Answer:
Demand Characteristics
Explanation:
Based on the information provided in the question regarding this situation it can be said that such a measure of not revealing the purpose initially is executed due to the problem of Demand Characteristics. This term refers to when a researcher expects certain outcomes from the participants so their behaviors adjust as they believe the researchers expectancy as an implicit demand. Thus ruining the results of the study, which is why the researcher in this situation decided not to reveal the purpose of the study to the participants.
