SEMINAR 22 October 2012: Joshua Goodman, John F. Kennedy School of Government, Harvard University

The Wages of Sinistrality: Handedness, Brain Structure and Human Capital Accumulation

Abstract

Handedness provides substantial insight into the role of brain structure in human capital accumulation. I review prior research showing that left- and right-handed individuals have different neurological wiring, particularly with regard to language processing. Using five data sets from the US and UK, I show that maternal left-handedness and poor infant health increase the likelihood of being left-handed, suggesting handedness can be used to explore the long-run impacts of differential brain structure generated in part by genetics and in part by poor infant health. Even conditional on infant health and family background, lefties exhibit economically and statistically significant human capital deficits relative to righties. Lefties score 0.1 standard deviations lower on cognitive skill measures and are not overrepresented at the high end of the distribution. Lefties have more emotional and behavioral problems, have more learning disabilities such as dyslexia, complete less schooling, and work in occupations requiring less cognitive skill. Differences between left- and right-handed siblings are similar in magnitude. Interestingly, lefties with left-handed mothers show no cognitive deficits relative to righties. Most strikingly, lefties have 10-12% lower annual earnings than righties, a difference one-third as large as the black-white earnings gap in these samples. A large fraction of this gap can be explained by differences in cognitive skills and emotional or behavioral problems. Lefties work in more manually intensive occupations than do righties, further suggesting that their primary labor market disadvantage is cognitive rather than physical. Observation of handedness may allow parents and schools to lower the initial age at which learning and behavioral problems are successfully diagnosed, increasing the chance for effective interventions.