# Smartphone Use During School Hours and Association With Cognitive Control in Youths Aged 11 to 18 Years

## TL;DR

Teenagers use smartphones for a third of school hours, which is linked to reduced cognitive control and attention.

## Contribution

This study provides empirical evidence linking frequent smartphone use during school hours to poorer cognitive control in adolescents.

## Key findings

- Youths spent 2.22 hours of the school day on smartphones, with older teens using them more frequently.
- More frequent smartphone checking was associated with lower inhibitory control, as measured by dʹ scores.

## Abstract

How much are youths using their smartphones during school instruction time, and what is the association of this use with cognitive control?

This cross-sectional study of 79 youths aged 11 to 18 years found that they used their smartphones during every hour of the school day, spending one-third of their school day on their smartphones. This use was associated with reduced cognitive control.

This study’s results suggest that frequent smartphone use during school reflects broader challenges in self-regulation with implications for learning and cognitive development.

This cross-sectional study of adolescents examines whether smartphone use during the school day is associated with poorer cognitive control.

Smartphones are a pervasive feature of adolescents’ daily lives, raising concern about how smartphones are used in contexts such as school that require sustained attention and self-regulation.

To describe youths’ smartphone use during each hour of the school day and examine whether smartphone use during school is associated with poorer cognitive control, a key developmental process underlying academic success.

This cross-sectional study of youths aged 11 to 18 years from the Southeastern US objectively assessed smartphone use every hour for 14 consecutive days between April 8, 2021, and February 2, 2022 (cohort 1), and February 1, 2023, and December 11, 2024 (cohort 2), providing thousands of data points to capture actual engagement.

The iPhone iOS (Apple) screen time report captured smartphone use at every hour. Cognitive control was measured in the older cohort using a go/no-go task, with the signal detection metric dʹ quantifying inhibitory control.

A total of 79 participants (mean [SD] age, 15.10 [2.04] years; 41 [51.9%] female) participated in the study. Youths were using their smartphones during every hour of the school day, spending a total of 2.22 hours of the school day on their smartphones. Youths aged 15 to 18 years spent more time on their smartphones during school hours than those aged 11 to 14 years (mean [SD], 23.28 [18.34] vs 11.57 [16.83] min/h; F1,76 = 28.82, P < .001, η2 = 0.28). Youths spent a mean (SD) of 40.14 (39.56) minutes on social media and 13.85 (25.22) minutes on entertainment apps during school hours. Youths checked their smartphones a mean (SD) of 64.46 (32.83) times during school hours. More frequent smartphone checking was associated with lower dʹ values (F1,28 = 4.8, P = .04, η2 = 0.15), indicating poorer cognitive control.

This cross-sectional study found that youths use smartphones approximately one-third of the school day; this use was associated with reduced cognitive control. These findings highlight the need for school-level policies and digital literacy programs that address not only overall screen time but also habitual smartphone-checking behaviors that fragment attention.