杏吧原创

CONSIDERING the attention autism gets, it鈥檚 surprising how rarely we hear of the condition some call its opposite, Williams syndrome.

This genetic disorder, which causes people to be over-affectionate, talkative and gregarious, is rarer than autism, affecting about 1 in 10,000 people. Yet, like autism, researchers see it as a unique window into the complex interplay of nature and nurture that shapes some important aspects of the human condition.

In The Boy Who Loved Too Much, we meet Eli D鈥橝ngelo, an American boy with Williams, who treats everyone he meets as his new best friend. He hugs bus drivers, waiters and strangers, tells them he loves them, and means it.

The book could have been exploitative, but instead it鈥檚 a moving portrait of a mother facing the fact that her child has a different future from the one she imagined. Few with Williams live independently as adults, because the syndrome is also associated with reduced intelligence and dexterity 鈥� and heart problems.

Writer Jennifer Latson tracks how the concerns of Eli鈥檚 mother evolve from how to teach stranger-danger to a child who sees everyone as his friend to how to stop him being a nuisance. Children like Eli can get away with a lot with their wide smiles and characteristic elfin faces, but, warns a teacher, their 鈥渃uteness has an expiration date鈥�.

Neatly interwoven with Eli鈥檚 story are the reasons scientists are fascinated. We sequenced the human genome over a decade ago, but many traits, particularly those involving personality, are governed by multiple genes with small additive effects, and their maze of complex interactions is proving hard to fathom. Williams, however, is caused by the loss of only about 26 genes, giving geneticists a valuable entry point.

For example, studying it has helped isolate genes for high blood sugar and hypertension. Another missing gene, GTF2I, seems to lead to raised levels of oxytocin, the so-called 鈥渓ove hormone鈥�. It can be tempting to conclude that this is why people with Williams are so affectionate.

A minor gripe is that Latson occasionally skates over the neuroscience without exploring the problems inherent in this reductionist view of human behaviour. Most of us do not feel that we are slaves to our oxytocin. And Latson implies that the hormone is a promising treatment for autism, when in fact trials have produced mixed results, and there鈥檚 a long history of medical treatments for autism turning out to be a placebo.

鈥淚n socially reserved Japan, heightened empathy is seen as a disability; not so in demonstrative Greece鈥�

Of course, some people with autism don鈥檛 want to be 鈥渢reated鈥�, anyway, because they say they鈥檙e not disabled, just different. Latson skilfully explores this connection with Williams. D鈥橝ngelo鈥檚 mother has been working hard to help Eli fit in, and cut back on the hugging. She is taken aback when a Williams expert asks if there is a right/wrong amount of hugging.

The question is highlighted by different cultural attitudes. In socially reserved Japan, for example, heightened empathy is seen as a clear disability. But in publicly demonstrative Greece, parents don鈥檛 consider the behaviour pathological at all.

It鈥檚 also revealing when Latson recounts a doctor telling parents how people with Williams see everyone else. For them, the 鈥渟ymptoms鈥� of not having Williams include saying 鈥淚 love you鈥� only a few times a day. Similarly, autistic people may say that being neurotypical includes too much eye contact, hugging and talking 鈥� just as neurotypicals would see children with Williams.

The fascinating journey shows D鈥橝ngelo鈥檚 mother learning to accept Eli鈥檚 differences 鈥� and those differences lessening as he matures. I only wish I could find out how their story pans out.

Read more: How sharing other people鈥檚 feelings can make you sick

This article appeared in print under the headline 鈥淵ou are my best friend鈥�