These days, it’s rare to come across a published study that describes a negative result. It’s even rarer when lots of people are interested. But keeping in the theme of missing heritability, a report in Biological Psychology was released a few days ago that found no common genetic variants significantly contributing to differences in personality. This should not be surprising for anyone who has been following the ongoing search for heritability. If height (a definitively heritable trait with an easy-to-measure quantitative output) cannot be easily explained by common variants in large studies, a search for genetic associations with less objective trait such as personality is certainly in trouble.
And that’s exactly what happened. “No SNPs reached genome wide significance (α = 7.2*10-8) and the SNP with the lowest p-value for each personality scale explains less than 0.5% of the total variance.” The usability of the psychological tests (and any personality test, for that matter) for a quantitative measure of personality is a contentious topic, discussed here and here by psychologists in the study’s wake. Boiling down an individual’s personality into a series of numbers is not a perfect science (“perfect science” is sort of an oxymoron in itself, isn’t it?) and one that would no doubt change over time (I had friends that took Myers-Briggs tests yearly to look at how the results changed). In any case, even if this sort of information could be easily ascertained, the discovery power will likely be low at current GWAS power levels. Considering personality as a “rare disease” (in one sense, every individual has a basically distinct personality, so it’s the rarest trait around), finding the (likely rare) variants that contribute to personality will indeed become a challenge.
It’s here where larger aggregated studies might come into play. Citizen science groups like DIYgenomics and research snippets/surveys in 23andWe can theoretically open the door to greater amounts of data than any single researcher can afford. Of course, such endeavors are subject to some limitations. Most importantly, traits in these citizen studies are self-reported. This means that self-perception will alter the results (whether consciously or sub-consciously). For instance, if a 23andWe research snippet asked “Do you consider yourself a good person?”, citizens’ perception of themselves will most likely steer the answer in a positive direction (although it may be an interesting experiment in genetic associations with self-perception itself, in observing the individuals who answer “No”). Personality test questions are often more advanced than this one, but may suffer the same problems.
Thanks to Razib Khan for getting this discussion going. It will be interesting to see where the investigation into the genetics of personality goes next.