The 2009 lecture is the first in a series dedicated to examining the mechanisms of access to consciousness in the human brain. It was devoted entirely to the question of the depth of non-conscious processing.
Can a stimulus be processed visually, semantically, and even influence our decisions and modify our behavior, without reaching consciousness?
Subliminal images are part of modern mythology, and continue to raise many fantasies. They are said to be used in advertising and certain election campaigns, even though their use is explicitly forbidden by French law. It is therefore important to assess, on a strictly empirical and objective basis, the depth and limits of the impact of such images on our cognitive functioning. More fundamentally, delimiting the contours of mental operations likely to be performed without consciousness is an indispensable step in developing a theory of the cognitive and cerebral mechanisms of consciousness. The contrastive method proposed by Bernard Baars (1989) aims to delimit the proper nature of consciousness by comparing two minimally different experimental situations, one of which is subliminal while the other is conscious. Subliminal priming is also an excellent method for studying cognitive architecture, limiting the influence of participants' strategies, intentions and beliefs.