The proposition of social learning was expanded upon and theorized by Canadian psychologist Albert Bandura. Bandura, along with his students and colleagues conducted a series of studies, known as the Bobo doll experiment, in 1961 and 1963 to find out why and when children display aggressive behaviors. These studies demonstrated the value of modeling for acquiring novel behaviors. These studies helped Bandura publish his seminal article and book in 1977 that expanded on the idea of how behavior is acquired, and thus built from Miller and Dollard's research. In Bandura's 1977 article, he claimed that Social Learning Theory shows a direct correlation between a person's perceived self-efficacy and behavioral change. Self-efficacy comes from four sources: "performance accomplishments, vicarious experience, verbal persuasion, and physiological states".