How is deception important for obtaining truthful information from a subject?
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Deception is important for obtaining truthful information from a subject, since a subject or participant will respond in a distorted or biased way, once he knows that his reactions or behavior patterns are being tested. A participant is not likely to act naturally and may try confirming the hypothesis or defying it with his behavior. So, in order to avoid the distorted data, the experiments are usually set up in a way where participants think that they are being tested/surveyed for something different than hypothesis.
Example / Application
For example, in the Asch experiment a volunteer is deceived in two ways. He thinks that he and other volunteers are participating in the study; he also thinks that they are being tested for the ability to accurately detect the lengths of lines. In reality, the so-called volunteers are actors hired to give certain answers, while the experiment is not testing one’s ability to detect . Both deceptions are a part of the experiment’s design and are necessary to get the truthful answer from the subject. Had the participant known who he was surrounded by and what he’s being tested for, he most likely would not have provided the answers he did.
Field, A. (2006). Discovering Statistics Using SPSS: Second Edition. London. Thousand Oaks. New Delhi. Sage Publication