The Dr. Fox effect is a correlation observed between teacher expressiveness, content coverage, student evaluation and student achievement. Contrary to popular belief, the (unknown) actor involved in the experiments was almost certainly not Michael Fox who would have been readily identified as an actor because of his frequent appearances as the coronor in the Perry Mason TV series (1957–1966), only 7 years before two experiments were carried out (1973)[1]

In the 1976 experiment two equivalent groups of students are given lectures varying in content coverage. After the lecture, students are required to evaluate the teacher on effectiveness. A test is also taken to measure the student achievement.

It is observed that student achievement is higher for higher content-coverage. However students are observed to rate high content-coverage lectures as better than low-coverage lectures only under conditions of low expressiveness. Under conditions of high expressiveness, no correlation is observed.

This lack of correspondence between content-coverage and ratings under conditions of high expressiveness is known as the Dr Fox Effect.[2]

In a recent critique of student evaluations of teaching, professor of law Deborah Merritt summarized the Dr. Fox Effect as it was observed in the first experiments: "The experimenters created a meaningless lecture on 'Mathematical Game Theory as Applied to Physician Education,' and coached the actor to deliver it 'with an excessive use of double talk, neologisms, non sequiturs, and contradictory statements.' At the same time, the researchers encouraged the actor to adopt a lively demeanor, convey warmth toward his audience, and intersperse his nonsensical comments with humor. ... The actor fooled not just one, but three separate audiences of professional and graduate students. Despite the emptiness of his lecture, fifty-five psychiatrists, psychologists, educators, graduate students, and other professionals produced evaluations of Dr. Fox that were overwhelmingly positive. ... The disturbing feature of the Dr. Fox study, as the experimenters noted, is that Fox’s nonverbal behaviors so completely masked a meaningless, jargon-filled, and confused presentation."[3]

See alsoEdit


  1. Donald H. Naftulin, John E. Ware, Jr., and Frank A. Donnelly, "The Doctor Fox Lecture: A Paradigm of Educational Seduction", Journal of Medical Education 48 (1973): 630-635; R. Williams and J. Ware, "Validity of student ratings of instruction under different incentive conditions: A further study of the Dr. Fox effect", Journal of Educational Psychology 68 (1976): 48–56.
  2. The Dr. Fox effect: a study of lecturer effectiveness and ratings of instruction.. URL accessed on 2008-12-25.
  3. "Bias, the Brain, and Student Evaluations of Teaching", St. John's Law Review 82 (2008):235-287, retrieved 2008-06-22.

External linksEdit

  • [1] Is it Time to Dump the 7%-38%-55% Rule?

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