Social Evolution Forum
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In Defense of the Blank Slate

War is not the necessary outcome of evolution. Image by Paul Keller, via Wikimedia.


Michael Shermer, the world’s most famous skeptic, recently posted a tweet that read “Sorry blank slaters & Peace & Harmony Mafia: Evidence of a prehistoric massacre extends the history of warfare.”

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He was referring to recently discovered archeological evidence that one small group of people massacred another small group of people 10,000 years ago in Kenya.

I couldn’t resist tweeting a reply to Michael, who I count as a respected colleague and friend: “I have to ask: how does an ancient massacre bear upon any of the assumptions of ‘blank slate’ psychology?”

There ensued an eruption of tweets that came and went, like so many other disturbances of the Twitterverse.  The matters at stake are anything but ephemeral, however, and bear upon the very nature of human psychology and culture from an evolutionary perspective. A blog post doesn’t provide much more opportunity for serious thought than a tweet, but I’ll try to say just enough to map out the intellectual territory and link to the deep end of the pool (the academic literature).

The concept of the human mind as a blank slate implies that people are unconstrained in how they behave. That is why I was puzzled by Michael’s tweet. If the human mind is a blank slate, then why couldn’t “war” have been written upon it as well as “peace” 10,000 years ago in Kenya?

Michael responded to my reply with this tweet: “Blank slate assumption: war is a modern invention w/no relation to our evolutionary propensity to aggression”. To my mind, that’s like mixing apples and oranges. How far warfare extends back in human history is one matter. The open-ended flexibility of the human mind is another. I don’t care how much they have been conflated in the past. If we’re interested in our capacity to behave in almost any fashion, then an ancient massacre tells us nothing. Zero. Zip.

So let’s get back to the central question of the human capacity to behave any which way.  But first let me tell you about two other blank slates.

The blank slate of natural selection.

As nearly everyone knows, natural selection requires three ingredients: variation, selection, and heredity. When these ingredients are met, then traits evolve that adapt organisms to their environments.  It is common for evolutionists to assume that all traits are heritable, in which case organisms are blank slates that selection can write anything upon. This is often called “adaptationist thinking” or “natural selection thinking” and it is arguably the most powerful tool in the evolutionary toolkit.

Even though evolutionists indulge in their own brand of blank slate thinking all the time, they do not defend it as literally correct. They know that not all traits are heritable, that phenotypic variation is constrained by developmental pathways, and all that. Thus, they easily back away from their blank slate assumption, but they still legitimately defend it as a valuable heuristic that is true much of the time.

The blank slate of the vertebrate immune system.

Immunologists distinguish between the “innate” and “adaptive” components of the immune system. The terms are a little confusing, because the “innate” component is a mind-bogglingly complex set of adaptations that evolved by natural selection to protect us from the onslaught of disease organisms. What makes them innate is that they are automated and don’t change during the lifetime of the organism. This is sometimes called “closed phenotypic plasticity” in the evolutionary literature.

The adaptive component of the immune system is capable of adapting defenses against disease organisms during the lifetime of a vertebrate organism. Briefly, the body produces approximately 100 million different antibodies. Each is capable of attaching to a narrow range of organic surfaces. Antibodies that succeed in attaching to disease organisms that evade the innate component of the immune system differentially proliferate. In other words, the adaptive component of the immune system is an open-ended evolutionary process that evolved by genetic evolution and adapts vertebrate organisms to their disease environments during their lifetimes.

Are immunologists justified in employing a blank slate assumption concerning what can evolve by the adaptive component of the immune system? Yes, in exactly the same sense as evolutionists employ adaptationist thinking for the study of genetic evolution.

The blank slate of human psychology.

Now let me ask you to think of the human capacity for behavioral and cultural change as like the vertebrate immune system. There is both an innate and adaptive component, which result in forms of closed and open behavioral phenotypic plasticity respectively. The adaptive component of human behavioral and cultural flexibility justifies the same kind of blank slate adaptationist thinking employed by evolutionists (based on heritable genetic variation) and immunologists (based on the variation and selection of antibodies). It’s that simple.

B.F. Skinner, the psychologist associated with the “blank slate” tradition more than any other, wrote this abstract for his 1981 article in Science magazine titled “Selection by Consequences”:

Selection by consequences is a causal mode found only in living things, or in machines made by living things. It was first recognized in natural selection, but it also accounts for the shaping and maintenance of the behavior of the individual and the evolution of cultures. In all three of these fields, it replaces explanations based on the causal modes of classical mechanics. The replacement is strongly resisted. Natural selection has now made its case, but similar delays in recognizing the role of selection in the other fields could deprive us of valuable help in solving the problems which confront us.

Skinner got one thing right and another thing wrong in this passage. He was right that human behavioral and cultural flexibility has an open-ended component similar to the adaptive component of the vertebrate immune system, which justifies the same kind of adaptationist blank slate thinking employed by evolutionists and immunologists. He was wrong that this kind of thinking replaces “explanations based on the causal modes of classical mechanics”. In evolutionary parlance, this is like saying that thinking in terms of ultimate causation replaces thinking in terms of proximate causation. Skinner’s reluctance to open the black box of proximate mechanisms led to the demise of the tradition of behaviorism in academic psychology—although it remains alive and well in branches of applied psychology, where the goal is to actually accomplish behavioral and cultural change. Every evolutionist worth his or her salt knows that a fully rounded evolutionary approach requires attention to both proximate and ultimate causation, or “function”, “phylogeny”, “mechanism” and “development”, to use Niko Tinbergen’s useful fourfold distinction.

I am reaching the limits of a blog post, but the bottom line is that “blank slate” adaptationist thinking is as essential for the study of human psychology and culture as it is for the study of genetic evolution and immunology. The polarizing distinction between “Evolutionary Psychology” and the “Standard Social Science Model” was a wrong turn from which we all need to recover.

If you have enjoyed dipping your toe into this subject, then I invite you to dive into the deep end of the pool with this 2014 article published in Behavioral and Brain Sciences titled “Evolving the Future: Toward a Science of Intentional Change”.  My co-authors, Steven C. Hayes, Anthony Biglan, and Dennis Embry, are accomplished applied behavioral scientists who come from the Skinnerian tradition and are experienced at accomplishing positive open-ended behavioral change. BBS is a commentary journal, which means that our target article is followed by approximately two-dozen commentaries from our academic colleagues and our reply, giving a sense of the spectrum of current scientific opinion that is out there. In the future, I hope that my friend Michael Shermer and other skeptics about the blank slate concept will base their blog posts and tweets on what is taking place at the deep end of the pool, rather than massacres that took place in the distant past.


Join the discussion


  1. David Whitlock says:

    I think the problem for those who consider that the brain cannot be a “blank slate”, is that they use the wrong starting point; the brain at birth. The brain at birth is obviously not a “blank slate”, it already has ~10^11 cells with ~10^15 connections. What about such a complex organization of matter could possibly be “blank”?

    A more appropriate time is not the moment of birth, but rather the moment of conception, where that unique, whole 46 chromosome genome comes together for the first time. At this moment the number of brain cells is zero. A brain with zero brain cells cannot be other than “blank”.

    All of the sensing, thinking, feeling, reacting and doing that brains accomplish, requires the cooperative action of ensembles of brain cells working together “in sync”. A single neuron can’t have a “thought” or a “feeling”, only ensembles of millions or billions of cells can instantiate thoughts.

    The genome specifies many things. It does not specify things as fundamental as how many heads the growing fetus will develop.

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    If phenotype properties as fundamental as number of heads are not “specified” genetically, what basis is there for asserting that more complicated and emergent phenotype properties like sensing, feeling and thinking (which are still mediated through details of the anatomy that develops through neurodevelopment) be genetically specified?

    Each cell in an adult has “the same” genome (coding and non-coding DNA sequences). The expression of the DNA has been regulated by epigenetic programming (the “only” difference between the totipotent zygote and the terminally differentiated nerve, muscle, liver, blood cells). There isn’t enough information in the 3×10^9 bases of the genome to specify the 10^12 cells and their relative interactions.

    Sensing of a specific signal by a cell requires a number of receptors. Each number of each type of receptor cannot be specified genetically for each cell, and the precision of genetic expression of receptor number cannot be sufficient for open-loop regulation of sensory neural networks. Those networks must be “tuned” to achieve pattern recognition, and the ultimate configuration(s) after that “tuning” must depend (to some extent) on signals from the environment that triggered the “tuning”.

    There might be some biases built into the expression of receptors at birth, and those “hard wired” neural networks might be sufficient to “jump start”, or to “boot up” more complex neural activities (oxytocin perhaps?) that are later refined the way the retinal connections to the visual cortex are refined. That “refinement” depends strongly on the sensory input that triggers the refinement.

    We know that a first language is almost entirely learned (in that essentially any human infant can learn essentially any human language as a first language with no accent). What basis is there for thinking that the (vastly simpler) cultural values are not “learned” as well?

    • Earthling says:

      ‘A brain with zero brain cells cannot be other than “blank”.’

      It also not a brain. Isn’t the fallacy of the blank slate that during embryonic development (of the brain), information is decoded from genes an imparted to the organism’s brain as innate behavior? Who is arguing that a small ball of cells has innate behavior, anyway?

  2. Michael Mills says:

    I am afraid you have re-defined the Blank Slate into what adaptationists typically refer to as facultative (vs. generally obligate) adaptations. But that was / is not its generally accepted meaning. The Black Slate / SSSM / cultural determinism does not generally posit underlying psychological adaptations which must first be understood to get a full, sophisticated understanding of behavior. Instead, they have argued that our general intelligence has given us the “capacity for culture” and that biology can be safely ignored since it is culture that fills the empty vessel of the mind. That perspective is sophomoric and does not deserve ‘defending.’

  3. Arthur Noll says:

    I think it could be helpful to consider the metaphor of “blank slate”. It implies that anything can be written or drawn. But actually, that isn’t true. All slates have a limited size, the chalk used to write limits how small you can write. You can’t write a novel on a slate, nor do really detailed fine drawing. It is a limited medium for expression.
    And that might seem like a trite observation, but it applies to what is being considered possible to “write with culture”, on human beings. The medium constrains what can be written on it this way.
    People, like other animals, have evolved to be very attracted to go on living as long as they can, and attracted to reproducing. But on a finite planet that has finite areas where it is possible to live and reproduce, people have learned how to stay alive so well that they grow population greater than what these finite areas can support. Since none of them volunteer to die, they fight about who lives. Since we are social creatures, we have fought as groups.
    Unless people are either constrained by outside forces, or constrain themselves, this looks like it will inevitably happen. A culture that tries to constrain reproduction, will not succeed if the medium being “written on”, can’t be taught to do this, and if one set of people succeeds at this but others don’t, they can be overwhelmed by the greater number who don’t constrain themselves this way.
    Only if something happens simultaneously to select those with brain structure able to see the need to constrain themselves, and do it, and the rest die, could you get a situation where a culture of restraint and peace, could have a chance of existing. Such a situation could possibly happen with a large dieoff of people who have overpopulated everywhere, have done so much damage that only small groups have a chance of surviving, and only if they behave with a high degree of efficiency about everything, including reproduction. Ability to constrain reproduction, can save the energy of that, for simply surviving the stress of a dieoff.
    I think we are on the edge of the possibility of such things happening.

  4. quidnunc says:

    I unfortunately can’t read the BBS article as it wants $28 for that privilege so I’ll limit my comment to saying the appropriation of “blank slate” is clumsy which in turn reminded me of an article Steven Pinker wrote in The New Republic a few years ago appropriating “scientism” as if the word itself was what needed to be rehabilitated which is a misguided enterprise when it’s use tracks valid criticism about a narrow chauvinistic view about the primacy of science. I feel similarly about “blank slate” which Marvin Minsky would have called a suitcase word. Unpacking it might reveal some unfairly maligned ideas but how much of that will there be among real excesses in thinking that we rightly point out using that label?

  5. Chris Kavanagh says:

    Although Shermer’s tweet was wrong, it seems like you are not really defending the ‘Blank Slate’ but rather redefining it to mean ‘recognising our capacity for social/cultural adaptation’. That seems to be an entirely different thing than the standard interpretation of a blank slate advocated by many theorists and as such it’s not really a compelling ‘defence’ of what the term is generally used to refer to.

    • quidnunc says:

      It was pointed out on twitter that Shermer probably should have said “noble savage”. It’s possible he ran it together because it’s one of three pillars in Steven Pinker’s The Blank Slate; From Wikipedia:

      “the blank slate (the mind has no innate traits)—empiricism
      the noble savage (people are born good and corrupted by society)—romanticism
      the ghost in the machine (each of us has a soul that makes choices free from biology)”

  6. Lorenzo from Oz says:

    Equilibrium thinking is not really “blank slate”: it is that the thing being modelled is at rest, and then looking at what happens when some factor upsets the equilibrium. The equilibrium may be quite complex but still be at rest. If it was a genuine “blank slate” adding a new factor would have no effect, because there would be nothing for it to have an effect on.

    Apart from that, I thought your co-authored paper was an enlightening survey including some fascinating case studies. (Besides, appreciating Elinor Ostrom’s work is a fine thing in itself.)

  7. Lorenzo from Oz says:

    My comment reads more clearly if “assuming” is added between “is” and
    “that” as in “assuming that the thing being modelled is a rest”.

  8. David Jones says:

    Even if anyone did claim ‘all traits are heritable’ that wouldn’t be a blank slate position characterised by you as a mind that ‘selection can write anything upon’.

    Even if all observable and current traits were heritable that in no way implies that any *imagined* trait could be implemented in the mind. It’s simply a statement about existing traits.