The Fluid Intelligence score reports how many numerical, logic and syntactic questions subjects were able to answer in two minutes. This was negatively correlated with strength of gray matter activation in the simple shapes matching task in tfMRI, with no age interaction. The shapes matching task incurs low cognitive demand, and it is plausible that higher intelligence requires less neural activity for this task, a mechanism that has previously been ascribed to “minimization of cognitive workload”31.
