At the end of every research project, however, participants should always receive a complete debriefing in which all relevant information is given, including the real hypothesis, the nature of any deception used, and how the data are going to be used.
Deception is okay and most of the time necessary for Social Psychological experiments in order to collect information about people without their personal bias. That said, deception is only valid to be used for research purposes as long as the persons being deceived are informed after the experiment.