Subliminal messaging works best if it's scary, according to a team at University College London (UCL).
Famously used to sell popcorn and Coca-Cola in US cinemas - it didn't work - subliminal messaging involves showing images so briefly that they're not consciously registered. It's illegal in most countries.
The team, led by Professor Nilli Lavie, showed fifty participants a series of words on a computer screen. Each word flashed up for just a fraction of a second.
The words were either positive - for example, cheerful, flower and peace - negative, such as agony, despair and murder; or neutral, such as box, ear or kettle. After each word, participants were asked to choose whether the word was neutral or 'emotional', and say how confident they were of their decision.
The participants got it right most often when responding to negative words – even when they thought they were simply guessing the answer. Showing each word for 33 milliseconds, negative words were identified 77 percent of the time, compared with 59 percent for positive ones.
"We have shown that people can perceive the emotional value of subliminal messages and have demonstrated conclusively that people are much more attuned to negative words," said Professor Lavie.
"Clearly, there are evolutionary advantages to responding rapidly to emotional information. We can't wait for our consciousness to kick in if we see someone running towards us with a knife or if we drive under rainy or foggy weather conditions and see a sign warning 'danger'."
Professor Lavie reckons the research may have implications for the use of subliminal marketing to convey messages, particularly for public service announcements such as safety campaigns.
We're wondering whether we could use it to put you off reading the competition.
The research is published in Emotion.