The correct answer to this open question is the following.
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When he attends a lecture on a topic he is very passionate about in psychology by a renowned Harvard Professor, he is influenced by the information the professor is presenting.
Let's have in mind that there are three basic ways to deliver your message and trying to influence it.
One way is pathos, an appeal based on emotion. It seems Ricardo likes the way the professor shares information about Psychology.
So pathos is the appeal to the emotion to try to convince an audience. Logos is the appeal to logic or the reason to try to convince the audience. Finally, ethos is the appeal to the reputation of the speaker.