Tuesday, May 1, 2012

30 Seconds to Determine if an Instructor is Helpful

In a study done in 1993 (Ambady & Rosenthal) 13 college teachers were videotaped and then these tapes were edited into one master videotape. Each teacher was presented multiple times for very brief exposures (approximately 10 seconds) on the master videotape. A panel of judges reviewed this master and rated each teacher for teaching effectiveness. These ratings were compared to the end-of-semester student evaluations. “On the basis of observations of video clips just half a minute in length, complete strangers were able to predict quite accurately the ratings of teachers by students who interacted with them over the course of a whole semester (p. 435).

In a replication of the original study, the authors used 13 high school teachers. One master videotape was developed in each instance with multiple very short clips of the teachers. Researchers were able to replicate the results of the previous study with this different sample of teachers.

In a third study, the time each teacher appeared on videotape was adjusted. On one master videotape, each teacher appeared 3 times for five seconds. One the other master, each teacher appeared three times for two seconds. “These analyses show that there were no significant differences in the accuracy of judgments based on video clips 10s, 5s, and 2s in length. In addition, there were no significant differences in the accuracy of judgments for the two samples of teachers” (p. 438).

Researchers found “that the ratings of complete strangers based on very thin slices of teachers’ nonverbal behaviors (video clips from 2s to 10s long) predicted with surprising accuracy the ratings of the same teachers by people who had substantial interactions with the teachers (students and supervisors, for example)” (p. 438).

In discussing the significance of the study, Ken Bain (1994) suggests “…students, with long histories of dealing with both highly stimulating and discouraging teachers, may develop an ability to guess quite accurately, even after only a few seconds of exposure, which professor will advance their education and which will not” (p. 14).

If students form impressions of teaching effectiveness based on very brief exposures, distance educators should pay particular attention to the tone and design of all initial activities in the course.


Ambady, N. & Rosenthal, R. (1993). Half a minute: Predicting teacher evaluations from thin slices of nonverbal behavior and physical attractiveness. Journal of Personality and Social Psychology 64. P. 431-441.

Bain, K, (2004). What the best college teachers do. Cambridge, MA: Harvard University Press.

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