In one experiment at a US university, half a class of students was allowed to use internet-connected laptops during a lecture, while the other had to keep their computers shut. Those who browsed the web performed much worse on a subsequent test of how well they retained the lecture’s content. Earlier experiments revealed that as the number of links in an online document goes up, reading comprehension falls, and as more types of information are placed on a screen, we remember less of what we see.
Greenfield concluded that “every medium develops some cognitive skills at the expense of others”. Our growing use of screen-based media, she said, has strengthened visual-spatial intelligence, which can strengthen the ability to do jobs that involve keeping track of lots of rapidly changing signals, like piloting a plane or monitoring a patient during surgery. But that has been accompanied by “new weaknesses in higher-order cognitive processes,” including “abstract vocabulary, mindfulness, reflection, inductive problem solving, critical thinking, and imagination.” We’re becoming, in a word, shallower.
Studies of our behavior online support this conclusion. German researchers found that web browsers usually spend less than 10 seconds looking at a page. Even people doing academic research online tend to “bounce” rapidly between different documents, rarely reading more than a page or two, according to a University College London study.
Such mental juggling takes a big toll. In a recent experiment at Stanford University, researchers gave various cognitive tests to 49 people who do a lot of media multitasking and 52 people who multitask much less frequently. The heavy multitaskers performed poorly on all the tests. They were more easily distracted, had less control over their attention, and were much less able to distinguish important information from trivia.