You might be reading something for a high school assignment, a novel or a technical in-depth summary of the current economic situation of the country, when suddenly, you realize that you’re just reading the words, but not really absorbing anything. In other words, you’re not comprehending the content in front of you!
You have likely experienced this countless times yourself, but have you ever thought about why it happens?
Before we start, it’s important to note that the answer to this question, and most other questions related to the mind and the central nervous system (especially cognition), is not well understood by researchers. The underlying physiological processes responsible for these functions cannot be explained by one solid answer backed by concerted scientific (experimental) evidence.
Here’s a fun fact: you may have certain beliefs that sound fairly intuitive, which may make you think that you know why your brain acts the way it does. However, in reality, it’s just one of the known flaws in human reasoning (this is called introspection illusion).
Simply put, all of this means that we don’t really know why we end up ‘reading on auto-pilot’ without comprehending any of what we read. Thus, the following, in essence, is just logical speculation that attempts to answer the question.
Reading on autopilot
The “keep reading but the mind wanders off” effect is very common, or at least more common that you might think. If you think that you are one of the few who suffer from this, and that most well-read people don’t, then I have only one thing to tell you…
When you read something, your brain is connecting the contents of your memory either in a new, or at least less-frequently used way. There is a theory in neuroscience – the Hebbian theory – that proposes an explanation for the adaptation of neurons in the brain when one is learning something. It specifies a learning rule stating that the connection between two neurons might be strengthened if the neurons fire simultaneously (Source).
In order for this to happen, it’s imperative that you be focused on the topic that you’re reading about. You should ‘do something’ with whatever it is you are reading and think about it, like visualizing a scene in your head, making a mental summary etc. These are the processes that are associated with working memory and can assist in the aforementioned forming of connections.
Now, when you’re thinking about something other than what you are reading, then your working memory is occupied/overloaded with other thoughts (e.g., when you are daydreaming). Consequently, you’re not able to make connections within your knowledge base, because you’re thinking about something else. So, you might have read a complete page, but your brain is unable to process it in any meaningful way.
Think of your attention as a spotlight on a stage, which directs and grabs your attention. You (mostly) only focus on what’s under the spotlight, although there is a lot of stuff going on outside the spotlight too. You end up focusing solely on the lead artist, because the spotlight is on them. However, that doesn’t mean you have completely shut out everything else that’s happening outside the spotlight. They’re there too; it’s just that you aren’t ‘involved’ with them to that degree.
Similarly, when you’re reading, but your mind is not completely engaged with the book, then you fail to completely understand what you just read, as your spotlight is focused elsewhere.
The attentional system
The brain is constantly bombarded with so much information from the outside world that it’s a surprise that more people don’t have killer headaches from the information overload. Fortunately, the human attentional system of the brain ensures that you only pay attention to the things you really need to.
According to Daniel J. Levitin, a scientist and the author of “The Organized Mind”, the human attentional system is divided into 4 parts: central executive mode, mind-wandering mode, attentional filter and attentional switch.
The more time you spend reading, the longer it remains a part of your environment. Consequently, the attentional filter gradually blocks out the book. This, in turn, means that your focus will need to be kept entirely by the central executive mind. This takes a significant amount of effort.
That’s why you feel exhausted after sitting through a 3-hour examination; just like other parts of your body, your brain needs glucose to function. Concentrating on something makes the brain work extra hard, however, which leads to you feeling tired.
Your brain is designed in a way that tries to minimize effort. Thus, it assigns the task of reading to the mind-wandering mode in a bid to minimize effort. The benefit of this is that you can still read with minimal effort while simultaneously thinking about something unrelated.
The down side, however, is that the mind-wandering mode is not very good at processing information (that isn’t random). As a result, you end up reading on autopilot without really interpreting most of it.