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How does screen time affect kids’ brains? The first results of a landmark study are alarming.

The National Institutes of Health recently began a $300-million study to examine the effects of screen time on developing brains.

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  • The study uses MRI scans to track the changes in the brains of children who use screens at varying amounts.
  • Early results revealed that kids who use screens for more than 7 hours per day show physical changes to the brain in the form of premature thinning of the cortex.
  • It will likely be decades before scientists truly understand how smartphones and other technologies affect the brain.

How does screen time affect the developing brains of young kids?

That's the big question behind a $300-million study conducted by the National Institutes of Health that's using MRI scans to examine changes in brain structure among children who use smartphones and other screen devices. The first batch of results from the study, which was highlighted by CBS's 60 Minutes on Sunday, shows that kids who spent more than two hours per day on screens scored lower on language and thinking tests.

Alarmingly, kids who spent more than seven hours per day on electronic devices showed premature thinning of the cortex, which Dr. Gaya Dowling of the National Institutes of Health described as a "maturational process" that typically happens later in development.

"We don't know if it's being caused by the screen time," said Dowling. "We don't know yet if it's a bad thing. It won't be until we follow them over time that we will see if there are outcomes that are associated with the differences that we're seeing in this single snapshot."

It will take a few years to get answers to some of the questions raised by the study. However, the most interesting results will likely come decades from now, when researchers can see the long-term effects of technology use on the brain. Dr. Dimitri Christakis of Seattle Children's Hospital, the lead author of the American Academy of Pediatrics' most recent guidelines for screen time, told CBS he's concerned about this uncertainty.

"In many ways, the concern that investigators like I have is that we're sort of in the midst of a natural kind of uncontrolled experiment on the next generation of children," Christakis said.

Most kids say they spend too much time on smartphones

American teenagers now spend more than four and a half hours on their phones per day, and that's not even necessarily counting additional time spent playing video games, watching TV or using the computer. It's no surprise that a generation of kids who'd be hard pressed to remember a time without smartphones have made them a big part of daily life—the iPhone came out in 2007, after all, so kids born after 1995 entered adolescence with touchscreens in hand.

Many kids are themselves concerned. A recent survey from the Pew Research Center found that 54 percent of U.S. teens said they spend too much time on their phones, and 60 percent of them consider spending too much time online to be a "major problem." The data seem to back that up, with today's teenagers reporting lower levels of drinking, sex and drug use, yet higher levels of depression and loneliness.

This year, Facebook, Apple and Instagram began offering tools to help users monitor and reduce their screen time, including features that let users set time limits and see how their screen time is allocated across different apps. Some of these features are designed to help parents restrict their children's screen time.

Of course, the best solution might be to wait to give your kid a phone until it's necessary. The American Academy of Pediatrics' recommends for "children younger than 18 months, avoid use of screen media other than video-chatting," and that parents "of children 18 to 24 months of age who want to introduce digital media should choose high-quality programming, and watch it with their children to help them understand what they're seeing."

​An unprecedented technology

Tristan Harris, a former Google manager who's spoken publicly on how Silicon Valley is intentionally making smart devices as addictive as possible, told 60 Minutes that some parents are under the false impression that smartphone use is analogous to chatting on the phone in past decades.

"... there's a narrative that, oh, I guess they're just doing this like we used to gossip on the phone, but what this misses is that your telephone in the 1970s didn't have a thousand engineers on the other side of the telephone who were redesigning it to work with other telephones and then updating the way your telephone worked every day to be more and more persuasive."

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Human brains remember certain words more easily than others

A study of the manner in which memory works turns up a surprising thing.

Image Point Fr / Shutterstock
Mind & Brain
  • Researchers have found that some basic words appear to be more memorable than others.
  • Some faces are also easier to commit to memory.
  • Scientists suggest that these words serve as semantic bridges when the brain is searching for a memory.

Cognitive psychologist Weizhen Xie (Zane) of the NIH's National Institute of Neurological Disorders and Stroke (NINDS) works with people who have intractable epilepsy, a form of the disorder that can't be controlled with medications. During research into the brain activity of patients, he and his colleagues discovered something odd about human memory: It appears that certain basic words are consistently more memorable than other basic words.

The research is published in Nature Human Behaviour.

An odd find

Image source: Tsekhmister/Shutterstock

Xie's team was re-analyzing memory tests of 30 epilepsy patients undertaken by Kareem Zaghloul of NINDS.

"Our goal is to find and eliminate the source of these harmful and debilitating seizures," Zaghloul said. "The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers we have been able to uncover some of the blueprints behind our memories."

Specifically, the participants were shown word pairs, such as "hand" and "apple." To better understand how the brain might remember such pairings, after a brief interval, participants were supplied one of the two words and asked to recall the other. Of the 300 words used in the tests, five of them proved to be five times more likely to be recalled: pig, tank, doll, pond, and door.

The scientists were perplexed that these words were so much more memorable than words like "cat," "street," "stair," "couch," and "cloud."

Intrigued, the researchers looked at a second data source from a word test taken by 2,623 healthy individuals via Amazon's Mechanical Turk and found essentially the same thing.

"We saw that some things — in this case, words — may be inherently easier for our brains to recall than others," Zaghloul said. That the Mechanical Turk results were so similar may "provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside of the study."

Why understanding memory matters

person holding missing piece from human head puzzle

Image source: Orawan Pattarawimonchai/Shutterstock

"Our memories play a fundamental role in who we are and how our brains work," Xie said. "However, one of the biggest challenges of studying memory is that people often remember the same things in different ways, making it difficult for researchers to compare people's performances on memory tests." He added that the search for some kind of unified theory of memory has been going on for over a century.

If a comprehensive understanding of the way memory works can be developed, the researchers say that "we can predict what people should remember in advance and understand how our brains do this, then we might be able to develop better ways to evaluate someone's overall brain health."

Party chat

Image source: joob_in/Shutterstock

Xie's interest in this was piqued during a conversation with Wilma Bainbridge of University of Chicago at a Christmas party a couple of years ago. Bainbridge was, at the time, wrapping up a study of 1,000 volunteers that suggested certain faces are universally more memorable than others.

Bainbridge recalls, "Our exciting finding is that there are some images of people or places that are inherently memorable for all people, even though we have each seen different things in our lives. And if image memorability is so powerful, this means we can know in advance what people are likely to remember or forget."

spinning 3D model of a brain

Temporal lobes

Image source: Anatomography/Wikimedia

At first, the scientists suspected that the memorable words and faces were simply recalled more frequently and were thus easier to recall. They envisioned them as being akin to "highly trafficked spots connected to smaller spots representing the less memorable words." They developed a modeling program based on word frequencies found in books, new articles, and Wikipedia pages. Unfortunately, the model was unable to predict or duplicate the results they saw in their clinical experiments.

Eventually, the researchers came to suspect that the memorability of certain words was linked to the frequency with which the brain used them as semantic links between other memories, making them often-visited hubs in individuals's memory networks, and therefore places the brain jumped to early and often when retrieving memories. This idea was supported by observed activity in participants' anterior temporal lobe, a language center.

In epilepsy patients, these words were so frequently recalled that subjects often shouted them out even when they were incorrect responses to word-pair inquiries.

Seek, find

Modern search engines no longer simply look for raw words when resolving an inquiry: They also look for semantic — contextual and meaning — connections so that the results they present may better anticipate what it is you're looking for. Xie suggests something similar may be happening in the brain: "You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences."

He also notes that it may one day be possible to leverage individuals' apparently wired-in knowledge of their language as a fixed point against which to assess the health of their memory and brain.

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