Stimulus-Response Science
Stimulus-response psychology has been out of fashion and favor for a long time now, not without reason. It is associated with behaviorism, physicalism, and conditioning theories of learning. We are not just physical mechanisms triggered into reflex behavior by outside stimuli! Indeed not: we are full of “intervening variables”, cognitive structures, streams of consciousness, mental images, trains of reasoning, flights of creativity, etc. We don’t learn by starting with a blank state and having patterns of S-R links stamped on it. Hence, the contemporary enthusiasm for cognitive science, consciousness studies, innate ideas, computational procedures, linguistic competence, mental representations, the language of thought, mental models, and all the rest. But let’s not defenestrate the baby along with the slush and slime: for the idea of the stimulus-response pairing, its ubiquity and utility, is logically detachable from its historical associations and connotations. We can drop the stuff about physical behavior and conditioning theory but retain the concept of the stimulus-response nexus, shorn of its regrettable past company. No more Clark Hull and B.F. Skinner, no more reductionism, no more preposterous simplemindedness; but plenty of stimulus-response connections, outright mentalism, and brain-mind configurations. We can let it all hang out (or in) while claiming that stimulus and response are ultimately what it’s all about. That is what I intend to do in what follows: defend internal conscious cognitive stimulus-response psychology (and beyond). Call it “cog-stim-sci”.
I have not set myself a difficult task. The idea is perfectly intuitive and natural, calling for no serious biting of the bullet. For example, pain is an inner response to an outer physical stimulus, and pain behavior is an outer response to an inner pain stimulus. The one elicits the other. There, what was so hard about that? It is important to notice that the elicitation relation between stimulus and response is not the ordinary causal relation as it obtains between physical events. The OED defines “stimulus” as “a thing that evokes a specific functional reaction in an organ or tissue” and “something that promotes activity, interest, or enthusiasm”. That is not true of common-or-garden causality (“efficient causation”). When a bomb causes a building to be reduced to rubble it does not evoke a specific functional reaction. The missing ingredient is captured by the word “functional”: I would paraphrase this as implying something teleological and normative. The stimulus evokes a response that is both purposeful and good for the organism. Thus, the purpose of evoked pain is to enable the organism to survive (where survival is deemed good for the organism); and the purpose of pain behavior is to do the same for the same reason—such behavior is designed to do good (promote health, fitness, reproductive success). That’s what the elicitation is for—but physical causation is not for anything. Gravity is not a stimulus that elicits the functional response of motion, but merely a cause of it. The blink reflex, by contrast, has as its purpose the avoidance of harmful intrusions in the eye—it has teleology and normativity. Maybe elicitation incorporates ordinary causation (de facto if not de jure) but it doesn’t reduce to causation. We are dealing with a richer concept than mere causation (conjunction plus necessary connection). We are dealing with a characteristic of life. This is why the word “response” is so frequently used in a question-answer context—as in “What is your response to that question?”. The question elicits a response in the form of an answer; it doesn’t merely cause an answer to enter the course of events. Elicitation is a relation on another ontological level, with its own distinctive nature and definition. Synonyms include: evoke, excite, stimulate, activate, incite, provoke, impel, instigate, innervate, prod, prompt, spark, quicken, trigger, spur, stir, goad, induce, invite, animate, propel, initiate. Stimuli do all these things in bringing about a response (reaction, answer, reply, reverberation, resultant). A thing is precisely a stimulus when it is a stimulus to something, as a response is a response to something: each looks forward or backward to its partner, with a kind of primitive (or not so primitive) intentionality; hence, stimulus and response come in pairs. Both can be internal or external: some stimuli are external (either distal or proximal) and some are internal (mental); and some responses are external (behavioral or physiological) and some are internal (also mental). The thesis is to be that all mental processes are one or the other: everything mental is either a stimulus or a response (sometimes both). The psychophysical organism is a stimulus-response machine or system or device or unit (nothing physical or unfree is intended by these labels—I could just as well have said “thing” or “entity”). Its mode of organization (or being) is to be a stimulus-response linkage: perception, consciousness, action, thought, knowledge, emotion, desire—the works.
Let’s consider some examples to get a feel for the conceptual scheme being proposed. External stimuli (distal and proximal) impinge on the organism eliciting a sensory response—a conscious experience. This in turn acts as a stimulus to belief formation, eliciting a particular belief. The belief may then elicit an action or utterance as response. We have a stimulus-response chain–a sequence of stimulus-response pairs. In between these items we will, no doubt, have micro-S-R links, occurring within the nervous system. All this is teleological-normative. Conscious states, for their part, function as stimulus and response, imperceptibly, privately. Actions will be elicited by suitable internal states—beliefs, desires, and intentions. These may be viewed as endogenously produced responses—responses to the eliciting states. Action (behavior) is the response part of an S-R pair.[1] Thought is a response to a felt problem, or a passing memory, or something imagined. Thought is not stimulus-free, though the stimulus may be completely internal. Speech is a response to a thought stimulus or some other inner state.[2] Knowledge is a response to evidence, sensory or testimony. If a logical inference is involved, with premises and conclusion, we may describe the premises as stimuli to the reasoning faculty and the conclusion as a response to these premises—it is elicited by the premises.[3] An emotion may be stimulated by a belief acting as a stimulus, or by a perceptual event, or by some subconscious perturbation. A desire will typically be a response to a need or lack. The mind is thus an S-R network, rather like the body and brain. It is perpetually stimulating and responding, activating and reacting, exciting and being excited. This is not like a purely physical inanimate system (e.g., a system of planets) that is characterized by causal relations between interacting parts governed by a physical force; it is characteristic of a living system. There are functional-normative S-R systems, on the one hand, and purely causal law-governed systems, on the other. The latter are mechanistic in the classic sense (lifeless); the former are organic (imbued with life).
Consider biology: is it a stimulus-response science? The terms “stimulus” and “response” owe their origin in psychology to Pavlov and Thorndike, but I wouldn’t be surprised if the underlying conception originated in physiological studies, especially the study of the nerve impulse. Physiologists were already familiar with the salivation reflex—the stimulus of food elicits the response of salivation (an unconditioned reflex). Evidently, the body responds with a variety of secretions when appropriately stimulated, so it is natural to think of physiology as an S-R science; it is then a short step to conceiving the mind in the same way, at least in some of its aspects (psychophysics was the first step). Reflexive S-R connections thus become the dominant paradigm of the new non-introspective psychology. But what about biology as a whole—does it have an S-R interpretation? It does as far as animal physiology and psychology are concerned, but what about evolutionary biology? Here is a suggestion: mutation is the stimulus and natural selection the response. A genetic change occurs randomly (think of this as a physical stimulus) and then nature operates by selecting the good mutations and eliminating the bad ones (think of this as a non-random adaptive response). The stimulus elicits a new life form via the selective response. This is like the stimulus of a new breed of dog, produced by human action (or randomly), eliciting a selective response from dog breeders in general. A stimulus is necessary if any selective response is to occur—either in natural or artificial selection. Or again, sexual selection takes a stimulus in the shape of a potential mate and produces a response in the form of an act of mating, and hence gene propagation. The splendid peacock tail is a stimulus that elicits an act of procreation on the part of the peahen. Then too, an earlier species can by natural variation act as a stimulus to producing a new species as response. The evolutionary process has a stimulus-response structure or logic. Every species comes from an earlier species acting as stimulus (to paraphrase Darwin). Adaptation is the organism responding to the stimulus of the environment. There are biological reactions to stimuli everywhere. The gene itself is both a stimulus to action and a result of such action (as it is passed on). Thus, the science of biology can be analyzed as a stimulus-response science in a number of respects.
The same is true of economics. We have all heard of an “economic stimulus package” such as lowering interest rates or injecting money into the economy or large-scale public works. These are intended to produce an economic response such as boosting investment or encouraging consumption. The policy is said to stimulate economic activity. It is purposeful and normative—the results are intended to be beneficial. It isn’t just mindless efficient causation like rainfall or volcanic eruption. Innovation is a stimulus that elicits productivity and prosperity, as perception is a stimulus that elicits thought and knowledge. The structure is the same. And isn’t the supply-demand nexus a species of the stimulus-response nexus? Supply varies and produces price variation, as demand can act as a stimulus to supply. This interaction is like the mutation-selection interaction: supply variations are like mutational variations, and then the market acts like natural selection—it exerts a demand effect, either producing more of the same or eliminating the new variation. Innovation resembles random genetic variation; demand resembles survival of the fittest. Economies are thus comparable to biological systems: there is competition in both spheres driven by creative acts (mutation or commodity production). Thus, economies progress and so do species—things get better designed as the process repeats itself. This is all stimulus and response, input and output, elicitation and selection. Economic activity is the operant conditioning of goods and services: it selects by reinforcement. Think of this as macro stimulus and response. The electric car comes to sweep the planet, as ants and termites once did. The same is true of political movements: industrial capitalism incites the rise of communism by way of reaction, oligarchs appear, great political powers form. There is a stimulus and a response at the macro level: this will have a teleological and normative dimension, as social changes produce better or worse conditions of life. The same dialectical pattern recurs, and it is not just mindless efficient causation. From the cell to society, from biological tissue to the body politic, we have armies of stimuli eliciting cavalcades of responses. Meanwhile the inanimate world chugs mindlessly along, indifferent to all this stimulating and responding, the mark of the living world. Not that there is any vital spirit or some such; but there is a different conceptual apparatus at the two levels, a kind of irreducibility (much debated).
The analogy with questions and answers is never far away. The stimulus is like a question and the response an answer: the stimulus occurs and then it is up to the responder to act in a certain way. There are degrees of freedom: it might not respond at all, or it might over-respond, or it might respond just right. It might give the right answer or the wrong answer. There are two agencies at work—the stimulating agency and the responding agency. So, a perception may lead to a particular belief or not, a nerve innervation may produce an action potential or not, a new product may take off or not, a political movement may be sparked or not, an educational program may lead to increased knowledge or not. The stimulating agency cannot act alone; it needs the cooperation of the responding agency.[4] Supply alone cannot create demand; an electrical impulse alone cannot cause a neuron to fire. The stimulus needs an audience, as it were, a receptive capable audience—as the questioner needs an answerer equipped with what it takes to answer. We don’t think that the action of the sun on its planets is a question-answer interaction: the movement of the planets is not an answering response to the force of the sun’s gravity, save metaphorically. This kind of interaction is pre-stimulus-response, a simpler mode of being. It has no meaning or purpose. But the stimulus-response nexus is imbued with purpose and value: the response to the stimulus is always good or bad in some way. The cell remains healthy, the organism survives, the economy prospers, people’s lives improve—or not, as the case may be. This is a different way of looking at the world, not a value-free mechanistic way. It separates the living world from the non-living world. In death there is no response to stimulation.
How does this perspective bear on causal theories of this or that—perception, memory, knowledge, action? Such theories have been popular and have been thought to unify the mind with the non-mental world—causation being a highly general type of relation. Can we reduce the causally defined notions to something close to the physical? Is perception, say, a causal “naturalistic” relation to the perceived world, no different in kind from the relation of spatial proximity or gravitational attraction or mechanistic impact? Is memory a causal relation to a past event, like an imprint in the sand? Is knowledge a special case of causal dependence? Is intentional action causation by reasons, as volcanic eruptions are caused by seismic activity? These all sound pleasingly no-nonsense, steps towards a unified world-view; but if the present reflections are on the right track, then this is an illusion born of a thirst for generality (homogeneity). For a more apt description of what is going on invokes the specialized notions of stimulus and response: the percept is a response to a present stimulus, memories are responses to past stimuli, knowledge is a response elicited by evidential stimuli, actions are responses to the inner stimuli of desire and belief. Again, these concepts are saturated with teleological-normative content, with the idea of a living thing; they are not just regular mechanical causation. They may include such causation, but they are not merely that—they are not just impingements of an inanimate force (gravitational, electromagnetic, impact-mechanical). The theories in question were right to perceive an analogy with natural biological objects and processes, but wrong to try to assimilate the phenomena to the realm of the inanimate. Perceiving is a living process like salivation or perspiration, not a non-living process like crystal formation or tectonic-plate displacement.
Metaphysically, there are three sorts of dependency relation in the world: causal relations, elicitation relations, and logical relations. These correspond to the inanimate, the animate, and the abstract (for want of a better term). Thus, cause and effect, stimulus and response, premise and conclusion. Just as we need to distinguish the third of these from the first, so we need to distinguish the second from the other two. That relation has come under fire because of its historical association with outmoded theories and metaphysical doctrines, but it is not difficult to detach it from those bad ideas, thus giving us a purified conceptual framework for thinking about a variety of subject matters. There is nothing to prevent us from developing thoroughly cognitive (and affective) stimulus-response theories, as well as outright phenomenological stimulus-response theories. The basic idea, derived from physiological biology, is sound, even if its early applications missed the mark. There is a whole world of stimulus-response elicitation waiting to be recognized as such—hence, stimulus-response science. Cognitive science was billed as a multidisciplinary enterprise, unifying separate disciplines under a common conceptual framework (basically computational); stimulus-response science casts its net more widely still, bringing in everything animate, thus allowing for theoretical integration at a high level.[5]
[1] We can recognize stimulus holism if we see fit—the mind acts holistically in the elicitation of action.
[2] Is Chomsky-style linguistics an S-R scheme? It could be if we regard language learning as the elicitation of an innate language program. Also, we could see performance as an outer response to the internal stimulus of competence.
[3] We can envisage the emergence of “response epistemology”: knowledge acquisition and theory formation could be seen as responses to evidential stimuli. This would be a type of naturalized epistemology, allowing the inclusion of animal knowledge.
[4] The OED defines “elicit” as “evoke or draw out (a response or answer)” and “draw forth (something latent) into existence” (labeled archaic). Here we see the idea of the response as residing in a separate entity, already prepared to deliver the response in question, containing it in embryonic form.
[5] I would not shun the label “ideology” to describe the position I am advancing. It is a high-level all-inclusive conceptual framework designed to find a general underlying order where heterogeneity appears to reign. It unifies, integrates, homogenizes. It is to the life sciences what matter and energy are to the physical sciences—abstract ontology.
