Most of us know what it's like to be tired. Whether we're studying at the library for an upcoming exam, trying to get something important done at the office, or doing chores we've been putting off for days at home, we often feel tired, incompetent, or incompetent. You are ready to do what you know you must do. Life is full of things to do. Sometimes we succeed and fight this fatigue, sometimes we fail and focus on less difficult tasks (activities that are usually not on a long to-do list).

Clarify the concept of fatigue

English can be blamed for our inability to clearly distinguish between fatigue, tiredness, and sleepiness. As a native German speaker, I can vouch that no other language is better at this (in German we use 'tired' and 'tired' in English, so we replace 'müde' and 'ausgelaugt' with 'erschöpft' in German. .'). As you may have guessed, we sleep for two reasons. I haven't slept in a while or it's dark outside. This feeling is associated with the circadian rhythm, a circadian cycle that can accompany a variety of physiological processes. One of these processes is the release of a hormone called melatonin, which usually occurs after sunset. The release of melatonin makes us sleepy and we fall asleep. So what do we do when we are asleep? You found it, you should sleep. 

On the other hand, we feel tired in the morning after a good night's sleep. Melatonin is invisible. Of course, the solution is not to go back to sleep. There are four characteristics to consider to unambiguously isolate fatigue from all relevant structures.

First of all, fatigue is the feeling of tiredness caused by performing strenuous activities. This is different from sleepiness due to the release of melatonin and the need for sleep. It's also different from boredom caused by a lack of stimulating activity (fatigue and boredom are more similar than you might think, but we'll get to that in a future blog post). In psychology, we are closer to the rule that if we continue to do the same activity we start to get tired (the onset can vary a lot, but it almost always happens before we start to feel drowsy and sleepy, so we go to bed).

Second, fatigue can and usually does persist even after we are separated from the activity that caused the fatigue. This is associated with a specific action but disappears when the action stops.

Third, fatigue occurs in a relatively short period (from minutes to hours). It is different from chronic fatigue syndrome (CFS), which is a long-term condition with low energy levels common in patients with a variety of physical and mental disabilities.

What happens when we are tired?

Fatigue affects information processing and decision-making. First, it means you tend to avoid activities that make you feel tired. Sometimes we phase out, which means we continue the activity but put less effort into it, other times it means we stop the activity completely and move on to something else. When you are tired of everyday life, you can often check your phone, drink coffee or simply go for a walk and think about something good, like the weekend or the weekend ahead. This is something I'm working on completely unrelated.

Most of the research linking fatigue and restlessness has been done in the lab, but I'm sure the effect is so strong that it will generalize to real life. The bottom line is that fatigue often hinders productivity and stands between us and the (unpleasant but necessary) necessities of life. According to social psychologist Michael Inzlicht, burnout can go from achieving goals to achieving desired goals. In addition to being unable to engage in the task at hand, fatigue appears to make us less inclined to engage in more demanding tasks, at least temporarily.

A quick detour to why fatigue feels weird

The purpose is usually quite intuitive given the other subjective experiences we often have. Pain tells us that something is harmful and urges us to avoid it in the future. Hunger tells us that we have little energy and motivates us to eat. Jealousy reveals the value of a relationship and shows the risk of losing it. Simply put, positive experiences usually represent good things for us, and negative experiences usually represent bad things for us.

Fatigue is different in this regard. While hard work at demanding tasks is certainly good for us (and evolutionarily it always is good for us), the accompanying experience (fatigue) feels unpleasant. Assuming that our minds and subjective experiences of the world evolved to help us act on our goals (and I do), this seems counterintuitive. Why do things that are good for us turn out to be so bad? Fortunately, people much smarter than me have come up with possible solutions to this apparent contradiction.