This is an interesting case study in how science interacts with sociology. Biologically, "fluid" intelligence (raw, general-purpose brain power) has an average

This is an interesting case study in how science interacts with sociology. Biologically, "fluid" intelligence (raw, general-purpose brain power) has an average peak in the late 20s: http://www.frontiersin.org/files/Articles/125555/frym-2014-00001-HTML/image_m/figure-2.jpg http://www.frontiersin.org/files/Articles/125555/frym-2014-0... So, for example, an average 10-year-old will have the same fluid intelligence as an average 80-year-old. (Not the same knowledge, of course, but the NYT is talking pure brain mechanics here.) However, in our society, children have low social status, and the elderly have high status. Hence, in a 10-year-old (or, per this article, even a 22-year-old just a few years from their lifetime peak), lower average intelligence is a sign of being "immature", "undeveloped", or "not an adult" (= a person competent to make their own life decisions). Meanwhile, no one would ever dream of (say) revoking the voting rights of anyone over 80, because their "brains don't work anymore". It's acceptable to take power away from the low status, but never the high status, so the scientific data is "interpreted" through that lens.