The present work consists of a study of the influence of individual differences, measured by a Low Frightening Open Field (LFOF) in the acquisition of the bar-pressing response and in discrimination learning. The subjects, 80 male Wistar rats, underwent the LFOF test and were deprived and shaped to bar-press for food. The factorial analysis of the results identified three fundamental factors: discrimination, conditionability and motor persistence. The conditionability factor turned out to be analogous to the one postulated by Eysenck for humans. The discrimination factor is explained in terms of susceptibility to extinction, directly related to defecation in the LFOF. And finally, the motor persistence factor refers to persistence in a given behavior which is opposed to the behavior aimed at stimulus seeking, which has also been identified in humans. © 1987.