DO STUDENTS WITH DIFFERENT CHARACTERISTICS TAKE PART IN PSYCHOLOGY EXPERIMENTS AT DIFFERENT TIMES OF THE SEMESTER

ABSTRACT In this study we examined 15 personality and demographic differences between psychology students who took part in experiments at different times of the semester and different times of the day. In general, few significant relations were found and those that did emerge were small in magnitude. Females and freshmen signed up for experiments earlier in the semester. Females took part in their first experiment earlier in the semester, as did students who were Protestant and who came from smaller home towns. Students low in self‐consciousness also tended to begin participating earlier. Extraverts participated earlier in the day than introverts. Results generally were consistent with previous findings of differences between research volunteers and non‐volunteers. However, it was concluded that because of their small magnitude and inconsistency from site to site, with a few precautions experimenters probably need not be concerned that timing effects threaten the external validity of psychological research outcomes. Copyright © 1991, Wiley Blackwell. All rights reserved