experimenter can justify the use of deception because?

If the full experiment is known by the subject then they may change their results so that their answers appear more sociably acceptable. Which does not give the correct results for the experimenter.

This information is cited from the American Psychological Association code of ethics...

(a) Psychologists do not conduct a study involving deception UNLESS they have determined that the use of deceptive techniques is justified by the study's significant prospective scientific, educational, or applied value and that effective nondeceptive alternative procedures are not feasible.

(b) Psychologists do not deceive prospective participants about research that is reasonably expected to cause physical pain or severe emotional distress.

(c) Psychologists explain any deception that is an integral feature of the design and conduct of an experiment to participants as early as is feasible, preferably at the conclusion of their participation, but no later than at the conclusion of the data collection, and permit participants to withdraw their data.

A researcher must obtain consent forms from their participants beforehand. After the experiment is over, a researcher must inform the participant of the deception during the debriefing process.

Answer can be found here...

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