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Attention Has Stamina
Concentration is often treated as a fixed trait: some people can grind through a demanding exam, while others inevitably fade. Heather Schofield and Supreet Kaur argue for a more useful model. The ability to sustain mental effort over time, which they call cognitive endurance, behaves less like an immutable talent and more like physical stamina. Performance usually deteriorates during a long task, but practice can slow that decline.
The researchers first noticed the pattern while analyzing standardized tests from around the world with Christina Brown and Geeta Kingdon. Even after accounting for differences in question difficulty, students did worse on items that appeared later in an exam. The decline was not evenly distributed. Children in poorer countries deteriorated at three times the rate of children in wealthier nations.
School routines offered one possible explanation. More affluent students were likelier to spend time reading silently, solving problems independently or otherwise maintaining active focus. Students in disadvantaged schools more often listened to lectures, copied from the board or practiced rote memorization. Those observations could not establish cause and effect, but they suggested that the school day itself might train—or fail to train—the capacity for prolonged thought.
Training the Act of Concentrating
To test that idea, the researchers randomly assigned 1,636 elementary-school students in India to three groups during study hall. A control group followed its usual routine: students copied a few math problems and then spent most of the period as they wished, producing little continuous mental effort. Two other groups practiced concentrating for 20 minutes at a time.
One practice group solved math problems in an adaptive tablet application. The program matched difficulty to each student’s ability but omitted game mechanics designed to capture attention. This group therefore received focused academic practice. The other group worked on adaptive mazes, tangrams and similar puzzles with no academic content. It tested whether repeatedly sustaining attention, rather than rehearsing school material, was the ingredient that mattered.
After six months, with only about 20 to 50 minutes of practice per week, both groups showed nearly the same improvement. Across tests of listening comprehension, reasoning and mathematics, their performance declined 22 percent more slowly over the course of an assessment than the control group’s did. Because academic exercises and nonacademic puzzles produced comparable results, the improvement appears to have come from practicing sustained concentration rather than from learning more math.
The effects also reached beyond the particular tablet activities. Students in both practice groups improved on standardized measures of sustained attention, including reaction-time tasks and searches for target symbols in a grid. Teachers rated them as less fidgety and better able to follow multistep instructions. Their grades in Hindi, English and mathematics were about 0.09 standard deviations higher than those of control students. The authors compare that academic effect with assigning a child to a classroom with seven fewer students per teacher: the concentration intervention produced roughly one half to three quarters of the benefit associated with that smaller class.
A Trainable Skill, Not a Moral Failing
The article connects the experiment to evidence from adult life. Data-entry workers make more mistakes as shifts progress, and the decline is steeper among less educated workers. California voters are also more likely to accept the default choice when a proposition appears later on a ballot, particularly in lower-income neighborhoods. Together, these patterns raise the possibility that unequal opportunities to practice sustained focus in school can compound into later inequalities at work and in civic life.
That broader conclusion remains a hypothesis rather than a direct result of the classroom trial. The experiment shows that brief, repeated practice can improve children’s endurance and grades over six months; it does not establish that weak cognitive endurance causes adult economic or political disparities. Nor does it test the article’s concern that short-form social media is reducing people’s tolerance for mental effort. The authors also acknowledge that research has not yet identified the most effective kind or dose of training.
Still, the comparison between the two practice groups points to a practical lesson. No specialized curriculum was required. Academic exercises and challenging games worked similarly as long as students had to maintain deliberate, active effort without constant entertainment. Puzzles, music practice and some video games may offer comparable training, although that extension still needs testing.
The central insight is both humane and consequential: mental fatigue is universal, and losing focus is not evidence of bad character. Cognitive endurance can be strengthened. In an environment built to make every moment frictionless, regularly doing something difficult for long enough to feel the strain may be exactly the exercise attention needs.