Smartphone checking during school hours linked to impaired cognitive control

Smartphone use among adolescents is nearly universal, with approximately 95% of US teens reporting access to a device and nearly half stating they are online almost constantly.² While the integration of these devices into daily life is well documented, their specific impact on the school environment—a setting requiring sustained attention and academic engagement—remains a significant area of clinical interest.¹

A recent study utilizing passive sensing methods provides a granular look at how smartphone use permeates the school day and its subsequent correlation with cognitive function.

Study design and population

The study included a sample of 79 youths (mean age, 15.10 years) recruited from the Southeastern US, categorized into an older cohort (high school, aged 15-18 years; n = 51) and a younger cohort (middle school, aged 11-14 years; n = 28). Researchers collected objective screen time data through daily screenshots of iOS screen time reports over a 14-day period. This method allowed for the extraction of hourly usage data, specifically focusing on school hours (8 AM to 3 PM).

The older cohort also participated in an in-person laboratory visit to complete an incentive-boosted inhibitory control task (Planet Task). This go/no-go task measured the ability to withhold responses to specific stimuli, with researchers using the signal detection theory metric d' to quantify cognitive control.

Universal use and temporal dynamics

The findings revealed that smartphone use during school is universal; not a single participant in the sample refrained from using their device during school hours. On average, youths spent 2.22 hours of the school day on their smartphones, which accounted for 28.5% of their total daily mean phone use (7.78 hours). Usage occurred during every hour of the school day, with a trend toward increasing screen time as the day progressed—averaging 16.01 minutes at 8 AM and rising to 22.26 minutes by 2 PM.

Significant age differences were observed. The older cohort spent significantly more time on their smartphones during school hours (mean, 23.28 min/h) compared with the younger cohort (mean, 11.57 min/h; P < .001). Interestingly, while younger adolescents logged less screen time during school hours on school days compared with nonschool days, there were no significant differences between the age groups in smartphone use after school hours.

Social media and habitual checking

In the younger cohort, social media and entertainment accounted for 69.8% of total school-hour screen time. Social media use alone averaged 40.14 minutes during the school day.

For the older cohort, researchers tracked “pickups,” or the frequency with which a student checks their phone. Participants checked their devices an average of 64.46 times during school hours, with some participants reaching as many as 143.50 pickups. Every participant in the older cohort checked their phone at least once during the school day.

Impact on cognitive control

The study found a critical distinction between total screen time and the frequency of use. While total screen time during school was not associated with performance on the inhibitory control task, the frequency of pickups was significantly linked to cognitive impairment. Analysis showed a significant association between school-hour pickups and mean d' (P = .04).

Youths who exhibited more frequent smartphone checking during school hours demonstrated lower d' scores, indicating impaired cognitive control. These results support theories suggesting that frequent interruptions and the inability to resist the short-term gratification of checking notifications may deplete attentional resources essential for academic success and self-regulation.

“That adolescents used their smartphones across every hour of the school day underscores the need for school-level policies and digital media literacy initiatives that directly address the impact of smartphone use and social media on adolescents’ cognitive and social well-being,” wrote investigators.

References

1. Telzer EH, Burnell K. Smartphone use during school hours and association with cognitive control in youths aged 11 to 18 years. JAMA Netw Open. 2026;9(3):e261092. doi:10.1001/jamanetworkopen.2026.1092
2. Anderson M, Faverio M, Gottfried J. Teens, social media and technology. Pew Research Center. December 11, 2023.