Brain scans have shown for the first time that subliminal advertising can be an effective means of getting a sneaky message across.

Simple messages flashed up before the eyes of volunteers were unconsciously registered by the brain, research showed.

An fMRI scanner recorded extra brain activity whenever an image was shown for a moment, even though the viewers were, at a conscious level, unaware of what they had seen.

The study suggests that George Bush was on to a vote-winner when his campaign team used subliminal advertising to brand Al Gore a rat in the 2000 American presidential elections.

The advert was pulled from the screen when it was realised that the word “rats” was being flashed up for a thirtieth of a second. Research at University College London reveals that such messages are absorbed by viewers. The key to the message being unconsciously understood, the study showed, is that the image reaches the retina and that the brain is unencumbered by other tasks.

When viewers were concentrating hard on another visual task, subliminal images of household objects failed to be registered by the brain. Behador Bahrami, who led the research, said: “What’s interesting here is that your brain does log things that you aren’t even aware of and can’t ever become aware of.

“These findings point to the sort of impact that subliminal advertising may have on the brain.”

The research also shows the limitations of subliminal messages; they are ignored by the brain if it is busy.The findings, reported in the journal Current Biology, overturn the established theory proposed by William James, the American psychologist, who said that subliminal messages would be absorbed whatever the circumstances.

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