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sification occurs. This means that an increased pressure to conform to culturally sanctioned gender roles results in a further differentiation in gender-role identification in boys and girls. Studies testing this idea showed mixed results. For example, Galambos et al. (1990) indi- cated that sex differences in masculine personality qualities (instru- mental qualities such as independence and leadership) increased in early adolescence, but sex differences in feminine personality quali- ties (expressive qualities such as sensitivity and kindness) did not. A longitudinal study by Priess et al. (2009) showed that adolescents did not become more stereotypical in their gender-role identity
across adolescence, and the authors contributed the lack of support for the gender intensification hypothesis to changed patterns of social- ization in present-day adolescents. In present day society boys are free to be more expressive and girls are promoted to be more independent than they were in the past. From another perspective, McHale et al. (2009), focused on the influence of the time youth spend in gendered social contexts on the development of their gendered personality qual- ities and interests. They also studied whether this was moderated by the increased levels of testosterone in early adolescence. By the age of 13, they found higher reports of feminine personality qualities and interests in girls and higher reports of masculine personality qualities and interests in boys. Through adolescence, the time in gendered social contexts generally showed to be associated with the development of more gender stereotyped qualities. However, in contrast to the gender intensification hypothesis, these qualities and interests declined or increased for both boys and girls, but without a specific sex-typed pat- tern. For some aspects measured, the pace of testosterone increase in early adolescence showed to have a moderating effect instead of the levels of testosterone.
Although there are indications that gendered personality qualities and interests tend to change during adolescence, for the majority of adolescents gender identity is in concordance with the assigned gender and seems to be fairly fixed from early childhood (Diamond and Butterworth, 2008). This is probably why relatively little research has been conducted on gender identity development in this age group.

Gender variant identity development

Little is known about the cognitive gender development of persons with a gender variant identity from very early on. One study by Zucker et al. (1999), in clinically referred gender dysphoric children, showed that gender dysphoric children had a developmental lag with respect to gender learning, compared to control children (without gender variant behaviors, interests or gender dysphoria). Although the gender-referred children showed the same sequence of cognitive gender development as the control children, their development appeared to be slower. From clinical experience, it appears that most gender dysphoric children are perfectly able to label their natal sex. Identifying with their natal sex, affective aspects included, is however another matter. Children as young as two years may indicate that they want to be the other gender, dislike the gender associated with their natal sex, and behave accordingly. They may even express anatomic dysphoria (“I do not want to have a penis” or “I do not want to have breasts”), and state that they want to be the other gender as soon as they can talk (Cohen-Kettenis, 2005a).
Prospective follow-up studies show that childhood GID does not invariably result in gender dysphoria or GID in adolescence and adult- hood. If the results from all outcome studies are combined, about 15% (range 2%–27%) of the children, who mostly had a diagnosis of child- hood GID, appear to remain gender dysphoric in adolescence or even fulfill criteria for GID (Steensma et al., 2011). One explanation of the relatively large percentages of desistence is that many mildly gender non-conforming children might have been included in the follow-up studies because the DSM-IV-TR criteria for a GID diagnosis were too broad, whereas the persistence of GID into adolescence is more likely if the gender dysphoria had been extreme in childhood (Wallien and Cohen-Kettenis, 2008). A recent study by Steensma et al. (2011), points to the importance of adolescence in early onset gender variant children. In their qualitative follow-up study, adolescents with a childhood diagnosis of GID, for whom the gender dysphoria had persisted or remitted into adolescence, retrospectively indicated the period between 10 and 13 years to be crucial. They identified three possible contributing factors to an increase or decrease of their gender discomfort and gender identification: 1) physical puberty;
2) the changing environment and being more explicitly treated as
one's natal sex (first years in high school); and 3) the discovery of

sexuality. The reported changes and consolidation in gender identity shortly before or in the early stages of puberty in this study corre- spond with the impression of some clinicians that, before puberty, gender identity is more malleable than later in adolescence or in adult- hood (e.g., Byne et al., 2012). It may be that pubertal hormones only steer the process. However, as the adolescents themselves indicate that the perception of others and their sexual feelings (and perhaps even related factors, such as body image) also play a role, it is more like- ly that in the process of consolidation of their experienced gender all these elements had to be experienced, explored, and weighed, particu- larly when gender identity was not yet firmly established in childhood. Adult gender dysphoria is not a homogeneous condition and there are various ways of classifying gender dysphoric individuals (see Lawrence, 2010, for an overview). In a significant number of natal males with gender identity problems (little is known about females), gender dysphoria only develops during or after puberty. In the early stages of puberty, these adolescents discover that they find wearing female clothing sexually exciting (Zucker et al., 2012). According to themselves and their parents, they often have not been particularly feminine in childhood. During ado- lescence, or much later, the role of sexual arousal diminishes or vanishes, and the desire to live permanently in the female role becomes so strong that they apply for gender reassignment. This late onset gender dysphoria thus seems to be erotically motivated (at least initially) and is denoted in the literature as autogynephilia, because Blanchard (1985) stated that the sexual arousal in these men is accompanied with the thought or image of one-self as a female. Therefore this form of gender dysphoria could be conceptualized as a paraphilia. Because they are usually sexually attracted to women, gender dysphoric individuals should, according to Blanchard, be classified on the basis of their sexual orientation: homosexual – in rela- tion to their natal sex – or non-homosexual. Blanchard's conceptualization has created much debate (e.g. Nuttbrock et al., 2011) and onset age has been proposed as a valid classification criterion as well (e.g. Nieder et al., 2011). Although sexuality certainly plays a role in late onset gender dysphoria, autogynephilic fantasies may not be the only reason why ado- lescents start cross-dressing. For instance, clinically some report that they
started cross-dressing as some form of comfort-seeking.
Irrespective of the underlying mechanism, in both the late and early onset routes, adolescence seems to serves as a crucial period, either because it consolidates an already existing development or because it initiates a development that eventually leads to a full blown gender dysphoria.

Factors related to gender variant identity development

Because gender identity generally develops in accordance with one's natal sex it is virtually impossible to assess the separate contri- bution of biological and psychosocial factors in normative developing individuals. Studies focusing on the development of gender identity in individuals with DSD and individuals with gender dysphoria or GID offer more possibilities to determine the relative contribution of these factors to the development of gender identity.