Evolution of Reflexes

Evolution of Reflexes

The reflex was one of the best ideas that Evolution ever had (second perhaps to articulated bodies). What could be better than an unlearned rapid response action to a threatening stimulus? It’s like having a lightning-fast gunslinger ready to get the organism out of trouble. You don’t have to wait ten minutes before your withdrawal response kicks in. The OED defines “reflex” thus: “an action performed without conscious thought as a response to a stimulus”. The reflex allows the organism to act adaptively (and hence survive) without having to think about it. Speed is of the essence: the organism needs to act quickly and efficiently—the quicker the better (this confers competitive advantage).[1] Bacteria were there first with their flagellar reflexes to chemical and temperature variables. Plants have similar mechanisms built in, though not so rapid—as with the tropisms (the plant doesn’t have to decide to face the sun). It is as if we have intelligence without brains. The smart reflex response is stereotyped, automatic, unlearned, appropriate, economical, and sudden (in the animal case). It can also be modulated in more advanced creatures so as to achieve a degree of fine-tuning. There is nothing unintelligent about it. No wonder, then, that the reflex, evolved so long ago, is still with us today, only now in multifarious forms: patellar, blink, tickle, startle, orienting, salivating, arousal, perspiring, withdrawal, vomiting, defecating, and more. The nervous system (including spinal cord) is a veritable reflex factory performing all sorts of useful functions. Most of our actions are reflex actions (think of digestion, respiration, bodily repair)—it’s all done for us independently of our will. Imagine if you had to figure it all out for yourself! We can’t make machines that duplicate it. The reflex is one of evolution’s great success stories, not to be taken for granted. It could have been used in a Paley-style argument for the existence of God—such exquisite design! There could be a cult worshipping the god of reflexes. And it extends across the animal kingdom, uniting us with our brothers and sisters in reflexology. It was Descartes who originally formulated the concept in Treatise on Man (1664). Darwin could easily have used it to prove evolutionary descent—look at our kinship-in-reflex with other species. The genes clearly invest a lot of capital in reflex creation: survival depends on it. The better the reflex the more the procreation. The reflex rules.

Nor is it limited to the body. The brain is clearly full of reflex action—that’s what the neurons do. They don’t pause to think; they react reflexively. But so does the mind proper: perception is a reflex action—the physical stimulus elicits a mental percept reflexively. It is fast, reliable, unlearned, involuntary, encapsulated, unwilled, automatic (no thinking necessary). The process is largely unconscious—no conscious thought is required. Even the birds and the bees can do it, despite their little brains. No intellection necessary. This is psychophysical reflex action, like pain production (our most trying reflex). And the reflex can also proceed from the inside to the outside, as the animal reacts reflexively to what it experiences: the frog flicks out its tongue having spotted the fly, the human infant winces and writhes with pain (reflexes are especially important to the not-too-brilliant neonate). This too is programmed by the genes—part of the animal’s hardwiring. Reflexes are instinctual, innate, God-given (as it were). In addition, there are intra-mental reflexes, as when a perception triggers an emotion, or a memory triggers a thought (vide Proust), or a word triggers another word (word association). The mind too is rife with reflexes—not surprisingly, given their evolutionary success. This is no doubt an extension of the original machinery: the mind comes to do what the body already does. The one evolved from the other. It didn’t spring into existence ab initio but built on what was already in place. Physical reflexes led to mental reflexes, mediated by the reflexive brain. In time, conditioned reflexes came to be, but they depend on prior unconditioned reflexes (salivation to a bell presupposes salivation to food). We can perhaps imagine a creature devoid of reflexes—it has to figure it all out and act on the basis of conscious reasoning—but that is far from being the actual situation here on planet Earth (or any planet where Darwinian evolution occurs).

I now want to suggest something heretical (so far it has all been banality). It is this: all action (mental or physical) is reflexive. I don’t mean that there is no such thing as conscious thought, or that conscious thought plays no role in the determination of action; I mean that conscious thought is itself reflexive, or is composed of reflexes. Reasoning, in particular, consists of reflexes—it is typically a string of them. This is most easily seen in the case of perception-based belief formation: the animal reflexively believes what its senses suggest. It doesn’t think about it; it just does it. It is genetically programmed to do it as a matter of instinct. It believes what it sees, reflexively; it can’t help itself. The response is automatic and fixed not a matter for contemplation. This is as it should be, because it is vital to the animal’s interests that it act quickly and decisively. It is the same with induction: the animal extrapolates from what it has observed to what it has not observed—immediately, automatically. There is no conscious thought about induction being a valid rule of inference. The general belief is formed reflexively not reflectively—just like other reflexes (compare Hume on inductive belief). Inductive reasoning is a useful adaptation to have (as well as being intrinsically reasonable, it goes without saying). And we can say the same about deductive reasoning: modus ponens, say, is a reflexive mode of reasoning—the mind just does it, without thinking (logicians think about it). Ditto for other logical rules. Logical reasoning consists of a series of reflexes (of course, it is not made correct by these reflexes). Hypothesis formation is no different: we and other animals have an instinct for it—and we typically do it rapidly and automatically, without pondering its justification. Thus, conscious thought consists of mental reflexes—reflexive transitions. And the same thing is true of intentional action: it too consists of reflexes. Beliefs and desires trigger intentions, which trigger actions.[2] No conscious thought is required to enact the transitions; we must not intellectualize the process, as if there are conscious thoughts about its justifiability—any more than the blink reflex is backed by thoughts concerning the inadvisability of letting projectiles hit your eyeball. Such thoughts are no doubt true, but you don’t need to have them for the reflex to do its work. The reflex spares you that responsibility—that’s the beauty of reflexes. You can thus engage in conscious thought without having to engage in conscious thought about your conscious thought.

You might object: what about deliberate drawn-out rational thought, say about where to go on vacation or whom to marry? Is that reflexive? It is true that there is no immediate movement from question to answer—you don’t automatically think “the south of France” once the question has occurred to you. You think about it, do some research, ask a friend. But all this input itself acts on you reflexively: each new piece of information triggers a belief, perhaps a desire, from which you hope to draw a conclusion. Then you finally decide, based on everything you know and want. But that transition is itself by way of being a reflex, because we are also programmed to act on the basis of the totality of our knowledge (and desire). We decide reflexively but holistically. Every component of the reasoning was reflexive, and the final outcome was itself a form of reflex—the reflex of doing what we think all things considered is the best (not that we formulate that principle explicitly). You can sometimes see an animal doing this as it pauses on the threshold—“Should I go out there or not?”—but its action is the automatic upshot of a survey of reasons for and against. Its final action is reflexively prompted by the totality of relevant facts (whether it’s raining, how cold it is, whether any danger lurks). Even the most reflective act is made up of pieces of reflexive action. Indeed, without such reflexes it is hard to see how we would think or do anything at all. We need primitive instinctual mental moves—intellectual reflexes, in effect. There is no such thing as purely non-reflexive thought and intentional action, as there is no such thing as non-reflexive bodily action. It is true that conscious thought can substitute for reflex action in certain cases, but when that happens it is just one sort of reflex standing in for another—as when you consciously close your eyelid with your hand for fear of incoming missiles (because your normal blink reflex has been abolished somehow). The contrast between reflexive behavior and so-called non-reflexive behavior has been greatly exaggerated, indeed misconceived. There is no such thing as completely non-reflexive behavior. That is not surprising given the evolutionary history. What we really have are successive modifications of the original plan—the initial simple primordial reflex. There is no sharp divide in this respect between the body and the mind. Descartes’ contrast between the instinctual reflexive body and the rational non-reflexive mind is erroneous. Reason is reflexive too.[3]

[1] There are short- and long-latency reflexes, depending on the number of neurons involved, but as a rule all reflexes are very fast—as fast as the nerve impulse can make them (nerves exist in order to implement fast reflexes).

[2] There are two marks of the reflex: it is not something chosen, and it is not something you can train yourself out of. You don’t choose to blink your eye when something approaches it (you can’t choose not to blink either), and you can’t learn not to blink by diligent effort. By these tests logical reasoning is reflexive: you don’t choose to reason by modus ponens or conjunction elimination (you can’t help it), and you can’t train yourself not to reason thus.

[3] I hope it is clear that no form of reductionist psychologism is intended by this paper. I am discussing the psychology of logic not its metaphysics and epistemology (justification, warrant). My point is that primitive logical transitions (inferences) are to be understood as corresponding to mental reflexes—logical validity is tracked by reflexes of the mind (“reflexism”). This is as it should be, since evolution has a general interest in the truth (though not a dogmatic interest). I would also say that moral reasoning is reflexive at its foundations: we reflexively (and rightly) think that pain is bad and pleasure good. We don’t learn this or reason it out; it isn’t a conclusion we have laboriously come to. It is the same with our disgust reactions—we reflexively recoil from the disgusting stimulus. It isn’t a matter of cultural indoctrination (though the disgust reaction can be modified and modulated by culture, as can many reflexes). Logical reasoning has the same basic psychological structure: inbuilt, hardwired, automatic, non-negotiable, involuntary, unreflective, immutable, elemental, given not chosen. It is part of our biological nature, a product of evolution with ancient roots. It is not, however, true in virtue of such biological facts. It is true in virtue of…but that’s another story.