Changes in subject performance during the semester: An empirical investigation.

Two experiments were conducted to probe for performance differences between early-semester subjects and late-semester subjects in an introductory psychology subject pool. In Experiment 1A, hypotheses regarding changes in performance included differential effort, changes in subjects' attention to the task, and changes in subjects' sensitivity. A signal detection paradigm was used, and 278 subjects were sampled over the course of the semester. No evidence of changes in subject performance was found, in spite of sufficient power to detect relevant patterns of change. The results of a replication (N = 135) were consistent with those of Experiment 1A. Experiment 2 (N = 118) employed a text comprehension task to examine possible differences in subject performance with a more cognitive task. Again, there was no evidence to support the idea that late-semester subjects were performing differently from early-semester subjects.