Dr. aoki used double-blind procedures in his experiments to reduce the potential for

In a double-blind study neither the participants nor the experimenters know who is receiving a particular treatment. 
Dr. Aoki used double-blind procedures in his experiments to reduce the potential for experimenter bias and participant bias. Experimenter occurs when the experimenter's expectations influence the results of the study, while participant bias occurs when the participant's behavior during an experiment is influenced by how the participant believes he or she is supposed to be behaving.