The 1947 perception experiments by Bruner and Leo Postman that established the foundational principle of constructivist psychology — human beings do not passively receive the world but actively construct it through existing cognitive categories.
In 1947 at Harvard, Jerome Bruner and Leo Postman ran a series of experiments that would reshape psychology. In the most famous, subjects were shown playing cards — most normal, a few altered (a red six of spades, a black four of hearts). Normal cards were identified instantly. The altered cards produced confusion, hesitation, and sometimes perceptual distress. Some subjects saw only color. Others saw only suit. Some reported seeing nothing at all, or seeing the correct card, or constructing hybrid percepts (a 'gray' card, neither red nor black). The subjects could not see what was in front of them because what was in front of them did not fit the categories they had already constructed. The studies, published in 1949 as On the Perception of Incongruity, established the New Look movement in perception research and supplied the empirical foundation for Bruner's lifelong constructivism.