Julian Jaynes

Ask someone to sit opposite you and to say words, as many words as he can think of, pausing two or three seconds after each of them for you to write them down. If after every plural noun (or adjective, or abstract word, or whatever you choose) you say 'good' or 'right' as you write it down, or simply 'mmm-hmm' or smile, or repeat the plural word pleasantly, the frequency of plural nouns (or whatever) will increase significantly as he goes on saying words. The important thing here is that the subject is not aware that he is learning anything at all. He is not conscious that he is trying to find a way to make you increase your encouraging remarks, or even of his solution to that problem. Every day, in all our conversations, we are constantly training and being trained by each other in this manner, and yet we are never conscious of it.