Why Behaviorism Failed as a Leading Theory in Psychology
The human mind, like the origin and development of life itself is not reducible to merely physical processesBehaviorism, as a scientific explanation for the mind, attempts to explain human behavior as caused by innumerable iterations of simple physical events. B. F. Skinner (1904-1990) a key behaviorist thinker, put it like this:
The simplest and most satisfactory view is that thought is simply behavior — verbal or nonverbal, covert or overt. It is not some mysterious process responsible for behavior but the very behavior itself in all the complexity of its controlling relations.

Behaviorism has a lot in common with Darwinism, the belief that we are all the outcomes of unguided, purposeless evolution. Both ideologies attempt to explain remarkable aspects of living things — i.e., the human mind or the astonishingly complex and specified biology of all living things — as caused by innumerable iterations of simple physical events.
Philosopher Jerry Fodor (1935–2017) was an atheist but he was not a strict physicalist. He was a non-reductive physicalist who thought that we could retain some concept of the mind, derided by many other philosophers as mere “folk psychology.”
Thus he saw the nonsense in Darwinian theory and wrote about it in What Darwin Got Wrong (Farrar Strauss & Giroux 2010). He also understood its similarity to behaviorism, another failed scientific attempt to explain human life. Thus, in their book Fodor and Massimo Piatelli-Palmarini also told the story of behaviorism’s demise.
The claimed irrelevance of mental states
Behaviorism holds that mental states are irrelevant to science and psychology — all that matters is the input‒output relationship of behaviors.
For example, suppose I am sad. My sadness, rather than being a mental state, is just my behavior when I report feeling sad. It is my moping, dour face, sighing, etc. Whether mental states even exist was a matter of contention among behaviorists — some thought they existed but didn’t matter: others questioned their very existence. All behaviorists believed that mental states are irrelevant to the science of psychology. Behavior, and only behavior, matters.
A key element of this approach was the behaviorist theory of how young children learn languages. In behaviorist theory, children learn language by trial, error and reinforcement. Babies babble, and when a baby’s babble sounds like “mom”, his mother smiles, thus reinforcing the behavior of saying “mom.” Thus the child learns to associate the sound “mom” with this mother. When a baby babbles a grammatically correct sentence, his mother’s smile reinforces that behavior, leading to the child learning grammar.
Behaviorists view all language as acquired in this way. The claim is similar to Darwinian claims that natural selection acting on random mutations produces the world of life, including ourselves. Behaviorism similarly holds that selection for sounds that have meaning and correct grammar from among the random variation of human sounds produces the astonishing variety and complexity of the language we use as adults.

How behaviorism met its end
In a 1959 review of Skinner’s book Verbal Behavior, graduate student Noam Chomsky demolished behaviorism as an explanation for language and as a serious scientific project for understanding language.
The behaviorist views the capacity for grammar as acquired in two ways: by reinforcement when proper grammar is used, and by context i.e., the meaning of the words as nouns, verbs, adjectives, etc.
But Chomsky pointed out that, in reality, young children show an inherent skill with grammar. They acquire language much more quickly and accurately than can be accounted for by behaviorist trial, error and reinforcement.

He also noted that behaviorist explanations fail because of “paucity of stimulus”. That is, there are simply not enough behavioral stimuli to account for the rate of language acquisition in children. As an example, he proposed the sentence, “Colorless green ideas sleep furiously”. Despite the fact that it’s meaningless, we all know that it’s a perfectly grammatically correct sentence.
But how could we know it’s grammatically correct, from a behaviorist perspective? It’s a safe bet that no one has ever spoken that sentence and been “reinforced” for speaking it. And because it’s meaningless, we can’t use semantic clues to identify correct grammar. We simply intuitively know that it’s correct grammar, despite the fact that we’ve never heard it before and it’s meaningless.
How do we learn language?
Chomsky proposed that we don’t learn grammar by behaviorist reinforcement. We know grammar instinctively, by virtue of a “Language Acquisition Device”, or a language organ, that enables us to use language accurately without the innumerable stimuli necessary under the behaviorist paradigm. Language is innate to humans, not acquired by behaviorist-type trial, error, and reinforcement.

One might say that human language is irreducibly complex, meaning that trial, error and reinforcement simply can’t account for its specified complexity, any more than random heritable variation and natural selection can account for living organisms’ specified complexity. Of course, Michael Behe has brilliantly applied irreducible complexity theory to evolution, and my colleagues Richard Sternberg and David Klinghoffer point out in a superb new book, Plato’s Revenge, that mere physical causation cannot account for the information and dynamism in living organisms. An idea in a mind is required for life.
Expanding on this insight, Denyse O’Leary and I discuss the inability of behaviorism and other materialistic theories to account for the specified complexity of the human mind in our new book The Immortal Mind.
Atheist Jerry Fodor correctly pointed out that, like behaviorism, Darwinian natural selection cannot account for evolution and for the specified complexity of living things. He called natural selection “empty” and not a genuine level of explanation. We agree and point out that similar materialist theories cannot account for the content of the human intellect and free will either.
The science is clear. Mind, not matter, is the source of life and the human mind, and the signature of Mind lives in us and in all living things.