Which genes are responsible for intelligence?

Over the past decade, there have been several studies suggesting potential gene variants that may be linked to IQ. 

Where, oh where, does intelligence come from?

Genes seem a sure bet--or at least a significant player in a pool of important factors.  After all, scientific studies have long suggested that intelligence, as measured by intelligence quotient (IQ) tests, is heritable.  If one of your parents has a high IQ, you are more likely to have a high IQ.  If you are a member of a pair of identical twins, you are more likely to have matching IQ scores than your fraternal counterparts.  Your IQ is also more likely to be on par with your siblings than your cousins.  IQ, like height or eye color, seems to pass through the ancestral bloodlines. Thus, there must be a few genes helping propagate those smarts.

Over the past decade, there have been several studies suggesting potential gene variants that may be linked to IQ.  Specific gene variants of APOE, a gene associated with Alzheimer's disease, seemed likely candidates.  Single nucleotide polymorphisms (SNPs) from the brain-derived neurotrophic factor (BDNF), a cholinergic receptor (CHRM2) and cathepsin D (CTSD), a gene linked to schizophrenia, also showed some promise.  All in all, about an even dozen different SNPs have popped up over the years as being significantly correlated with IQ scores.  But a new study, led by Chris Chabris and David Laibson, suggests that none of these are linked to intelligence when you have a statistically powerful sample size.  The group used three independent data sets with thousands of participants--and none of the findings were replicated.

So why look for intelligence genes at all? Chabris, a psychological scientist at Union College, believes that they can help identify interesting molecular pathways and neural circuits in the brain.

"I don't view finding genes as an end in itself.  It's not that interesting to have a list of random letter and number acronyms listed next to some trait.  That doesn't add much to our knowledge," he says.  "But once we know something about the gene, then we can connect intelligence at the psychological level to biology in a new and potentially more interesting way."

He argues that by identifying the genes associated with a trait like intelligence, scientists can then ask probing questions:  Which biological systems or pathways are those genes involved in?  Where in the brain are their proteins produced?  What is the evolutionary history of those genes?  It can offer scientists, he maintains, a whole new way of understanding the biology of the mind.

Which is why it was a disappointment--and a bit of a surprise--that none of the previously identified genes could be linked to IQ scores. 

Chabris is quick to point out that the results of his study do not mean that the previous studies were flawed:  rather, intelligence is probably a lot like height and may involve a variety of different genes.

"The way height seems to work--why some people are taller and shorter than others within a normal range--seems to be the additive effect of hundreds or even more individual genes, each of which just add or take away that one millimeter," he says.  "There's probably something similar at work in intelligence and other psychological traits."

So what will it take to further our genetic understanding of intelligence?

Chabris' answer is fairly simple:  larger sample sizes.

"Social science traits are complex.  There is no single gene causation like you see in something like Huntington's disease," he says.  "So there are probably multiple or even hundreds of genes at play.  We need to increase our sample sizes by a large degree of magnitude, 100,000 subjects or even more, so we can find the genes that only have these small effects.  Once we nail those down, then we can look at what I think is the coolest question, which is how can we further understand how the brain works by looking at these genes at the molecular level."

He concedes it's a daunting task.  "It's probably going to be a lot more complicated than we hoped.  If it's a thousand genes, well, that's quite a lot to wrap your mind around.  But the field as a whole is probably capable of figuring it out."

What do you think?  What role do genes play in intelligence?

LinkedIn meets Tinder in this mindful networking app

Swipe right to make the connections that could change your career.

Getty Images
Swipe right. Match. Meet over coffee or set up a call.

No, we aren't talking about Tinder. Introducing Shapr, a free app that helps people with synergistic professional goals and skill sets easily meet and collaborate.

Keep reading Show less

Can the keto diet help treat depression? Here’s what the science says so far

A growing body of research shows promising signs that the keto diet might be able to improve mental health.

Public Domain
Mind & Brain
  • The keto diet is known to be an effective tool for weight loss, however its effects on mental health remain largely unclear.
  • Recent studies suggests that the keto diet might be an effective tool for treating depression, and clearing up so-called "brain fog," though scientists caution more research is necessary before it can be recommended as a treatment.
  • Any experiments with the keto diet are best done in conjunction with a doctor, considering some people face problems when transitioning to the low-carb diet.
Keep reading Show less

A world map of Virgin Mary apparitions

She met mere mortals with and without the Vatican's approval.

Strange Maps
  • For centuries, the Virgin Mary has appeared to the faithful, requesting devotion and promising comfort.
  • These maps show the geography of Marian apparitions – the handful approved by the Vatican, and many others.
  • Historically, Europe is where most apparitions have been reported, but the U.S. is pretty fertile ground too.
Keep reading Show less

Want to age gracefully? A new study says live meaningfully

Thinking your life is worthwhile is correlated with a variety of positive outcomes.

Surprising Science
  • A new study finds that adults who feel their lives are meaningful have better health and life outcomes.
  • Adults who felt their lives were worthwhile tended to be more social and had healthier habits.
  • The findings could be used to help improve the health of older adults.
Keep reading Show less