Full Idea
Only in the cleverest animals such as dogs and apes does the need for activity, and with that boredom, make itself felt.
Gist of Idea
Boredom is only felt by those clever enough to need activity
Source
Arthur Schopenhauer (Parerga and Paralipomena [1851], III:50)
Book Reference
Schopenhauer,Arthur: 'Essays and Aphorisms [from Pand P]', ed/tr. Hollingdale,R.J. [Penguin 1970], p.126
A Reaction
But it is much more frequently young creatures, of almost any kind, that seek constant activity, and get continually restless. The most active adults need not be the cleverest.