The idea that intellect had something to do with cranial capacity was – and to some people, still is – an attractive one, and generations of researchers tried to find new ways to measure brain size and shape, and match it with apparent intellectual performance.
They also underwent brain scans to measure their brain size.
Other possible factors that might explain or influence the altruistic behavior—such as higher cognition (measured by brain size), hunting in groups, or stronger social bonds between group members—showed either much weaker correlations or no correlation at all with helping behaviors.
Telencephalic volume fraction outperforms residuals-based measures of brain size at separating birds by social structure.
Robin Dunbar used the volume of the neocortex -- the "thinking" part of the brain -- as his measure of brain size, because this accounts for most of the brain's expansion within primates.
The notion that lemurs are unintelligent has been perpetuated by the view that the neocortex ratio (as a measure of brain size) indicates intelligence.
Although this is an indirect measure of brain size, the advantage is that the endocranial cavity does not change with age as long as skull development is complete.
Previous studies have used either volume or mass as a measure of brain size.
Researchers measured differences in brain size and in sulci shape and location factors that have been shown to reflect the underlying cortical organization of the brain in previous studies.
For each generation, he dissected the parents and measured their relative brain size to decide which offspring to breed, selecting those with the biggest and the smallest-brained parents to create two lines.
