Analia Marzoratti

Uncovering why some teen brains thrive on multitasking

Reference: Patelaki, E., Foxe, J. J., Mazurek, K. A., & Freedman, E. G. (2022). Young adults who improve performance during dual-task walking show more flexible reallocation of cognitive resources: a mobile brain-body imaging (MoBI) study. Cerebral Cortex, 33(6), 2573–2592.

Teenagers worldwide are commonly thought of as impulsive and rebellious. Evidence is scattered all over popular media, from James Dean’s character in “Rebel Without a Cause” to Katniss Everdeen or Harry Potter. In line with this portrayal, a new study from Patelaki et al. (2023) suggests that the adolescent brain may contradict all our assumptions about the negative effects of multitasking on performance. These researchers used neuroscientific tools to demonstrate just one more example of how adolescents just can’t help contradicting adults, even in the ways that their brains work.

The multitasking brain

In research, “multitasking” means engaging in two tasks at the same time. However, multitasking is a misnomer: the human brain is not built to do multiple things at once (1). A key finding in cognitive psychology and neuroscience research is that when we are behaviorally multitasking, our brain is really just switching quickly between tasks (1,2). Skilled multitaskers are simply speedy task-switchers. However, regardless of how quickly this switch occurs, multitasking still results in neural resources being distributed across multiple brain regions. In an effect called dual task interference, this distributed, competing activity often leads performance on one or both tasks to suffer (2,3). This effect can have serious implications. For instance, if you text and drive, both your grammar and your steering will suffer.

Cognitive-motor interference (CMI) theory

The cognitive-motor interference (CMI) theory suggests that performance is particularly reduced when one engages in cognitive and motor tasks at the same time, calling on completely different brain networks (3). For many, this makes intuitive sense; we stay extra still when we have to think. Many studies show that individuals are less accurate on cognitive tasks performed while walking than sitting, and that they more varied in the patterns and pace of their walking while also performing a cognitive task. However, most of the research used as evidence for the CMI theory has focused on middle-aged or older adults (3). Various dual-task studies have found that, unlike most adults, some teenagers show no CMI effects on their cognitive or motor performance. These teenagers also tend to respond more slowly while walking than sitting, and show steadier, slower walking speeds while performing a cognitive task. Yet few studies have examined how the brain might enable these behavioral trends.

Cognitive tasks in danger of multitasking

            Response inhibition, or the ability to stop, change, or delay a response, is essential for daily life (4). For example, if you get angry at somebody, response inhibition is part of what keeps you from throwing things at them. This skill is commonly studied using a Go/No-Go task. For this task, participants see a series of image or sound stimuli and must press a button for each new stimulus (Go trials) and not press a button if the stimulus is a repeat of the previous one (No-Go trials; seefigure below). Accuracy in not pressing the button for stimulus repeats is a measure of response inhibition. Go/No-Go task accuracy and neural responses to its performance are particularly impacted by dual task interference – that is, people tend to perform worse on the Go/No-Go task when they are attempting another task at the same time (4).

Depiction of the Go/No-Go Task used in the study to estimate response inhibition skill. Participants are instructed to respond on Go trials and withhold response on NoGo trials.
Figure adapted from Patelaki et al. (2023).

How they designed this study

Patelaki and colleagues had 26 young adults (ages 18-30 years) perform a Go/No-Go task (see figure above) in fourteen randomly ordered 4-minute blocks of two conditions: the dual-task (DT) condition during which they walked on a treadmill, and the single-task (ST) condition during which they sat still. For another block, participants walked on the treadmill with no task (ST-walking). Participants wore mobile electroencephalography (EEG) caps throughout to capture the brain’s electrical activity, a direct reflection of neural firing. The researchers measured the consistency of participants’ walking using motion capture technology. Task accuracy was calculated by dividing the number of correct button-presses on Go trials, or hits, by the number of incorrect presses on No-Go trials, or false alarms.  Researchers conducted further analysis comparing brain activity and performance across participants whose accuracy improved while walking (dual-taskers; 14 participants) with those who did not improve, showing the same or lower accuracy while walking (non-dual-taskers; 12 participants).

What the study found

            Surprisingly, the results went against the CMI hypothesis: participants on average scored higher on the task while walking than sitting, with no meaningful differences in response time (see figure below). Both dual-taskers and non-dual-taskers also showed more consistent walking patterns overall when they were also performing the task. Dual-taskers tended to respond more quickly while walking than did non-dual-taskers, but both groups showed about the same levels of accuracy while walking.

Differences between single-task (ST; left) vs. dual-task (DT; right) conditions among the whole cohort of adolescents in (A) accuracy scores, (B) response times (RT) during Go-trials, (C) and walking variability. Figure adapted from Patelaki et al. (2023).

Importantly, though brain activity was similar among non-dual-taskers across conditions, brain responses to Go and No-Go trials among dual-taskers showed differences between conditions. After a correct No-Go trial (when they inhibited a button-press), brain response patterns related to conflict monitoring, or keeping watch for things that stand out, were less intense among dual-taskers while walking than while sitting (5). Before and after false alarm No-Go trials (incorrect button-presses), dual-taskers in walking conditions also showed less intense brain response patterns related to starting motor movements (before) and identifying mismatches between that movement and the task’s goals (after; 5). Most of these cross-condition differences in brain activity showed up in frontal regions related to inhibitory control (4,5). Altogether, this evidence suggests that dual-taskers performed better on the cognitive task while walking due to differences in their brain’s strategies for responding to and learning from error trials. These participants showed differences while walking in their cognitive flexibility, or how they “train” their inhibitory control system based on experience.

Why this matters

This study is among the first to examine the trend of improved young adult performance under dual-task conditions: young adults were more accurate while walking, and walked more consistently while concentrating on a cognitive task. Patelaki et al. provide a neuroscientific explanation for this counterintuitive finding, suggesting that teens whose performance improves when multitasking may show flexible adaptation of systems for controlling (or inhibiting) responses. In sum, though we might think of young adults as impulsive or rebellious, at the level of the brain, it may be that many have more control over their responses than most adults.