Wechsler (1955, p.27) suggests that for some subjects it may be advisable to make encouraging remarks during testing on the WAIS. The present study investigated the effects of such encouragement upon WAIS IQs, taking into account a personality variable which has been shown to mediate the effects of reinforcement, Locus of Control. Forty-eight female introductory psychology students were selected from a class of 128 on the basis of their scores on Rotter's I-E Locus of Control Scale. They were pre-tested on the Naylor-Harwood Adult Intelligence Scale, and assigned to groups for testing on the WAIS. Subjects who were given encouragement (verbal reins forcement) during WAIS testing did significantly better than those who were not. The observed tendency for subjects external in Locus of Control to be more strongly affected by the encouragement than internals was not significant. In the light of the inevitable differences between examiners in their interpretations of Wechsler's recommendation, it is concluded that there may be reason to doubt the comparability of scores reported by different examiners. Further research is necessary, however, to determine whether this effect is mediated by Locus of Control.