Tooby ea.’s First Law of Psychology

John Tooby, Leda Cosmides, and H. Clark Barrett The Second Law of Thermodynamics Is the First Law of Psychology: Evolutionary Developmental Psychology and the Theory Of Tandem, Coordinated Inheritances: Comment on Lickliter and Honeycutt (2003) Psychological Bulletin 2003, Vol. 129, No. 6, 858–865.


Selection built anti-entropic mechanisms into organisms to orchestrate transactions with environments so that they have some chance of being organization-building and reproduction-enhancing rather than disordering. … This means that the individually unique and unpredictable factors in the web of developmental interactions are a disordering threat to normal development. [Quotes reversed from original.]

Organisms as Seen Through the Eyes of the Physicist

 We as human beings are easily seduced into taking the familiar for granted, as requiring little explanation. Consequently, it is very revealing—almost a revolutionary change in sensibility—to reexamine key issues in psychology and biology through the lens of physics, chemistry, and probability theory. In particular, the second law of thermodynamics (in both its classical and informational versions) is a fundamental law of biology and psychology as well as of physics because organisms and their brains are physical systems. …


 Entirely without agency, the interaction between the properties of reproducers, errors in copying, and the enduring properties of the world naturally cause order to accumulate along (some) lineages of physically reproducing systems—something that would otherwise be a thermodynamic miracle.

Lessons for Psychology From Thermodynamics and Darwinism

The most basic lesson is that natural selection is the only known natural process that pushes populations of organisms thermodynamically uphill into higher degrees of functional order, or even offsets the inevitable increase in disorder that would otherwise take place.

… Selection brings about a functional coordination between the stable, long-term properties of environments and the stable, cross-generationally recurrent, reliably developing (and hence predictable or prespecifiable) properties of organisms.

The Developmentally Relevant Environment as a Second System of Inheritance

Reliably developing species-typical design is caused just as much by the evolutionarily stable features of the world as by the genes; they jointly determine the phenotype.

“no organism reacts to every aspect of the environment: Instead, the developmental programs rely on and interact with only certain define. Over evolutionary time, genetic variation in developmental programs (with selective retention of advantageous variants) explores the properties of the environment, discovering those that are useful sources of information in the task of regulating development and behavior, and rendering those features of the environment that are unreliable or disruptive irrelevant to development.”

The fact that we have all been here before is a very good thing, because it is only this regularity of interaction, from generation to generation, that allows organisms to climb toward a tolerable level of functional organization and inclines them away from depending on the aspects of the environment that are unpredictably variable and hence disordering.


The general idea seems to be that organisms and their environments co-evolve into evolutionary stable systems that adapt to disordering aspects of the environment. But one should note that:

  • By ‘stable’ it is simply meant that it endures for long-enough for selection to have an effect: not that anything is necessarily absolutely stable.
  • Organisms that adapt to disordering aspects of their environments are in some aspects changing and hence not completely stable.
  • An organism may share its environment, so that there are linked evolutions between organisms even without direct interactions.
  • Even for an isolated situation, the resultant system is not necessarily pre-determined by the initial conditions: it is only that the resultant system is viable and can resist alternatives, at least for a while.
  • It is not argued that any particular aspect of an organism must persist: it could be that over a series of adaptations every aspect of the organism changes unrecognizably.
  • The above theory can be partly rationalised with physic’s second law by noting that organisms are not closed systems.
  • On the other hand, a prediction of physics’ second law would seem to be that organisms necessarily disorder their environment, so that the closed system comprising both organism and environment obeys the second law.
  • Then again, an assumption of the second law of thermodynamics is that the overall system is stochastic and in particular (1) has a fixed space of possible microstates and (2) is subject to the law of large numbers. Thus a closed system need not be subject to the second law if it contains an organism that adapts in such a way as either to evade the law of large numbers or to be genuinely innovative, as they often seem to be.

Dave Marsay


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