USA Today had an article about the relationship between crabbiness and IQ as people age. Here are the quotes from Jacqueline Bichsel of Morgan State University in Baltimore:
* A hunger for knowledge and adventure seems to sharpen minds in early adulthood and middle age, but after age 60, it's not the most gung-ho but the most disagreeable people who are the smartest.
* Before age 60, those with a more open personality as evidenced by an eagerness to learn new things and to gain experiences were the brightest. After 60, an open personality had no relationship to intelligence, and personality overall mattered less. In the older ages, the most agreeable had the lowest IQs.
* Seeking out information and being open to adventure could build general knowledge at younger ages, Bichsel suggests. But in older adults, this accumulation of facts may do less to promote intelligence. Instead, more challenging and argumentative people may be giving themselves more of the mental workout needed to keep their minds young.
* Better educated, wealthier adults, who generally have higher IQs, may not react cheerfully to the patronizing treatment that is often given to the elderly, says Park, an expert on cognitive aging at the University of Illinois, Urbana-Champaign. Such people "have more of a sense of mastery and entitlement. So it could be high ability that's causing their disagreeable quality and not vice versa."