Subliminal ads impact brain activity
International research shows subliminal advertising techniques do have an impact on brain activity - but the question over whether this influences consumer behaviour remains unanswered.
Scientists at the University College London (UCL) have found the first physiological evidence that invisible subliminal images do attract the brain's attention on a subconscious level.
The findings challenge previous scientific assumptions that consciousness and attention go hand-in-hand.
"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," Bahador Bahrami from the UCL said.
"We show that there is a brain response in the primary visual cortex to subliminal images that attract our attention without us having the impression of having seen anything.
"These findings point to the sort of impact that subliminal advertising may have on the brain."
However, Dr Bahrami said the study did not attempt to look at whether subliminal messages actually influence an audience's spending decisions.
"I believe that it's likely that subliminal advertising may affect our decisions but that is just speculation at this point," he said.
Using functional magnetic resonance imaging (fMRI), the study looked at whether an image a viewer wasn't aware of - but one that reached the retina - had an impact on brain activity in the primary visual cortex.
Subjects wore red-blue filter glasses that projected faint pictures of everyday objects such as pliers and an iron to one eye and a strong flashing image known as "continuous flash suppression" to the other.
This erased the subjects' awareness of the faint images so that they were unable to localise the faint images on screen.
Subjects performed either an easy task picking out the letter T from a stream of letters, or a task that required more concentration in which subjects had to pick out the white N or blue Z from the same stream.
The subjects' brains blocked out the subliminal image and the fMRI scan did not detect any associated neural activity.
This finding that the brain does not pick up on subliminal stimuli if it is too busily occupied shows that some attention is needed for even the subconscious to pick up on subliminal images.
"This is exciting research for the scientific community because it challenges previous thinking that what is subconscious is also automatic, effortless and unaffected by attention," Dr Bahrami said.
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