Using Support Material for Increased Audience Participation
According to Elbert Bowen and colleagues: "The attention span of even an interested cooperative listener is startlingly short. . . . Experimentation indicated that listening spans are a matter of only seconds or fractions of a second . . . The speaker is faced not with holding attention but with constantly regaining it, performing in such a way as to bring the listeners back alive as often as possible." 
Figure 6-5. Involve your audience to keep them tuned in.
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