When a potential kemmering is found, hormonal secretions are further stimulated until one partner establishes either a male or female dominance. This transformation process is thorharmen . Genitals engorge or shrink accordingly, until the partners are each fully male or female. The process is still not fully understood, but it seems impossible or incredibly improbable for two Gethenians going through kemmer together to acquire the same sex. Once the individual's sexuality has been established, it cannot change during the same kemmer-period.
Normal individuals have no natural preference to either sexual role.
However, certain hormonal drugs do exist which can establish a preferred sexuality if a Gethenian so chooses. This is not a widespread practice. The culminant phase of kemmer, thokemmer , lasts two to five days, during which sexual drive and capacity is at a maximum and coitus actually occurs. Thokemmer ends rather abruptly. With the termination of pregnancy and the ensuing lactation, the individual becomes once more a perfect androgyne.