Recent work in psychology has found that exposure to certain stimulus change the behavior of humans when exposed to subsequent stimuli, without the humans realizing consciously that this is the case.
There are multiple types of priming and the topic is still debated in scientific circles. It would be important, nevertheless, to start cataloguing the type of priming effects that have been observed, possibly to allow people to help themselves through them and to ensure legal protection from third parties (e.g., advertisers) seeking to profit from them.