In Inquiries, Galton devised psychology’s first word association test. He wrote 75 words, each on a separate piece of paper. Then he glanced at each word and noted his response to it on another piece of paper. He went through the 75 words on four different occasions, randomizing the words each time. Three things struck Galton about this study. First, responses to stimulus words tended to be constant; he very often gave the same response to a word all four times he experienced it. Second, his responses were often drawn from his childhood experience. Third, he felt that such a procedure revealed aspects of the mind never revealed before:
Perhaps the strongest of the impressions left by these experiments regards the multifariousness of the work done by the mind in a state of half-consciousness, and the valid reason they afford for believing in the existence of still deeper strata of mental operations, sunk wholly below the level of consciousness, which may account for such mental phenomena as cannot otherwise be explained (Galton, 1883)