Attention teachers far and wide: It may not be so much what or how you teach that will reap high student evaluations, but something as simple as an enthusiastic tone of voice.And beware, administrators, if you use student ratings to judge teachers: Although student evaluations may be systematic and reliable, a Cornell University study has found that they can be totally invalid. Yet many schools use them to determine tenure, promotion, pay hikes and awards.

These warnings stem from a new study in which a Cornell professor taught the identical course twice with one exception -- he used a more enthusiastic tone of voice the second semester -- and student ratings soared on every measure that second semester.

Those second-semester students gave much higher ratings not only on how knowledgeable and tolerant the professor was and on how much they say they learned, but even on factors such as the fairness of grading policies, text quality, professor organization, course goals and professor accessibility.

And although the 249 students in the second-semester course said they learned more than the 229 students the previous semester believed they had learned, the two groups performed no differently on exams and other assessment measures.

"This study suggests that factors totally unrelated to actual teaching effectiveness, such as the variation in a professor's voice, can exert a sizable influence on student ratings of that same professor's knowledge, organization, grading fairness, etc.," said Wendy M. Williams, associate professor of human development at Cornell. Her colleague and co-author, Stephen J. Ceci, professor of human development at Cornell, was the teacher evaluated by the students in a course on developmental psychology that he has taught for almost 20 years.

"The effect of the presentation style also colored students' reactions to factors unrelated to the teaching, such as the quality of the textbook and teaching aids used," she added. Yet the textbook and teaching aids were the same both semesters.

Williams' and Ceci's study are published in the September issue of Change, a journal for administrators in higher education.

"Given the omnipresent power of course evaluations in academia today, one might think that their accuracy and appropriateness have been extensively studied," Williams and Ceci write. "The sad truth is that we still know very little as yet about how students arrive at their judgments about teaching effectiveness. Based on the present data, we know that it is at least possible for student ratings to be extremely systematic and reliable, yet invalid!"

Williams and Ceci decided to undertake the study after Ceci took a teaching skills workshop at Cornell during the intersession between the fall and spring semesters. That spring semester, Ceci taught the identical course but with one teaching skill he had learned in the workshop: He used an "enthusiastic style" of teaching by employing more pitch variability and more gestures.

Using three different validity checks to ensure the students took the evaluations seriously and that the composition of the class was the same, Williams and Ceci made the deliberate effort to ensure that there was a reliable difference in Ceci's demeanor between the two semesters while keeping the material and content of the lectures, textbooks, exams and teaching aids virtually identical.

"With some coaching, teaching in a more enthusiastic style is a fairly easy change to effect. Yet the improvement in ratings due to this simple change can make the difference between being awarded tenure and not being awarded tenure and other important career milestones," Williams said.

Williams and Ceci advocate for more opportunities for teaching faculty to train in techniques that can enhance their students' ratings, especially if these ratings are used by administrators to make important career decisions. They also call for more research to ensure better and fairer means of evaluating teaching effectiveness.

As former Mayor Ed Koch of New York City used to ask, "How'm I doing?" Williams and Ceci suggest that instructors would be well advised to ask their students the same. "As in politics, the answer may have more to do with style than substance," they conclude.