The effects of feedback on performance and factors associated with it were examined in a large introductory psychology course. The experiment involved college students (N = 464) working on an essay examination under 3 conditions: no feedback, detailed feedback that was perceived by participants to be provided by the course instructor, and detailed feedback that was perceived by participants to be computer generated. Additionally, these conditions were crossed with factors of grade (receiving a numerical grade or not) and praise (receiving a statement of praise or not). The task under consideration was a single-question essay examination administered at the beginning of the course. Detailed feedback on the essay, specific to individual's work, was found to be strongly related to student improvement in essay scores, with the influence of grades and praise being more complex. Generally, receipt of a tentative grade depressed performance, although this effect was ameliorated if accompanied by a statement of praise. Overall, detailed, descriptive feedback was found to be most effective when given alone, unaccompanied by grades or praise. It was also found that the perceived source of the feedback (the computer or the instructor) had little impact on the results. These findings are consistent with the research literature showing that descriptive feedback, which conveys information on how one performs the task and details ways to overcome difficulties, is far more effective than evaluative feedback, which simply informs students about how well they did. (Contains 7 tables, 1 figure and 1 footnote.)