Unconscious manipulation of free choice in humans

Andrea Kiesel
Annika Wagener
Joachim Hoffmann
Andreas J. Fallgatter
Christian Stcker
University of Wuerzburg
Germany

Evidence for unconscious cognition has been reported mainly for two-choice-reaction-time-tasks: Subliminally presented stimuli accelerate or delay responses afforded by supraliminally presented stimuli when they activate the same or different responses. Our experiments extend these findings by showing that unconscious stimuli even affect free choices between two response alternatives. Lateralized readiness potentials indicate that the subliminal stimuli activate the motor responses they are associated with. Participants tend to select the pre-activated response. Thus, it is possible to manipulate actions that are phenomenally experienced as freely willed without the actor becoming aware of the manipulation. However, the unconscious manipulation is limited to a response bias that participants overcome in a substantial amount of trials. Therefore, we conclude that humans are by no means at the mercy of unconscious manipulation, as they can resist it in most cases.