Submission from Professor Tim Smith and Dr Rachael Bedford to the Education Committee inquiry:

Screen Time: Impacts on education and wellbeing

Professor Tim Smith is Director of the Cognition in Naturalistic Environments (CINE) Lab at the Creative Computing Institute, University of the Arts London and fellow of the Centre for Brain and Cognitive Development, Birkbeck. He is an expert in studying how audiovisual media shapes viewer cognition and learning during viewing and across lifespan. The work of Prof. Smith’s lab has informed international practice in media production, policies around screen time and the experimental techniques used to study the direct impacts of screen media on viewers.

Dr Rachael Bedford is an Associate Professor at the University of Bath and Head of the Bath Babylab. She is an expert in infant neurocognitive development, specialising in the impact of screen time on infant and toddler cognitive development, as well as the emergence of neurodevelopmental conditions such as autism and ADHD.

Our Perspective:

In this submission we will focus our evidence on the below term of reference with a specific focus on early years (0-5 years-of-age).

What is the current understanding of how screen time can support and impact children’s development and educational outcomes, including the effect on concentration and behaviour?

Evidence:

The cognitive foundations for a child’s eventual educational success are developed in the first few years of life. Neural plasticity is greatest during infancy and toddlerhood, a period during which screen time is increasingly present due to the ease of use of portable touchscreen devices, potentially amplifying the impact such use has on cognitive development and health. However, research on screen time in 0-5 year-olds is relatively sparse, often limited to more established technologies (e.g. TV) and correlational, lacking the rigorous methods required to attribute causality.

We will focus our evidence review on three interrelated developmental factors that are important for children to concentrate and self-regulate their behaviours in an educational context: attention, executive function, and sleep.

Does screen time impact children’s attention and executive function?

• A young child’s ability to control how they attend to one part of their sensory world over another is a critical cognitive skill developed during the first few years of life that predicts later concentration abilities, self-regulation behaviours and executive functions (a suite of cognitive abilities including attention control, inhibition, working memory and cognitive flexibility; Hendry, Jones & Charman, 2016; Rothbart, Sheese, Rueda & Posner, 2011).
• Attentional selection results from the interaction between exogenous control (stimulus-driven and automatic, e.g. looking at a flashed cue) and endogenous (goal-driven and voluntary, e.g. inhibition of looking to a distractor) processes which can be studied by recording eye movements even in pre-verbal infants (Smith & Saez De Urabain, 2017).
• Although largely under genetic control, the development of attention is also subject to environmental influences (Posner, Rothbart & Voelker, 2016), including the intensely artificial sensory stimulation of screen media.
• Studies investigating associations between early screen media exposure and attention have reported greater attentional problems and greater Attention Deficit and Hyperactivity Disorder-related (ADHD) behaviours in children who have more screen time (Zimmerman & Christakis, 2007; Nikkelen et al., 2014). However, these effects are moderated by socioeconomic backgrounds, parenting style and the educational-appropriateness of the content (see Kostyrka-Allchorne, Cooper and Simpson 2017 for review).  When the TV content presented is age-appropriate or scaffolded by parental support, the longitudinal impact of TV exposure on developmental outcomes either goes away or becomes beneficial (e.g. Barr, et al. 2010).
• The above evidence is based on correlational evidence which cannot be used to attribute causation to the screen time exposure due to their inability to show the direction of effects or to fully discount confounding factors. Direct evidence of immediate changes in attention control is provided by studies in which children have been shown different types of screen content and the immediate changes in attention control are objectively measured. For example, exposure to fast-paced fantastical cartoons have been shown to impair children’s executive functions and inhibitory control and quicken exogenous attention more than exposure to less-intense educational content (Lillard and Peterson 2011; Kostyrka-Allchorne, Cooper and Simpson 2017).
• In our research, we have shown that these immediate screen time impacts may be due to the intense audiovisual design of children’s entertainment TV increasing exogenous control of attention whilst endogenous control is overloaded due to the complexity of comprehending the content (Smith, Mital & Dekker, 2021; Essex, Gliga, Singh & Smith, 2022). Media content designed to be age and developmentally-appropriate, place less demands on immature attention and cognitive capacities and as a consequence show less immediate impacts on attention control (Essex, Gliga, Singh & Smith, 2022). Exposure to such high-quality content has also been shown to be associated with better executive function in children, especially those from lower socioeconomic backgrounds (Linebarger, Barr, Lapierre and Piotrowski, 2014)
• The increase in infant and toddler use of touch screen devices (Bedford et al., 2016) may amplify effects, as these portable devices bring the intense visual stimulation into the hands of the child. We undertook the UK’s first longitudinal study of touchscreen use and cognitive development: the Leverhulme Trust and Wellcome-funded Toddler Attentional Behaviours and Learning with Touchscreens (TABLET) project. Infants were recruited into our study based on whether their daily exposure to touchscreen devices (mobile phones or tablets) was above (High Users) or below (Low Users) the average at 12 months-of-age (10 minutes). Their attention and visual processing abilities were assessed using screen-based gaze-contingent eye tracking tasks in the lab at 12-months, 18-months and 3.5-years-of-age. We found that High Use infants exhibited greater exogenous control of attention (they were faster to look at the odd-one-out; Portugal et al. 2020; 2021), but had poorer endogenous attention control i.e. they were slower to disengage and shift attention and they were more likely to look towards an irrelevant distractor instead of learning to inhibit this as required by the task (Portugal et al. 2021).
• To investigate whether high touch screen use was related to behavioural differences in contexts similar to a classroom we administered a battery of executive function assessments at 3.5-years-of-age, e.g. a spin-the-pots memory game and snack delay inhibitory control task (Portugal et al. 2023). Children who had high touchscreen use showed significantly reduced working memory and cognitive flexibility. This effect became non-significant when controlling for background TV, suggesting that these effects may be due to the overall media environment not specifically to touchscreen exposure. Impulse/Self-control was not significantly associated with touchscreen use but was negatively associated with non-child-directed television (i.e. more TV exposure associated with lower impulse control; Portugal et al. 2022). The longitudinal design of the TABLET study allowed us to control for pre-existing confounds such as age, sex, socioeconomic status, child IQ and temperament as these were matched in the High and Low Users at the start of the study (12 months-of-age), suggesting that the screen exposure may be the driving factor in these EF differences.
• Both the attention control and EF differences between High and Low Users were only significant when considering concurrent touch screen use or stable high versus low use over the last 2.5 years, meaning that it isn’t clear whether it was the earlier exposure that led to later developmental differences or the current exposure having a short-term impact.
• Our evidence of negative associations between greater touchscreen use during toddlerhood and poorer EF (specifically working memory and cognitive flexibility; Portugal et al, 2022) mirror earlier associations reported between TV exposure and EF (e.g. Zimmerman & Christakis, 2007; Nikkelen et al., 2014) although further nuanced studies are required to capture how different types of touchscreen use including parental involvement, interactivity and the educational nature of content may moderate these associations similar to what has been shown for TV (Linebarger et al., 2014). The need for further precision in capturing how toddlers are using touchscreen devices is emphasised by conflicting evidence of EF associations with some studies reporting negative associations between touchscreen use and inhibitory control (McNeill, Howard, Vella, and Cliff, 2019; Lawrence, Narayan, and Choe, 2020) but no associations with working memory or cognitive flexibility, whilst other studies show the opposite pattern of effects, similar to our TABLET findings (Lui, Hendry, Fiske, Dvergsdal, & Holmboe, 2021).
• Conclusion: The evidence presented above shows an established pattern of negative associations between screen time (both TV and touchscreen use) and individual developmental differences in attention and executive function in 0-5 year-old children. Such cognitive skills are essential for children to concentrate and regulate behaviour within educational environments. However, the absence of intervention studies in this area mean that caution should be taken before interpreting these differences as being caused by the screen exposure independent from other confounding factors such as family socioeconomic status, parenting style, the age-approrpriateness of the screen content or its interactivity. More rigorous scientific evidence is needed.

Does screen time impact children’s sleep?

• During the first few years of life children spend a substantial proportion of their time sleeping. Sleep is vital for brain maturation, clearance of neurotoxins and insufficient quality sleep has a significant negative impact on child development (Mindell et al., 2010). Atypical sleep patterns in the first two years of life are associated with impaired physical, emotional, social functioning (Magee, Gordon & Caputi, 2014) and long-term mental, physical health problems, lower cognitive and academic performance (Kelly, Kelly, & Sacker, 2013). The negative impacts of sleep on development are amplified during this age range due to heightened neural plasticity.
• Media use has in adults and older children has been frequently linked with inadequate sleep in children and adolescents (see Cain & Gradisar, 2010 for review). There is high consensus across studies for a consistent pattern linking increased screen time with shorter total sleep time and delayed bedtime (Lund et al., 2021).
• Similar evidence for the negative association between screen time on sleep quality in infants and toddlers is also beginning to emerge. Using parent-report screen time and child sleep questionnaires, studies have reported a significant effect of screen time on sleep: increased amount of TV viewing is associated with parent-reported sleep problems (Garrison, Liekweg & Christakis, 2011), shorter night-time sleep duration (Cespedes et al., 2014), reduced quality of sleep (Brockmann et al., 2016), and irregular naptime and bedtime schedules (Thompson & Christakis, 2005), adjusting for known confounds including socioeconomic status. These studies predominantly focus on associations with TV, failing to capture the recent dominance of mobile screen use in young children (OfCom, 2023).
• To investigate how toddler touchscreen use related to sleep we conducted an online survey of 715 parents of 6- to 36-month-olds across the UK reporting on child media use (daily exposure to TV and use of touchscreens), sleep patterns (night-time and daytime sleep duration, sleep onset - time to fall asleep, and frequencies of night awakenings; Cheung Bedford, Saez De Urabain, Karmiloff-Smith & Smith, 2017). Controlling for age, sex, TV exposure and maternal education, we found a significant association between higher touchscreen use and reduced night-time sleep, increased daytime sleep and longer time to fall asleep (sleep onset). Our results showed that increased touchscreen use was associated with decreased overall amount of sleep (night time and naps combined) such that for every hour of touchscreen use there was an overall reduction in sleep by 15.6 minutes.
• Our findings have subsequently been replicated in samples across the world (Axelsson et al., 2022; Morman, Morgan & Adams, 2019; Twenge, Hisler & Krizan, 2019).
• Whilst the evidence for negative associations between screen time and sleep in childhood are well established (Viner, Davie & Firth, 2019), causal evidence that it is the screen exposure itself driving the effect, or an understanding of the underlying mechanism (i.e. melatonin suppression by blue light exposure; increased physiological arousal; displacement of other healthy bedtime routines) is lacking.
• In adults, intervention studies have demonstrated the causal impact of screen time on sleep by comparing matched screen/non-screen content immediately before bed (Chang et al., 2015). In a recent review of interventions, Martin et al. (2021) state that it is not possible to know whether screen time causes sleep changes in children independent from other pre-bed changes created by interventions.
• Conclusion: There is substantial evidence of negative associations between screen time and sleep problems in older children and adults and emerging equivalent evidence in infants and toddlers, including specifically associated with mobile screen use. Sleep problems are known to have a major impact on a child’s immediate concentration skills the next day and long-term problems can impact their ability to develop the cognitive skills required for concentration and self-regulation in a classroom. However, the absence of specific screen time interventions in young children means that caution should be taken when interpreting the screen exposure as causing the sleep problems. Further studies are required to understand the influence of individual differences on these effects or whether they can be moderated by the type of content and context of screen use.

Next steps and overall summary

• In order to understand if screen time is causing developmental differences in attention, executive function and sleep intervention studies in which a child’s screen use is altered are needed. Evidence from such intervention studies would provide robust motivation for policy and practice change around how children, parents and educators are advised about the pros and cons of screen time.
• To address this need, we are currently conducting the first pilot and feasibility randomised controlled trial (RCT) of a parent-administered screen time intervention (PASTI) and its impact on attention and sleep in 18-30-month-old children (ISRCTN 58249751; supported by Nuffield Foundation).
• In parallel to the PASTI RCT, we are conducting an extensive series of engagement activities with families and early-years educators in order to understand the daily challenges they face around screen time with 0-5 year-olds. These activities have confirmed that the rapidly changing technological landscape is causing confusion and fear about how best to use screen time to promote healthy child development. The inadequacy of the scientific evidence and the time lag between the adoption of new technologies by families and the research understanding their impacts on children is too great for early-years practice to be based on current evidence. Further targeted funding for research studies to fill this gap is urgently required.
• Returning to the main terms of reference for this submission, the current evidence suggests that 0-5-year-old children’s development of concentration, self-regulation behaviours and sleep may be negatively associated with unconstrained screen time (both TV and touchscreen use) but there is limited evidence that screen time is causing these differences. It is currently unclear whether the use of developmentally-appropriate content (e.g. educational TV) presented at times other than the hour before bed may protect against these negative associations and perhaps even support development in some children. More precise research methods for measuring types of screen use in children and targeted intervention studies are required to guide future constructive use of screen time in young children.

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