However, this post hoc hypothesis is challenged by some tomboys' personal experiences and by modern research that suggests that tomboyishness is heavily influenced by genetic and prenatal factors. *
Historically tomboys were defined by boyish behaviour (especially more physically active, technological and scientific interests) and wearing boys' clothing. In recent times, as the use of "traditional" girlish clothing such as dresses, blouses and skirts steadily declines among western females, the distinction has become more and more one of behaviour. A general increase in the popularity of woman's sporting events (see Title IX), and other activities that were traditionally male-dominated, is today broadening tolerance and lessening the impact of "tomboy" as a pejorative.
Childhood genders are handled somewhat differently for tomboys and 'sissy' or girlish boys. Tomboyism generally enjoys much more social approval and support than femininity in young males. However, gender scholar Judith 'Jack' Halberstam has noted that while tomboyism is often tolerated or even encouraged in young girls, older girls and adolescents who display masculine traits are often repressed and punished as well. Thus, youthful gender expressions are increasingly linked to sexuality and evaluated in relation to heterosexual norms.
Famous tomboys in fiction include Jo March from Little Women, Alicia Lambert from Step by Step, Scout Finch from To Kill a Mockingbird, and George (Georgina) from The Famous Five (by Enid Blyton). Depictions of tomboys in other media include Peppermint Patty of the Charlie Brown cartoons and Velma of the Scooby-Doo franchise.
Most tomboys grow up to identify unambiguously as women. They may retain a large degree of their childhood tomboyishness, or may become more feminine as they grow. In the latter case, this may result from naturally changing over time, making a conscious effort to appear more feminine, or a combination of the two. Some of these adult women have openly expressed regret for their tomboy youth.