POINT-OF-TIME EFFECTS ACROSS THE SEMESTER - IS THERE A SAMPLING BIAS

Prior research has yielded inconsistent findings regarding differences between university participant-pool students who volunteer early or l ate in the semester. This issue is important because external validity may be threatened when researchers take samples from university parti cipant pools. In the present study, point-of-time effects were investi gated via measures of procrastination, motivation, locus of control, a nd cued recall. The findings suggest that slight differences exist bet ween early and late volunteers on some measures of personality and mot ivation; however, there were no point-of-time effects for cued recall. The data indicate that if performance-based measures (e.g., cued reca ll) are under investigation, potential differences in personality and motivation may be attenuated because of the demand characteristics of laboratory settings.