Fig. 10. The resource modulation hypothesis posits that losses in chemical and structural brain resources associated with normal aging modulate the effects of common genetic variation on cognitive performance. As normal aging moves individuals’resources from the top to the middle portion of the resource function, constant amounts of genetic variation translate into increasingly larger performance differences. With depleted resources, genetic effects are expected to dwindle again. The colored circles represent eight individuals with different combinations of genetic polymorphisms as they move from early adulthood over old age to dementia or terminal decline. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)