SUGGESTED ANSWER TO QUESTION 2B-1

Based on what you learned in this lesson about experimenter bias, we cannot conclude that rats from Strain A learn the maze more quickly than do rats from Strain B. Even if the students were trustworthy and attempted to perform the experiment correctly, their expectations might influence the study's results. A study similar to this one was performed by Rosenthal and Fode (1963). They found that when student volunteers were told that a strain of rats was expected to learn a maze quickly, their rats learned more quickly than did the same strain of rats tested by other students who were told that the rats would learn the maze slowly. It seemed that the students' expectations regarding the rats performance may have influenced how they handled the rats, and that these differences in handling caused differences in their rats' performances. There was no evidence of deliberate fraud on the part of the students. They probably were not aware of the fact that their expectations influenced their rats' performances.

If experimenters' expectations could possibly affect the results of a study, they should be "blinded" (kept unaware) of what is going on in the study. In addition, when participants' expectations could possibly affect the results of a study, they also should be blinded. This is called a double-blind procedure (see page 61 of the textbook) because both the experimenters and the participants are unaware of which participants are receiving which manipulations in a study.