Few would argue that the student evaluation of faculty is an exact science, but even the most hardened skeptics might be surprised by the latest findings on how easy it is for professors to influence students who are filling out the ratings forms.

A new study shows that giving students chocolate leads to improved results for professors. “Fudging the Numbers: Distributing Chocolate Influences Student Evaluations of an Undergraduate Course,” is set to be published in an upcoming edition of the journal Teaching of Psychology.

While they were graduate students at the University of Illinois at Chicago, the paper's authors, Benjamin Jee and Robert Youmans, became interested in what kind of environment instructors created right before handing out the evaluations. Their theory: Outside factors could easily play a role in either boosting or hurting a professor's rating.

The experiment involved about 100 students in three different lecture sections taught by the same instructor. In each section, half the students were given chocolate on the day of the mid-semester evaluation, and half were not. Jee, a postdoctoral fellow in psychology at Northwestern University, said he had noticed that professors distributing candy around the time of evaluations was "a fairly common practice."

In all three cases, the groups that received the chocolate gave their professor a higher rating than did those in the control group, even though the instructor wasn't the one handing out the sweets. In fact, the person doing the distribution identified himself as being unaffiliated with the course. Students were told the chocolate was left over from a prior event.

Still, the researchers surmise that the simple gesture of the offer, from no matter the source, was enough to increase the students' perceptions of the instructor. For instance, on the question "Teacher is Enthusiastic About Conducting the Course," students in the group offered chocolate responded with an average score of 3.92, versus the control group's 3.58 (on a five-point scale). On a "friendliness" question, the instructor received a 4.2 from the chocolate group and 3.9 from the control group.

The findings are significant given that student evaluations can be used in a professor's tenure evaluation, and that many responses are now published online for anyone to view. Research has shown that factors such as a professor's "hotness" or perception as an easy grader can positively influence the ratings.

"Some professors live and die by these things," said Youmans, now an assistant professor of psychology at California State University at Northridge. "Frankly, professors are judged by these because they are quantifiable. Obviously they are imperfect, but that's balanced against the fact that they give you some measure of teaching effectiveness."

Youmans said the study isn't an attempt to criticize the student evaluation of faculty as a valueless exercise. But by showing how easily manipulation can occur, the researchers say they want colleges to keep the evaluation results in context.

"There are lots of factors that affect a student's evaluation of a professor," Jee said. "Some will be hard to change and may be legitimate. Our argument is not that instructors should benefit by giving chocolate but that all evaluations should be given in more standardized ways to limit the effects of extraneous things like how they are handed out."

Youmans said colleges should consider instructing those who distribute evaluations not to give anything out along with them. Faculty might also get a more accurate read of students' opinions if they give out the forms a few weeks before the end of a term, he said.

"It's a worry that evaluations are given out at the end, when maybe a student has just walked out of a bad exam in another class and come in with a negative mindset," Youmans said.

As a rule, he doesn't hand out chocolate at evaluation time. But before students take tests? That's a different story.