TED Talks are making an impact. One reason is TED presenters speak for no more than 18 minutes. Scripture and neuroscience support this limit.
In scripture, the human job description is to “have dominion,” or proper power (Gen.1:26-28). That’s easy with car keys. They can’t resist when I pick them up. I have power over them. Dominion is different with people, however. They can resist. Dominion between individuals is shared. You have some, I have some.
This is ancient knowledge recently confirmed by neuroscience. Beginning in the 1980s, researchers at Harvard used neuroimaging to measure actual behavior change. They noticed a profound shift. Take communication. The old model was: if I initiate a conversation, I have 100 percent dominion over you the listener. I know what you “need” to hear. I know how long I “need” to talk. But researchers discovered there is no empirical evidence this approach is effective. It robs listeners of dominion.
Preaching is a form of communication. In the prevailing model, preachers have all authority over what congregants “need” to hear and how long a sermon needs to be. If people afterward say they loved the sermon, it was effective. Lives are being changed.
Not true. Harvard researchers discovered there is no empirical evidence this approach is transformational. For example, immediately after a sermon, listeners only remember 50 percent of what was said. By the next day it drops to 25, and a week later, 10. The percentage actually doing something about a sermon is even lower.
The more effective model is sharing authority. You have some, I have some. If we apply the Harvard research to preaching, we see that effective preachers discern how much actual authority they have versus how much authority listeners have. They do this by measuring how long listeners pay attention before they tune out. Effective preachers recognize people can hear a sermon but not be listening (teens are quite adept at hearing but not listening). In fact, there are limits to how long people can listen.
What are those limits? Neuroscientists are identifying how long most people can pay attention before they tune out. The range seems to be in the area of 10 to 18 minutes. TED organizers reached the conclusion that 18 minutes works best. Nobody, no matter how famous, wealthy, or influential is allowed to speak more than 18 minutes on a TED stage—it doesn’t matter if your name is Bill Gates, Sheryl Sandberg, or Bono.
TED’s 18-minute rule works because the brain burns energy, consuming lots of glucose, oxygen, and blood flow. As the brain takes in new information and processes it, millions of neurons are firing at once, burning energy and leading to fatigue. 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, the more information we are asked to take in, the heavier and heavier it gets. On average, after 18 minutes, we drop it all, failing to remember most of what we heard.
This is why TED curator Chris Anderson says 18 minutes “is long enough to be serious and short enough to hold people’s attention.” He adds, “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. It has a clarifying effect. It brings discipline.”
Preachers could use some of this discipline. This is the time of year when pastors map their fall preaching calendar. Why not also map how long they preach? On average, the most popular evangelical pastors preach twice as long as a TED speaker. Why?
Culture. Seminary culture, mainly. I know this firsthand. I’ve preached over 650 sermons. I was trained in two seminaries. I’ve taught preaching in two seminaries. The prevailing seminary culture assumes sermons must be 30-, 40-, 50-minutes. But seminary profs never told us why.
It’s helpful to remember culture is simply what people are accustomed to. When Henry Ford introduced the assembly line, he recognized it was dehumanizing. He knew a few workers would quit in the first year. Ford missed the mark—913 walked off the job. So he raised wages and kept rehiring, hoping Ford workers would get used to it. They did.
I’m not saying 30-, 40-, 50-minute sermons are dehumanizing. I’m saying they don’t fit human nature. They don’t share dominion (you have some, I have some). And they’re not transformational. The preachers I know have hearts of gold and mean well. They want to preach transformational sermons, but when they go past 18 minutes, the transformational impact drops like a rock.
It’s difficult to seek the flourishing of the city if a sermon doesn’t yield a flourishing faith. Sermons that exceed 18 minutes don’t produce human flourishing faith. Effective communicators recognize this. In 15 minutes, John Kennedy inspired a nation to go to the moon. In a 15-minute TED talk, Facebook COO Sheryl Sandberg inspired millions of women to “lean in.” Steve Jobs gave one of the most popular commencement addresses of our time at Stanford University and he did it in 15 minutes. Simon Sinek’s 18-minute 2009 TED Talk has been viewed by almost 40,000.000, launching the “Start With Why” movement. These talks are transformational.
I know preacher want to transform lives. That requires the congregation pays attention. Human nature indicates there are cultural limits to how long listeners can pay attention. I’m generally not prescriptive, but if it’s no more than 18 minutes, shouldn’t preachers cap sermons at 18 minutes?