 In late 2009 , Docter noticed his pre @-@ teen daughter , Elie , exhibiting similar shyness . " She started getting more quiet and reserved , and that , frankly , triggered a lot of my own insecurities and fears , " he said . He imagined what happens in the human mind when emotions set in . The idea to depict it through animation excited Docter , who felt it the ideal form to portray " strong , opinionated , caricatured personalities . " He began researching information about the mind , alongside Jonas Rivera , a producer , and Ronnie del Carmen , a secondary director . They consulted Paul Ekman , a well @-@ known psychologist who studies emotions , and Dacher Keltner , a professor of psychology at the University of California , Berkeley . Ekman had early in his career identified six core emotions — anger , fear , sadness , disgust , joy , and surprise . Docter found surprise and fear to be too similar , which left him with five emotions to build characters around . Other emotions considered for inclusion during the development process were schadenfreude , ennui , pride , and hope . Keltner focused on sadness being an emotion that strengthens relationships . Both emphasized how emotions organize social lives and the structuring of interpersonal interactions . 
