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Media multitasking 'brain shrink' claims unproven


Are there too many screens in your life?

"Multitasking makes your brain smaller," the Daily Mail reports. UK researchers found that people who regularly "media multitasked" had less grey matter in a region of the brain involved in emotion.

brainThe researchers were specifically interested in what they term media multitasking; for example checking your Twitter feed on your smartphone while streaming a boxset to your tablet as you scan your emails on your laptop. In the study, 75 university students and staff were asked to complete a questionnaire about their media multitasking habits. The researchers compared the results with MRI brain scans and found that people with the highest level of media multitasking had a smaller volume of grey matter in a region of the brain called the anterior cingulate cortex (ACC), which is believed to be involved in human motivation and emotions.


The clinical implications are not clear - motivation and emotions were not assessed and all of the participants were healthy and intelligent. Importantly, this study was essentially a single snapshot in time so it cannot prove cause and effect. The idea that this section of the brain has shrunk was not established by this study. It may be that people who used more media forms had a smaller size of this area of the brain to start with, and this could have influenced their media use.


Where did the story come from?
The study was carried out by researchers from Graduate Medical School in Singapore, the University of Sussex and University College London. It was funded by the Japan Science and Technology Agency. The study was published in the peer-reviewed medical journal PLOS One. PLOS One is an open access journal so the study is free to read online. The Daily Mail's reporting of the study gives the impression that a direct cause and effect relationship between media multitasking and brain shrinkage has been proven. This is not the case.


The Daily Telegraph takes a more appropriate and circumspect approach, including a quote from one of the researchers who points out that further cohort-style studies are required to prove (or not) a definitive causal effect.


What kind of research was this?
The researchers say that existing literature on the topic has suggested that people who engage in heavier media multitasking have poorer cognitive control (ability to concentrate and focus on one task despite distractions, to flexibly switch between thoughts, and to control thinking and emotions).

They conducted this cross-sectional study to see if there was an association with increased media multitasking and any differences in the size of the grey matter in the brain. As this was a cross sectional study it cannot prove causation - that is, that the level and combination of media use caused the brain to shrink. The study can't inform whether there has been any change in brain size at all or whether people with increased media use already had this brain structure.


A better study design would be a prospective cohort study that carried out regular brain scans of people over time from a young age to see whether their level of media use (for example through work or study) influenced their brain structure. However, aside from any ethical considerations, it is likely there would be significant practical difficulties with such a study design; try telling a young person that they couldn't text while watching TV for the next five years and see how far that gets you. Also a cohort study would still be likely to be subject to potential confounders.


This cross-sectional study finds an association between higher media multitasking and a smaller volume of grey matter in the ACC portion of the brain that is believed to be involved in human motivation and emotions.


Despite the apparent link, a key limitation of the study is that, being cross-sectional, its assessment of brain size and structure has only provided a single snapshot in time, at the same time as assessing media use. We do not know whether there has actually been any change in the person's brain size at all. The study cannot tell us whether using multimedia has caused this area to reduce in size, or conversely whether having this reduced ACC size influenced people's use of more media forms at the same time.


Furthermore, motivation, emotions and ability to concentrate were not assessed in any of the participants, so it is unclear whether the observed differences in volume had any clinical relevance. The media makes reference to previous studies that suggested an association with poor attention, depression and anxiety, but this was not assessed in this study. It should also be noted that all the participants were educated to at least undergraduate degree level, implying a high level of cognitive control.


Further study population bias included that they were only selected if they had familiarity with computers and media technologies so there was no control group who did not use as many multimedia types.


Another limitation of the study is that the media multitasking score is unlikely to be precise, as it was reliant on the participants accurately estimating the amount of time they spent using each media type per week, and how much time there was cross-over of activities.


Overall, while of interest, this study does not prove that using multiple forms of media causes the brain to shrink.





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