Does grey matter? In the brain, it's more than the obvious pun. Now a study tells us it really does matter. It suggests the thicker the grey matter, the more intelligent someone is.

Grey matter is the outer most region of the brain with the characteristic 'wrinkled' appearance. It's called the cerebral cortex and covers the cerebrum. This grey matter is what makes us human, giving us awareness, attention and consciousness. Other essential qualities such as language, thought and memory may also stem from our cerebral cortex. Earlier studies showed us that in general, animals with bigger brains have thicker cortexes.

But a strict link between intelligence and the thickness of grey matter hasn't emerged until now. In this study, scientists studied brain scans and DNA samples from nearly 1,600 14-year old teenagers. They were also tested for verbal and non-verbal intelligence. When researchers analyzed their DNA samples to look for gene variants that might explain the differences in the intelligence tests, they found something.

The teens with a gene variant caused by something called a single nucleotide polymorphism had thinner grey matter on the left side of the brain. And'they also tested lower on the intelligence tests. This gene, called NPTN, encodes a protein known to work on neuronal synapses and affects neuronal plasticity.

In other words, it affects how well neurons communicate with one another, which explains its significance to functions of the grey matter. It's clear that NPTN, while important, is not the only gene that determines intelligence. However, it does give us clues to how intelligence is built in humans.