As your textbook explains, _________ are usually the most effective supporting materials if you want to increase the emotional appeal of a persuasive speech.

The answer is "examples".

A persuasive speech is delivered to persuade the gathering of people to feel a specific manner, to make a specific move, or to help a particular view or cause and examples are the best material one can use to increase the persuasive affect as people tend to believe and like what actually happens more than mere words. Quoting specific examples of a topic can surely increase the persuasive effect manifolds.