Scientists have discovered 40 new genes that appear to be linked to intelligence, and the find could help neurologists understand how the human brain develops key functions associated with thinking.

While the influence of these genes on intelligence is expected to be "minuscule" - a wide variety of factors are known to contribute to our IQ and general intelligence - the discovery could one day allow researchers to untangle the complicated web of 'nature and nurture' when it comes to identifying the fundamental causes behind our range of intellects.

Led by Danielle Posthuma from the VU University Medical Centre Amsterdam in the Netherlands, the study combined existing genomic data of nearly 80,000 unrelated adults and children of European descent, and identified mutations across 52 genes that were related to their intelligence scores, according to a variety of tests.

The research was carried out using two different forms of genetic analysis. One identified mutations in a group of 22 different genes, which in combination could account for almost a 5 percent difference in intelligence measurements.

A second analysis that compared whole genes rather than mapping specific mutations found a total of 47 genes, 17 of which had also been found using the first analysis.

All up, 40 of the total number of genes found by both methods hadn't been previously implicated in intelligence.

To double-check their findings, the researchers applied their results to another genome-wide association study. Since this one didn't come with a ready-made set of IQ measurements, they used education level as a rough approximation for an intelligence score instead.

Nearly all of the mutations they'd spotted in their previous research once again indicated a relationship with intelligence, while 15 of the 47 genes they'd found in the second analysis also popped up again.

Comparing the identified genes with a database of known pathways identified the genes that were already known to play a role in synapse formation, guidance of the nerve's axons, and neural differentiation.

One of the strongest correlations between genetics and intelligence were mutations found in a gene called FOXO3, and the coding that promotes its expression.

FOXO3 is part of a pathway that triggers cell death as a result of certain chemical stresses.

Interestingly, the team also found a number of other relationships between genes and characteristics to do with body mass, schizophrenia, and Alzheimer's disease.

In recent years, the evidence has piled up in support of the view that genes determine the range of many cognitive functions associated with something called 'g factor' - a general measure of cognitive ability that dates back to the early 20th century.

The history of looking to our biology - and especially our genes - to help explain differences in human intelligence is one that has been fraught with controversy, often due to our valuing some cognitive abilities over others.

So while it pays to be cautious, research like this can also help us identify which traits can be influenced by education, diet, or even the microbes in our guts.

And knowing more about the relationship between our cognitive characteristics and our genes might even help us understand more about the evolution of our intelligence, and which direction it's headed.

This research was published in Nature Genetics.