Rosenthal and Jacobson (1966) sought to test the experimenter expectancy effect by examining how much of an outcome teachers' expectancies could have on a group of children. Earlier investigations in this area were also conducted by
Rosenthal (1963). He worked with children in a research lab, giving each one a rat and telling them it was either bred for intelligence or for dullness. The children were put in charge of teaching the rats how to learn mazes.
Rosenthal's results showed that the rats that were believed by the students to be smart, were able to learn the mazes much quicker. What the children did not know, i.e., what Rosenthal had kept hidden, was that the rats were chosen at random. There were no rats that were especially bright or dull. Another case of the experimenter expectancy effect was that of the horse known as "Clever
Hans". It seemed to be able to read, spell, and solve math problems by kicking his leg a number of times. The horse was tested and passed, but what the experts did not realize was that their own hopes for the horse to answer the questions, were giving the horse signs on which he based his answers. That is, if someone on the committee raised his/her eyebrows in anticipation of the oncoming correct answer, the horse would stop stomping. Once again, the experimenter's cues decided the outcome of the tests. Acting on these results,
Rosenthal and Jacobson hypothesized that teacher's expectancies would cause them unintentionally to treat the students they thought to be bright in a different manner than those they thought to be average or even less bright. Rosenthal and Jacobson used some materials that were important in the completing their investigation. The experimenters used students and their teachers as the subjects of their study. As part of their experiment, they even chose which grades the students would be in. They also used Flanagan's Tests of