Hot off the press
This month, cognitive neuroscientist Duncan Astle from Cambridge University and perceptual psychologist Helen Keyes from Anglia Ruskin University shed light on screen time and the right/left crossover in the brain, and they spoke with Katie Haylor.
Duncan - There’s been in the last 10 15 years, a dramatic rise in the amount of screen time and probably the most salient example of which is social media. So the way in which we interact with each other in a social way has fundamentally changed, and people are increasingly worried that this is having a negative effect on our psychology and in particular and our mental health.
Katie - So tell us specifically about what this paper was looking into.
Duncan - So it's really hard to study because firstly everybody uses social media now, so there are people who are kind of social media and naïve. Essentially all the data we have is correlational, so it's looking at how much screen time you use or the kind of thing you do and relationships with things like mood and feelings, things like anxiety and depression. And of course it's really difficult to disentangle causal relationships.
Last week a paper came out in the Journal of Social and Clinical Psychology which has the great title of No More Fomo, you know what Fomo stands for?
Katie - Fear of Missing Out?
Duncan -. Exactly right. So “No more fear of missing out, limiting social media decreases loneliness and depression”. So what they did which is quite novel is rather just looking at correlational evidence they tried to do an intervention study. They took 150 people, they randomly allocated them to two groups and in one group they were instructed to limit their use of social media to 10 minutes per day per platform. So with a maximum of 30 minutes per day.
So the idea behind it being is that if social media does play a key causal role in people's feelings of depression and loneliness, then limiting it ought to boost well-being. So they followed these people over three weeks and each week they used the Beck depression inventory (a really standard kind of questionnaire checklist for measuring people's mood) and essentially what they found was that the people who were in the limited group did indeed have a significant reduction in feelings of depression and loneliness over the period of the intervention.
Katie - How old were these people? Because you tend to focus on children's development right? So are children particularly vulnerable, do we know if kids are particularly vulnerable to I guess “social media induced fomo”?
Duncan - These are adolescents, these are probably a little bit older than I would often study. So in our lab we mainly study kids who are late primary school but actually lots of young kids have Facebook accounts.
So this study is nice in many ways and it's quite novel. But there are some red flags. Number one as we often say in our lab the devil's in the control group. So what do the control group do and the answer is nothing. The control group is the kind of treatment-as-normal. Responses on questionnaires and checklists can be massively influenced by expectation. And so it's a problem that the control group don't have any kind of intervention, just having a no intervention control group it's very hard for us to know what's really driving the effect.
Second red flag is check carefully that the groups are matched before you start the intervention. So the group of kids who restricted their social media use, they were already using less social media than the other group and it may be that one thing they did in their analysis was only include those children who they think successfully adhered to the intervention and that the more prolific social media users are therefore not included in the analysis. And that could be really really important.
Katie - So bearing in mind what should people take away from this study?
Duncan - It's a nice initial idea of how you can go about studying these things, so seeing whether small short term interventions in people's social media use can have an impact on mood and feelings. But the challenge is in getting the right design and my suspicion is that in reality it's not as simple as saying social media is good or social media is bad. So a study coming out the previous year showed that for the vast majority of teenagers, social media or moderate social media use is a key way in which they engage with their community and they feel like they belong. And that for some individuals who already have symptoms of anxiety and depression, high social media use can exacerbate those symptoms.
Type of social media and context are probably really really important. I’m constantly asked about what is the right amount of screen time for my child. And the answer is there is no amount, probably context and purpose are more important than the overall amount.
Katie - Helen, do you have any thoughts?
Helen - Yes. I think that story sounds really interesting, I'd like to see a study that could disentangle whether it’s not doing social media that might be helpful or whether it's doing something else instead of social media that might be helpful.
So if I wasn't spending time on social media I would more than likely be reading a novel which we know has really strong protective factors for your mental health and it makes you more empathic with other people. So we would really need to control for that by using maybe screen time watching telly or doing something else that is similar to social media but not engaging in the community aspects of that. So that's what I would like to see.
Katie - Helen, Mark has got in touch to ask, “why are we wired so that the right side of the brain controls the left side of our body and vice versa. Wouldn't it just be so much easier if it was the other way around?”
Helen - That's a great question. It's one of the questions I get asked most often in my perception lectures and I love it. We call this idea decussation, where the left hemisphere largely controls movement in the right body and vice versa. And you can see this most commonly if someone's had a stroke or damage to one half of their brain. You can see they will lose movement or lose some function of the opposite side of their body. So we've known about this for a long long time.
There are some really interesting exceptions to this. For example smell doesn't decussate at all, all that information from the left nostril goes directly to the left brain and from the right nostril goes directly to the right brain. Also hearing is partially uncrossed. So in some cases it decussates and in some case it doesn't. So we might ask why this would happen that's the more interesting question. Some people believe it's advantageous to have it this way and indeed if you do large 3D models involving lots of connections and networking, there is a slight advantage which we don't really know why but there is a slight advantage in that you are slightly more robust against wiring errors when you cross over when you decussate, we’re not quite sure why.
But I'm not necessarily a fan of this as a theory in terms of what drives this. Because why then wouldn't smell decussate, why wouldn't hearing completely decussate if it was just advantageous for us to do so? A much more interesting theory is twist theory and it describes a nice evolutionary quirk that might have driven this situation.
We know that invertebrates. So animals and our species that don't have a backbone, don’t decussate so the left side of the brain controls the left side of their body and vice versa. It's only vertebrates that this happens with. So that's quite interesting in and of itself. And if you look at invertebrates, their nervous system comes from the brain largely along their belly, whereas with vertebrates the opposite is true. So our spinal cord goes along our backbone above our digestive tract. It’s a direct flip. And twist theory suggests that at some stage a precursor to the vertebrates twisted its head around 180 degrees.
And it explains quite a lot. It explains obviously why the crossover would happen, but it also takes into account why smell doesn't cross over. So this all happens above where this twist would have happened, the olfactory bulb is right at your nose, so left nostril goes directly to left olfactory bulb without any need for it to have crossed over. And similarly the auditory nerve would come into the brain just where the twist was happening. So that would explain why some auditory processing is crossed and some isn't. So it seems like it's an evolutionary quirk that didn't have any particular reason, that there was no particular advantage, but there hasn't been enough of a driver and of an advantage to detangling for it to change.