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On paper, a second and a half doesn’t seem like a long time — but in practice, it’s more than enough time to dramatically influence a social interaction.

“When my brother told my parents he was getting married, they thought he was too young, and there was this long pause on the phone before they said congratulations. You can’t undo that,” William von Hippel, a psychology professor at the University of Queensland in Australia, told Harvard Business Review in an interview earlier this year. “Everybody knows what it means when nothing comes out of your mouth for a second and a half.”

And just as split-second pauses can reveal what we’re thinking, they can also shape how we’re perceived: In a recent episode of the Harvard Business Review’s podcast, William von Hippel, a psychology professor at the University of Queensland in Australia, explained that speed — how quickly you can process and react in social situations — is one of the key components of charisma.

In a recent study on the subject, von Hippel and his colleagues asked volunteers easy general-knowledge questions and timed the responses. (The speedier participants could come up with an answer in about 400 milliseconds, while the slower ones took more than twice as long.) The volunteers were all recruited as groups of friends, allowing the researchers to question each one about how charismatic they believed their friends to be; when they matched up each person’s quiz scores to their friends’ assessments, they found that the quicker ones were also considered the most charismatic.

The study authors left it up to their subjects to define “charisma” for themselves, but on the podcast, von Hippel argued that it manifests as the ability to move nimbly through any given situation. “Charisma is mental quickness,” he said:

[Speed is] a sign that you have the capacity to draw things out of your memory that are going to be most useful in a particular circumstance. If you ask me a difficult question, or we’re engaged in social banter — I need to be witty, maybe, or I need to quickly defuse the situation, or I need to put you in your place. None of which can be accomplished if I take too long … The speed of our response is critical for an enormous number of the kinds of social interactions we engage in.

But not, it bears noting, speed at the cost of accuracy. Charismatic people don’t just blurt out whatever comes to mind, he explained; rather, they’re able to arrive at the correct response more quickly: “If you’re fast, the advantage is that you can pause, so to speak. You can rifle through a bunch of possible responses in your mind and give the appropriate one before anyone can detect that you actually paused,” he said. A few milliseconds make all the difference.