Science Questions

Do subliminal CDs work?

My name is Julielani Chang and I live in Davis, California and I have a question. My question is, is there any scientific basis to the companies that sell or claim that subliminal CDs could actually alter your behaviour simply by tapping into your unconscious mind? Julielani Chang, Davis, California

We put this to Ian McLaren, Professor of Cognitive Psychology at the University of Exeter.

Ian -  The answer to this question is no, but with a hint of yes to it.  I’ll start with the bad news: These CDs are unlikely to be an easy way to acquire new knowledge such as a new language for example, before considering evidence to subliminal learning itself, subliminal learning means learning that takes place below the normal threshold for awareness.  An example would be learning a list of words by listening to them while you were asleep.  If you were able to recall the words afterwards when you are awake, then that would be evidence for subliminal learning.  The problem with demonstrations of this kind, and there have been some, is that there is often insufficient control to ensure that the listener is really asleep.  When these studies are done well using EEG monitoring to ensure that the subject is genuinely asleep, the results tend to be unimpressive.  There is little evidence of above chance recall of the words.  So in this sense, these CDs are unlikely to work.

There is however some evidence for a different kind of learning under subliminal conditions.  Even though the listener cannot recall the words, we can show that they've had a detectable impact on them.  We use a different test in which I’ll ask you to say the first word that comes into your mind and I’ll give you a cue word.  Imagine a list you'd been exposed to contains the word “Traffic.”  If I now cue you with the word jam, you'll be quite likely to offer traffic as a response.  But if the list had instead contained the word “strawberry,” then that would be the more likely response to my cue.  This in fact does seem to occur on the subliminal presentation of words.  Psychologists see it as an example of priming where experience with a word makes it more accessible, more readily available in some way.  But this is not new learning.  It’s better thought of as modulation of memories that you already have.  So I'm afraid this “yes” part of my answer is not likely to be terribly useful to you when it comes to acquiring new information.

March 2010