample of the widespread effect of inescapable shock on agonistic behavior that did not involve exposure to shock during testing. In that experiment, groups of rats were given the typical triadic treatment of escapable, yoked inescapable, or no shock and then tested for dominance in a series of round-robin food-competition tests.…”

Variabilidade e repetição operantes aprendidas após estímulos aversivos incontroláveis

“…O uso de choques elétricos no tratamento e água no teste, conforme feito no presente experimento, acarreta, ao menos, duas diferenças básicas em relação à maioria dos estudos sobre desamparo: a natureza aversiva/apetiviva dos estímulos e a não similaridade física entre eles. Embora alguns autores tenham descrito desamparo em contextos envolvendo estímulos não aversivos (por exemplo, Enberg, Welker, Hansen & Thomas, 1972;Rosellini, 1978), outros estudos descreveram ausência do desamparo quando manipularam arranjos combinando estímulos aversivos/apetitivos no tratamento e teste (Capelari & Hunziker, 2005;Mauk & Pavur, 1979;Rapaport & Maier, 1978). Uma possível explicação, proposta por Capelari e Hunziker (2005) para a não ocorrência do desamparo nesse tipo de arranjo experimental, é que a aprendizagem que se estabelece na fase de incontrolabilidade só se generaliza para o teste se ambas as fases envolverem estímulos semelhantes entre si.…”

Aprendizagem discriminativa após choques incontroláveis

“…Alguns estudos mostram que estí-mulos apetitivos incontroláveis dificultaram a aprendizagem frente ao reforço negativo (Goodkin, 1976;Sonoda, & Hirai, 1992) e que choques incontroláveis reduziram a aprendizagem reforçada positivamente (Calef, Choban, Shaver, Dye & Geller, 1986). Porém, ao contrário, outros estudos não mostraram generalidade entre contextos: choques incontroláveis não afetaram aprendizagem reforçada positivamente (Rapaport & Maier, 1978;Rosellini, 1978), e eventos apetitivos incontroláveis não interferiram na posterior aprendizagem de fuga (Beatty & Maki, 1979).…”