Under the radar: Subliminal cues do work after all, says study

France 24 / AFP
28.08.2008
By Marlowe Hood

A study published on Thursday has given what is claimed to be the first evidence to the contrary — that our decisions can, in fact, be influenced by subconsciously-perceived cues.

An unusual experiment, recounted in the British-based journal Neuron, could go a long way to explaining the mystery of what is often called intuition, its authors say.

“Humans frequently invoke an argument that their intuition can result in a better decision than conscious reasoning. Such assertions may rely on subconscious associative learning,” said lead author Mathias Pessiglione of University College London.

For example, a poker player who somehow always knows when to fold or call a bluff may be picking up on telltale signals from his opponents, using a part of his brain unrelated to conscious thought.

Previous studies have shown that people, like rats or dogs, could be conditioned to respond to unconsciously perceived stimuli. A subliminal image linked to an electrical shock, for example, will — after repeated jolts — cause a person’s palms to sweat with anticipation.

But these are so-called “automatic” responses that do not involve conscious thought.

The new study is the first to show that such cues can influence deliberate choices too.

In the experiment, 11 men and nine women aged 18 to 39 were repeatedly exposed to one of two symbols sandwiched between a pair of abstract images.

The symbols flashed for only 33 or 50 milliseconds, not long enough to be consciously perceived.

After seeing each trio of images, the volunteers — told to “follow their instincts” — had the option of pressing on a button, knowing that one of the symbols corresponded to winning a euro, and the other to losing one.

About half way through each “learning session,” which consisted of 120 decisions, most volunteers began to earn money, which they had been told they could keep.

On average, they made the “right” choice 63 percent of the time, though some individuals scored far better than others.

Pessiglione used magnetic resonance imaging (MRI) to find out what part of the brain was activated during the experiments and found that a region called the ventral striatum responded to the subliminal visual cues.

“Even without conscious processing of contextual cues, our brain can learn their reward value and use them to provide a bias on decision making,” he said.

The study implies that humans may not be immune to the kind of subtle, below-the-threshold-of-awareness[…]

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