How could researchers determine whether extended use of digital devices leaves people unable to focus? A straightforward test would compare the ability to focus among students who engage in a great deal of digital activity with those who seldom engage in it. Many researchers have taken that tack. They often test children from infancy to about age six separately from older children, reasoning that the young brain is more vulnerable to change.
And the results? For both older and younger children, the average of dozens of studies reveals a modest negative correlation: More screen time is weakly associated with poor attention regulation.
Now, this kind of study has an obvious limitation—it finds a correlation, but correlation is not causation. Thus, although one is tempted to conclude that digital activities negatively impact attention, it’s also possible that children who have greater difficulty focusing attention find digital activities more appealing than children who do not have such challenges.
Researchers have tried to address this problem by conducting longitudinal studies. That means they measure screen time and attention (at, say, age nine), and then measure them again in the same children months or years later. If more screen time at age nine predicts worse attentional control at age 11—even after accounting for the level of attentional control at age nine—that suggests screen time may contribute to later attention problems. Conversely, if worse attentional control at age nine predicts increased screen time at age 11, that indicates that attention difficulties may lead children to use screens more. The temporal sequence can help clarify the direction of causality.
Using this method, most studies of younger (birth to pre-K) or older (K–12) children support the hypothesis that screen time is associated with poorer attentional control. The size of the observed relationship varies, but on average, it’s small.