The longer we spend on a task, the more our thoughts drift away from it. By about 20 minutes in, people report being off-task close to half the time.
That is the conclusion of a large meta-analysis by Anthony Zanesco, Ekaterina Denkova and Amishi Jha of the University of Miami. It was published online in Psychological Bulletin on February 29, 2024.
Half a million answers to one question
Mind-wandering is often estimated to fill 30% to 50% of our waking moments. What was less clear is whether it grows steadily while we are trying to focus.
To find out, the authors searched the literature for studies that interrupted people during a task with “probes” asking whether their attention was on the task or elsewhere. Crucially, they only used studies that shared their raw, participant-level data, which let them model each person’s attention over time.
They found 68 research reports, with almost half a million probe responses from more than 10,000 individuals. Samples came from North America, many European countries and Taiwan, plus online volunteers. The most common task, used in about a quarter of samples, was the sustained attention to response task, a standard laboratory test of attention.
In the studies with simple on-task or off-task answers, people received about 30 probes on average, and the last one came around 26 minutes into the task.
Focused at first, drifting later
Across all those studies, people reported mind-wandering on average about 40% of the time.
At the start, people were roughly three times more likely to say they were on-task than off-task. Then the odds of being off-task rose by about 5.5% with each successive probe and about 6.2% with each additional minute.
That adds up quickly. By the 20th probe, the probability of being off-task reached 46.64%. By the 20th minute it reached 49.33%, nearly even odds.
The pattern was consistent. A significant linear rise appeared in 80% of the individual study samples, 71 out of 89. The authors’ estimates suggest most future studies should see the same climb.
Some tasks hold attention better
The rate of increase varied. Mind-wandering rose more slowly in studies that used more probes or lasted longer overall, though those two features largely went together. Tasks with longer gaps between probes showed steeper increases when the task itself was long.
Task type mattered too. Compared with the sustained attention task, people reading text started out with less mind-wandering, and their mind-wandering grew more slowly over time. Flanker tasks, another attention test, also showed a smaller rise.
The authors note that studies with larger standard errors tended to report larger slopes, a funnel plot asymmetry they report alongside the main results. They link the steady climb to other changes seen within long tasks, such as growing boredom and performance that worsens with time-on-task.
Their bottom line, in the paper’s own summary, is that people “are focused on something other than their current task upward of 50% of the time toward the end of the task.”
Study Details:
- Title: Mind-Wandering Increases in Frequency Over Time During Task Performance: An Individual-Participant Meta-Analytic Review
- Authors: Anthony P. Zanesco, Ekaterina Denkova, Amishi P. Jha
- Journal: Psychological Bulletin
- Publication Date: February 29, 2024
- DOI: 10.1037/bul0000424