Assessing sexual behaviour in young people (15 to 17 years old)

Emotional development 

Acceptable sexual behaviour - green flag 

12- to 17-year-olds undergo a second socialisation phase which involves 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.  

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 

Being in love, relationships and feelings 

Acceptable behaviour - green flag 

Young people experiment with different forms of relationships. Serial monogamy is the most common: several monogamous relationships come in succession.  

85% of over 15-year-olds have been in love at one time or another, and most have short-term relationships. The duration of the last or current relationship evolves from less than six months (21%) to less than three months (27%).  

Most young people find loyalty, respect and appreciation very important in their relationships. They also want to be able to communicate with their partner.  

Dutch research confirms that for most young people, they still have sex within a steady relationship. For 75% of boys and almost 90% of girls, the most recent sex partner was a steady partner. A minority were not in love with their last partner. 

Any steady partner becomes increasingly important, for example, as a source of social support. Sex also becomes more important within the relationship. 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

! Enhanced vigilance is advisable in the event of: 

• promiscuous behaviour;  
• anxious, clingy young people: these young people fall in love more easily and have sexual experiences at an early age. They also cross their own boundaries more easily. Avoidant young people have difficulty forming relationships. They have sex at a later age, and state that they find sex less important. 

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, by wearing clothing in which breasts and/or private parts are visible). 

Red flag response guidelines 

Sexual experimentation 

Acceptable behaviour - green flag 

Young people experiment with different forms of sex. This does not happen in public.  

Sexual behaviour evolves from touching breasts or having breasts touched under clothing, and touching genitals and having them touched, to naked sexual contact. Oral sex with peers.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Moderately transgressive behaviour due to the negative impact: 

• wearing sexually provocative clothing; 
• exhibiting provocative behaviour; 
• engaging one-off in sexually risky behaviour, such as not using contraception or not protecting against STDs. 

5% of boys have previously had sex with a prostitute. This is transgressive behaviour because it is not appropriate for the age. 

Furthermore, 0.2% have already paid for sexual contacts. If it is sex with another young person in return for payment, this is transgressive behaviour due to lack of voluntary engagement.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

Repeatedly engaging in sexually risky behaviour, such as not using contraception or not protecting against STDs. This is seriously transgressive behaviour due to the repetitive nature of the behaviour and the negative impact. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

• Manipulating or forcing others to prostitute themselves (e.g., teenage pimps). 
• Engaging in inappropriate sexual acts within the family. 
• Prostituting oneself and offering sexual acts in return for payment. 
• Sexual contact with animals.  

Black flag response guidelines 

Masturbating 

Acceptable behaviour - green flag 

85% of boys and 38% of girls have masturbated at some point during this stage. 

A small minority claim to have masturbated in front of a webcam. Masturbation with vaginal or anal penetration can occur.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Being conspicuously preoccupied with masturbation.  

• Feelings of guilt after masturbation occur in 5% of boys and 4% of girls.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• Compulsive masturbation (chronic and/or in public) without deriving pleasure from it. 

• Interrupting tasks to masturbate.  

Red flag response guidelines 

Severely transgressive behaviour - black flag 

Causing genital injuries to oneself or others is severely transgressive behaviour as it compromises integrity. 

Black flag response guidelines 

Sexual jokes and sexual language 

Acceptable behaviour - green flag 

• Sexually suggestive jokes that are not offensive. 

• Sexually explicit conversations with peers (online and offline). 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Behaviour may be intended as a joke for the young person, but crosses the boundary for other people. For example: 

• one-off sexual teasing, for example, sexual comments about body parts, appearance or clothing; 

• engaging in obscenities, including online.  

Moderately transgressive behaviour due to lack of consent from the other person: 

• one-off voyeurism, for example in toilets and shower rooms;  
• intentionally exposing and showing buttocks (mooning) and genitalia; 

• one-off use of sexually explicit language, noises, drawings (lewdness), sexual graffiti (serious and shocking).  

Moderately transgressive behaviour due to the difference in development:
having sexually explicit conversations with younger children. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

Repeated acts of sexual harassment, for example: 

• continually calling someone a 'whore' or 'gay'. 
• sexual comments about body parts, appearance or clothing; 
• engaging in obscenities, including online;  
• repeated voyeurism, for example in toilets and shower rooms;  
• attempting to undress others without their consent; 
• repeated use of sexually explicit language, noises, drawings, sexual graffiti (serious and shocking). 

Red flag response guidelines 

Sexual arousal and sexual fantasies 

Acceptable behaviour - green flag 

Sexual interests and desires grow during this stage of growing up.
85% of 15-year-old boys have previously been aroused, and this reaches nearly 100% at the age of 18. 

In girls, this process is slower: from 70% at the age of 15 to 93% at the age of 18. 'Because I felt aroused' is a reason young people give for having sexual intercourse for the first time.  

Boys fantasise about sex more than girls. This does not mean that they are already ready for sex. 25% of boys and 40% of girls say they are not yet ready for sex. 

For boys, it is not always possible to satisfy their need for sex for various reasons, such as having strict parents or not finding a girlfriend.  

They often want to have sex at this age, but are just unable to.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• One-off obscene phone calls, voyeurism. 
• One-off sexual arousal from displaying the genitalia to acquaintances, for example, masturbating in public or in front of a webcam, or from physical contact with strangers.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• Repeated obscene phone calls, voyeurism. 
• Repeated sexual arousal from 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 

Sexual intercourse - the first time 

Acceptable behaviour - green flag 

Young people have different sexual norms and motives for having or not having sexual intercourse. Both autonomous motives (it's fun, exciting, thrilling) and intimacy (being emotionally close).  

Most young people still have sex within a steady relationship. For 60% of boys and slightly more than 75% of girls, the most recent sex partner was a steady partner. A minority were not in love with their last partner. Young people gradually develop their 'sexual career'. 15- to 17-year-olds go from touching breasts and genitalia, or having them touched (under clothing) to naked sex. At the age of 18.6 years, 50% of Dutch young people have already had sexual intercourse for the first time.  

At the age of 17.9 years, 50% of young people have also experienced oral sex. Anal sex generally follows a little later and only a minority take this step. 36% of girls and 23% of boys with sexual experience have a sexual issue. Girls suffer from low libido, arousal and orgasm problems, and pain. Boys suffer from premature ejaculation and excessive sexual desire. 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

Having sex due to motivations stipulated or controlled by others. For example, because someone feels guilty, or to compensate for one's image and negative feelings.  

Excessive sexual desire is related to an inability to adapt or stop one's own behaviour. 5% of boys and 3% of girls suffer from this.  

! Enhanced vigilance is advisable in the event of: 

• finding sex unpleasant: 7% of 15-17-year-old girls actually find sex unpleasant; promiscuous behaviour: having several sexual partners at the same time can be a signal of abuse; 
• lack of voluntary engagement: insistence on sex. 1% of boys () of this age have previously given money or some other reward for sex. Less than 1% of boys and girls have previously received money or something else in return for sex. The usually do not feel good about it afterwards (shame and regret);  
• due to feelings of guilt and shame about sex: this is stated more often by Turkish and Moroccan girls. Causing someone to have these feelings is transgressive behaviour; 
• because it is not appropriate for the development: having anal sex once as a girl because you want to remain a virgin; 
• having anal sex once without protection against STDs. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• One-off sexual contact in exchange for a reward (e.g., money) or using blackmail or coercion. 
• Sexual contact (anal, oral or genital) with an unequal partner, for example, a younger child. Sexual contact in which the other(s) is sexually hurt during the sexual game, without the consent of all parties. 
• Sexual contact without consent. 
• Forcing someone once and under (group) pressure to participate in sexual games or sexually suggestive contact using power, coercion, authority, blackmail, drugs, money or manipulation, including online. 

• Having repeated anal sex without protection, for example, against STDs. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

• Repeated sexual contact in exchange for a reward or using blackmail or coercion. 
• Sexual contact (anal, oral or genital) with an unequal partner (for example, a younger child), where the other(s) is/are sexually hurt during the sexual game, without consent. 
• Repeatedly forcing someone and under (group) pressure to participate in sexual games or forcing sexually suggestive contact using power, coercion, authority, blackmail, manipulation, violence and aggression (for example with a knife), including online.  

Black flag response guidelines 

Watching pornography 

Acceptable behaviour - green flag 

76% of 15-year-old boys indicate having seen pornography in the past six months. This figure rises over the years to 91% among 18-year-old boys. 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Considerable interest in pornography and obsessively preoccupied with sex (including masturbation). 

• Compulsively watching pornography can cause relationship problems and the feeling of not being able to stop the behaviour.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

• Continual interest in aggressive pornography, sexually aggressive thoughts and games.  

• Interest in and possession of images of child sexual abuse. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

• Making naked images of children who are much younger.  
• Intentionally distributing naked images is severely transgressive behaviour, because there is no consent.  

Black flag response guidelines 

Online sexuality - sexting 

Acceptable behaviour - green flag 

Young people in this stage of growing up flirt online and chat with peers about sex. 

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; 
• 57% of boys and 42% of girls had a date with someone they met online 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. 

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Having sex online with a stranger. 
• Arranging a date to have sex with a person they have met through a dating app. This is moderately transgressive behaviour if the young person does not inform anyone or say where the date is. 

• Coercing others to engage in sexting. For example, 24% of young people have already been coerced into sexting. About 50% of young people have already seen or been forwarded a naked photo.  

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

A small group takes sexual videos of others and impulsively shares them, without understanding the possible consequences.  

• Recording online sex without being asked is seriously transgressive behaviour due to the lack of consent. 
• Making sexually explicit threats, including in writing and online. 
• Taking or forwarding naked photos of someone without being asked and without sufficient understanding and awareness of the possible consequences. 

Red flag response guidelines 

Severely transgressive behaviour when sexting - black flag 

• Repeatedly making and/or sharing sexually explicit videos of others without consent and understanding the possible consequences.  
• Distributing sexual images without being asked is severely transgressive behaviour due to the lack of consent.  
• Intentionally distributing naked photos of someone without being asked and without sufficient understanding and awareness of the possible consequences.  

• Around 10% of 15-17-year-olds admit to forwarding a naked photo they have received.  

Black flag response guidelines 

Sexual orientation 

Acceptable behaviour - green flag 

Young people can potentially develop homosexual feelings. If a person feels attracted to someone of the same sex, it takes quite a while before they refer to themselves gay, bi or lesbian. 

At an average age of 16.1, young people are aware what their sexual orientation is. On average, they don't come out with it until 1 to 2 years later. Sexual orientation is not set in stone. 66% of people have subsequently switched sexual orientation a few more times.  

Young people who are attracted to the same sex have sex with a peer around the same age as heterosexual young people: on average at 16 for a boy and at 17 for a girl.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

! Enhanced vigilance is advisable in the event of: 

There may be confusion about a person's sexual orientation. Feelings and experiences are not always clear. Young people may be very aware of negative attitudes about homosexuality or just know too little about it.  

Bullying, nasty comments, ridicule, gossiping or shunning on the basis of sexual orientation is less common than in younger girls and boys, but still causes minority stress (additional stress or tension minorities are confronted with). 

Yellow flag response guidelines 

Gender identity and stereotypes 

Acceptable behaviour - green flag 

Expectations regarding sexuality are often rather gender stereotypical. There is a double standard: for girls, having sex is negative for their status; for boys, it is the opposite. 

Girls are expected to set boundaries; boys are expected to take initiative. These gender-unequal expectations play an even more important role in cultures where family honour is important (Afghan, Turkish, Moroccan and Surinamese-Hindu cultures).  

Transgender young people can be given sex hormones starting at age 16. Sexual contact can be uncomfortable and transgender young people often go through different sexual development. For example, they often avoid sex or have contacts that are not really aligned with their own desires.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

! Enhanced vigilance is advisable in the event of: 

Unwritten rules make it difficult for girls to discover their own desires and boundaries. Boys may suffer from the pressure to have sex.   

Not all transgender young people dare to come out for their feelings.  

Yellow flag response guidelines 

More on the Developmental Chart 

How is the Developmental Chart used? 

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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.