A cognitive consistency theory of person perception and attitude change in which the elements, often depicted as vertices of a triangle, are a person (p), another person (o), and an attitude object (x), the relations between the three elements, represented by the sides of the triangle, being either positive or negative according to p's attitudes and beliefs. The model represents p's cognitions, and it can exist in a state of either balance, if none of the relations is negative or if two are negative, or imbalance, if just one of the relations is negative. In some later versions of the theory, the state of the model with three negative relations is considered ambiguous or non-balanced. According to the theory, an imbalanced state of the model, with just one negative relation, is dynamically unstable and has a tendency to become balanced, which means that one or more of the relations tends to change. For example, if Peter (p) hates classical music (x) but falls in love with Olivia (o), who tells him that she loves classical music, then there is one negative and two positive relations, and Peter's attitude towards either classical music or Olivia is likely to change, unless he can change her attitude towards classical music or his belief about her attitude. The theory was developed by the Austrian-born US psychologist Fritz Heider (1896–1988), first published in an article in 1946, and later presented in his book The Psychology of Interpersonal Relations in 1958, and the US psychologist Theodore M(ead) Newcomb (1903–84) contributed to its development in 1953. See also positivity bias (2).