Aristotle on Audience Responses

Rhet. 3.14.9-10 (Freese, LCL)

Further, engaging the hearer’s attention is common to all parts of the speech, if necessary; for attention slackens everywhere else rather than at the beginning…Wherefore, when the right moment comes, one must say, ‘And give me your attention, for it concerns you as much as myself’; and ‘I will tell you such a thing as you have never yet heard of, so strange and wonderful.’ This is what Prodicus used to do; whenever his hearers began to nod, he would throw in a dash of his fifty-drachma lecture.