Why are some people smarter?

The next couple of weeks will be nerve-wracking for most students, as they start to sit their summer exams. I had a random thought in my head when I woke up this morning, and I thought I should share it with the world – why are some people smarter than others?

Albert Einstein: one of the most respected scientists of all time, died on the 18^th of April 1955 (55 years to this day). At his autopsy, his brain was something of a disappointment: it turned out to be a little smaller than the average Joe’s. Indeed, later studies have suggested a minimal link between brain size and intelligence. It seems that in brain terms, quality surpasses quantity. 

One important factor seems to be how well our neurones communicate with each other. A neuroscientist in the Netherlands found that smarter brains seem to have more efficient connections between neurones – that is, it takes fewer steps to relay a message between different regions of the brain. 

According to an article published in the Journal of Neuroscience, another key factor is the myelin sheath encasing the neuron fibres, which affects the speed of electrical signals. A North American scientist has found a correlation between IQ and the quality of the myelin sheaths. 

We still don’t know exactly how much genes contribute to intelligence, with various studies coming up with estimates ranging from 40 to 80 per cent. This wide range of estimates might have arisen because genes contribute to IQ as we get older, according to a study published last year. A British scientist compared the intelligence of 11,000 pairs of twins and found out that at the age of 9, genes explain 40 per cent of the variation, but by 17, they account for roughly two-thirds. 

How could that be? Perhaps the genes affect how our brain rewires itself as we mature. Alternatively, they may dictate whether someone is likely to seek out stimulating experiences to help their brain grow and develop.