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Looking at Patterns, Not People

Scott L. Feld

The Social Atom: Why the Rich Get Richer, Cheaters Get Caught, and Your Neighbor Usually Looks Like You. Mark Buchanan. xii + 242 pp. Bloomsbury, 2007. $24.95.

Physicist Mark Buchanan brings wide knowledge, thoughtfulness and great enthusiasm to the task of analyzing social phenomena. In The Social Atom, he argues that the mind-set of his profession can be as useful for understanding and explaining social life as for studying the physical world. If we step back from our customary focus on individual psychology, he says, and view people as "social atoms" that obey rather simple rules (which are not unlike the laws of physics), we may discover certain patterns, or "lawlike regularities."

Buchanan illustrates the approach with a very simple example: the way channels emerge when people move in crowds. In the midst of initially chaotic movements, one person begins to follow another in an effort to avoid collisions, and streams of movement emerge. People move within these channels because they provide the paths of least resistance. As more people join such streams, there is greater pull on others to join in the flow, and the particular channels become self-perpetuating.

In this way, patterns can emerge "accidentally"—that is, in the absence of any compelling reason for taking a particular form—and can maintain themselves. Such processes can underlie more than just physical movements. Buchanan suggests that fads, fashions, prejudices, norms and customs can all be results of such emergent processes.

Indeed, one of Buchanan's main messages is that the behavior of people in a group does not necessarily reflect the individual preferences of the members of the group. For example, he describes Thomas Schelling's classic simulations that showed that a high degree of racial segregation can easily arise in a society whose members don't have strong prejudices; all that is necessary is that individuals avoid living in communities in which their own racial group would be greatly outnumbered.

Buchanan further supports his point—that patterns in groups can emerge apart from individual preferences—by describing several classic social-science findings. For example, Philip Zimbardo's experiment setting up a mock prison at Stanford showed how ordinary, well-intentioned students could be easily induced to behave very cruelly.

Why do these things happen? The theoretical approach that Buchanan takes to answer this question is to isolate a few primitive properties of a social atom; these, when combined in some interactive process, produce predictable consequences for phenomena as varied as conflict and inequality. The approach has enormous appeal and promises to accelerate the development of the science of society. However, too much of the book focuses on supposedly essential properties of individuals, and not enough is devoted to understanding the emergent patterns.

Furthermore, in searching for explanations for social phenomena, Buchanan repeatedly commits two types of logical errors. The first of these is the simulation fallacy. A simulation typically shows that a particular proposed mechanism "could" produce an observed pattern. However, a simulation provides no evidence that the proposed mechanism is necessarily important or even relevant in some particular situation in which the pattern is found. Identifying "possible" causes only contributes to a scientific understanding of society when the conditions under which those causes are applicable and the extent of their applicability are empirically demonstrated and understood.

Buchanan's second logical mistake is the evolution fallacy. Creating an adaptive story for a human characteristic is not evidence for that characteristic; nor is the absence of such a story evidence against it. After referring to compelling empirical evidence for a human tendency toward reciprocal altruism, Buchanan seems to question the empirical conclusion based on the survival value of reciprocal altruism. The fallacious argument is that if something exists, it must have evolved for adaptive reasons. It is especially ironic that Buchanan falls into this trap, because physicists generally avoid such thinking. For example, it would be uncharacteristic for a physicist to describe or understand the properties of magnetism based on their fitness for survival.

Despite a little too much focus on what might be possible in the social world rather than what we actually know about it, Buchanan has provided a stimulating introduction to the developing science of society. I hope that his lucid presentation will inspire others to do the challenging work needed to advance this fascinating area of study.

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