Psychology professor Steven Pinker addressed the role of language in studying human nature in front of a crowded room at Sherman Fairchild Hall yesterday evening.

Pinker’s lecture, the fifth in an informal seminar series hosted by the Harvard Society for Mind, Brain, and Behavior (HSMBB), centered on issues discussed in his new book “The Stuff of Thought: Language as a Window.”

Human nature, Pinker said, can be studied by looking at how language works in our everyday lives.

“Humans are very, very touchy with their social relationships. When boundaries are breached there’s an emotional cost,” Pinker said.

Popular culture and television proved to be fertile ground for examples, as Pinker drew upon scenarios from the romantic comedy “When Harry Met Sally,” as well as a number of instances of impromptu profanity by celebrities.

“Using taboo words forces the listener to trigger negative thoughts,” he said.

Pinker pointed out that semantic distinctions can make a big difference when economic costs are involved. He asked students to consider the terrorist attacks of Sept. 11, 2001.

“When a person is asked how many events occurred that day, the answer can vary from one, in reference to the single terrorist plan, to two—as in the number of buildings destroyed,” said the psychology professor. “The cost of semantics in this case happens to be $3.5 million per destructive event, according to the insurance policy.”

Alec J. Kunkel ’12, a self-professed fan of Pinker, attended the seminar with the hope of getting his copy of the professor’s book autographed. “He has an ability to take immensely complex ideas and break them into grasp-able concepts that are comprehensible to everyone,” he said.

“He has an unyielding willingness to say where his data leads without being restrained by the political and social consequences,” Kunkel said.

Co-chair of HSMBB Judy E. Fan ’10 said that the speaker series was designed to give students the opportunity to learn in a relaxed environment.

Previous speakers have included philosophy professor Sean D. Kelly and speakers from four of the seven Mind, Brain, and Behavior tracks.

“In order to create a more social and academic community, we try to reach out to diverse guest speakers,” Fan said. “We ask speakers to talk about what they’re currently interested in.”