Passage Summary: Researchers watched people describe cartoons; those who used their hands talked faster and smoother than those who didn't, leading researchers to believe hand-waving helps the brain find words.

Conclusion: Gesturing assists speakers in the mental process of retrieving phrases more efficiently.

Reasoning: In a study, people who were allowed to use hand gestures spoke more rapidly and had fewer repetitions than those who were restricted from gesturing.

Analysis: This argument assumes that because two things happen together—waving hands and talking fast—one must be the cause of the other. To make this argument airtight, we need to guarantee that the speed and lack of repetition are actually caused by the ease of finding words. It’s as if the author is watching a conductor and assuming the baton is what's actually generating the music. Look for an answer that cements this connection, leaving no room for other explanations.