The Science Behind TED’s 18 -Minute Rule
by Carmine Gallo, author of Talk Like TED: The 9 Public Speaking Secrets of the World’s Top Minds (March 2014, St. Martin’s Press)
“TED curator Chris Anderson explained the organization’s thinking this way:
It [18 minutes] is long enough to be serious and short enough to hold people’s attention. It turns out that this length also works incredibly well online. It’s the length of a coffee break. So, you watch a great talk, and forward the link to two or three people. It can go viral, very easily. The 18-minute length also works much like the way Twitter forces people to be disciplined in what they write. By forcing speakers who are used to going on for 45 minutes to bring it down to 18, you get them to really think about what they want to say. What is the key point they want to communicate? It has a clarifying effect. It brings discipline.
The 18-minute rule also works because the brain is an energy hog. The average adult human brain only weighs about three pounds, but it consumes an inordinate amount of glucose, oxygen, and blood flow. As the brain takes in new information and is forced to process it, millions of neurons are firing at once, burning energy and leading to fatigue and exhaustion. Researchers at Texas Christian University are finding that the act of listening can be as equally draining as thinking hard about a subject. Dr. Paul King calls it ‘cognitive backlog.’ Like weights, he says, the more information we are asked to take in, the heavier and heavier it gets. Eventually, we drop it all, failing to remember anything we’ve been told. In King’s own research, he found that graduate students recall more of the information they learn when they go to class three days a week for 50 minutes instead of one day a week for three hours. Although most students say they’d prefer to get the class over with at once, they retain more information when receiving the information in shorter amounts of time…”
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