Sex is the difference between genetic female (XX) and genetic male (XY). Gender is the social assignment or self-categorization as a woman or man (or neither). Gender-typed refers to behavior that is expected for a person's gender. Cross-gender typed refers to behavior that is expected for the different gender than the person has. Gender typing refers to the process of gender socialization.  

The theoretical approaches regarding gender development?

Which biological influences are there?

There are different theories that focus on biological influences on gender.

According to the evolutionary psychological theory, gender differences are created by the reproductive benefits and helped humans survive during the course of evolution. Boys often play physical games. This would have reproductive benefits for later, namely in finding friends, hunting and competitions between men. Girls like to maintain social relationships and care for other people. The reproductive benefits for later would be for taking care of a baby. 

The biosocial theory focuses more on the physical differences between man and woman, which both have social and behavioral consequences. For example, men are physically stronger and larger, while women have more nurturing capacities, such as breast milk for a baby.

Neuroscience focuses on how hormones, brain structure and brain functions are related to gender differences in development. The hormone androgen is more common in men and exists to a lesser extent in women. The hormone influences physical development and functioning from the prenatal period onward. Hormones can have organizing or activating influences on the nervous system. The organizing influences arise when certain sex hormones influence the brain differentiation and the organization during prenatal development and in puberty. An activating influence hdescribes the fluctuations in the level of the sex hormone influence the simultaneous activation of certain parts of the brain and corresponding behavioral reactions. Men and women show small differences in brain structure. However, this has no effect on the results of cognitive performance.

Gender dysphoria is a diagnosis that can be found in the DSM-5 referring to children who experience suffering, because they cannot identify with the gender assigned to them at birth. Transgenders are individuals who do not identify with their gender at birth, they may prefer to identify with the opposite gender, with both sexes or with no gender. Cisgender refers to individuals who identify with the gender they have been assigned at birth. When women produce too much androgen during the prenatal period, this can lead to congenital adrenal hyperplasia (CAH). This is a condition involving the formation of male or partly masculinized genitalia. Androgen insensitivity syndrome (AIS) is a condition during prenatal development in which androgen receptors do not function well in men, which hinders the formation of male external genitals. The child is then born with female external genitals.

Which cognitive influences are there?

 Self-socialization is the process during development where the cognitions of children lead to the perception of the world and to act in accordance with their expectations and beliefs. Self- socialization regarding gender happens when children seek to behave according to their gender identity.   

There are four important cognitive theories about gender development:

• Cognitive development theory (Kohlberg)
• Gender schema theory
• Social identity theory (Tajfel and Turner)
• Social-cognitive theory (Bandura)

Cognitive development theory (Kohlberg). This theory states that understanding gender includes three phases: gender identity, gender stability and gender constancy. In the first phase, gender identity, children around thirty months old, start to label themselves as a boy or as a girl. Children at this age, not yet see it as something permanent. In the second phase, that of gender stability, children from three to four years begin to realize that their gender is stable. But children of this age do not yet understand that gender is independent of someone's appearance. In the third phase, gender consistency, children around 6 years, realize that their gender remains constant over time and in all situations. At this age they also learn to behave according to their gender.

Gender schema theory. This theory states that children show gender-typed behavior at a young age. Namely, as soon as they are able to label themselves and others by gender. The understanding of gender development is based on the construction of the gender schema. A gender schema is an organized mental representation (concepts, beliefs, memories) about the gender, including gender stereotypes. More often they do remember events where the gender fits the situation, than where the gender is inconsistent. Liben and Bigler stated that children use two types of filters when processing information. The first is the gender schema filter, a first evaluation of information on the basis of whether it is important information for the own gender. The second is the interest filter, a first evaluation of information based on personal interest.

Social identity theory (Tajfel and Turner). This theory states that gender is the most central social identity in life. Social identity theory focuses on the influence of group membership on self-concepts and interaction with others. An ingroup bias is associated with being a member of a group and is the tendency to evaluate individuals and characteristics of their own group as superior compared to another group. The ingroup bias is related to the ingroup assimilation, a process in which individuals have adapted by meeting the standards of the group and to demonstrate the group's characteristics to the outside. Gender is not the only social identity that shapes people's lives. More attempts are being made to understand how multiple identities affect a person. This is called intersectionality: the interconnection of social identities such as gender, race, ethnicity, sexual orientation and class, mainly in relation to overlapping experiences of discrimination.

Social-cognitive theory (Bandura). This theory states that learning occurs through tuition, enactive experiences and observation. Tuition refers to direct teaching. Enactive experiences refer to learning through the reactions their own behavior has evoked in the past. Observation is the most common. This is simply learning by observing other people. This is done according to four processes: attention (noticing certain behavior), memory (storing this behavior), production (practicing this behavior) and motivation to repeat this behavior.

What are the cultural influences?

Cultural and social factors influence gender development. The macro-system of the bio-ecological model includes an important characteristic, namely the opportunity structure. These are the economic and social resources offered by the macrosystem and human understanding of the resources. Possibilities for members of a cultural group may vary depending on, for example, gender or income. According to bio-ecological perspectives, socialization focuses on certain microsystems preparing children for adulthood. 

The television treats men and women differently, there is strong stereotyping in terms of appearance, personal characteristics, work and the nature of the roles of the characters. Children who watch a lot of television have stronger stereotypical views about men and women and a greater preference for gender-typed activities. Books and computer games also appear to show strong stereotypes.  

How does gender development take place?

What are the milestones in infancy and toddlerhood?

Babies and toddlers distinguish between men and women, although they cannot understand what it means to be a man or a woman. Later they begin to develop expectations about the objects and activities typically belonging to men and women. At the age of three, most toddlers can label their own gender and the gender of others.

Which milestones are there in the age of 3-5 years?

Preschoolers learn stereotypic behavior, characteristics and roles associated with each gender. A typical stereotype they learn: affiliative characteristics are associated with women and assertive characteristics with men. However, they have no awareness of gender constancy. Also, gender segregation happens a lot. This is the tendency to approach peers of the same gender and to avoid peers of the opposite gender. Gender segregation also promotes the development of behavior that belongs to one's own gender. 

Which milestones are there in middle childhood?

At primary school, around the age of six, the awareness of gender constancy arises. Children become more flexible in gender stereotyping. When they are 9 or 10 years old, they learn to understand that gender roles are social conventions instead of biological outcomes. They recognize that not all children behave according to their gender. The children also develop a kind of awareness in thinking, they start to recognize gender discrimination and label it as unfair.

The gender roles in social interactions seem to reflect differences in the balance between assertion and affiliation. Assertion is the tendency to take action yourself through competitive, independent or aggressive behavior. Affiliation is the tendency to make connections with other people through emotional openness, empathy and cooperation. Boys are more often distinguished by assertion, while girls distinguish themselves through affiliation. Although, this is not exclusively determined. These two concepts are often combined in one style: collaboration. Collaboration is the mixing of assertion and affiliation, such as taking initiative for a joint activity. This is more common in girls.

Girls are more inclined to behave differently than what is expected of their gender. On the other hand, it is less common for boys to behave differently than their gender.   

Which milestones are there in adolescence?

In adolescence, there is a period of increasing gender role intensification or increasing gender flexibility. Gender role intensification is the increased concern to stick to traditional gender roles. Gender role flexibility is the recognition of gender roles as social conventions and the adoption of more flexible attitudes and interests. This is more common in girls than in boys.     

Cross-gender interactions become more normal during adolescence and this opens the way to romantic relationships. Adolescence is also a period in which relationships between people of the same sex become closer.

How to compare boys and girls? 

If gender groups are compared in terms of behavior, it is often the case the genders differ only slightly from each other and there is a lot of overlap and similarities. In addition, there is a lot of variation within the groups, not all members of the same gender are the same. It is important to consider both the magnitude of the differences between the averages of the groups and the amount of overlap in their distributions. This statistical index is called an effect size. In various studies, contradictory results are found. To create an overall pattern, scientists use a statistical technique called meta-analysis to summarize the average effect size and statistical significance.

What are the differences in terms of physical growth?

An important factor in sexual development is the presence or absence of androgens. In men, the Y chromosome will regulate the release. Puberty means dramatic physical changes. This period is characterized by the ability to reproduce. In this period, menstruation starts for women (menarche) and men develop the possibility to ejaculate (spermache). All these changes go hand in hand with psychological changes and behavioral changes. This often changes the body image, the perception of and feelings about your own body. More girls than boys have a negative body image. Additionally, physical ripening happens in a stage called adrenarche, this is a period in which sexual attraction begins and in which the adrenal glands mature, creating an important source of sex steroids.

What are the gender differences between cognitive abilities and academic achievement?

IQ scores are generally equal in men and women. Despite this, women get higher marks, finish their school earlier and also obtain their diplomas earlier than men. In addition, women are advanced in learning to talk and develop better in the language than men. The spatial qualities also play a role. Men perform better in some visual-spatial tasks. Boys are also somewhat better at counting than girls.

There are several explanations for these differences:

• Biological influences: research shows that there are sex differences in brain structures that are partly due to the influence of sex-related hormones in the developing brain. Androgen, for example, affects areas of the brain associated with spatial skills.
• Cognitive and motivational influences: children are mostly motivated in areas where they see themselves as competent and they find interesting and important. Gender stereotypes can influence the topics that are important to boys and girls.
• Influences of parenting: mothers have more interaction with daughters than with sons. This can explain why girls learn language a little easier than boys. The expectations of parents can be a stronger predictor of the child's later performance than the early-age performance. 
• Influences of teachers: some teachers use gender stereotypes, which can influence the interactions with the students. They can expect better school performances from girls and of boys they do expect that they are better at calculating, which can lead to different assessment and attention.
• Influences of peers: the interest of children can be shaped by the activities and values ​​they associate with their classmates and peers. For example, a study shows that students whose friends were positive about science and mathematics were more likely to show interest in a science-related career. 
• Cultural influences: gender differences in mathematics were less in countries with higher percentages of hig educated women. Gender differences in overall academic success and verbal performance were less among children from neighborhoods with a higher income, among children of highly educated parents and among children of egalitarian heterosexual parents.

What are the differences in terms of interpersonal goals and communication?

Boys emphasize dominance and power as goals in their social relationships, while girls more often emphasize intimacy and support. Girls normally talk more about personal thoughts and feelings. Girls more frequently use collaborative statements, while boys make more direct statements. This is related to each other: boys who want to show dominance use more direct speech. It can also be seen in the upbringing, mothers more often use affiliate speech and fathers more often controlling speech. Girls more often tend to play domestic scenarios, which are structured around shared and affectionate interchange, while boys more often play competitive games, structured around dominance and power. This pattern is fairly the same in different cultures. However, in Asian cultures affiliation is seen both for boys and girls as important in communication.

A statement can be high or low in terms of affiliation and assertion. This leads to four categories of speech acts:

• collaborative statements: high in both affiliation and assertion, such as a proposal for a joint activity.
• Controlling statements: high in assertion, but low in affiliation, such as orders or negative comments.
• Obliging statements: high in affiliation, but low in assertion, such as an expression of consent.
• Withdrawal: low in both affiliation and assertion, such as not responding to another person.  

In a study of children aged 5 and 7 years, collaborative statements appeared to be the most common. In the 7-year-old children, the percentage of collaborative statements was considerably higher for pairs of girls than for boys.

What are the differences in aggressive behavior?

The differences in aggressive behavior between boys and girls are not nearly as big as expected. A distinction is made between direct and indirect aggression. Direct aggression refers to the overt or verbal actions that intend to cause damage. Indirect aggression refers to attempts to hurt someone in the field of social status or group acceptance, through hidden aggression, such as someone's gossip or social exclusion. Men show more direct aggression than women, but women show more indirect aggression than men. 

There are various explanations for these differences in aggressive behavior. The first is the biological influence. Men have more of the hormone testosterone. When there is danger or threat, the level of testosterone rises and therefore also the aggressive behavior, this is an indirect effect. On average girls have more empathy and sympathy than boys, which can also be related to the differences in aggression. Parents seem to be more tolerant of aggression in boys than girls. In addition, there is an association between rough parenting and physical aggression in later life, this association is stronger for boys. Boys more often engage in more aggressive sports than girls. Exposure to violent media can stimulate aggression in children who are already vulnerable to aggression. Finally, cultures differ on the level of aggression seen as normal. Exposure to violence has a greater impact on boys than on girls.

Sexual harassment can be both physical (e.g. unwanted contact) and verbal (e.g. unwanted remarks). Many people are affected by it. In a study in the US, two of the most common forms of sexual harassment were unwanted sexual comments or gestures and to be called gay or lesbian. Girls experience more negative effects of sexual harassment than boys.