The Arithmetic of Human Behavior
The human world is different from other natural phenomena after all, although the difference is not in any way beyond the reach of rationality. Human behaviors are responses to information, but unlike physical forces information does not force things. Input-output connections, made in the mind, are as diverse and changeable as the minds that contain them. On one hand this produces uncertainty-with one input leading to many outputs. But on the other hand this allows us to efficiently utilize disjunctive mechanisms-with many inputs leading to one output-and produce reliable outcomes in spite of uncertainty. These disjunctive mechanisms, in various guises, are most everywhere.There is, however, a mismatch between the logic of disjunctive mechanisms (A or B or C...leads to D), and the conjunctive logic (A and B and C...leads to D) of the understandings we generally rely upon. And there is a corresponding mismatch with rational and scientific ideals, traditions that have thrived using conjunctive reasoning and prize explaining the most with the least. We strive to explain mechanisms that are by nature prolific and diverse in parsimonious and unified terms. The idea is not that conventional explanations always come to the wrong conclusion. They can be right for the wrong reasons. Correlations between commonalities in a disjunction's inputs and its outputs can mimic the uniformities conjunctive explanations require. But even when these conclusions are useful, right for the wrong reasons explanations are always less informative than they seem, and can be treacherously misleading.The book explores misunderstandings and errors arising from these mismatches, and what can be done to correct them: in general understandings and reasoning, decision making and planning, research methods, and quantitative analysis. A practical problem is that we cannot readily replace conjunctive understandings with disjunctive ones. Our minds are not built to handle the myriad possibilities, probability estimates, calculations, and data handling required by disjunctive explanations. In the section on qualitative solutions the book discusses strategies that work within our limitations. This is not just a matter of separating out the useful from the misleading: a matter of applied reasoning and sound heuristics. Different information is sought, and different expectations, skills, and institutions are required to gather and make the best use of it. When the data collection and computational resources are available disjunctive systems can be tackled head-on. The section on quantitative solutions present a statistical approach, called Disjunctive Mapping, whose analyses are based on computing the sums of the probabilities of the various ways outcomes occur, and measuring the influence of individual factors in the contexts of each of those ways.