Magicians, dictators, advertisers and scientists all know it. It is possible to influence people without them even realising it. The technique, known as “priming”, involves introducing a stimulus – a word, an image or a sound – that has an effect on a person’s later behaviour, even if they cannot remember the stimulus in the first place.
For example, studies have suggested that the type of music played in a store can influence the amount of German or French wine bought and that people are more patriotic if they were previously shown flags of their country. However, some of these results have not been well replicated.
Many academics and advertisers claim that this sort of priming is “unconscious” or “subliminal”. Yet, this claim often lacks rigorous support. Consciousness can be poorly controlled for or confused with the concept of attention. People may have very briefly paid attention to the type of music or words used for priming, or directly looked at images before their attitudes or actions were measured (even though they claimed they could not remember it).
But now cognitive neuroscientists from institutions including the University of East London have finally shown that images of objects can even prime us when we are paying attention to something else – by measuring brain activity.
In the first study, people were repeatedly shown pictures of two familiar objects (for example, a car or a dog) – one on the right side and one on the left side of the screen. Observers’ attention was randomly directed to one of these two locations: a square frame was flashed briefly to one side of the screen to make a participant look in that region. The objects were then shown, both in the region the participant was looking at and in the region they were ignoring, for a fraction of a second – too short to be able to consciously perceive the ignored object.