The roots of the social constructionist movement in psychology are related to the criticism of the objectivism assumed by positivist concepts of knowledge. Among the most popular variations of the social constructionist theories is the gender role theory as an early form of social constructionism. The focus on power and hierarchy reveals inspiration stemming from a Marxist framework, utilized for instance by materialist feminism. Social constructionism is the concept that there are many things that people know or take to be reality that are at least partially socially situated. for example, Harvard psychologist Steven Pinker write that some categories really are social constructions.