From David Rock, of HBR and author of Your Brain at Work:
“These types of findings explain the success of social media. We're giving people something that deeply excites the brain in highly condensed form, which keeps them coming back. After all, the brain is built to minimize danger, and maximize rewards, and in a modern society with few real dangers, we focus on the most rewarding activities that take the least effort (minimizing effort is also seen as a reward).
Here's how social the brain is: the brain network that is always on in the background is a region involved in thinking about yourself and other people. This network is so ubiquitous it has been labeled the "default network." When not doing anything else, the brain's favorite pastime is to think about people. We actually turn this region down when we do any active processing, such as doing math. One study showed that inactivity for just two seconds switched the default network back on.
Here is the seed of the problem. Social media can be so rewarding, that it overwhelms our ability to focus on other things. Our brain has terribly weak circuitry for inhibiting impulses, especially impulses that look delicious. Like our limited ability to do complex calculations in our heads, impulse control is a limited resource that tires with each use. For decades, food marketers have used this poor impulse control against us, to the point that there are now literally more people overweight than starving in the world, in large part due to empty calories that are all too readily available. Our minds may be going the way of our waistlines, as a result of "empty neural calories": fodder for the brain that stimulates but doesn't fulfill.
There is a circuitry for "seeking" and a circuitry for "liking." The liking response settles down the excitement of the seeking circuitry. Without the liking response, we're like the rat pressing the level over and over to get a little dopamine hit, forgetting all about food and rest.
The circuitry activated when you connect online is the seeking circuitry of dopamine. Yet when we connect with people online, we don't tend to get the oxytocin or serotonin calming reward that happens when we bond with someone in real time, when our circuits resonate with real-time shared emotions and experiences. On Twitter, you won't feel satisfied the way you might if you chatted in person with 50 people at a conference.
An overabundance of dopamine — while it feels great, just as sugar does — creates a mental hyperactivity that reduces the capacity for deeper focus.
Throughout history, whenever a new technology emerged that dramatically changed how people interacted, it took time for our human practices to catch up. When the automobile first came out, people would drive at all speeds, in every direction. Eventually road rules and speed limits were put in place, and the world was a safer place. Facebook per se is not evil, just as cars are not evil. However our relationship with the automobile is safer overall with some rules in place, combined with good driver education.”