G. Stanley Hall,
Senescence, the Last Half of Life
(1922)
“ Again, we have made great progress along another line, namely, in distinguishing physiological and especially psychological from chronological age, but here we have little consensus of either method or result beyond the early teens. Yet no observer of life can fail to doubt that there is the same and perhaps even, on the whole, greater average diversity among individuals in mental age as they advance along the scale of years. ”
