Susan Buhrs

Over the course of the past years, the intensity of the use of Touch Screen Devices (TSDs), such as smartphones and tablets, has increased enormously. Children – in all age categories – are known to be one of the greatest user groups: statistics show that 70% of 10-year-old Dutch children own a smartphone, increasing to almost 100% in children aged 13 and older. With these numbers, public concern has risen with regard to potential negative effects of TSD use on their health and daily lives. With news headlines firmly stating a proposed negative effect of TSD use in children (e.g. “How smartphones weaken attention spans in children and adults” and “Children who spend seven hours or more on smartphones and tablets are changing the structure of their brains and risking lower IQs and declining memory and cognitive function”) and current scientific literature not being extensive enough to close this debate, the societal relevance of this research question becomes clear. Although current scientific output tries to answer several questions, a lot is still left to be discovered.

Because of this scientific gap, the global goal of this thesis is to explore a possible relation between TSD use and the health of children and young adults. To do so, the first goal is to gain more insight into the relation between TSD use and several domains of neuropsychological functioning in young children (goal 1). Second, an attempt is made to make statements about the association between TSD use and the physical, and also briefly the mental, health in children (goal 2). Lastly, an explorative experiment was performed in a young adult to gather some first results on a potential association between the emission of radiofrequency electromagnetic fields – as caused by TSDs – and heart rate variability (goal 3) as a marker of general health.

Methods

Before describing the goals, the set-up of the studies in this thesis is briefly described. For goals 1 and 2, 38 children aged 5 – 11 from a Dutch primary school were included. Neuropsychological tasks were conducted by a standardized protocol and their individual health was mapped out via an interview, focusing on the incidence and severity of headache, abdominal discomfort, mood complaints and general health complaints. TSD use was measured via an interview, specifying among others the amount of use and content of use of TSDs. For goal 3, an experiment was performed in psychophysiological laboratory, which provided the opportunity to explore the link between radiofrequency electromagnetic fields (RF-EMF) – as emitted by TSDs – and heart rate variability (HRV), a marker of global health.

Goal 1: Exploring the relation between TSD use and neuropsychological functioning in children

The first goal of this thesis was to explore a possible association between the intensity of TSD use and neuropsychological functioning in 5 – 11-year-old children.

Neuropsychological – or neurocognitive – functioning is a broad concept and can be seen as a collection of specific brain functions that are necessary for everyday life. In this thesis, three cognitive domains were mainly focused on: interference suppression, working memory and nonverbal intelligence.

Interference suppression

Suppressing interfering information is something humans do on a daily basis. It is a necessary skill to control one’s mental processes and responses, to ignore an internal or external prompt, and to perform an alternative action. Preschool years is the period in life in which this skill develops rapidly.

Scientific literature on the potential association of TSD use and interference suppression, is scarce. Some studies describe a negative relation between the amount of mobile use and performance on an interference suppression task in young children and adults. A so-called reduced ability to filter out interference is described as one of the possible causes of this effect.

In this thesis, a cross-sectional study was performed on the association between TSD use and interference suppression, as measured by the Bivalent Shape Task (see chapter 2 for the psychometric properties of this task). The Bivalent Shape Task was administered as a digital task. Logically, one would expect the reaction time in response to interfering stimuli to be shorter in older children than in younger children. This was indeed found. However, in our study sample, TSD use was associated with a much smaller difference in reaction time when comparing older children with moderate to high TSD use to young children with moderate to high TSD use (chapter 3). Potential causes or mediating factors for this finding may be found in changes in the electrophysiological level of brain activity or a difference in attention keeping skill.

In addition, a gender-specific effect was observed: in the group of children with moderate to high TSD use, the older boys demonstrated a longer RT than the younger boys (with a vice versa effect for girls). A potential explanatory factor for this finding may lie in a different content of TSD use for both genders, but much is still left to be explored.

Working memory

Next to interference suppression, working memory is also a key neuropsychological function, and also develops enormously during childhood.

In current scientific literature, several studies have reached consensus that the mere presence of one’s own smartphone reduces the performance in a working memory task in students: lower accuracy and longer response time are observed. So-called ‘Fear of Missing Out’ (FoMO) is considered to be a moderating factor on the effect of smartphone presence: the higher the level of FoMO, the greater the decrease in performance. It should be noted that not all evidence points in the same direction; next to the proposed effects of smartphone presence on working memory, it has also been described that gaming, performed on TSDs, is (weakly) positively associated with working memory performance. Comparable research in younger children is not available.

In this thesis, the digital version of the Corsi Blocks Tapping Task was used to assess working memory performance in children (see chapter 4). The results of our study show that moderate to high TSD use significantly decreases the odds of answering a memory task item correctly for girls, but significantly increase the odds for boys. Additionally, there are strong indications that moderate to high TSD use is related to an increase in the Corsi Span and the cumulative score in boys, but not in girls.

This finding could potentially be explained by two hypothetical mechanisms related to the positive correlation between gaming – which is one of the main reasons boys use a TSD - and working memory. The first hypothesis is called the ‘core training hypothesis’. This hypothesis states that repeated strain on a cognitive system induces plastic changes in its neural substrates and therefore an improvement in performance. The second hypothesis is called the ‘learning to learn hypothesis’, which describes the improvement in skills that are used in many different situations, such as rule learning and cognitive resource allocation.

Nonverbal intelligence

A potential relation between TSD use and nonverbal intelligence has been under debate for quite some time now. The fact that TSDs are currently often used in the educational setting to enhance learning, makes this debate even more relevant and at the same time more complicated.