Note on method.

Abstract

For some years now Professor Clark Hull has been instructing psychologists, by both precept and example, in logic and scientific method. He would doubtless be gratified at such concrete illustration of the effectiveness of his teaching as an attempt to apply it to his own doctrine. One can only applaud when he urges that a system of scientific theories be internally consistent, that it constitute a deductive system with the minimum necessary number of assumptions and that specific implications of (deductions from) these postulates be checked by empirical fact. Competent psychological theorists-and there are some-have always practiced these things. The burden of his complaint about current theories would hence appear to refer to their want of attention to his other requirements, namely, clarity and explicitness in definitions and postulates. For examples of these virtues he refers us to Newton or, in case we "may not be overly familiar with the technical details of classical mathematical physics," to Euclid. This is good counsel indeed. If, as history seems to indicate, the several sciences are going in the direction of deductive systems (some would say, even, a deductive system), it behooves us to look at geometry, the deductive system par excellence. The geometers have had ample time-two thousand years-and practice aplenty in handling such systems and we may well learn from them. It might be noted in passing that it took the geometers their 2,000 years to make the definitions and postulates of Euclidean geometry explicit, in the sense of leaving as little as possible undefined, and they are not satisfied yet: this in a system that is purely deductive, in which the selection of postulates is wholly arbitrary and which is not required at any point to check with

The problem of stimulus equivalence in behavior theory.

“…= Io . M38i> , (1) in which 6 represents the amount of excitatory potential susceptible to diminution through the generalization process, and D is the difference in j.n.d. 's between the point on the stimulus continuum at which reinforcement occurred and the point at which the test stimulus was applied.…”

“…In his presidential address (18,14), Tolman remarked incidentally that the writer's theory of adaptive behavior contains no explanation of stimulus equivalence. 2 At about the same time, Adams complained (1,10) in a particular context that the writer has given no definition of the term stimulus. In a certain important sense both criticisms involve the same question.…”

“…The author is indebted to Dr. Donald T. Perkins for the mathematical derivation of equation 7, p. 20 ff 1. In the same connection Tolman expresses the belief that there is in the writer's system a corresponding lack of an explanation of response equivalence.…”

Symbolic technique in psychological theory.

“…In the longer non-elliptical vernacular this would be: Experimental extinction © implies by definition that a certain object or organism A acts in relation to another object or organism B at the time of a certain stimulus (1), and that this is repeated at the time of a like stimulus (2), and that frustration as defined in ® or the negative of a reinforcing state of affairs as defined in ® exists at a third time, and that the certain object or organism A does not act in relation to the other object or organism B at the time of another stimulus (4) like the first.…”

The logical character of the motivation concept. II.

“…2 There is a kind of wan humor in calling most psychological theories in their present form ' implicit definitions' or ' postulate systems.' Most psychological theories have been formu- 1 The logical character of the motivational concept. I. PSTCHOL.…”