Have you ever learned a new word (or heard of an obscure sea mammal or an ethnic dance) and then encountered it several times in the space of a few days? You come across it in the news, you overhear it mentioned on the bus and on the radio, and the old issue of National Geographic you’re thumbing through falls open to an article on it. . .
This is priming (fortified with a few low-grade coincidences). When yon skim the newspaper, half-listen to TV, or drive on the motorway, you ignore most of what’s going on around you. Only a few things command attention. Paradoxically, it is unconscious processes that choose which stimuli to pass on to full consciousness. Prior exposure to something (priming) lowers the threshold of attention, so that that something is more likely to be noticed. The upshot is that you have probably encountered your ‘new’ word or car many times before. It’s just that now you’re noticing.
Excerpt from: Priceless: The Myth of Fair Value (and How to Take Advantage of It) by William Poundstone
