The elements of G: psychometric and neuroanatomical evidence that working memory is constitutive of general cognitive ability

General cognitive ability, or general intelligence (g), has been studied by psychologists and neuroscientists for over a century. Despite progress in our understanding of how g is linked to the brain, there is not a consensus on what g itself is. Part of the reason for this is that it is difficult to distinguish the mental abilities that are necessary for g from mental abilities that are not necessary for, but still associated with, g. The lesion method of cognitive neuroscience, which uses data from individuals with brain damage, makes it possible to find distinctions between mental abilities that are normally tightly linked. Here, I used the lesion method of cognitive neuroscience to explore which cognitive abilities were and were not distinct from g. I found that working memory – the ability to maintain and manipulate information for short periods of time – was the only mental ability that could not be separated from g. The area of brain damage that was most strongly linked to deficits in both g and working memory was the arcuate fasciculus, which contains connections between frontal and posterior brain regions. Other mental abilities did not show the same pattern of association between deficits and areas of brain damage after controlling for g. My work contributes to our understanding of the definition of g, and suggests that improving our knowledge of how the brain is linked to working memory could be valuable for understanding of how the brain is linked to g.