Rising Sun Roll and new tricks

Who says you can’t teach an old dog new tricks?

The implication is that old dogs (and old people) learn less well than the young, and that old folks are set in their ways. It’s one of the oldest proverbial sayings in the language. The earliest example of it in print is in John Fitzherbert’s The Boke of Husbandry, 1534:

…and he [a shepherd] muste teche his dogge to barke whan he wolde haue hym, to ronne whan he wold haue hym, and to leue ronning whan he wolde haue hym; or els he is not ...