This study aimed to investigate the effects of a chronic mild stress (CMS) protocol on operant discrimination learning. Twelve male Wistar rats were separated into 2 groups: CMS and control (n ϭ 6). CMS subjects underwent a stress protocol, whereas control subjects remained in their cages with food and water ad libitum. After this period, all subjects underwent successive discrimination training sessions. Water and sucrose preference tests were conducted for both groups. There were no differences between groups in the liquid preference tests (p Ͻ .4), and discrimination learning (p Ͻ .7). However, CMS subjects showed higher response frequency than control subjects during the discrimination training (p Ͻ .004). Data suggest that exposure to CMS protocol can alter locomotor performance without affecting the discrimination accuracy.

Resumo: O desamparo aprendido pode ser definido como uma dificuldade de aprendizagem encontrada em sujeitos que tiveram uma história prévia com estímulos incontroláveis. No estudo desse fenômeno com humanos, alguns aspectos específicos relacionados ao controle experimental podem interferir na obtenção e na análise dos dados, entre eles: o estímulo empregado na fase de tratamento, a tarefa utilizada na fase de teste (geralmente a resolução de anagramas) e, finalmente, a condição de incontrolabilidade e as questões éticas relacionadas a ela. Estes aspectos foram discutidos criticamente no presente trabalho, considerando suas implicações na análise dos dados. Palavras-chave: desamparo aprendido em humanos, questões metodológicas, anagramas, questões éticasAbstract: Learned helplessness can be defined as a difficulty in learning found in subjects who had a history with uncontrollable stimuli. In the study of this phenomenon in humans, some specific aspects related to experimental control can interfere with the data acquisition and data analysis. Those aspects are: the stimulus employed in pretreatment; the task used in testing (generally anagram solution testing); and, finally, the uncontrollability condition and its ethical issues. Those aspects were critically discussed in this article, taking into account their implications for data analysis.