We have lived with a constant companion for more than a decade now. Many people cannot imagine a day without a screen in front of their face. On average we interact two to three hours a day with our smartphones, that is, two entire workdays a week. Why do we spend so much time with these things? Professor Sebastian Markett and colleagues published a study in 2017 about the influence of social networks on the nucleus accumbens. In the interview, he explains what his research is about.

How did this research idea arise?

From a psychological perspective, the smartphone is very interesting. Twelve years ago there were no smartphones and in this short period of time a new technology has turned our lives upside down and completely changed how we communicate and spend our free time. I’ve thought repeatedly about Steve Jobs’ presentation of the first iPhone. He said: ‘Every once in a while, a revolutionary product comes along that changes everything.’ This sentence is very true. Our society has changed greatly since the smartphone. In a study we investigated how much time our test subjects spent with their smartphones. The results were very striking, namely, that we look at the little screen three to four hours a day on average. Our thesis was then that our reward system must play a large role here.

How did you research this?

We programmed an app that was able to record smartphone behaviour. The issue here was not to see what exactly someone wrote or looked at on their smartphone; rather the app recorded how many minutes a day they used their smartphone, how often it was unlocked and how often particular apps were used. Over a time period of five weeks we recorded the key data for the social-media behaviour of 62 test subjects. In the study we concentrated on Facebook and looked at how often the subjects opened Facebook on their smartphones and how long they used Facebook. Thus, for five weeks the data of the test subjects was reported to our server. Afterwards we took high-resolution images of the brains of the test subjects using an MRT scanner. Individual parts of the brain can be measured on these MRT images, and the measurements concerning the reward system – the nucleus accumbens – were then correlated with the data about Facebook usage.

Was is the nucleus accumbens?

The nucleus accumbens is the central interface of our reward system. Everything that brings us pleasure triggers activity in the nucleus accumbens, releasing the neurotransmitter dopamine. Drugs such as cigarettes and alcohol also affect our reward system directly or indirectly. We know from other studies that activity in the nucleus accumbens has a motivating effect.

And what is the connection between the reward system and cell phone usage?

The more time someone spends on social-media apps, the smaller the volume of their nucleus accumbens. The amount of time we use Facebook seems to have such an enormous influence on our brain that it can be demonstrated on a neuroanatomical and a neurophysical level. Thus we see a connection on an anatomical level between Facebook behaviour and our brain structure.

It is, however, completely unclear what this means functionally. We do not know whether the smaller volume of the nucleus accumbens triggers a stronger usage of social networks, or whether, conversely, the increased usage of social networks leads to a change in this region of the brain. Further studies are needed to find out what the ultimate cause of the small reward centre is.

What does that mean for us?

In order to answer this question clearly, we have to find out, first of all, whether the smaller volume of the reward system is the cause of increased Facebook usage, or whether our reward system perhaps shrinks when we consume a lot of social media.

However, it is clear that anything addictive, including drugs, affects the nucleus accumbens directly or indirectly. A connection exists between a decreased volume of the nucleus accumbens and consumption behaviour, for example, with nicotine or alcohol. For this reason, our knowledge about the connection between Facebook consumption and the volume of the reward system is in any case also an initial indication for addition research.

Interview: Paula Pensky

Summer Special "Living together"

Episode 1 with Cultural Anthropologist Prof. Dr. Silvy Chakkalakal

Episode 2 with Sociologist Prof. Dr. Steffen Mau and his new book about his Eastern Homeland

Episode 3 with Economics professor Marcel Fratzscher (Ph.D.) about a strong social state

Episode 4 with Prof. Dr. Patricia Ribault about the French-German project Behavioral Matters