Emotional, psychological problems

But such cases are rare, they said.

The Singapore Children's Society gets about one such case a year.

Mr Ng, a clinical psychologist at Raffles Hospital, noted that it was uncommon for young children to pick up such behaviour.

He said: "For a child to take up such a proactive position, he has probably experienced sex.

"Children can pick up such behaviours when others perform sexual acts on them, or through engaging in pornography, which is so easy to access today."

Recalling the case where the 6-year-old boy tried to have sex with his sister, which happened two years ago, a counsellor said the boy and his family eventually had to undergo counselling.

We are not naming the counsellor to protect the children's identities.

Measures also had to be taken to ensure that the two children were not left alone at home.

Exposure to sexual acts when one is not emotionally or psychologically sound would also be one of the causes of such behaviour, said Mr Ng.

He added: "Puberty is a stage where children are especially prone, as they are curious and want to experiment."

He had previously come across a case in which an 8-year-old girl had a habit of stimulating herself before she slept.

It got so bad that she couldn't sleep without doing it, said Mr Ng.

Dr Carol Balhetchet, director of youth services at Singapore Children's Society, said that chemical imbalances and mental disorders may cause children to display such hyper-sexualised behaviour.

She said that some children who feel that they have little control in their world engage in such behaviour, because controlling the sensations they feel is the only thing they can do.

Constant exposure to pornography, which often depicts aggressive sex, may also create wrong notions of powerand control.

She said: "It's dangerous, because such obsessions can lead to criminal offences. It may reach a stage where they cannot control themselves, and feel as though they need to fulfil those obsessions."

Such behaviour could possibly be a sign that the child was sexually disturbed or molested when they were younger, said Dr Balhetchet.

The situation at home and family structure is another contributing factor, said Dr Yeo.

He said: "Some behaviours may be learnt from friends, but most of the time, it starts at home."

Some of these children are so knowledgeable about sexual activities, they are able to discuss orgasms, and how they are more stimulated when they are touched in certain areas, he said.

Warning bells should go off when children engage in excessive masturbation, visit pornographic sites, use suggestive words in their speech, start keeping late nights,and dress provocatively, said Dr Yeo.

When treating such cases, Mr Ng said, such patients would need medication for their hormones.

He added: "We will also teach them when, how and who they should have sex with,and show them pictures of those suffering from sexually-transmitted infections.

"This way, they will be able to go through a reasoning process which will make it more likely for them to stop the behaviour."

Mr Ng added that some impulse control measures can be adopted, such as eating sweets or chewing gum when urges come on.

Dr Balhetchet said counsellors would also help the family and child understand the hyper-sexualised behaviour. Precautionary measures such as not leaving children alone at home will be taken.

She said: "We take a multi-prong approach, and, hopefully, get to the root cause of the behaviour, rather than just treating the child's symptoms."

This article was first published in The New Paper.