The problem with cats is that they get the exact same look on their face whether they see a moth or an axe-murderer.

The joke hinges on incongruity: a moth is trivial, while an “axe-murderer” is an extreme threat, yet the cat’s face allegedly registers both with the same unreadable intensity. Poundstone uses exaggeration to satirize the common perception that cats are emotionally opaque and difficult to “read,” unlike dogs or humans. Beneath the punchline is a small commentary on projection: people interpret animal expressions through human expectations of fear, curiosity, or alarm, and are frustrated when the animal doesn’t supply the cues we want. The line also plays on the comic idea that cats possess a cool, detached composure even in situations where panic would seem appropriate.