--- title: This Common Activity Is Reducing Your IQ, According to Research description: Lack of sleep affects intelligence canonical: https://time.com/3841225/can-missing-an-hour-of-sleep-take-points-off/ author: Eric Barker article:opinion: true article:content_tier: free article:published_time: 2015-04-29T23:43:21.000Z article:modified_time: 2026-08-04T07:43:14.762Z article:section: Ideas og:title: This Common Activity Is Reducing Your IQ, According To Research og:description: Lack of sleep affects intelligence og:url: https://time.com/3841225/can-missing-an-hour-of-sleep-take-points-off/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt7da4e3ac74b06ae3/6987eda6e20a87db4ca89292/iq.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 5101 og:image:height: 2869 og:image:alt: Brain og:type: article twitter:card: summary_large_image twitter:title: This Common Activity Is Reducing Your IQ, According To Research twitter:description: Lack of sleep affects intelligence twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt7da4e3ac74b06ae3/6987eda6e20a87db4ca89292/iq.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # This Common Activity Is Reducing Your IQ, According to Research > Sponsored content. 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Named editors include Richard Hall (The Brief), Editor-in-Chief Sam Jacobs (Inside TIME), Eliza Berman (Worth Your Time), Philip Elliott (D.C. Brief), Justin Worland (Future Proof) and Harry Booth (In the Loop). Health Matters is written by TIME's health desk. #### How do I sign up for a TIME newsletter? Go to time.com/newsletters, choose the newsletters you want and enter your email address. There is no cost and no subscription requirement. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-network-2026q3/newsletters?i=1fde311d-c8b6-46af-a7cb-d02b4118b6b2&cr=time-nl-network-2026q3-v1) ## Video: Humans Evolved To Get Less, But Better Quality, Sleep [Watch (HLS stream): Humans Evolved To Get Less, But Better Quality, Sleep](https://cdn.jwplayer.com/manifests/obu1caIx.m3u8) (1:13)  _Published 2015-12-15. A Duke University study hypothesizes it was early human ancestors' change from sleeping in trees to on the ground that lets us sleep less today._ by [Eric Barker](https://time.com/author/eric-barker/) ## Eric Barker Apr 29, 2015 11:43 PM UTC  Active human brain Active human brain Getty Images by [Eric Barker](https://time.com/author/eric-barker/) ## Eric Barker Apr 29, 2015 11:43 PM UTC Missing an hour of sleep turns a sixth grader’s brain into that of a fourth grader. Via [NurtureShock](http://www.amazon.com/gp/product/B0054U5ENY/ref=as%5Fli%5Fss%5Ftl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0054U5ENY&linkCode=as2&tag=spacforrent-20): --- > “” --- There is a correlation between grades and average amount of sleep. Via [NurtureShock](http://www.amazon.com/gp/product/B0054U5ENY/ref=as%5Fli%5Fss%5Ftl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0054U5ENY&linkCode=as2&tag=spacforrent-20): --- > “” --- Not only does it affect intelligence, lack of sleep also reduces impulse control. Via [NurtureShock](http://www.amazon.com/gp/product/B0054U5ENY/ref=as%5Fli%5Fss%5Ftl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0054U5ENY&linkCode=as2&tag=spacforrent-20): --- > “” --- And when we’re tired it’s actually harder to be happy. We can recall negative memories more than positive ones when we’re exhausted. ### 5 Horrible Habits You Need to Stop Right Now  Do Not Email First Thing in the Morning or Last Thing at Night “The former scrambles your priorities and all your plans for the day and the latter just gives you insomnia,” says Ferriss, who insists “email can wait until 10am” or after you check off at least one substantive to-do list item. Chris Pecoraro—Getty Images  Do Not Agree to Meetings or Calls With No Clear Agenda or End Time “If the desired outcome is defined clearly… and there’s an agenda listing topics–questions to cover–no meeting or call should last more than 30 minutes,” claims Ferriss, so “request them in advance so you can ‘best prepare and make good use of our time together.'” Sam Edwards—Getty Images/Caiaimage  Do Not Check Email Constantly Batch it and check it only periodically at set times (Ferriss goes for twice a day). Your inbox is analogous to a cocaine pellet dispenser, says Ferriss. Don’t be an addict. Tools like strategic use of the auto responder and Boomerang can help. Jetta Productions—Getty Images  Do Not Carry a Digital Leash 24/7 At least one day a week leave you smartphone somewhere where you can’t get easy access to it. If you’re gasping, you’re probably the type of person that most needs to do kick this particular habit. by nacoki ( MEDIA ARC )—Getty Images/Flickr RF  Do Not Let People Ramble Sounds harsh, but it’s necessary, Ferriss believes. “Small talk takes up big time,” he says, so when people start to tell you about their weekends, cut them off politely with something like “I’m in the middle of something, but what’s up?” But be aware, not everyone agrees with this one (and certainly not in every situation), and you may want to pay particularly close attention to norms around chit chat when traveling internationally. Reza Estakhrian—Getty Images Via [NurtureShock](http://www.amazon.com/gp/product/B0054U5ENY/ref=as%5Fli%5Fss%5Ftl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0054U5ENY&linkCode=as2&tag=spacforrent-20): --- > “” --- **_Read next:_** [**_These Are the 10 Richest Women of All Time_**](http://time.com/money/4153560/10-richest-women-all-time/) To learn how to get the best night’s sleep of your life, click [here](http://www.bakadesuyo.com/2013/09/sleep-astronauts/). **Join over 180,000 subscribers.** Get a free weekly update via email [here](http://eepurl.com/o6uAD). Related posts: [Night owls vs. Morning people: who comes out ahead?](http://www.bakadesuyo.com/night-owls-vs-morning-people-who-comes-out-ah) [What 10 things should you do every day to improve your life?](http://www.bakadesuyo.com/what-10-things-should-you-do-every-day-to-imp) [How little sleep can you get away with?](http://www.bakadesuyo.com/how-little-sleep-can-you-get-away-with-29037) ## Transcript [00:00] If you're already on your third cup of coffee you might [00:01] not believe this, but humans evolved to get less and [00:05] better sleep than our ancestors. Duke University [00:08] researchers analyzed a database of sleep patterns for [00:10] hundreds of mammal species with an emphasis on 21 [00:13] primate species. Using statistical techniques they were [00:16] able to rank how far removed From humans each [00:18] primate species was. They found humans get [00:20] significantly less sleep than most other primates. Seven [00:23] hours on average versus as many as 17 for gray [00:26] mouse lemurs. But humans also get a greater [00:28] proportion of REM sleep, the stage associated with [00:31] dreaming, boosting creative thinking and the [00:32] consolidation of memories. Is the lack of sleep due to [00:34] artificial lights? Studies have already shown tv and [00:37] computer screen stop the production of melatonin. [00:39] Making it harder to fall asleep. Yet the Duke [00:41] researchers reported a separate study found people in [00:43] three different hunter / gatherer societies, without [00:45] electricity sleep a little bit less than people with [00:48] electricity. Instead, the researchers have hypothesized [00:50] that the reason for our shorter deeper slumber Its [00:53] early human ancestors shift from sleeping on trees to [00:55] on the ground. While sleeping by fires and in large [00:57] groups protected us from predators, humans also [01:00] would have avoided dangers like falling from great [01:01] heights. And this would have allowed them to survive [01:03] the vulnerability that comes with deeper and more [01:05] efficient stages of sleep. Eventually those suited for the [01:08] different sleep pattern passed on more of their genes. 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