This week I learned about a condition called Williams syndrome, a disorder that neuroscientists have called the most compelling model available for studying the genetic basis of human behaviour.
It affects an estimated one in 7500 births, making it one-tenth as common as Down syndrome. Like Down syndrome, it can cause intellectual disability, heart defects, coordination problems and small stature.
What sets Williams syndrome apart are the behaviours that go along with the deletion of 26 genes from part of chromosome 7.
Children with Williams syndrome can't interpret socially fearful situations, and as a result have an extremely socially outgoing and friendly demeanour. They show no shyness around strangers and, with a language ability beyond their years, come across as cheerful and extroverted. They're known to hug strangers and can carry on conversations with anyone they meet.
There's a unique set of behaviours at play, and scientists have narrowed them down to the influence of three genes.
Meanwhile, a 2010 study examined our ability to discriminate between attributes such as race and gender.
Researchers found people with Williams syndrome could easily tell the difference between people based on gender but not race. They were capable of forming stereotypes based on gender differences but not based on racial differences.
The scientists think our brain's ability to process social fear influences our impressions of race, but not gender.
The connection between social behaviour and genes is a fascinating one. These connections are complex and only beginning to be understood, but studies such as this give us an insight into the origins of human behaviour and the biological factors that influence it.