Peirce believed that there are two kinds of natural phenomena. First there are those events which involve “dyadic relations,” such as obtain in the “physical forces . . . between pairs of particles.” The other kind of event entails “triadic relations”:
All dynamical action, or action of brute force, physical or psychical, either takes place between two subjects . . . or at any rate is a resultant of such action between pairs. But by “semiosis” I mean, on the contrary, an action, or influence, which is, or involves, a cooperation of three subjects, such as a sign, its object, and its interpretant, this tri-relative influence not being in any way resolvable into actions between pairs.
If A throws B away and B hits C in the eye, this event may be understood in terms of two dyadic relations, one between A and B, the other between B and C. But if A gives B to C, a genuine triadic relation exists. “Every genuine triadic relation involves meaning. “An index sign is part of a dyadic relation. An index refers to the object it denotes by virtue of really being affected by that object. Examples of indexes: a low barometer as an index of rain , the cry of warning of a driver to a pedestrian. A symbol, however, is something which stands to somebody for something in some respect or capacity. “The index is physically connected with its object . . . but the symbol is connected with its object by virtue of . . . the symbol-using mind.”
Dyadic events are, presumably, those energy exchanges conventionally studied by the natural sciences: subatomic particles colliding, chemical reactions, actions of force-fields on bodies, physical and chemical transactions across biological membranes, neuron discharges, etc.
Triadic events, on the other hand, characteristically involve symbols and symbol users. Moreover, a genuine triadic relation cannot be reduced to a series of dyadic relations. Peirce seems to be saying that when a symbol user receives a symbol as “meaning” such and such an object, we may not understand this event as a sequence of dyadic events or energy exchanges even though dyadic events and energy exchanges are involved: sound waves in air, excitation of sensory end-organ, afferent nerve impulse, electro colloidal synaptic event, efferent nerve impulse, muscle contraction, or glandular secretion.
Peirce’s distinction between dyadic and triadic behavior has been noted before, but so pervasive has been the influence of what might be called dyadic behaviorism that Peirce’s “triadic relation” has been recognized only to the degree that it can be set forth as a congeries of dyads. Morris, for example, interprets Peirce’s triad as implying that in addition to response and stimulus there is a third factor, a “reinforcing” state of affairs. This is like saying that Einstein’s special theory will be accepted only to the degree that it can be verified by Newtonian mechanics. Like Newtonian mechanics, dyadic theory can account for perhaps 98 per cent of natural phenomena. Unfortunately the phenomenon of talking-and-listening falls in the remaining 2 per cent.
What would happen if we took Peirce seriously? That is to say, if we retain the posture of behavioral science which interests itself only in the overt behavior of other organisms, what are we to make of observable behavior which cannot be understood as a series of dyadic energy transactions? What has happened in the past is that we have admitted of course that there is such a thing as symbol mongering, as naming things, as uttering sentences which are true or false, as “rules” by which names are assigned and sentences formed. We have admitted that such activity is a natural phenomenon and as such is open to scientific investigation. But what kind of scientific investigation? We have gotten around the difficulty by treating the products of symbol-mongering formally, by what Carnap calls the formal sciences (logic, mathematics, syntax), while assigning the activity itself to a factual science, in this case learning theory, which has not, however, been able to give an account of it. It is no secret that learning theorists will have no truck with symbols and meaning. Most textbooks of psychology do not list the word symbol in their indexes. Indeed, how can learning theory, as we know it, give an account of symbolic activity? If we are to believe Peirce, it cannot. For the empirical laws of learning theory are formulations of dyadic events of the form R = f(O), in which R = response variables and 0 = stimulus variables. *
* Actually the dyads should be segmented in some such order as 0 = f(S), in which 0 = the organic variables and S = the stimulus variables; lb = f(Ia), in which I = the intervening neurophysiological variables within the organism; and R = f(O), in which R = response variables, or measurement of behavior properties.