The Conceptual Representation and the Measurement of Psychological Forces

The central claim is that psychological forces possess directedness that cannot be defined as physical direction or determined by Euclidean geometry; representing them requires a geometry of hodological space, which specifies the properties of paths and directions within a person's life space. Crutchfield's 1939 review in the Journal of Applied Psychology noted that the monograph rounds out the system of concepts introduced in Principles of Topological Psychology, and that only with this volume does the justification for the earlier work's detailed discussion of connected and unconnected regions become visible . The topological representation permits explicit definitions of behavioral directions and relationships—equality, oppositeness, degrees of unity—which in turn permit careful statement of the conditions for measuring psychological forces. The monograph thus supplies the dynamic concepts that the purely structural topological framework lacked.

Hodological space is a geometry designed to represent the directions and distances of psychological locomotion within a life space—the totality of regions and paths relevant to a person's behavior at a given moment. Lewin argues that direction in psychology cannot be reduced to physical direction because the psychological 'toward' or 'away from' a goal is defined by the structure of the life space, not by coordinates in physical space. The book devotes roughly its first seventy pages to definitions of direction and relationships between directions, using examples such as mazes with one-way doors, the round-about-route, and the insane asylum to illustrate how hodological space handles differentiation and barriers . Crutchfield characterized this section as working out a geometry applicable in psychology, distinct from the Euclidean geometry that governs physical motion .

The fifth chapter, comprising roughly ninety pages, systematically surveys possible experimental means of measuring forces. Crutchfield's review described it as 'by all odds the most thorough treatment of this problem which we have had to date' . Methods include measuring one force by another in the obstruction box, using velocity of locomotion as an indicator of relative force strength, and analyzing frequency of crossing as a criterion of the difference between opposing forces. The conceptual relation between force, valence, and tension is developed: valence is defined as the property of a region attracting or repelling the person, while force is the tendency to locomote in a given direction. The book explicitly frames itself as a contribution to theoretical psychology rather than a textbook of experimental findings, aiming to reformulate concrete problems through a rigorous conceptual framework .

Reviews acknowledged the monograph's theoretical importance while noting its difficulty. Crutchfield called it 'a creative work of great significance' and 'the most important publication he has issued to date,' but added that 'there is nothing easy about it' and that two or three readings might be prescribed . He identified flaws of presentation, including a failure to make coordinate parts of the outline cover coordinate points of content, and called for 'drastic revisions' in the system of concepts. Peatman's review in the American Journal of Orthopsychiatry summarized the work's three tasks—positioning force within psychological concepts, clarifying its logical and geometrical aspects, and discussing empirical laws and measurement—noting the inclusion of a glossary, bibliography, and index . The reviews collectively position the book as an advanced theoretical contribution, not an accessible introduction.

The 1935 collection A Dynamic Theory of Personality assembled papers from 1927 to 1933 that illustrated the experimental origins of Lewin's concepts but did not present a systematic theoretical framework. The 1938 monograph supplies that framework for one crucial component: the representation and measurement of psychological forces. Crutchfield noted that the present work is 'intimately related to the principles of topological psychology previously described by the author' and serves as a further step in the development of Lewin's elaborate theoretical system . Where the earlier collection showed dynamics emerging from experimental work, the monograph builds the conceptual apparatus—hodological space, coordinating definitions of force, the relation between valence and force—that allows those dynamics to be stated with mathematical rigor.

The conceptual apparatus developed here—force, valence, tension, life space—provides the theoretical vocabulary Lewin later applied to group dynamics and social change. The monograph's treatment of overlapping force fields and conflict situations with stable and labile equilibria directly informs his later analyses of group decision and resistance to change. However, the 1938 book is concerned with individual psychological forces within a life space, not with group-level phenomena. Lewin's later work extends the framework by treating groups as wholes with their own life spaces and force fields, but the fundamental concepts of direction, force, and measurement that make those extensions possible are worked out in this monograph. The book thus represents a transitional moment between the topological psychology of the mid-1930s and the social psychology of the 1940s.