Why it is hard to find genes associated with social science traits: theoretical and empirical considerations.
OBJECTIVE
We explain why traits of interest to behavioral scientists may have a genetic architecture featuring hundreds or thousands of loci with tiny individual effects rather than a few with large effects and why such an architecture makes it difficult to find robust associations between traits and genes.


METHODS
We conducted a genome-wide association study at 2 sites, Harvard University and Union College, measuring more than 100 physical and behavioral traits with a sample size typical of candidate gene studies. We evaluated predictions that alleles with large effect sizes would be rare and most traits of interest to social science are likely characterized by a lack of strong directional selection. We also carried out a theoretical analysis of the genetic architecture of traits based on R.A. Fisher's geometric model of natural selection and empirical analyses of the effects of selection bias and phenotype measurement stability on the results of genetic association studies.


RESULTS
Although we replicated several known genetic associations with physical traits, we found only 2 associations with behavioral traits that met the nominal genome-wide significance threshold, indicating that physical and behavioral traits are mainly affected by numerous genes with small effects.


CONCLUSIONS
The challenge for social science genomics is the likelihood that genes are connected to behavioral variation by lengthy, nonlinear, interactive causal chains, and unraveling these chains requires allying with personal genomics to take advantage of the potential for large sample sizes as well as continuing with traditional epidemiological studies.
Christopher F. Chabris is with the Department of Psychology, Union College, Schenectady, NY. James J. Lee, Gregoire Borst, and Steven Pinker are with the Department of Psychology, Harvard University, Cambridge, MA. Daniel J. Benjamin is with the Department of Economics, Cornell University, Ithaca, NY. Jonathan P. Beauchamp, Edward L. Glaeser, and David I. Laibson are with the Department of Economics, Harvard University.
Christopher F
CF
Chabris
James J
JJ
Lee
Daniel J
DJ
Benjamin
Jonathan P
JP
Beauchamp
Edward L
EL
Glaeser
Gregoire
G
Borst
Steven
S
Pinker
David I
DI
Laibson
D000293:Adolescent; D000328:Adult; D001519:Behavior; D001686:Biological Phenomena; D005127:Eye Color / Q000235:genetics*; D005260:Female; D005796:Genes; D036281:Genetic Research; D055106:Genome-Wide Association Study; D006200:Hair Color / Q000235:genetics*; D006801:Humans; D008297:Male; D010551:Personality / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012641:Selection, Genetic; D012942:Social Sciences; D011795:Surveys and Questionnaires; D055815:Young Adult