Assessing sexual behaviour in teenagers (12 to 14 years old)

Emotional development 

Puberty is a period of inner insecurities.  

12- to 17-year-olds undergo a second socialisation phase that includes a turbulent period. Sexuality and body awareness become very important.  

They push boundaries and are very self-absorbed. Thinking develops from operational to abstract. They experiment with seducing and kissing. 

Teenagers look for the answers to their (psychological and sexual) questions. They have (sometimes explicit) conversations with peers to look for answers, both online and offline. 

Acceptable behaviour - green flag 

• Turbulent period. 
• Sexuality and body awareness become very important. 
• Teenagers push boundaries and are very self-absorbed. 
• Development from operational to abstract thinking. 
• Experimenting with seducing and kissing.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

! Enhanced vigilance is advisable in the event of: 

• depression; 
• isolation; 
• somatising (developing physical symptoms); 
• low self-image. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of: 

• self-mutilation; 
• substance use; 
• depression; 
• suicidal thoughts; 
• withdrawing or running away; 
• promiscuous behaviour; 
• somatising; 
• low self-image; 

• delinquent behaviour. 

Red flag response guidelines 

Physical development 

On average, teenagers start puberty at the age of 11. Various changes take place in the body, such as bodily hair, breast development, voice breaking, more rapid growth. 

The first menstruation (also called menarche) occurs on average at age 13. But having a first period at the age of 10 or 15 is also perfectly normal.  

Boys start puberty later than girls. When boys start puberty, the first ejaculation occurs, either through masturbation or during sleep (wet dream).  

Acceptable behaviour - green flag 

The development of secondary sexual characteristics and growth sometimes leads to insecurity. In girls, weight gain prompts more dissatisfaction with their bodies and a desire to be slim. During puberty, boys grow toward the 'ideal of beauty' and therefore become more satisfied with their bodies at this phase of life. This sometimes happens after a brief dip at the start of puberty.  

The opinions of others become increasingly important. Early adolescents are highly sensitive to rejection and criticism.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Provocative and seductive behaviour toward adults (Lolita behaviour) is moderately transgressive behaviour due to the difference in development. 

! Enhanced vigilance is advisable in the event of: 

• dissatisfaction with the body and physical changes; 
• anxiously hiding and covering the body; 
• prominently displaying the body; 
• exhibiting provocative and seductive behaviour toward adults (Lolita behaviour). 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of: 

• demeaning or humiliating oneself or others with sexual games (for example, with clothing in which breasts and/or private parts are visible). 
• self-destructive behaviour. 

Red flag response guidelines 

Being in love, relationships and feelings 

Acceptable behaviour - green flag 

Teenagers display a growing sexual interest and curiosity for the other.  

Although they still feel partial shame and guilt about sexuality, the average 12-14-year-old nevertheless thinks positively about sexuality.  

Contacts become more personal and individual. More than 80% of boys and girls have been in love at one time or another. Over 50% have had a girlfriend or boyfriend. Relationships are usually quite superficial. 

Teenagers with visual, hearing or physical disabilities find it more difficult to find a partner. They have less experience and adopt a more dependent attitude.  

Peers become more important than parents as a source of support and information. Contacts with the opposite sex become more personal and individual. Hanging out with peers of the same sex evolves more toward hanging out with a mixed group of friends. 

Green flag response guidelines 

Sexual jokes and sexual language 

Acceptable behaviour - green flag 

Sexual jokes that are not offensive. 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Some of the behaviour that may be intended as a joke for teenagers, crosses the boundary for others. For example: 

• one-off sexual teasing, for example, sexual comments about body parts, appearance or clothing; 
• intentionally exposing and showing buttocks (mooning); 
• one-off use of sexually obscene language, noises, drawings (lewdness) or in written form (e.g., sexual graffiti); 

• having sexually explicit conversations with younger children is moderately transgressive behaviour due to the difference in development. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

Repeated acts of sexual harassment, for example: 

• continually calling someone a 'whore' or 'gay'. 
• making sexual comments about body parts; 
• about appearance or clothing; 
• repeated use of sexually vulgar language, sounds, drawings (lewdness); 

• making sexual graffiti which is serious and shocking.  

Rec flag response guidelines 

Sexual experience - sexual intercourse 

Acceptable behaviour - green flag 

• Around 20% of 12-14-year-olds have already kissed with their tongue. 
• 15% of boys and 9% of girls have experience feeling and caressing another person. 
• 2% to 3% of teenagers have already experienced sexual intercourse and oral sex. 
• 84% of 12-14-year-olds nevertheless consider themselves too young to have sex.  

• Among younger teenagers, the reasons for having sexual intercourse are more focused on the other person, rather than on their own pleasure and enjoyment.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Given the young age, sexual intercourse with a peer is moderately transgressive behaviour, even with mutual consent. 

Because of their young age, precocious adolescents may be less comfortable and less likely to show what they find nice. They are less likely to ask the partner what he or she finds nice. As a result, they sometimes overstep their own or their partner's boundaries.  

! Enhanced vigilance is advisable in the event of: 

Promiscuous behaviour, for example: 

• having different sexual partners at the same time; 

• wearing sexually provocative clothing. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• Asking others to perform sexual acts, such as anal, oral or genital sexual contact, without clear consent. 
• Forcing one-off sexual contact using power, coercion, authority, blackmail, drugs or manipulation, whereby the voluntary engagement of the other person is compromised. Inserting sharp objects into one's vagina or anus, or someone else's. 
• One-off anal, oral or genital sexual contact with peers, without clear consent.  

• Visiting a prostitute at this age is not appropriate to the level of development. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

• Manipulating or forcing others to prostitute themselves (e.g., as a teenage pimp). 
• Engaging in inappropriate sexual acts within the family. 
• Offering sexual acts in return for payment: prostituting oneself. 
• Having sexual contact with animals. 
• Repeatedly forcing others under (group) coercion to participate in sexual games. 

! Enhanced vigilance is advisable in the event of: 

• Forcing sexual contact with the use of power, coercion, authority, blackmail, manipulation, violence and aggression (e.g., with a knife);  
• repeated sexual intercourse, anal sexual  contact and other sexual acts, without consent; 
• sexually hurting the other(s) during the sexual game;  
• causing genital injuries to oneself and to others;  

• sexual acts with a clearly unequal partner: for example, with younger children. 

Black flag response guidelines 

Sexual arousal and fantasies 

Acceptable behaviour - green flag 

Sexual daydreams and fantasies occur in a majority of 12-14-year-olds. On average, the first sexual fantasies occur in boys at 11.6 years and in girls at 13.3 years. The content of these fantasies is erotic and increasingly focuses on potential partners.  

Sexual arousal is also common in teenagers. About 66% of boys and 33% of girls have felt sexually aroused at some point.  

'Because I felt aroused' is a reason young people give for having sexual intercourse for the first time.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• One-off voyeurism, for example in toilets and shower rooms (moderately transgressive behaviour due to the lack of consent of the other). 
• Sexual arousal from a one-off displaying of the genitalia to acquaintances (for example, masturbating in public or in front of a webcam) or from physical contact with strangers.   

 ! Enhanced vigilance is advisable in the event of: fears linked to (violent) sexual fantasies. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• Repeated voyeurism, for example in toilets and shower rooms. 
• Attempting to undress others without their consent. 

• Sexual arousal from repeatedly displaying the genitalia to acquaintances (for example, masturbating in public or in front of a webcam) or from physical contact with strangers. 

Red flag response guidelines  

Severely transgressive behaviour - black flag 

Intentionally watching a (gang) rape.  

Black flag response guidelines 

Masturbating 

Acceptable behaviour - green flag 

At the age of 13.3, 50% of teenagers have already experienced masturbation.  
35% of 12- and 13-year-old boys have masturbated, compared with 6% of girls.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Being conspicuously preoccupied with sex, including masturbation. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

Compulsive masturbation, incessantly and/or in public, without deriving pleasure from it. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

Causing genital injuries to oneself or others is serious transgressive behaviour when this occurs without mutual consent and it compromises integrity. 

Black flag response guidelines 

Watching pornography 

Acceptable behaviour - green flag 

41% of boys and 7% of girls at this age have seen pornography in the past six months, mostly online.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Teenagers who watch pornography online more often may suffer various consequences. For example, being less satisfied with their sex lives and viewing women as objects of lust.  

Research suggests there is no exclusively causal relationship, but a significant interest in pornography may be a signal for further follow-up.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of: continual interest in aggressive pornography, sexually aggressive thoughts and games, or images of child sexual abuse. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

Making or distributing images of child sexual abuse is serious transgressive behaviour. Making illegal pornography is also transgressive behaviour.  

Black flag response guidelines 

Online sexuality - sexting 

Teenagers find information and arousing images online. For a small proportion of 12-14-year-olds, sexual contacts also take place online, for example flirting and chatting about sex.  

Acceptable behaviour when sexting - green flag 

Dutch research shows an overwhelming majority of young people who are active online (12 - 25 years old) have flirted online at some point in the past year: 

• 82% of boys and 73% of girls; 

• 10% of boys and 5% of girls had sex online or after online contact in the past year. 

When young people perform a sexual act in front of a webcam, they generally do it because they find it fun, exciting or arousing themselves. Nevertheless, there are significant differences between boys and girls: 

• 62% of girls don't like being asked a sexually suggestive question, compared to 13% of boys. 
• 70% of girls who have previously been asked to perform sexual acts in front of a webcam find this annoying, compared to 29% of boys. 2% of adolescents aged 12-14 report taking and sending naked photos themselves. 

12–14-year-olds are not yet very active on dating apps. Only 5% of girls and 4% of boys have previously used such an app.  

You can find more figures in our facts and figures on sexting among young people.  

Green flag response guidelines 

Moderately transgressive behaviour when sexting - yellow flag 

When teenagers are online more often, they are also more at risk of coming into contact with images they do not want to see. Or to engage in sexually risky behaviour that they later regret. Such as: 

• having sex online, for example by masturbation via a webcam;  
• having sex online with a stranger, via a webcam;  
• arranging a date to have sex 'in real life' with a person they have met through a dating app;  

• coercing others to do sexting. 10% of young people have previously been coerced into sexting. 13% of young people have previously been shown or forwarded a naked photo. 

Yellow flag response guidelines 

Seriously transgressive behaviour when sexting - red flag 

• Making and sharing sexually suggestive videos of others, impulsively and without understanding the possible consequences. 
• Recording online sessions, without consent. 
• Engaging in sexual contact in exchange for a reward or money. 

• Making sexually explicit threats, including in writing and online.  

Red flag response guidelines 

Severely transgressive behaviour when sexting - black flag 

• Sharing naked photos of someone without being asked to, well aware of the possible consequences. 2% of teenagers admit to forwarding a naked photo they have received. 
• Repeatedly making and/or sharing sexually explicit videos of others without consent and understanding the possible consequences.  
• Intentionally sharing sexual images online, without being asked to.  

Black flag response guidelines 

Sexual orientation 

Acceptable behaviour - green flag 

Homosexual feelings are very common at puberty, in both boys and girls, mainly because of their unstable sexual identity. 

Various interpersonal situations can trigger sexual feelings. Research shows that 20 to 40% of teenagers sometimes kiss or caress someone of the same sex. A smaller percentage (mostly boys) have masturbated together or in a group.  

Teenagers who develop a non-heterosexual orientation often become aware of their feelings of same-sex attraction during this phase of life. In a group of boys who were followed up for several years after coming out, the first feelings of attraction to boys occurred on average at the age of 13.4 years.    

Dutch research shows that 1% of this age group has already been in love or in a relationship with someone of the same sex.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Homo-negativity is more common at this stage of growing up than in adolescents. Teenagers are confronted with negative views of homosexuality that create fear, panic and serious doubt about their own sexual orientation.  

! Enhanced vigilance is advisable in the event of: fears, panic and serious doubt about one's own sexual identity. 

Yellow flag response guidelines 

Gender roles and stereotypes 

Acceptable behaviour - green flag 

Teenagers understand that boys and girls can behave differently in accordance with gender roles. On the other hand, the social pressure on gender stereotyping increases and is applied to sexual relationships.  

With the transition to secondary education, more teenagers begin to behave in accordance with their own gender roles. In a small group, feelings of gender dysphoria may persist (a strong sense of dissatisfaction with the gender they were born and grew up with).  

Green flag response guidelines 

More on the Developmental Chart 

How is the Developmental Chart used? 

View all ages 

Download the Developmental Chart as PDF 

This document covers all behaviours, emotional expressions and methods of responding at any age. It also contains the sources of the scientific literature on which the Developmental Chart is based.