Online deception (e.g., gender switching) is a potential problem in internet sci­ence. Because of the anonymity and the spatial distance to the experimenter, types of deception like category deception, attractiveness deception or identity concealment can easily be achieved in online studies. Considering possibilities to deal with this thread, two questions need to be asked. First is there a motivation for the type of deception in the context of the study and second is there any pos­~1ibility lo check participants' data for accuracy (e.g. online address books).

Nine online studies (7 online questionnaire studies [restricted and unrestricted]; 2 online interview studies [different instant messengers]) were analysed related to online deception on sex and age. All studies had a serious scientific background find weren't related to issues who could encourage deception like personal ap­pearance or mating strategies. Validation has been made through online available address books and data from registrations (e.g., in panels).

The results revealed that gender switching (M=1.9%, Range 0.0% to 6.3%) as well as age deception (M = 5.4%; Range 0.0% to 9.4%) were rare events although it can not entirely be clarified if deception is on purpose or maybe occurred because of borrowing one's account to a friend or colleague. Although it seems likely that the motivation to fake data is low in the context of scientific online studies.