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  • Writer's pictureJakob Nielsen

Infant Screen Use Leads to Reduced Cognitive Skills at Ages 4 & 9

Summary: Should infants be heavy users of tablets and television? Two studies comparing children over time raise a cautionary flag because early screen use (at 12 months of age) was correlated with a drop in cognitive scores at ages 4 and 9. A study at 2 and 3.5 years of age found less harmful effects.

Two studies of infants’ use of screens at age 1 both find that extensive screen use leads to problems later in childhood. Having several studies come to the same conclusion, despite differences in research methodology, always strengthens my belief in the findings. A third project studied toddlers aged 2 and 3.5 years and found only minor harmful effects when the same children were remeasured at age 5.5.

Study 1: Singapore Brain Scans

Evelyn Law and 14 colleagues from the National University of Singapore and several other research labs studied a group of 437 Singaporean children when they were aged 12 months, 18 months, and 9 years. The top-line finding was that additional screen use at 12 months led to a drop at age 9 in executive function, as measured by cognitive testing and assessed by the children’s teachers.

(Here, “executive function” does not refer to behaving like a corporate vice president. Instead, it’s a set of mental processes that enable people to successfully plan, focus attention, remember instructions, and juggle multiple tasks. These higher-order cognitive abilities are essential for managing time, paying attention, changing focus, planning and organizing, and remembering details.)

More specifically, each additional hour of daily screen use at 12 months was associated with a drop of 1.42 scaled score points in the executive function testing at 9 years of age. Making sense of these numbers is hard, and there’s also the problem that the original data was collected in 2010, at a time when computer tablets were rare. (The iPad was launched that year but was not in common use yet.) The authors refer to “screen use,” which they measured without differentiating between computers, tablets, mobile devices, and televisions.

Think of our children and their future. What age is appropriate for them to interact with computers? The study suggests we must wait longer than the first year of life. (Image by Midjourney.)

Of course, if you want to follow a cohort of experimental subjects over many years, the first data will inevitably be old by the time the study is published. So I’m not criticizing the scientists, just pointing out that more research would be beneficial for today’s technology environment.

The authors are particularly excited about their measurements taken when the children were 18 months: at this age, the kids were subjected to electroencephalography (EEG) scans of their brain function, and the research documented a correlation between these brain scans and both the study participants’ screen use when they were 12 months old and their cognitive function when they were 9 years old.

Thus, the EEG scan can provide an early warning of the potential harms of various technology use at a life stage when infants can’t complete traditional IQ tests. For example, in the picture below, the left brain scan is averaged across children who had less than one hour of daily screen time half a year before the test, whereas the right scan is averaged across children who had more than four hours of daily screen time. The scans show a value called relative theta, which makes no sense for those of us who are not neurologists. Still, the important points are that (a) it’s correlated with a decline in cognitive function 7.5 years later and (b) it’s also correlated with screen use 6 months earlier. Therefore, these brain scans are important for researchers, even if they are not a practical tool for parents.

Illustration from the paper.

A possible explanation given in the paper is that infants have difficulty processing video content, a phenomenon known as video deficit. Understanding complex and unfamiliar screen content (usually designed for older children and adults) requires substantial cognitive resources in the form of bottom-up attention. This leaves insufficient resources for prefrontal, top-down attention, affecting the typical development of executive functions.

Study 2: Japan 4-Year Study

Ippei Takahashi and many colleagues from Tohoku University and other medical research facilities in Japan conducted a longitudinal study of 7,097 children assessed at ages 1, 2, and 4. In contrast with the Singapore study, no brain scans were collected. Still, on the other hand, the Japanese researchers could follow 16 times as many kids, giving them greater statistical power and the ability to measure more details.

At age 1, children were assessed for the average amount of screen time spent per day. This data was collected between 2014 and 2018 — several years later than the Singapore data. This timing means that participants might have been using tablets, though the paper doesn’t report on the specific devices used by the children when they were 1.

The children were studied again when they were 2 and 4 years old, using the Ages & Stages Questionnaires, Third Edition. This is a well-validated research instrument that asks parents to rate their children for communication (babbling, vocalizing, and understanding), gross motor (arm, body, and leg movement), fine motor (hand and finger movement), problem-solving (learning and playing with toys), and personal and social skills (solitary social play and playing with toys and other children). It’s certainly a weakness that this study relied on parents’ observations. In contrast, the Singapore study performed cognitive testing supplemented with teachers’ ratings of their students, which are probably somewhat more objective than parents’ ratings of their offspring. Still, in the Japanese study, all participants were rated the same way, and the research instrument is highly credible, based on past research. So whether we believe the absolute score for a specific child, the relative differences between groups of children should be valid.

In analyzing the findings, the researchers controlled for many covariants likely to impact children’s intelligence, such as household income, the mother’s educational attainment, maternal postpartum depression, and maternal bonding disorder. After removing the effects of the covariants, significant results were found from the children’s screen time at age 1 relative to their degree of developmental delay at age 4.

The baseline was considered to be children with one hour or less of screen time per day at age 1. Unfortunately, this group was not further subdivided so that we can tell if, for example, half an hour per day results in the same score as a full hour or whether there would be benefits from reducing screen time even further, below the one-hour limit. (The current WHO recommendation for infants is an hour or less of screen time per day, but that doesn’t necessarily mean this is the optimal limit.)

Relative to this baseline of one hour or less per day, scores were substantially worse at age 4 for those kids who had used screens for 5 hours or more per day when they were one. So, 3 years later, one can still measure the impact of extensive screen use in infants.

The developmental-delay scores at age 4 were as follows for children with 4 hours or more of daily screen time at age 1. (All scores are relative to a value of 1 for children with an hour or less of screen time at age 1.)

  • Communication: 2.68

  • Problem-solving: 1.91

  • Personal and social skills: 1.60

  • Gross motor skills: 1.44

  • Fine motor skills: 1.35

I’m not generally discussing the scores collected when the children were two years old because I find the long-term effects more interesting. But it’s worth noting that the developmental delay in fine motor skills was much worse at age 2 than 4 (1.74 at age 2, dropping to 1.35 at age 4). It’s possible that any adverse effect from screen use on fine motor skills is only temporary and might have fallen further if the children had also been measured at age 6. (Though we don’t know. I’m merely speculating here.)

The scores for communication, problem-solving, and personal/social skills were also worse for children with 2-4 hours of screen use at age 1, though not as bad as for the 4+ hours group. Interestingly, the two motor skills scores were better for this group, though the differences were not statistically significant. Thus, either there was no impact on motor skills from 2-4 hours of screen use, or such moderate screen use might have given those kids a slight leg up, maybe due to early practice interacting with user interfaces.

Study 3: French Study of Toddlers Aged 2 and 3.5 Years

Shuai Yang from the Université Paris Cité and Université Sorbonne Paris Nord in France and many colleagues presents findings from studying 13,763 French children at ages 2, 3.5, and 5.5 years of age.

In contrast to the first two studies (which tested infants at age 1), the new study only finds a minor negative impact from screen use at age 2 when the same children were tested at age 5.5. An interesting detail from the new research is that screen exposure during family meals (when the children were 2) had a much worse impact on their cognition at age 5.5 than screen use at other times of the day. This is true even if the “screen use” was a TV running in the background. The effect of watching TV during meals was more than 10 times worse than the effect of a 1-hour increase in screen time daily.

The research highlights that TV during family meals disrupts children’s auditory and visual focus, reducing effective communication between parents and children. This challenges a child's capacity to understand language sounds and to articulate themselves.

Several key differences between the new research and the previous studies:

  • The French study concerned screen use at age 2, whereas the Japanese and the Singapore studies concerned screen use at age 1. These studies show that screen use at age 1 is much more damaging than screen use at age 2.

  • The French study controlled for more factors than the two Asian studies. In particular, the French researchers measured the children’s intelligence at age 2 and collected various patenting measures that were not available in the two Asian studies. Controlling for these additional factors reduced the size of the effect that was attributed to screen use at age 2.

  • The new study had a less-detailed metric for screentime exposure, lumping all use of 2 hours or more per day into a single category. This may have led them to miss the impact of extensive screen use of 4 hours or more, which was especially detrimental in the two earlier studies.

While more research is undoubtedly needed for practical recommendations, for now, it’s probably safest to let little kids focus on physical play instead of spending too much time in the virtual world. (“Kid playing” by Midjourney.)


  • Evelyn C. Law, Meredith X. Han, Zhuoyuan Lai, Shuping Lim, Zi Yan Ong, Valerie Ng, Laurel J. Gabard-Durnam, Carol L. Wilkinson, April R. Levin, Anne Rifkin-Graboi, L. Mary Daniel, Peter D. Gluckman, Yap Seng Chong, Michael J. Meaney, and Charles A. Nelson (2023): “Associations Between Infant Screen Use, Electroencephalography Markers, and Cognitive Outcomes,” JAMA Pediatrics 2023;177(3):311-318. doi:10.1001/jamapediatrics.2022.5674

  • Ippei Takahashi, Taku Obara, Mami Ishikuro, Keiko Murakami, Fumihiko Ueno, Aoi Noda, Tomomi Onuma, Genki Shinoda, Tomoko Nishimura, Kenji J. Tsuchiya, and Shinichi Kuriyama: “Screen Time at Age 1 Year and Communication and Problem-Solving Developmental Delay at 2 and 4 Years.” JAMA Pediatrics 2023, Published online August 21, 2023. doi:10.1001/jamapediatrics.2023.3057

  • Shuai Yang, Mélèa Saïd, Hugo Peyre, Franck Ramus, Marion Taine, Evelyn C. Law, Marie-Noëlle Dufourg, Barbara Heude, Marie-Aline Charles, and Jonathan Y. Bernard (2023): “Associations of screen use with cognitive development in early childhood: the ELFE birth cohort.” Journal of Child Psychology and Psychiatry

This article was first published on August 7, 2023, was updated on August 28, 2023, adding Study 2, and updated again on September 18, 2023, adding Study 3.


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