The discussions presented here explore the range of behaviour that can be influenced by information that is not available to consciousness, and in so doing they help to describe the relationship between consciousness and cognition. What do we gain by being aware of our cognitions, and what kind of behaviour is under the influence of unconscious knowledge? Can we perceive and record events without being aware of their presence, and later behave differently as a result of those still unconscious events? The essays here evaluate the evidence for these implicit effects upon behaviour in the domains of perception, memory, learning, and thinking.
The possibility of a dissociation between consciousness and behaviour has a long history. Psychologists have long been intrigued by demonstrations of perception without awareness, or subliminal perception. These demonstrations have had a very mixed reception, and our essays here contain echoes of ancestral debates about methodological problems in attempts to separate those effects that are controlled by conscious cognitions from those effects in which awareness has played no part. The long history of subliminal perception has allowed the opportunity for some wild claims to be made about the efficacy of subliminal techniques in clinical therapy, in the marketing of self-help audio tapes ("stop smoking', 'play better golf', 'improve your sexual confidence', 'lose weight'. . .), and as a theft deterrent in shops, among the popular applications. Legislation in some countries specifically prohibits the use of subliminal messages for marketing purposes. The existence of commercial applications, and legislation to restrict their use, does not mean that subliminal messages are effective, of course, merely that some people believe them to be effective. The evidence has not been overwhelming. Laboratory effects tend to be small even when they are reliable. This problem leads to questions about the generality of subliminal effects, and questions about methodology. If effects are small and inconsistent, then what can their influence be upon everyday behaviour? Size and inconsistency may be simply a product of laboratory methods failing to capture the critical conditions in which unnoticed events result in cognitive records. Just as proponents of the generality of subliminal perception have appealed to the evolutionary advantages of monitoring environmental events while dedicating mental resources to the main task in hand, proponents of implicit learning have suggested that it must be pervasive because consciousness is an evolutionary recent phenomenon. Animals without consciousness can learn, and so they are learning, by definition, implicitly. This begs the question of how we can know that an animal, or indeed another person is con-