Male and female posture "stereotypes" are created by culture and education.
Eakins and Eakins described unladylike behaviour*:
It is considered unfeminine or unladylike for a woman to "use her body too forcefully, to sprawl, to stand with her legs widely spread, to sit with her feet up ... to cross the ankle of one leg over the knee of the other. And depending on the type of clothing she wears, "she may be expected to sit with her knees together, not to sit cross-legged, or not even to bend over."
Males show a dominant behaviour and body posture (staring, taking more space, legs apart, head erect, hands on hips), while females show a submissive behaviour and body posture(lowering eyes, cocking head, knees together). For a sissy, it makes more sense to show submissive behaviour.
- *Malandro, Barker & Barker 1989
- Malandro, Loretta A., Larry L. Barker and Deborah Ann Barker (1989). Nonverbal Communication, 2nd ed. Reading MA: Addison-Wesley.