Assuming that a speaker will be dull before listening to the speech is an example of which of the following types of barriers?

The scenario described illustrates a self-fulfilling prophecy, where preconceived expectations about a speaker can influence the listener's perception and experience of that speech. When an audience enters with the belief that the speaker will be dull, they may unconsciously tune out or become disengaged, ultimately validating their initial assumption. This mindset can lead to a negative feedback loop, where the speaker may actually become less engaging because of the audience's disinterest, thus fulfilling the prophecy of dullness.

Self-fulfilling prophecies highlight the importance of openness and willingness to engage with new information or perspectives, as preconceived notions can significantly distort the actual experience. In public speaking, this illustrates the impact of audience perception on both the speaker's delivery and the overall effectiveness of communication.

The other types of barriers suggested do not capture this dynamic in the same way and focus on different aspects of communication challenges.