When a new and noteworthy study is introduced into the literature, it is important that we as readers evaluate it for its strengths and weaknesses, and take a closer (critical) look in order to decide for ourselves whether its conclusions can be believed without skepticism. So that’s what we’re going to do!

The Study

At the beginning of the month, a Brazilian study was published that explored the possible associations between preschoolers’ screen usage and motor skills. This study assessed children between 4 and 6 years old from 30 preschools in a single Brazilian city. Screen use habits, along with physical activity, sleeping habits, and other behaviours were assessed by interviewing each child’s caregiver(s) and having them fill out a survey. The children’s motor skills were measured using an assessment called the “Motor Development Scale”, which was carried out over 30 minutes by health professionals. This scale, according to the researchers, was able to assess multiple aspects of each child’s motor skills - including fine and global motor function balance, spatial organization, and temporal organization. Each child’s performance in this interview (whether or not they could complete certain tasks) was combined into a score called the “General Motor Quotient” or GMQ, which was finally categorized into either “low motor skills” or “normal or superior motor skills”.

The Findings

A number of interesting findings emerged in this study, including the following:

• Excessive screen use (over 2 hours per day) increased the risk of a low motor skill score by 72%.
• Inactivity increased the risk of a low motor skill score by 90%.
• Appropriate sleep activity (defined by the researchers as 9-11 hours) lowered the risk of a low motor skill score by 51%.
• Daytime sleeping lowered the likelihood of a low motor skill score by 33%.
• Lower motor skill scores were more likely for boys, children aged 5-6, and children born premature or with a low birth weight.
• Lower motor skill scores were more likely for children from middle- or lower-class families. (This is likely due to the fact that children in the upper classes may have more opportunities to participate in activities such as organized sports).
• More than 55% of the children ate while watching television.

While these are some interesting and important claims, we cannot simply walk away with this information - our interaction with the research does not stop here. Now, it is important to evaluate the study’s process as a whole for its positive qualities as well as any limitations.

The Strengths

• Large sample size. This study looked at an impressing sample of 926 children. Because we so often see studies making claims about the entire world’s population of children based on findings from as low as a dozen toddlers being assessed, it is a positive surprise to see a study using a sample this large! When it comes to believing what any given study claims, a study that assesses a larger number of children has taken a larger chunk of the population (all children) into consideration, essentially meaning that the findings from those children will be more applicable to the population that they are coming from.
• Motor skill assessment. This study assessed childrens’ motor skills in a 30-minute session with a trained healthcare professional. The quality of this assessment is much better than other measures of motor skills, which often only entail asking the parents to report on their child’s skill or activity level. This way, with the measure being adminsitered by a professional instead of reported by parents, we are able to get a more accurate assessment of each child’s motor skills - leading to more accurate calculations with these data in the mix.
• Multiple factors. This study looked at many factors that could potentially be contributing to lower motor skill scores. The inclusion of many factors can be seen as the researchers showing transparency - even though they are looking at screen use as the culprit of lower motor skills, they still know that it likely isn’t acting alone. By showing that screen usage is not the only (or even the most important) factor associated with lower motor skills, and disclosing the fact that many other factors are at play in the relationship as well (including sleep and general activity) is ben eficial because it shows us more of the whole picture instead of zooming in unfairly on screen usage.

The Limitations

• Lack of sample diversity. While this study boasted quite a large sample in their research and assessed children from a large number of preschools, it is necessary to note that the entire sample of children was taken from the same geographic region close to one city center - leading to a sample that was not very diverse in terms of location or economic class, as was admitted by the researchers. This is an important limitation for us to remember because, when evaluating findings from research in a different country, it is not always guaranteed that the findings apply cross-culturally. This is especially risky when the sample is limited in diversity, as seen here.
• Dichotomization of motor skills. In this study, the children’s level of motor skill ability was “dichotomized”, or broken up into 2 categories - either low motor skill or normal/superior motor skill. Dichotomization is somewhat frowned upon in research because it limits the conclusions that can be drawn from the study’s results. By using dichotomization, what used to be a spectrum of motor abilities that children can fall anywhere on turns into something of a “yes or no” question which severely limits where children can land. For example, if GMQ was dichotomized with scores under 5 being categorized as “low” and scores 5 and above being “normal/superior”, you can potentially have two children scoring 5.9 and 6.1 on the scale (very similar scores) but being placed into two categories and being evaluated as totally different when the truth is not so extreme. With this being done to the motor skills variable in this study, we lose the opportunity to see fine-tuned differences in motor skills and how they relate to screen usage.
• Cross-sectional research. As I have mentioned in previous blog posts, this is probably the most important limitation in many studies that often goes unnoticed. Cross-sectional research means that in this study, information on the children’s screen usage and motor skills were collected at only one point in time. This means that any child’s change over time due to screen usage cannot be assessed in this study, and that children were instead compared to other children instead of to themselves. Because this research was cross-sectional, we are actually unable to use this study to say that any of the examined factors CAUSES low motor skill scores - we can only say that they are associated with one another, seriously limiting the conclusions that can be drawn from the research.

The Takeaways

To discuss what I believe to be the main takeaway from this study, we have to take a closer look at two specific findings:

• Excessive screen use increased the risk of a low motor skill score by 72%.
• Inactivity increased the risk of a low motor skill score by 90%.

While the proposed links between screen use and low motor skills appears to be large, the link between inactivity in general and low motor skills is even larger. Since the two concepts - screen usage and inactivity - are unfortunately very closely related, it can be argued that what is truly at play here is a link between inactivity in children and lower motor abilities.

In fact, the researchers in this study refer to scren media use as a type of sedentary behaviour in their writing, apparently assuming that the two are one and the same. Here is where my main takeaway comes into the picture.

While screen usage and sedentary behaviour can often be the same thing (i.e. children sitting and watching television or playing on a mobile device), it doesn’t always have to be this way! It is possible to separate screen usage from inactivity - and even to bring screen use into physical activity - by choosing screens for your child that incorporate physical activity, movement, and utilization of motor skills. I have proposed a few ways to do this in a previous blog post.

In conclusion, it may be possible to break the link between screen usage and lower motor skills by breaking the link between screen usage and inactivity - which is, in my opinion, the true culprit in this story.