A researcher is testing the hypothesis that caffeine makes people more talkative. Participants are randomly assigned to drink either regular coffee or warm milk. His assistant, who is unaware of the condition participants were in, then interviews them and finds that those who drank coffee indeed used a greater number of words during the interview. This leads the researchers to assume that the hypothesis was supported. What is the major threat to the validity of their conclusion? Question 49 options: some participants may have been more sensitive to caffeine than others participants had expectancies about how the drinks would affect them the research assistant may have biased the results due to her knowledge of the hypothesis b & c only