Investigação longitudinal dos efeitos de diferentes contingências com estímulos apetitivos e aversivos sobre o desamparo aprendido / Longitudinal research on the effects of different contingencies with appetitive and aversive stimuli upon learned helplessness

AUTOR(ES)

Emileane Costa Assis de Oliveira

DATA DE PUBLICAÇÃO

2007

RESUMO

The learned helplessness hypothesis was put forward by Seligman &Maier in 1976 under the assumption of generality among all stimulus conditions, aversive or otherwise, and as an explanatory model of human depression. This proposition allowed for some experimental manipulations aimed at reversing the effect, using, among others things, positive reinforcement during a "therapy" phase. With that in mind, the present research attempted to investigate whether: (a) animals that showed signs of helplessness in an escape test also show a learning deficit with positive reinforcement, whether or not involving stimulus control; (b) the exposure to positive reinforcement may cancel out helplessness and (c) helplessness interferes with resistance to change, measured during a second, positively reinforced, discrimination learning (reversal). Rats were first exposed to controllable (C), uncontrollable (I) or no shocks (N) and then to an escape test. Three groups (n=4) were selected: one that displayed helplessness (group I) and two that learned to escape (groups C and N). After that, all subjects were exposed to (1) positive reinforcement of lever pressing (shaping, CRF and ten sessions of discrimination between FR and extinction), (2) the same escape test, (3) ten sessions of discrimination learning with reversed discriminative stimuli. Other four animals were exposed only to sessions of positive reinforcement. All animals learned discrimination and reversal, and three out of four animals of group I remained helplessness in the second escape test. These results suggest that helplessness did not generalize to a positively reinforced task and that exposure to positive reinforcement did not cancel out helplessness for most subjects. Results are discussed considering the selective effect of helplessness, which occurs under some conditions, but not under all. The fact that therapy with positive reinforcement did not reduce the learning deficit observed with negative reinforcement suggest that if helplessness result from learning that it is impossible to control the environment, this knowledge does not include all stimuli in a generalized manner, but only one (or some) certain stimuli class. The identification of the characteristics that define these classes (electric shocks, aversive stimuli, among others) should also be the purpose of future research.

ASSUNTO(S)

aprendizagem por discriminação positive reinforcement stimulus control discrimination learning major depression desamparo aprendido controle de estimulo reforço positivo depressão learned helplessness

Documentos Relacionados

• Efeitos da exposição a estímulos aversivos e apetitivos incontroláveis sobre o comportamento verbal em contingências de reforço positivo
• Effects of aversive contingencies on lying behavior: Cues and detection.
• Efeito do hypericum perforatum, em preparação homeopática e fitoterápica, sobre o desamparo aprendido em ratos
• Tomada de decisão e desvalorização pelo atraso de estímulos apetitivos e aversivos em fumantes
• Um estudo de efeitos de instruções sobre desempenhos mantidos sob controle de estímulos quando as contingências mudam sem sinalização