The onset of adolescent egocentrism tends to occur at about age 11–13 which is considered early adolescence. Since an adolescent is thought to develop the formal operational stage of thinking during this time, the personal fable phenomenon is thought to develop as well. There are studies that support this hypothesis, showing that it is during early adolescence that the personal fable is most prominent (this includes both the uniqueness and invulnerability aspects of personal fable). It has also been shown that both feelings of uniqueness and invulnerability increase significantly from age 11 to age 13.