There is an ideal length for a presentation. TEDx has already worked it out.

Doesn’t matter who you are or how life-changing your area of expertise is you’ve only got 18 minutes tops to give a TED talk. This is no arbitrary number there’s science behind it. Science you can put towards giving a winning pitch or presentation.

We’ve already talked about the chemicals swirling around in the brain and which ones help get and support attention. Now let's talk about how long they last.

Attention spans are getting shorter as technology takes over our lives. Where once we’d happily huddle around a fire and listen as someone recites Beowulf for 3 hours the modern person would switch off after between 15 and 20 minutes. That’s why TED talks sit in the middle of this range.

The news for people who like to waffle gets even worse. Attention decays from the 5-minute mark. So, you really need to grab people in the first quarter of your presentation. Really grab them.

Because as our attention disappears it's replaced by anxiety. That’s what makes us become irritable and bored. At this point we are experiencing some of the same changes in our body we do when we are in physical pain.

So why do people go on past that 20-minute mark?

There are lots of reasons. Because they can, is one of the most common. Another is because people feel they will lose the audience if they don’t have enough information. Science tells us that is never the case.

In fact, humans find listening and keeping information to be a physically demanding thing. Listening requires alertness which means we aren’t relaxed. And the more information we get the more our “cognitive backlog” increases. This term was first coined in the 80s by researchers that made the analogy that every piece of new information we take in is like a new weight being added to our brain. After 20 minutes that loading can cause our brain to just drop everything and keep nothing.

If you absolutely must present for longer than 20 minutes what can you do to keep the audience with you? Give them a break.

It can be a literal break – getting them to stand up or do an activity that means they can’t cross their arms (which helps dispel negative body language). Or by changing the topic or mode of delivery. Video is really useful here.

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Video not only gives the audience a break and a chance to reset but also the speaker. You can watch the audience during a video and see how they react, check out their body language and the mood in the room.

But leave them wanting more if you can – curiosity is a powerful driver in human behaviour. As is pleasure. The shot of pleasure that your audience get when you finish under the expected time is a great way to maximise your good impression.

 
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This article was taken from our Book of Stun. For more on this and other cool stuff, order your free copy today.