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6 Degrees of Your Brain

Your brain is fantastically well connected, giving it immense creative power.

Key points

  • Anyone on earth is only about four friendships away from anyone else.
  • Being separated by only a few hops gives power, both for social networks and brain networks.
  • All of the regions that compose your brain are only about two degrees of separation from each other.
  • Creativity is enhanced when we make new connections among ideas in our brains.
 Gage Skidmore/Flickr
Kevin Bacon.
Source: Gage Skidmore/Flickr

You are probably familiar with the idea that anyone on earth is just six degrees of separation from anyone else on the planet. Each degree corresponds to one friendship link in the web of a social network.

Six degrees of separation is why the Kevin Bacon parlor game works: any film star can be connected to Bacon by way of six or fewer shared productions. Elvis Presley, for example, is two degrees away from Bacon, and most other actors are a similar distance on the network. While Bacon is especially well connected in Hollywood social networks, the rest of us are also quite close to each other. Remarkably, we are likely closer than six degrees away from each other: a recent study of Facebook friend networks put the value at about four.

People are endlessly fascinated with the interconnectedness of humanity, and with good reason. It is a unifying and hopeful way of thinking about our shared world. Our vast web of relationships has supercharged human endeavor in the modern, globalized world.

What is it about the structure of our friendships that makes us all so well connected, and granted us this power? Social networks achieve what is called “small world” connectivity. The reason that you can reach anyone via just a few friendship links is obviously not because you are friends with everybody. Instead, most of your friends are probably nearby, or at least in the same state or country, while a handful of your friends are more distant—perhaps on the other side of the world. In addition, you may have friends who are very well connected across continents, giving you easy access to their jet-set networks.

 Daniel Graham
A portion of a brain network.
Source: Daniel Graham

It turns out that your brain is also a small world. Dividing the brain up into a few hundred regions, the latest high-precision studies indicate that any brain part is very close to practically every other brain part. In fact each brain region is probably about two degrees of separation from almost any other (in monkeys). Many areas, including core regions for vision, touch, and motor control, are just one degree away: they are directly connected to each other.

Each brain region is made up of millions of neurons. So how close is a neuron in one region to any neuron in another region? Though comprehensive data are lacking, the value is probably about three or four degrees of separation for most pairs of neurons. Clearly, the brain is supremely well connected.

As with social networks, the brain achieves this connectivity through a mix of local connections and longer-distance links. No part of the brain is connected to every other part, like a telephone switchboard. Most of a brain region’s connections are local, while a few are longer-range. In addition, some regions appear to be hubs of exchange, much like your jet-set friends with contacts around the world.

The small world-like pattern of connections appears to be a prerequisite for sophisticated brains like those of mammals. Mammal brains studied in detail so far all show similar patterns of connectivity. And our brain’s connectivity may go some way in explaining why we humans are so creative.

Andrea Piacquadio/Pexels
Source: Andrea Piacquadio/Pexels

The brain is capable of tremendously varied communication within itself, and this is part of why it possesses great power. The network inside our heads derives its power through its connectedness, in the same way that social networks do. Think about how social networks have gotten more and more integrated—especially in the Internet Age. During this time, our social networks have also become obviously more powerful. We can connect, coordinate, and exchange information with practically anyone else on Earth if we try.

The secret is that the better connected a network is, the easier it is to exchange more and different types of information, and to synthesize information into creative new forms. It is no exaggeration to say that it takes a network to raise new ideas. The interplay of ideas from a wide social network is what first allowed humans—and no other species—to create visual art, literature, music, dance, perfume, fine food, roller coasters, and countless other delights of the mind and senses. We even invent parlor games about connectedness on friend networks.

Drawing on our outside networks, creativity can be sparked within each of our own minds. It comes about because we can selectively match together thoughts, personal memories, knowledge of the world, imagery, and emotions that are distributed all across the brain. As I argue in my book An Internet in Your Head, your brain may possess internet-like mechanisms for making sure all these flexible exchanges of information go smoothly.

So the next time your mind is wandering, go with it. You might just connect ideas together that have never been combined before, thanks to the two degrees of separation in your brain.

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Backstrom, L., Boldi, P., Rosa, M., Ugander, J., & Vigna, S. (2012, June). Four degrees of separation. In: Proceedings of the 4th Annual ACM Web Science Conference (pp. 33-42).

Horvát, S., Gămănuț, R., Ercsey-Ravasz, M., Magrou, L., Gămănuț, B., Van Essen, D. C., ... & Kennedy, H. (2016). Spatial embedding and wiring cost constrain the functional layout of the cortical network of rodents and primates. PLoS Biology, 14(7), e1002512.

Kennedy, H., Van Essen, D. C., & Christen, Y. (2016). Micro-, Meso- and Macro-connectomics of the Brain. Springer Nature.

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