I’ve been thinking about the term complexity lately. What got me started was that I was mulling over an idea presented in the book “This Is Your Brain on Music,” which argued that musical complexity increases people’s enjoyment of music, up until a point, when it then starts to decrease it. For instance, most people enjoy your average pop song more than a nursery rhyme, and your average pop song is indeed harmonically, melodically and tonally more complex than most nursery rhymes. However, most people don’t enjoy free jazz or atonal classical music, which is in fact much more complex than pop music. Too much complexity turns them off.

But the problem is that complexity is a relative term. If you’re a fan of Bach’s fugues, and have spent eight hours a day for the past 10 years listen to them, you might find the fugues much easier to follow than a rap song. Does that mean fugues are less complex than rap music? For some people yes, for some people no. At which point the meaning of the term seems to evaporate.

In reference to evolution, we often hear that species become more complex over time. We started out as one celled creatures, now we have eyes and arms and legs. But does “more stuff” equal complexity? My body is indeed made up of many cells, but if you take a look at one of my cells and compare it to the classic one celled creature, are my cells more complex? It would seem hard to determine. Are they more complex, or just plain different? How do you weigh these sorts of things?

It would seem the only real application of the term complexity is to describe the definition of the term complexity.