In a study, students received rats they believed to be genetically bred as "maze-bright" or "maze-dull" rats. for the next several days, students trained and recorded how long it took for their rats to complete a maze. although the rats were genetically the same breed, the "maze-bright" rats showed improvement in their performance every day, whereas the "maze-dull" rats did not. this study is examining which of the following?
a. reactivity
b. observer bias
c. observer effects
d. socially desirable responding