Abstract
The open field and swimming maze tests are frequently used as part of a behavioural assessment battery in reproduction or developmental toxicology studies in the rat. Interpretation of the results of these tests is very difficult when the body weight of the rats is not similar in the various treatment groups. In order to better understand this problem, data from approximately 500 untreated rats tested under identical conditions were analysed with respect to body weight. No correlation was found in water maze performance or open field motor activity. A very slight but significant correlation was identified, however, in the time spent by female rats in various regions of the open field, with the smaller rats spending more time in the corners of the testing arena.