Two factors are important in understanding heckling. First, heckling is a negative comment on the speaker. This negative feedback tends to lower speaker effectiveness. Second, the relationship between the heckler and the audience member is important. If the audience member sees himself as more closely aligned to the speaker, heckling will increase speaker credibility. If he sees himself as more similar to the heckler, heckling will decrease speaker credibility. Two experiments are reported. Ingroup hecklers (students at the same college) lowered credibility and attitude relative to nonheckled and no-speech controls. (Author)