ABSTRACT
Choice of experimental design is very important in every study because the choice affects what conclusions one is able to draw. The present article argues in favour of parametric designs where the most important situation variable, or variables, is changed systematically in order to observe how different levels of this variable affects the behavior under study. A non-parametric design is one where for example a brain-lesioned group and a control group are tested with a single value on all variables. Data from studies of behavioral effects of septal lesions are used for illustrating these points. Two-dimensional parametric designs showed that the behavioral changes in the brain-lesioned group compared to a control group depend upon level of water deprivation in appetitively motivated tasks and shock intensity in aversively motivated tasks. The implications of these results were analyzed in a more detailed three-dimensional parametric design. This study showed that the behavioral changes following septal lesions are response-rate dependent in the sense that the septal animals showed increased response rates only when the baseline rates were above a certain level. In parametric studies of avoidance behavior, the control of the shock parameters is very important. The present article discusses the use of continuous versus the use of brief electric shocks with a fixed duration. It is shown that the traditionally-used continuous shocks, where the animal’s escape latency controls the duration of each shock, causes several problems that very well could jeopardize the conclusions one is able to draw. In addition, brief shocks have other advantages: the acquisition of the avoidance task is much faster, the stressfulness of the task is probably less than what is the case with continuous shocks, and the experiments may even be cheaper to conduct.
