Plutarch De recta ratione audiendi 4

[4] In all cases, then, silence is a safe adornment for the young man, and especially so, when in listening to another he does not get excited or bawl out every minute, but even if the remarks be none too agreeable, puts up with them, and waits for the speaker to pause, and, when the pause comes, does not at once interpose his objection, but, as Aeschines puts b it, allows an interval to elapse, in case the ¹ speaker may desire to add something to what he has said, or to alter or unsay anything. But those who instantly interrupt with contradictions, neither hearing nor being heard, but talking while others talk, behave in an unseemly manner; whereas the man who has the habit of listening with restraint and respect, takes in and masters a useful discourse, and more readily sees through and detects a useless or false one, showing himself thus to be a lover of truth and not a lover of disputation, nor froward and contentious. Wherefore it is sometimes said not unaptly that it is even more necessary to take the wind of self-opinion and conceit out of the young, than to deflate wine-skins, if you wish to fill them with something useful; otherwise, being full of bombast and inflation, they have no room to receive it.

[4]

Directions concerning Attention.

Well then, silence is at all times a singular ornament of a youth, but especially if he does not interrupt the speaker nor carp and except at every thing he says, but patiently expects the conclusion, though his discourse be none of the best; and when he has done, if he does not presently come over him with an objection, but (as Aeschines directs) allows time to add, if he please, to what has been said, or to alter, or retract. Whereas such as turn too suddenly upon a speaker neither hear nor are heard themselves, but senselessly chatter to one another, and sin against the laws and rules of decorum. But he that brings along with him a modest and unwearied attention has this advantage, that whatever is beneficial in the discourse he makes his own, and he more readily discovers what is false or impertinent, appearing all the while a friend to truth rather than to squabbling or rashness. Therefore it was not ill said, that such as design to infuse goodness into the minds of youth must first exclude thence pride and self-conceit more carefully than we squeeze air out of bladders which we wish to fill with something useful; because, while they are puffed up with arrogance, there is no room to admit any thing else.