Assessing sexual behaviour in toddlers (18 months to 3 years)

Emotional development 

Acceptable behaviour - green flag 

From 18 months on, toddlers want to do everything themselves, and impose their will. Taking into account the will of others is difficult. Toddlers can already purposefully provoke others to get a reaction, for example, by taking off their clothes and saying naughty words. They are stubborn and resist authority (the 'no' period). In addition, toddlers may be obedient out of self-interest.  

Toddlers interact with their peers. They experience emotions such as jealously, pride, fear or anger, and have difficulty sharing. Receiving a compliment makes them happy. They can recognise emotions in others, but cannot yet judge whether these are 'genuine' or 'simulated'. 

Toddlers do not always know their role is when someone is angry with them. Regulating frustrations starts off gradually. Their emotional well-being depends on a balance between self-determination and being guided in the right way.  

Toddlers use language with supporting gestures as a means of communication, whereby they often talk about their own sexual games. Toddlers imitate words, sounds and intonations.   

Furthermore, they do not yet have an inner conscience, guilt or ability to empathise. Others need to impose rules and norms. They blame external causes for transgressive behaviour.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Seeking negative attention. 

• Heavy tantrums of frustration and aggression, and the fear of rejection as a result. 

! Enhanced vigilance is advisable in the event of: exhibiting internalising and externalising problem behaviour: tantrums, hurting themselves, annoying others. 

Yellow flag response guidelines 

Interest in bodily parts - looking at or touching genitalia 

Acceptable behaviour - green flag 

Toddlers insert various (small) objects into their orifices out of curiosity, such as a pea in their nose, mouth or ears.  

Potty training is one of the main features of this period. Consequently, there may be more interest in their genitalia.   

From the age of 1, most toddlers are interested in the genitalia of others. Almost all 1-year-old toddlers look at, want to touch or name genitalia.  

Toddlers' main urge in this regard is curiosity and a desire for knowledge. Toddlers therefore sometimes want to peek through open toilet, bath or bedroom doors. Looking at naked people, or touching breasts or genitalia also occurs. 

They first show interest in their parents' bodies, and then those of their siblings and other children.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Insisting on looking at someone's genitalia without consent and/or in public. 
• A one-off attempt to expose someone's genitalia without consent and/or in public. 
• Putting their tongue in the mouth of a person they are kissing. 
• Wanting to touch a person's breasts once, when the context does not allow it or when the person indicates they do not want to be touched.  

 
! Enhanced vigilance is advisable in the event of: 

• inserting objects into the anus, or another child's anus, whether during sex games or otherwise; 
• noticeably often playing sexual games and showing sexually explicit behaviour. For example, rhythmically stimulating the genitalia, imitating sex with dolls or their peers (with clothes on); 
• sexual games when the context does not allow it. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of: 

• repeatedly inserting sharp objects into the anus or vagina, or some other child's anus or vagina. They may harm themselves or the other child; 
• repeatedly insisting on looking at someone's genitalia; 
• repeatedly attempting to expose someone's genitalia without consent and/or in public; 
• touching the genitalia of children and adults once with their mouth, without consent (oral contact); 

• Wanting to touch a person's breasts repeatedly, when the context does not allow it or when the person indicates they do not want to be touched. 

Red flag response guidelines 

Severely transgressive behaviour - black flag 

! Enhanced vigilance is advisable in the event of: repeatedly touching the genitalia of children and adults with their mouth, without consent (oral contact).  

Black flag response guidelines 

Sexual experimentation - sexual games 

Acceptable behaviour - green flag 

By the end of the toddler period, toddlers can play stereotypical sexual games. Fully 25% of 2- to 5-year-olds sometimes play doctors and nurses.  

Hugging each other and kissing on the mouth is not exceptional. Children invent situations where they play adult roles, which involve sexuality. In the sexual role play, toddlers imitate adults. 

These kinds of games help children discover their bodies. They familiarise them with social interaction. Children identify with the behaviour of their role models. They unconsciously appropriate some of the characteristics of their role models, and therefore shape themselves.  

Green flag response guidelines 

Moderately transgressive behaviour - yellow flag 

• Noticeably often playing sexual games and sexually explicit behaviour such as rhythmically stimulating genitalia, mimicking sex with dolls or with their peers (with clothes on).
• Playing sexual games when the context does not allow it is moderately transgressive behaviour.   

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of: 

• Children demeaning or humiliating themselves or others with sexual games; 

• hurting others during the sexual game: for example, biting, pinching. 

Red flag response guidelines 

Sexual jokes and sexual language 

Acceptable behaviour - green flag 

At the age of 3, some children start their naughty word phase, often in the context of potty training. 

They find it fun to say words such as 'poo', 'willy', 'piss' and 'caca'. It is a game intended to be fun and trigger a reaction from adults. Among parents of 2- to 5-year-olds, 84% say this often happens.  

Moderately transgressive behaviour - yellow flag 

Repeatedly saying 'naughty words' when the context does not allow it.   

Yellow flag response guidelines 

Masturbating - stimulating genitalia 

Acceptable behaviour - green flag 

Toddlers discover that touching and playing with their genitalia is pleasurable. Parents in various countries have observed this behaviour until (approximately) the age of 10. From the ages of 2 to 6, 25% of boys and 16% of girls play with themselves. They do not touch or stimulate their genitalia to experience an orgasm, but it can lead to one. 10% of children between the ages of 4 and 10 play with themselves until they reach orgasm. Toddlers do not yet make the connection between sexual behaviour and orgasm. This is something they learn later and apply during puberty. 

In general, girls stimulate their genitalia more indirectly than boys. Examples of some familiar methods: rocking on a rocking horse, squeezing their thighs and "mounting" dolls, other toys or a parent's knee. Not all children exhibit this auto-erotic behaviour to the same extent. 

12% of boys and 20% of girls use an object to stimulate themselves. This may be accompanied by softly moaning, irregular breathing, or blushing. 

Toddlers sometimes play with themselves for comfort. Their playing with themselves then develops through frustration and as compensation. This behaviour can also occur if they are bored, or in a state of fear or excitement.  

Green flag response guidelines 
 

Moderately transgressive behaviour - yellow flag 

Playing with oneself in public is moderately transgressive behaviour, due to the inappropriate context. 

! Enhanced vigilance is advisable in the event of sexualised behaviour: 

• Children noticeably often playing with their genitalia in a context that does not allow it. 
• Children hurting themselves during self-stimulation. 

• Children forcing themselves on other children. 

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

Children repeatedly playing with themselves in public is seriously transgressive behaviour, due to the repetitive nature and inappropriate context.  

! Enhanced vigilance is advisable in the event of repetitive sexualised behaviour: 
Children noticeably often playing with their genitalia. 

Red flag response guidelines 

Being naked - frolicking and cuddling 

Acceptable behaviour - green flag 

Toddlers aged between 1.5 to 3 still sometimes walk around naked or in underwear. Toddlers like to frolic and cuddle, hugging others, giving kisses and sitting on their laps. Toddlers have very different needs in this regard.  

Green flag response guidelines  

Moderately transgressive behaviour - yellow flag 

Children intentionally exposing and showing their genitals or buttocks (mooning) in public is transgressive behaviour due to the public context. 

Frolicking and cuddling with strangers, infants or toddlers against their will is moderately transgressive behaviour due to lack of mutual consent.  

Yellow flag response guidelines 

Sexual images - interpretation when seeing sex 

Acceptable sexual behaviour - green flag 

Toddlers may interpret sexual images as arguments or fights, and be frightened by them. Little is known about the effect on young children when they see images of sexual arousal or sexual intercourse.  

Green flag response guidelines 
 

Moderately transgressive behaviour - yellow flag 

! Enhanced vigilance is advisable in the event of confusion or anxiety due to confrontation with sexual images.   

Yellow flag response guidelines 

Seriously transgressive behaviour - red flag 

! Enhanced vigilance is advisable in the event of repeated anxiety due to confrontation with sexual images. 

Red flag response guidelines 

Gender identity and stereotypes 

Acceptable behaviour - green flag 

From the age of 2 to 2.5 years old, toddlers know whether they are a boy or a girl and what gender other people belong to (gender identity). This realisation is based on external characteristics. Toddlers sometimes think this may change later. 

Toddlers see that they are different from other children, for example, "I have a willy and you don't". Toddlers also begin to behave more in accordance with their own gender roles. They know which behaviours are "masculine" and "feminine".  

Green 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.