Why Daydreaming Is Good for You

Source: Cristina Conti/Shutterstock

Humans spend a ridiculous amount of time daydreaming; in some individuals, as much as 50% of their time not spent sleeping, according some estimates. The technical term psychologists use to describe this phenomenon is mind-wandering and a growing body of research has been produced on it in the last decade or so.

Probably the most obvious question about daydreaming is why we do it when we could be doing some other, more useful, more lucrative, or survival-enhancing actions instead. What could possibly be the evolutionary advantage of just sitting, doing nothing, with one thought seemingly randomly following another?

A recent study gives us some clues about the benefits of daydreaming. This study was conducted on mice, not humans, and so, since the majority of human mind-wandering experiments rely on self-reports about when, how often, and how we daydream, a completely different methodology was needed.

The experimenters got the mice to look at two very different visual stimuli — two images that looked quite different — while scanning their primary visual cortices. The primary visual cortex is the first stop in visual processing and it is a part of the brain that we know relatively much about, partly because it is retinotopic; that is, there is a somewhat inexact but straightforward spatial correspondence between the image on the mouse's retina and the patterns of neuron firings in the primary visual cortex. The activation in the primary visual cortex when the mice were looking at the two different images was also significantly different.

As the next step, the mice were left alone, looking at a monochrome grey wall. Some of them were in what researchers describe as a 'quiet waking' state, which just means they were neither asleep nor frantically running around. In this state, the primary visual cortex of the mice was still very active, and their activity tended to be similar to their activity when looking at one of the two images. So while the mice were no longer looking at these images, they were spontaneously, and, unrelated to any tasks, contemplating them. This would be the equivalent of human mind-wandering.

But the surprising results are based on what happened next: The more mind-wandering the mice did, the more different the neural activation that corresponded to the two images had become. So mind-wandering sharpened the difference of the neural signature of the two perceived images.

This is an effect closely related to perceptual learning—the phenomenon in which perceiving something modifies how the very same thing will be perceived later. For example, seeing a lot of cats makes us recognize cats more quickly. We know that even visualizing has an impact similar to perceptual learning. The mouse experiments show that mind-wandering has a similar effect.

While it needs to be acknowledged that the minds of humans and mice are very different and the images that flash in the mouse's mind may be a much more impoverished version of daydreaming than what we humans experience, these findings do point toward some form of evolutionary advantage of daydreaming. Daydreaming is not a pointless and idle activity. It has great impact on how all the things we have perceived before are organized and made sense of.

These findings also have potentially crucial implications for our daily lives. In the last decade or so, the time we spend daydreaming or mind-wandering has seriously diminished, mainly because of the use of smartphones. As long as we have a smartphone in our pocket, it is less likely that we spend time daydreaming, given that there are social media feeds to check, online games to complete, and messages to write. Much less time remains for daydreaming, which — if it is true that daydreaming plays an important role in the organization of perceptual stimuli — could have serious consequences for our mental life.