Stimulus-Recovery-Adaptation in Complex Systems

Below are two pictures from a book I'm currently reading on strength training titled Scientific Principles of Strength Training. While the topic of strength training may seem completely unconnected from school or economics, it couldn't be more important to understanding how complex systems work (i.e. your brain during learning or the economy during the business cycle).

Stimulus-Recovery-Adaptation

The first picture below describes what happens during a single workout.

Some stimulus is presented during a workout (i.e. running, lifting, etc.), which actually induces a drop in performance due to fatigue. After appropriate recovery, you return to your baseline level of performance and then an adaptation occurs that allows you to perform more work the next time around. Eventually this adaptation reaches a peak before slowly declining again if no new stimulus is presented.

There are a couple important things to keep in mind with this model. The stimulus must be disruptive to homeostasis, meaning you are asking your body to do something it hasn't previously done. If you can do 100 push ups in a row, doing 25 push ups is not a stimulus. You will have to do more to overload your system and disrupt homeostasis.

Second, once you've reached a new performance peak, a new stimulus has to occur. That means in order to improve, ever larger and larger stimuli are required to continue progress. This is where the Navy SEAL motto, "The only easy day was yesterday," comes from. As your performance levels increase, you actually have to work harder to continue improvement.

This leads to the second diagram, which illustrates what several sessions look like over time. As you can see, session one is essentially the first diagram above, except that a new stimulus is presented before the decline in performance begins. This pattern repeats indefinitely if development is to continue with minor deviances to allow full recovery as the stimuli create larger amounts of fatigue.

Now that you understand the process of stimulus-recovery-adaptation, you can start to see it everywhere. For us, the two most important applications are learning in general and economics more specifically.

Learning in General

Learning in general follows this same pattern. Much like your body, your brain is a complex system which requires homeostatic disruption for learning to occur. If you continue to study the same thing you studied yesterday and never increase in difficulty, you won't experience progress (just like the 25 push ups example wouldn't spur progress).

For a student studying math, this might involve attempting to understand basic calculus after learning about algebra and trigonometry. Obviously, this will provide a novel stimulus that is larger than the ones required for the previously mastered subjects in math. That is why we teach students calculus later in school than algebra or trigonometry, just like we ask someone to try 100 push ups after they have shown the ability to do the 25, 50, and 99.

Economics

For our class more specifically, the economy is a complex system like the body or brain. That means growth requires stimulus. In fact, economics already has terms like "fiscal stimulus" and diagrams such as the business cycle, which mirror the second diagram above almost identically.

When you view economic ideas like "bubbles" and "overheating" through this new lens, you can understand quite easily that the stimulus leading up to a crash or crisis was simply too big for the current economy to recover from adequately. Stimuli need to be big enough to induce a performance drop so that recovery and adaptation can occur, but not so big that future growth is hampered by the need for excessive recovery that allows performance to decline and return to baseline as the first diagram above shows.

Bubbles are therefore the equivalent of asking someone to do 100 push ups when their current performance level is only 50 push ups. Of course they are going to crash afterwards. The stimulus was too large to adequately recover from. A stimulus of 55-60 would have been more appropriate.

Summary

1. Create a stimulus that goes beyond your previous abilities
2. Recover appropriately once a performance drop occurs
3. Adapt to a new peak performance level
4. Repeat as necessary for continued progress