Biosocial theory  Biosocial Theory is a theory in behavioral and social science that describes personality disorders and mental illnesses and disabilities as biologically-determined personality traits reacting to environmental stimuli. Biosocial Theory also explains the shift from evolution to culture when it comes to gender and mate selection. Biosocial Theory in motivational psychology identifies the differences between males and females concerning physical strength and reproductive capacity, and how these differences interact with expectations from society about social roles. This interaction produces the differences we see in gender. Linehan wrote in her 1993 paper, Cognitive–Behavioral Treatment of Borderline Personality Disorder, that "the biosocial theory suggests that BPD is a disorder of self-regulation, and particularly of emotional regulation, which results from biological irregularities combined with certain dysfunctional environments, as well as from their interaction and transaction over time"  According to a 1999 article published by McLean Hospital, "DBT is based on a biosocial theory of personality functioning in which BPD is seen as a biological disorder of emotional regulation. The disorder is characterized by heightened sensitivity to emotion, increased emotional in-tensity [sic] and a slow return to emotional baseline. Characteristic behaviors and emotional experiences associated with BPD theoretically result from the expression of this biological dysfunction in a social environment experienced as invalidating by the borderline patient." The interaction between evolved sex differences of reproductive capacity and physical strength and experiences in society are stressed in this theory. Jealousy and differences in long-term mate selection between males and females are also explained by this theory. Evolutionary emphasis proposes that mate value preferences stay constant, but this is not entirely the case as differences and changes in those mate preferences among and across countries implies cultural influences. This shift from evolution to social cultural experiences is what is emphasized in Biosocial Theory. The important aspect of this theory is that women and men biologically have different roles – Men are physically stronger and bigger while women bear and nurse children. The differences between the biological sexes interact with societal expectations to form the assumptions that men should hold more power and status while women hold lesser roles in society. Because of this, psychological difference increases between males and females as they try to adjust to their biologically and culturally influenced social roles. The adjustment to expected social roles is based on a cost-benefit analysis that typical sex roles are more functional and satisfactory with less effort than those of non-typical sex roles. This implies that it is more beneficial if a man enters a male-dominated occupations and women should assume positions in female-dominated occupations. However, occupations in our society may be staffed equally well by both men and women, and societal views are constantly changing even though biological differences stay constant.