Call to scientists: Stop excluding left-handed people from scientific studies

Left-handed people are rarely included as study subjects for brain or genetic research because the differences with right-handed people cause noise in the final results. However, left-handed people form about ten percent of the entire population and their brains and genes contain interesting information about the functioning of both halves of the brain as well as about several psychiatric disorders. 'Research into left-handed people is therefore interesting because of the noise they cause', thinks neuroscientist Roel Willems from the Donders Institute for Brain, Cognition and Behaviour at Radboud University Nijmegen. With the opinion article he calls upon his fellow researchers to stop excluding left-handed people from studies.

Missed chance for the neurosciences 'One of our studies from 2009 clearly shows why research into left-handed people is so vital', says Willems. 'According to the textbooks, facial recognition takes place in the right half of the brain. Our research revealed that the same process takes place in both halves of the brain in the case of left-handed people, but with the same final outcome. That is a fundamental difference. And left-handed people might process other important information differently as well. The minimal amount of research into this is, in my view, a missed chance for the neurosciences.'

Data from left to right According to Willems, the same applies to genetic research. Schizophrenic and psychotic patients are more likely to be left-handed. Up until now little has been done with that information to clarify the genetic links with the disorders concerned. 'Databases without left-handed people are not representative for the population and in view of the large number of genetic databases currently being set up, ignoring left-handed people is not wise', says Willems. In addition to the opinion article in Nature Reviews Neuroscience, Willems and his colleagues at the Max Planck Institute in Nijmegen are setting up the website www.mpi.nl/handedness, where left-handed people are encouraged to participate in research.