Persistent effects of subliminal stimulation: sex differences and the effectiveness of debriefing

Persistent and non-trivial effects of unconscious stimuli have been reported (Sohlberg & Birgegard, 2003). This raises the ethical question of whether informing participants about such stimuli effectively returns them to a normal state. Two experiments (sex-mixed, N = 70 and 118) tested two kinds of debriefing to participants following subliminal (tachistoscopic) attachment-related or control stimulation. Measures were the Beck Depression Inventory, Structural Analysis of Social Behavior, and Retrospective Attachment. Results showed persistent effects. Simple debriefing about the stimulus was effective in preventing these, while more elaborate debriefing also describing the effects and mechanisms for them was less effective. Persistent effects were also strongly related to participant sex, but debriefing effects were similar in men and women with regard to the purpose of debriefing. The findings have implications for ethical recommendations for subliminal research, and suggest that this unexplored area requires more attention.