Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
April 01, 1999
Hard to compare brain sizes across racial groups, professor says
For the past decade, some researchers have claimed that the racial group or gender with the largest brain in proportion to body size is the most intelligent, but work by a University of Guelph neuropsychologist suggests such statements are premature.
"The quality of data on brain size is surprisingly poor and inconsistent," said Michael Peters, a professor in the Department of Psychology. "Much more work, and better work, needs to be done before large, sweeping statements about relative brain sizes in different racial groups can be made."
Peters recently conducted a study with collaborators from universities at Dusseldorf and Magdeburg in Germany and Harvard University in Boston. It reveals that there are many aspects of brain size measurements that make it extremely difficult to compare brain sizes across different racial groups and the sexes. Excerpts from the research appeared recently in the Academic Press journal "Brain and Cognition."
One problem is body size differences across racial groups and the sexes, Peters said. Researchers typically compared brain size in proportion to body size. This is problematic because different racial groups vary both in overall body size and in "body architecture," he said.
For his study, Peters and his colleagues examined and summarized information from military databases that included a variety of countries and different ethnic groups. Military forces collect extensive information for practical purposes (sizing of garments, helmets and design of equipment), and the data are advantageous because they cover individuals who meet certain age and health standards, Peters said.
For example, Asians and Caucasians showed considerable differences in body length that are mostly accounted for by differences in leg length. Thus, leg length plays a large role in determining overall brain-in-proportion-to-body size. "How should one perform a statistical correction for body length when trying to compare brain sizes. Should leg length play a large role in such corrections? That would make little sense," Peters said.
"Similarly, women on average are smaller than men. But in controlling for body size in order to compare relative brain sizes, how does one take into account the fact that women are not just scaled-down men?"
Peters and the other researchers outlined many other complications in the measurement of brain size, including great variation in how these measurements are made. "Considering the number of unknowns and the missing elements in the knowledge base, it is surprising that some contemporary academics have made broad statements about brain size differences between different ethnic groups without qualifying such statements," Peters said.
Peters, a University of Guelph faculty member since 1975, typically studies handedness and motor control and is funded by NSERC. But he became fascinated with statements about brain size, intelligence and race that were widely circulated over the past 10 years.
Contact: Michael Peters, Department of Psychology, University of Guelph (519) 824-4120 Ext. 8530 or 3597. For media questions, contact Communications and Public Affairs, Ext. 3338.