Re: Do Subliminal Messages Really Work? If so, why? If not, why not?

Many psychological experiments have shown people respond to information 
that they are not aware of receiving. eg. Corteen and Wood (1972) asked 
participants to report back a stream of text read into one ear while other 
words were fed into the other ear. It was found that those words presented 
subliminally (into the unattended ear) that the participants had previously 
been trained to associate with an electric shock produced sweating etc. 
though the participants remained unaware that they had heard them.

This has had some helpful results eg. Silverman (1978) managed to reduce 
neurotic overeating in obese patients by subliminally presenting reassuring 
messages but has also led to Science Fiction "horror" stories about people 
being conditioned by subliminal advertising eg. Killashandra by Anne 
McCaffrey.

Explanations of why it works are limited to theoretical models of what 
might be happening as psychologists are unable to see inside the brain. It 
is thought that the brain can both actively direct what is being attended 
to and process this information thoroughly but at the same time roughly 
process other events in the surrounding environment just in case attention 
needs to be swapped to them.

Main source. The Oxford Companion to the Mind edited by R. Gregory (1987)