Some years ago a reader in San Diego sent me "an ancient legend that has shown up in college classrooms for at least 20 years." He told this story:

"A group of psychology students was learning the psychological principle of positive reinforcement from a very boring lecturer. To relieve the tedium, the students concocted a scheme whereby they would all look up and smile whenever the instructor spoke from the left-hand side of the room."The professor soon began to stand exclusively on the left side as he taught. According to another version of the story, they trained him to lecture with one hand stuck into his coat a la Napoleon Bonaparte, and speaking in terse, clipped sentences."

My "Trained Professor" file contains many versions of this campus legend. In the usual scenario, the students smile, nod and maintain eye contact when the professor exhibits the desired behavior; they fidget, frown and look around when the professor does anything else.

I've heard of one class that supposedly trained its professor by using foam coffee cups the students had brought to class. The students listened intently when the professor did what they wanted him to but tore up the cups and fiddled with the pieces at other times.

In some of these stories, results of the training are sometimes as simple as conditioning the teacher to lecture from one side of the room or to write on only half the chalkboard. In others, the teacher is induced to stand on a desk or an overturned wastebasket while lecturing.

This legend is based upon a technique that B.F. Skinner, the father of behavioralism, called "operant behavior." The underlying principle, often demonstrated in animal experiments, is that any behavior followed by reinforcing stimuli, such as food or praise, is more likely to occur again.

Skinner, who died in 1990, not only developed techniques for animal behavior modification, he also claimed to have applied the system to a human subject, specifically to a rival psychologist who was conducting a seminar. Skinner's story is likely the basis of the campus pranks and legends.

It concerned Erich Fromm, one of his critics. In 1958 or '59, as Skinner described the incident in a book of reminiscences, he heard Fromm speak in the seminar:

"He gesticulated a great deal as he talked, and whenever his left hand came up, I looked straight at him. If he brought the hand down, I nodded and smiled. Within five minutes he was chopping the air so vigorously that his wristwatch kept slipping out over his hand."

Mike Monahan of Atlanta wrote me recently saying that he heard Skinner tell this anecdote in a lecture at Georgia Tech University in 1985, but with a variation. Skinner claimed that he first reinforced his subject's use of "chopping motions" as he spoke, and then caused him to cease this new behavior during the course of the same lecture.

Another version of the anecdote, credited to Skinner, appears in a 1975 book and concludes, "By the end of the lecture, he was chopping the air like Hitler." This sounds like a prototype for the version quoted earlier that mentions a lecturer adopting Napoleon's characteristic stance and a militaristic speaking style.

Various accounts of other classes training professors appear in psychology textbooks, and occasionally the authors introduce personal experiences. For example, in "Introduction to Psychology" (1986) Dennis Coon claims that:

"This trick has been a favorite of psychology graduate students for decades. For a time, one of my professors delivered all of his lectures from the right side of the room while toying with the venetian blind cords. (We added the cords the second week.)"

I don't want to spoil an appealing story by casting doubt on it, but it seems to me that most descriptions of students modifying professors' behavior, Skinner's included, sound a bit too good to be true, at least not 100 percent true.

After all, a psychologist who reviewed the professional literature wrote this recently in a folklore newsletter: "I have not come across a scientifically rigorous account of a lecturer's behavior being controlled in this way."

Nor have I, though I'm still looking.- "Curses! Broiled Again," Jan Harold Brunvand's fourth collection of urban legends, is now available in paperback from Norton. Send your questions and urban legends to him in care of the Deseret News.