“Natural Selection” and Human Behavior


Let’s talk about evolution. Or better yet, let’s talk about human behavior, and how our understanding of it was influenced by evolutionary theory. For context, we will want to mention B.F Skinner, a researcher at Harvard in the 1950’s, who had far reaching impacts in the field of psychology, and an emerging practice of it called behaviorism, especially in its terminology and future usage. Most of his work is still held in great regard today, and although not taken as holy writ, has been the foundation of future research and adaptations of the original work. Skinner viewed behavior in a novel way, one influenced by Darwin’s evolutionary theory.

“Reflexes are intimately concerned with the well-being of the organism. Reflex behavior which involves the external environment is important in the same way. If a dog’s foot is injured when it steps on a sharp object, it is important that the leg should be flexed rapidly so that the foot is withdrawn… Such biological advantages “explain” reflexes in an evolutionary sense: individuals who are most likely to behave in these ways are presumably most likely to survive and pass on the adaptive characteristics to their offspring.” (Skinner, 1953).

His work on conditioning was different than that of Ivan Pavlov’s. While Pavlov worked with reflexes and stimulus pairing, specifically,  Skinner worked with learned (or operant) behavior and used the philosophical lenses of adaptation to do so.

“The process of conditioning also has a survival value. Since the environment changes from generation to generation, particularly the external rather than the internal, appropriate reflex responses cannot always develop as inherited mechanisms… Since nature cannot foresee, so to speak, that an object with a particular appearance will be edible, the evolutionary process can only provide a mechanism by which the individual will acquire responses to particular features of a given environment after they have been encountered. Where inherited behavior leaves off, the inherited modifiability of the process of conditioning takes over.” (Skinner, 1953).


Selection by Consequences

In Skinner’s theoretical framework for the analysis of behavior, he sets reflexes apart from behaviors omitted as a modifiable response to reoccurring conditions. Operant behavior that had been altered in some way by past consequences. Or, in layman’s terms; experience.

A behavior which occurs following an event with similar conditions to one experienced before, would either have taken on adaptive features to better access/avoid that stimulus, or, if the original behavior failed, would not be likely to omit again in those similar conditions. This is the foundation of behavioral learning theory, and what Skinner called “selection by consequences”.  This form of selection focuses on the consequences of their behavior in order to predict and describe the rate by which they occur in the future. Behaviors, in this sense, can either be strengthened or weakened via selection. We can see this in some of the terminology still used in behavioral science today:

Reinforcement- Responses from the environment that increase the probability of a behavior being repeated. (ie. When a behavior is “rewarded”, it happens more often).

Punishment- Responses from the environment that decrease the likelihood of a behavior being repeated (ie. When a behavior is “punished”, it happens less often).

Extinction- When a conditioned stimulus is no longer paired with an unconditioned stimulus. Or, if the learned (operant) behavior is no longer reinforced; leading to a decrease in future usage of that behavior. (ie. When there is no more “reward”, the behavior has no purpose to reoccur).


In each of these terms above we can see the impact of environmental conditions, and the usefulness of behavior, to describe and predict how it is used, and why. This had vast philosophical repercussions for psychology at the time. Viewing learning and experience in an evolutionary sense had wide reaching advantages in the field of psychology. During this period (1950’s), psychoanalysis was still the mainstay of many professionals, but had glaring weaknesses in treating habitual disorders, or even features within disorders. The Freudian “talking-cure” was adept at having individuals speak about their internal events, their past, and conceptualizing the Id, Ego, and Superego as explanatory factors for their behaviors and interpretations on their dreams and thoughts; but there was no direct observable translation to healthy action following this treatment. It also gave many professionals with similar training, wild variation in interpreting.



The Unconscious Mind vs. Selection By Consequences

One psychoanalyst might attribute excessive smoking to a childhood event, while another might attribute it to a symbol of the cigarette/flame itself. The explanation did not come from the event, or any clue from the environment around the individual; it was all estimation of events that could not be seen. When the past was used as a descriptor, it was often speaking of formative childhood and adolescent experiences, not the direct past or future. In a strict behavioral sense; these are explanatory fictions. Circular definitions that cannot be proven or disproven.

Comparing this to Skinner’s fledgling analysis of behavior, you can see the drastic differences in a hypothetical example of cigarette smoking:

Freudian- Psychoanalytic Interpretation (“The Unconscious Mind”) The unconscious mind acts as a repository, a cauldron, of primitive wishes and impulses… The making of a fire and everything connected therewith is filled through and through with sex symbolism. (Freud,  A General Introduction to Psychoanalysis.  1935)
Skinnerian- Behavior Analytic Interpretation (“Selection by Consequences”) The first time a cigarette was lit and smoked, that behavior was reinforced by the consequence (reinforcement). The probability of future smoking behavior was increased by which ever stimulus acted as a reinforcer (taste, chemical interaction, social, etc).


You will notice under the behavior analytic interpretation; the behavior is adaptive. If smoking that cigarette was pleasing to the individual, they would seek it more in the future. If it was aversive, they would be more likely to avoid it. It is adaptation within the lifetime of the individual. It requires no intergenerational passing of information or traits. It adapts because it serves a function.

Applications of the classifying of behaviors by function, complex social phenomena, and even verbal behavior itself have been conducted using this evolutionary-minded theory of why behaviors occur, and asking the question “for what reason?”. But this is not limited to direct experience. With this explanation, a behavior would not even need direct influence from a specific condition. This is where “rule-governed” behavior is explained. Let’s take a look at a rule governed behavior that might effect the smoking behavior above:

  • SURGEON GENERAL WARNING: Tobacco Smoke Increases The Risk Of Lung Cancer And Heart Disease, Even In Nonsmokers.

According to Skinner, the “rule” serves as a contingency specifying stimulus. Humans are able to learn from the experiences of others, and can adapt our behavior based on observation and instruction. Those stimuli serve as the consequences that either reinforce, or punish, behavior which in turn effects future probability of those behaviors being omitted.

One could either smoke a cigarette and find it displeasing, or they could be given a warning. Supposing that the cigarette, and the instruction, carried enough punishing value, the smoking behavior would decrease. Both are viable consequence events that can effect rates of future behavior.

This topic focused specifically on changes of behavior of an individual, but can also be used in much broader scope as well (especially with rule-governed behaviors). There is growing interest in the field researching was is called meta-contingencies. This theoretical framework does not exclude “thoughts” either, and labels them as “private events”, behaviors in their own right. While we may not touch on that today, keep these theories in mind. They might be adaptive for you.


Questions? Comments? Leave them below!


  1. Cooper, J. O., Heron, T. E., & Heward, W. L. (1987). Applied behavior analysis. Columbus: Merrill Pub. Co.
  2. Skinner, B. F (1945). The operational analysis of psychological terms. Psychological Review, 270-277.
  3. Skinner, B. (1960). Science and human behavior. New York: Mc Millan Company.
  4. Darwin, C. (1872). The origin of species. New York: D. Appleton.
  5. Freud, S. (1935). A general introduction to psychoanalysis. New York: Washington Square Press.


Image Credits: http://www.pixabay.com, Getty Images, North American Energy Advisory (2017)


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