What Does Entropy Have to Do With Psychology?

Pioneers of evolutionary psychology John Tooby, Leda Cosmides, and H. Clark Barrett argue that “the Second Law of Thermodynamics is the First Law of Psychology” in a 2003 paper of that very name.

The Law of Entropy

The Second Law of Thermodynamics, also known as the Law of Entropy, states that in a closed system, energy must always dissipate from high-energy to low-energy concentrations. Your cup of coffee will always release its heat into the surrounding air and cool off over time; it will never spontaneously heat up without pouring in outside energy. Opening up the system to outside energy input, the coffee cup itself may gain energy when put into the microwave, but the energy does not come from nowhere. Most of our energy comes from the Sun, and the amount used to produce habitable order pales in comparison to the amount constantly being dissipated into the empty void of space.

A related form of the Law of Entropy refers to the statistical necessity of disorder: There are only so many ways to build a sandcastle, but there are infinitely many more ways for that sand to be dispersed. Of any given possible interactions or possible states of matter, most of them are disorderly chaos. Unlikely pockets of order, high in energy cost to maintain, can exist, but zooming out far enough, entropy will always increase.

What does any of this have to do with psychology?

The First Law of Psychology

The paper outlining the “First Law of Psychology” constructively criticizes psychology as a field whose preconceptions about physics and biology are often misinformed—and it frankly reads more like a biology paper. I recognize the irony that this is probably the case because I am exactly the paper’s target audience: a psychologist who has not taken a physics or biology course in years.

This makes me, depending on your stance, either the best or worst person to tell you why you should care about entropy if you care about psychology.

Most of us seriously take for granted the fact that our world is ordered. Beyond universal laws found in mathematics and the natural sciences, order is rare in the universe. For every orderly star or galaxy formation, there are billions more light-years of disorderly, mostly empty, space. Rarer still is any self-perpetuating, orderly system that consumes energy to keep its form (i.e., life).

Entro, Evo, Info

Most of us understand the principles of natural selection: survival of the fittest, the genes of those who reproduce will be passed on, and successful traits being selected for over time. Even this explanation takes for granted the unlikely order that results. Most variation within and across species, in accordance with the Law of Entropy, will be disorderly failures. Only a small, select few traits and behavioral adaptations will stand the test of time.

This means that entropy directly gives rise to the process of evolution and that evolution outputs something akin to information: the set of characteristics that are fit to survive and self-propagate. This is precisely the argument made by psychologist Steven Pinker in his book Enlightenment Now, in a chapter entitled “Entro, Evo, Info” (Entropy, Evolution, and Information). These three processes are inexorably linked and are central to understanding human behavior.

Any stable psychological phenomenon, even those which seem entirely socially constructed, owes its existence to a precise configuration that wards off entropy, consuming energy to maintain its form in an open system relationship with the outside world. Whatever laws we observe in psychology are stable pockets of order, selected precisely because they are anti-entropic (not in the final analysis, but in the sense that we may expend outside energy to maintain biopsychosocial stability). That is why the Second Law of Thermodynamics is the First Law of Psychology.