Groupthink Versus the Wisdom of Crowds: the Social Epistemology of Deliberation and Dissent Miriam Solomon Temple University

The Southern Journal of Philosophy (ZOOS) Vol. XLN

Groupthink versus The Wisdom of Crowds: The Social Epistemology of Deliberation and Dissent Miriam Solomon Temple University

Abstract

Trust in the practice of rational deliberation is widespread and largely unquestioned. This paper uses recent work from business contexts to challenge the view that rational deliberation in a group improves decisions. Pressure to reach consensus can, in fact, lead to phenomena such as groupthink and to suppression of relevant data. Aggregation of individual decisions, rather than deliberation to a consensus, sur- prisingly, can produce better decisions than those of either group deliberation or individual expert judgment. I argue that dissent is epistemically valuable, not because of the discussion it can provoke (Mill’s and Longino’s view about the benefit of dissent), but because dissenting positions often are associated with particular data or insights that would be lost in consensus formation. Social epistemologists can usefully pay attention to various methods of aggregation of individual opinion for their effectiveness at realizing epistemic goals.

1. Introduction Philosophers from Plato to Mill to Popper to Rawls and Longino have made critical discussion and deliberation central to their social epistemologies. The claim is that rational dialogue between two or more individuals improves reasoning over what can be accomplished by individuals working alone. Longino (1990, 2002) even goes so far as to claim that objectivity is constituted by such critical discourse, provided that the discourse satisfies constraints such as tempered equality of intellectual authority, public forums for criticism, respon- siveness to criticism, and some shared standards of evaluation. Faith in the practice of rational deliberation is widespread and largely unquestioned. Moral and political philosophers depend on it as much as epistemologists and philosophers of science, often writing of “deliberative democracy” or “discursive democracy.” Characteristically, the Kantian focus on individual reason has been replaced by various ideals of group reason. For example, in Rawls’s “original position’’ a community of individ-

28 Groupthink versus The Wisdom of Crowds uals rationally deliberates along impartial guidelines (the “veil of ignorance”) in order to select shared principles of justice. In Habermas’s “discourse ethics,” participants rationally deliberate with one another from their actual social positions, attempting to reach consensus. Faith in the practice of rational deliberation extends to applied ethics as well as ethical theory. The following statement, from the University of Michigan Pediatric Ethics Committee, is typical of contemporary approaches: “What experimentation is to medicine, rational deliberation is to ethics.”’ While rational deliberation involves a community, rather than an individual working in isolation, the criticisms and responses to criticism are thought of as transparent to each reflective individual. Deliberation corrects errors, uncovers presuppositions, and sometimes transmits additional evidence. Each individual in the community is thought of as capable of recognizing their own errors and presuppositions when they are pointed out by others, and of accepting evidence discovered by others. This is a very ”internalist” view of deliberation, in a sense of the word “internalist” that is widely used among epistemologists. (It is also somewhat individualist, despite the depen- dence on community, but that is not my topic here.) For example, Roderick Chisholm characterizes internalism this way: “If a person S is internally justified in believing a certain thing, then this may be something he can know just by reflecting upon his own state of mind” (Chisholm 1989, 7). The core of the position is that justifications for belief are internal to each individual knower and, typically, not only internal but also available to reflection. The contrast is with “externalism,” according to which one can be justified, or have knowledge, without being able to say why one is justified or has knowledge. Thus externalists claim that the reasons for justification or knowledge are not (or not readily) available to individual cognizers, either because the reasons do not enter conscious awareness or because the reasons (or causes) are external to individual minds. It might be thought that social epistemology is all externalist, since by definition social epistemology concerns itself with epistemic phenomena that go beyond the individual. Nevertheless I maintain that this area of work (namely, on deliberation and criticism) in social epistemology is internalist in character, because the epistemic phenomena discussed are available to reflection and because when an epistemic phenomenon involves more than one individual (e.g., when one person points out problems in another’s work) the epistemic assess- ment is based on reflection by each and all of the individuals concerned. Again, the contrast is with externalism, in which epistemic assessments are not based on reflection or intro- spection at all.

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This kind of internalism in social epistemology should not be confused with “conservative” social epistemology (as described by Hilary Kornblith [1994] and endorsed by him as well as Philip Kitcher [ 19931). “Conservative” social epistemology has more to do with individualism and with rejection of construc- tivism than it has to do with internalism. Generally speaking, work in social epistemology by philosophers has not been “internalist” in the way described above. Certainly Hilary Kornblith and Alvin Goldman are clear in their common position that social practices are to be evaluated instrumentally for their conduciveness to truth, rather than intrinsically for their rational cogency. For example, Goldman (2002) claims that infants get their first beliefs through a process he calls “BABA”: the bonding approach to belief accept- ability. Goldman suggests that beliefs are contagious when there is a prior bond of affection between individuals. It turns out that BABA is reliable, and the reliability of BABA is under- stood through evolutionary psychology: those with affective bonds will have less incentive to deceive one another than those without affective bonds. The epistemics of BABA are not transparent to reflection. I am basically in agreement with Goldman and Kornblith’s “externalist” approach (although I would describe myself as less conservative, in that I think that terms such as “justified” and “knows” are usefully applied to communities, in addition to individuals). In this paper, I am using the externalist (or instru- mentalist) perspective to look at group deliberation, discussion, and criticism. I do not assume truth in particular as the goal (as do Goldman and Kornblith), although all that I say is consistent with truth as a goal. I am also taking a thoroughly naturalistic approach, drawing on previous empirical work on epistemology of groups. It will turn out that the traditional “internalist” philosophical picture of rational deliberation is a myth and not an episte- mologically useful myth (i.e., it is not an ideal toward which individuals or groups can or should strive). This is surprising because the practices of group rational deliberation seem so obvious: Helen Longino even says that her explication of objectivity in terms of the four criteria of knowledge comes from “an intuitive distinction between knowledge and opinion that I take to be shared .... Those who reject the conditions have a different concept of knowledge, or perhaps, a concept of something else” (2002, 174). Surprises can be useful in epistemology. Epistemology is most helpful when it leads to normative recommendations that are surprising in that they are counterintuitive or in contra- diction with established practice. Furthermore, against the background of a few significant surprises, commonsense recommendations become more interesting because they cannot be

30 Groupthink versus The Wisdom of Crowds taken for granted. So it would make the enterprise of social epistemology more valuable to have some surprises, such as a counterintuitive recommendation or an unexpected negative consequence of commonsense normative practice.

2. Some Surprising Empirical Results

A good deal of work in social epistemology is done in business schools, out of the philosophical limelight. This is perhaps because of the business school emphasis on outcomes, typically financial outcomes, in organizational research. This makes the work relevant to naturalistic epistemologists, especially those who evaluate epistemic practices instrumentally. Here are some surprising results:

1. Group deliberation often produces worse decisions than can be obtained without deliberation. (Often enough for epistemic concern.) 2. A group of nonexperts often produces better decisions on a topic than does an expert about that topic. (Thus challenging the traditional deference to the expert.) 3. If group deliberation does take place, outcomes are better when members of the group are strangers, rather than colleagues or friends. 4. Groups and organizations sometimes don’t know what they know.2

Let me say a little about each of the results, to give you the flavor of the research and the significance of the results. The “groupthink phenomenon was first described by Irving Janis in 1972.3 It occurs when a group of individuals aims to reach consensus on a controversial topic. Peer pressure, as well as pressure from those in authority (if present in the group), leads dissenting individuals to change their minds and, perhaps as important, not to share their knowledge of contrary evidence. The dynamics of groupthink frequently lead the group to a polarized position, not to an average or a neutral aggregate of individual opinions. Often cited examples of groupthink include Kennedy’s “Bay of Pigs” fiasco and NASA’s decision to launch the Challenger spacecraft. To take the first example, the “Bay of Pigs” fiasco (in which the Kennedy administration attempted to overthrow the Castro government by secretly returning a small brigade of Cuban exiles to Cuba), Janis rejects the official explanation in terms of right-wing political pressure, difficulties of a new presidency,

31 Miriam Solomon secretiveness about the planning and individual fears about reputations. Or at least, he claims that the official explanation is not enough to explain what actually happened: a process in which knowledgeable and intelli ent advisors succumbed to the dual illusions of unanimity an% invulnerability, suppressing both their own doubts and the doubts of others and acting with docility under Kennedy’s leadership. While there is some controversy about whether the groupthink phenomenon occurs in just the way that Irving Janis describes, there is little doubt that factors such as peer pressure, pressure from authorities, pressure to reach consensus, and the salience of particularly vocal group members who may anchor decisions lead groups into making poor decisions. It doesn’t help much if individuals “try harder” to be unbiased or independent; we are unaware of, and largely unable to resist, the social factors causing groupthink and related phenomena. Solomon Asch’s and Stanley Milgram’s classic experiments in the 1950s and 1960s show the strength of pressures to conform and Tversky and Kahneman’s classic work in the 1970s shows the power of cognitive biases such as salience and anchoring. As James Surowiecki (2004,xix) puts it, “too much communication, paradoxically, can actually make the group as a whole less intelligent .” Does this mean that group deliberation is worthless? It means that the results are doubtful, unless the group follows a structured procedure designed to avoid groupthink (and other biasing phenomena) and produce better decisions. There are a number of suggestions about what such a structured procedure should be. Janis himself recommends nondirective group leaders, encouragement of (rather than mere toleration of) dissent, and several independent groups or subgroups charged with the same problem (in order to see whether or not they come up with the same result). Surowiecki (2004)recommends diversity of group membership, claiming that it brings different perspectives to a group. Cass Sunstein (2003)recommends both diversity and active encouragement of dissent. Sunstein also goes further and explores the kind of diversity that is relevant to particular problem domains. Epistemically useful diversity is not the same as political diversity, although it may be coexten- sive with political diversity for some problem domains. In general, epistemically useful diversity results when different individuals use their differences in their investigation of the problem domain. These suggestions are all reasonable, but they have not been formally tested and evaluated. Even Janis expresses the concern that the suggestions will have “undesirable side effects” (1982,252). Some leaders, for example, might be unable to tolerate dissent without subtle or overt disapproval, which will then squash dissent. Or some leaders, for example, might be

32 Groupthink versus The Wisdom of Crowds incapable of neutrality, especially when a group is coming to a consensus on a view that the leader disagrees with. Or, for example, criticism and dissent might produce anger and demoralization that distracts the group from its epistemic goals. So it is not enough to make plausible-sounding suggestions for improvement: it is important to show that the suggestions can be implemented and that they lead to the desired results. The experimental work is not there yet. The Tipping Point (ZOOO),a current best-seller by Malcolm Gladwell, describes a phenomenon similar to groupthink, but more extended in time, society, and place: how inventions, fashions, or behavior become widely accepted in a society. He tries to explain “the tipping point,” which is the point at which the behavior in question “cascades,” spreading quickly through a population. The explanation is not that there is a rational public discussion of benefits and risks of change. Rather, Gladwell explains “social epidemics” in terms of three causes: “the Law of the Few, the Stickiness Factor, and the Power of Context.” The general idea is that the new behavior is first adopted by some individuals who are regarded by others as being “in the know” (Gladwell calls them Mavens). Then the behavior is infectious, so that others who see it also adopt it (Gladwell thinks that some specially talented people help with this-he calls them Salesmen). Finally, in the right context of favorable connections between individuals (Gladwell describes individuals with many and diverse social connections as Connectors), adoption of the new behavior reaches “the tipping point.” An example that Gladwell gives is the spread of Hush Puppies as a fashion in the mid-1990s. Hush Puppies were down to sales of about 30,000 per year when a few trendy young people in the East Village and Soho in New York (the Mavens) bought them from resale stores. They were noticed by influential fashion designers (the Connectors), and the aesthetic was catchy enough that these designers used the shoes in their shows. Through the fashion designers and their multifarious connections, wearing Hush Puppies spread through the nation, reaching annual sales of over 2 million. Hush Puppies do not “deserve” their success any more than a whole range of funky shoes adopted by trendy people at different times. Hush Puppies became successful because the influential fashion designers (the Connectors) saw the Mavens (the trendy young people in Soho) wearing them. It could easily be that a group of trendy young people on South Street, Phila- delphia, started wearing Classic Loafers (Sperry Top Siders) in 1994. But the influential fashion designers never got to Philadelphia and never saw them. Thus, Classic Loafers never reached the “tipping point.” Another example described by Gladwell is the comparison of Paul Revere’s ride from Boston northward with William Dawes’s

33 Miriam Solomon ride westward. Both men carried the news that the British were coming. But Revere’s news tipped, and Dawes’s didn’t; Revere got the troops out and Dawes did not: that’s why most of us have not heard of Dawes. The difference was that Revere was a Connector, knowing many people in many different walks of life, and Dawes was not. Revere knew just whose doors to knock on to spread the message that the British were coming (that is, he knew who the Salesmen were). Revere was also a Maven, which is why the stable boy who overheard the British plans made sure to tell Revere. Finally, Revere was charismatic and trust- able, ensuring that his message was “sticky” (that is, he was himself a Salesman). (Typically, the three characteristics of Maven, Connector, and Salesman do not all coincide in one person! In that way, this example is unusual.) Surowiecki’s recent book, The Wisdom of Crowds (2004), presents a surprising result: large groups of untrained people are often better at decision making than an elite (expert) few. He shows this result in a wide variety of domains. The original example is from Francis Galton (Darwin’s half-cousin) who discovered in 1906 that the “vox populi”-a group of approximately 800 people visiting a fair in Plymouth-made an excellent estimation of the weight of a fat ox. In fact, the mean of the estimates was 1,197 pounds and the actual weight was 1,198 pounds. Individuals who were expert in the weight of oxen (farmer, butchers) did not individually do as well. Galton himself was surprised by the accuracy of the result: he had a cynical view of the outcome of democratic choice when ordinary people vote. A more recent example described by Surowiecki is the excellent results of the Iowa Electronic Market, which generally outperforms major national as well as individual political pundits, in predicting the outcome of presidential and other US. and foreign elections. The Iowa Electronic Market is open to anyone but is not very large (approximately 800 traders), not especially demographically diverse (mostly men, mostly from Iowa) and not composed of political experts. It works like gambling odds: people can buy and sell futures contracts based on how well they think a candidate will do in an upcoming election. The Iowa Electronic Market works so well that others are imitating it: for example, Eli Lilly is experimenting with using internal stock markets and hypothetical drug candidates to predict whether new drugs will gain FDA approval (Surowiecki 2004, 221). Note the difference between this and the more commonsense practice of consulting with an expert. A final, startling example that Surowiecki reports is the case of the missing submarine. In 1968 the US. submarine Scorpion disappeared. The Navy had only the vaguest of information about where it might be: somewhere in a circle twenty miles in

34 Groupthink versus The Wisdom of Crowds diameter and thousands of feet deep. Craven, a naval officer, assembled a diverse group of experts and asked each to individually calculate their best prediction of the submarine’s path and final location. There was no discussion or consultation of these experts with each other. John Craven combined the calculations using Bayes Theorem and came up with an aggregate prediction. It turned out to be just 220 yards from the discovered location of the Scorpion. (See Surowiecki 2004, xx- xxi.) These three examples are not isolated cases; it is not possible to dismiss them on the ground that they are due to chance or good epistemic luck. Surowiecki’s book gives so many examples that it is inescapable to conclude that he is onto an epistemic phenomenon. It is important not to conclude, however, that the crowd is always wise. As the examples of “groupthink” and “tipping point” show, the crowd may be unwise or indifferent to good epistemic results. Observe that in Surowiecki’s examples the groups do not deliberate, do not attempt to come to a consensus, and do not attempt to compromise. The “group decision” is a calculated average opinion in the case of the Galton example and a resultant market value in the case of the Iowa Electronic Market and a calculated vector sum in the case of the missing submarine. In the case of the Galton example, the group doesn’t know what it knows or that it knows. In the case of the Iowa Electronic Market, each individual does know the price of the contracts, but they do not necessarily know what they know: they do not know that this is a good prediction of election results (unless, of course, they know from past results how well the Iowa Electronic Market does in general). So, again, they do not know what they know or that they know. In the case of the missing submarine, it is stretching things even to say that the group knows; certainly they do not know that they know. These are clear examples of externalism in social epistemology. Another result that Sunstein mentions is that investment groups and corporate boards composed of strangers do better than investment groups and corporate boards composed of friends (2003, 27-8). Apparently, groupthink phenomena, which often produce polarized and inaccurate decisions, are more likely when members of a group have social connections to one another. 3. Analysis of the Empirical Results According to Surowiecki (who, it seems, inductively arrives at his conclusions5) there are three important conditions for a crowd to make a good aggregate judgment: independence, diversity, and decentralization. Independence means that each

35 Miriam Solomon individual makes a judgment on his or her own. There is no discussion, or even knowledge of other’s opinions. Diversity means that the individuals are sufficiently different with respect to the knowledge and perspectives that they have. “Sufficiently different” needs specifying for each case (I’ll say more about that below). Decentralization means that the process of aggregation treats each person’s decision similarly: every vote counts for the same and there are no “experts” or “authorities” whose votes are weighted more heavily than others. These conditions help us understand why the aggregated decisions of a crowd can be epistemically superior. There is a bit of mystery about “the wisdom of crowds.” Surowiecki says that when averaging the opinions of a large group of diverse, independent, decentralized people “the errors each of them makes in coming up with an answer will cancel each other out” (2004,10). He has in mind that the diversity is such that individual biases cancel each other out (227).Independence means that phenomena such as groupthink cannot take place. And decentralization prevents any individual from having undue influence in the aggregated decision, making sure that no bias gets magnified. While Surowiecki explains why the aggregated decisions of a crowd are not epistemically faulty in these three respects, he does not explain why the aggregated decisions often do so well. I’ll try to do this. When decisions are aggregated, individual opinions are all used in calculating the aggregate decision. Individual opinions are often based on particular pieces of information that may not be generally known. When an individual is overruled in discussion, or changes her mind because of peer pressure, that information is lost to the group. So aggregation without deliberation preserves information. Interestingly, Sunstein says something similar in his discussion of the epistemic benefits of dissent. In Why Societies Need Dissent (2003)he argues that dissent is valuable because it keeps the most information available to a community. Thus he implicitly claims that different judgments are different at least in part because they are based on different information. Dissent is even worthwhile when the dissenting opinions are, overall, judged implausible. It is not, however, worthwhile when dissenting opinions are “speaking nonsense” (Sunstein 2003, 7). The difference between Surowiecki and Sunstein on this matter is that Surowiecki is interested in the overall, aggregate judgment without deliberation and Sunstein allows-indeed encourages-both deliberation and a more informal process of coming to an overall decision. While their emphasis is different, they are not really disagreeing with one another. They agree on the central claim: dissent (i.e., different assessments by differ-

36 Groupthink versus The Wisdom of Crowds ent individuals) is valuable because it preserves and makes use of all the information available to the community. I have also said something very similar in Social Empiricism (2001) where I argued that, in scientific inquiry, dissent is valuable because it keeps all the empirical successes available to the community and that consensus, when it takes place, should not result in the loss of any of these successes. I use “empirical success”‘j rather than “information” because my book deals specifically with scientific knowledge. Here are the details from Social Empiricism.

Three conditions for a normatively appropriate dissent:

1. Theories on which there is dissent should each have associated empirical success. 2. Empirical decision vectors7 should be equitably distributed (in proportion to empirical successes). 3. Nonempirical decision vectors should be equally distributed (the same number for each theory). Note that consensus is the special case in which the amount of dissent goes to zero. Three conditions for a normatively appropriate consensus: 1’. One theory comes to have all the empirical successes available in a domain of inquiry. 2’. This same theory comes to have all of the empirical decision vectors, since all scientists working productively (with empirical success) are working within the one theory.

3’. Any distribution of nonempirical decision vectors is OK, but typically more will develop, over time, on the consensus theory, as the old theories fade away. During dissent, and thus in the early stages of consensus formation, dissent’s require- ment of equal distribution of nonempirical decision vectors holds.

Social Empiricism also sets out similar conditions for the dissolution of consensus, since consensus is not viewed as an “end point” of inquiry. Three conditions for a normatively appropriate dissolution of consensus: 1”. A new theory has empirical success that is not produced by the consensus theory. (So, the new theory deserves attention.)

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2”. Empirical decision vectors come to be equitably distributed. 3”. Nonempirical vectors come to be equally distributed.

The justification for these conditions is not given here, but it rests on the superior outcomes (better scientific results) when the conditions are satisfied. That is, the justification is instru- mental. Case studies in the recent history of science are used to show this. In general, according to Social Empiricism, consensus is usually epistemically undesirable. It is not enough for one theory to have the most evidence; it must have all the empirical successes for consensus to be appropriate. Most of the time, dissent is epistemically better for science. (I stress the epistemic desirability, rather than overall desirability, since there can sometimes be political reasons for coming to consensus. Medical practice and environmental science are two areas in which consensus has political advantages. These political advantages may or may not outweigh the epistemic disadvantages of coming to a consensus.) Note that this discussion of the epistemic benefits of dissent differs from the more widely known arguments by Mill, Popper, Longino, and others who claim that dissent is valuable because the criticism from dissenting perspectives leads everyone to correct and improve their position. On the latter view, dissent is valuable because it improves everyone’s views through criticism and response to criticism. On the former view, dissent is valuable even when no discussion occurs. Of course, dissent could be valuable for both reasons: that it keeps information available and that it encourages criticism. As discussed above, however, there is room for skepticism about the results of criticism, since sometimes deliberation makes things worse rather than better. If the main epistemic benefit of dissent is that it keeps information available, then not just any dissent is worthwhile. (Contrariwise, if dissent is epistemically worthwhile because it encourages criticism, then any dissent is worthwhile, so long as it stimulates the dissenter to produce good criticism.) Dissent is worthwhile only when the dissenting positions are each associated with relevant information. The dissenting positions don’t need to have overall plausibility, but they do need to bring information to the table. This is close to what I said about science in Social Empiricism, where I argued that theories on which there is dissent should each have associated empirical successes. A final point. Let’s go back to the case of the fat ox. In order to calculate the aggregate judgment of the weight of the ox, Galton took an arithmetic mean of individual judgments. Why calculate an arithmetic mean? Why not calculate the median?

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Or perhaps some other function of individual judgments? For example, one could weight more heavily the judgments of farmers and butchers than the judgments of other people. Farmers and butchers have more expertise than laypersons, so perhaps their judgments should count for more. Or, for example, one could leave off the top and the bottom estimates on the grounds that these are probably outliers. These ques- tions about how to aggregate individual judgments take us into the domain of social choice theory, in which there have been a number of interesting results recently. (See, for example, List and Pettit 2002.) It is sufficient to note here that all the methods of aggregation are, in an epistemic sense, external: neither the crowd nor any of the individuals composing the crowd are in fact calculating the aggregate judgment. In the case of the fat ox, Galton is making that calculation. In the case of betting markets such as the stock market or the Iowa Electronic Market, the market is making the calculation. In the case of the missing submarine, the non- submarine-expert applied mathematician makes the calculation. So in all these cases, the groups do not know what the information they have amounts to. We might say informally, “the group does not know what it knows.” More precisely, for the stock market and the Iowa Electronic Market, the knowledge is represented, so the group knows, although it does not know that it knows. For the fat ox and the missing submarine, the knowledge is not represented (unless Galton or the applied mathematician calculates it), so the group does not know (in one sense), and it does not know what it knows (in another sense). In this attempt at linguistic precision, we begin to stretch the limits of our language of “know.” The more data processing or even data mining that goes into the calculation of the aggregate result, the less plausible it is to say that the group “knows” the result. All that can be said is that the group has all the information required in order to know but does not know which information (of all that it knows) is the relevant information. “Data mining,” sometimes called “knowledge discovery in databases (KDD)” is defined as “The nontrivial extraction of implicit, previously unknown, and potentially useful information from data” (Frawley, Piatetsky-Shapiro, and Matheus 1992). It uses powerful computational tools such as neural networks and decision trees to analyze given data. It identifies patterns in the data and uses those patterns to make predic- tions that aid decision making. It is valued precisely because no individual notices these patterns when perusing the typically huge databases on which data mining techniques are used. Data mining shows the importance of having the data in a form in which the computational techniques can be applied, that is, stored in a single database to which algorithms can be applied.

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When data are physically distributed (e.g., possessed by different institutions) or stored in a variety of forms (e.g., some in human memory, some on paper, some in one database, some in another), then we are even further from knowing anything that is “in the data” because the data are not in a form that is amen- able to the computations of data mining. There are an infinite number of ways to calculate an aggregate decision from a group of individuals’ decisions. Arrow’s possibility theorem and its descendants (including List and Pettit’s “discursive dilemma” or “impossibility theorem”) suggests that compromises need to be made when applying the usual constraints on such calculation.8 Such compromises reinforce the sense that aggregate decisions are not ”in the data” of the individual decisions, but are various different interpretations of data, each satisfying different constraints. In these circum- stances, it is a stretch to say that the group “knows.” After all, which of the many different interpretations of data does it know? 4. Conclusion Discussion and criticism are widely thought to be essential for both scientific research and political deliberation. Dissent is traditionally valued because it leads to criticisms and responses to criticism. This paper gives reason to be skeptical about the outcomes of discussion and criticism. In particular, it gives reason to be skeptical about the widespread epistemic ideal of encouraging a group to deliberate with one another until they reach consensus. Instead, this paper gives another reason to value dissent, namely, that normatively appropriate dissent preserves information in a way that can be useful to the group. Finally, the paper suggests that epistemically useful results can be obtained by various ways of aggregating group information. Notes Many thanks to Deborah Tollefsen and David Henderson for arranging this conference, and to the Spindel family for their support and hospitality. I’m grateful to Alison Wylie in particular for her stimulating commentary, and to the audience for their many suggestions. See http://www.med.umich.edu/psm/pecJstaffhfo.htm For this way of describing the epistemic situation, I draw on Goldman (20041, who quotes Sandy Berger, national security advisor under President Clinton, who was speaking of the FBI on 9/11. This was in his Victims of Groupthink (1972). The second edition of the book was titled simply Groupthink (1982) and it is this edition that I am using. Surowiecki does not explore the reasons for this, although he does mention that the results of polls fluctuate more than the results

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of the Iowa Electronic Market. I qualify this because Surowiecki does not say explicitly how he arrives at his recommendations for aggregate decision making. The recommendations follow the discussion of particular examples. Exactly how to characterize “empirical success” need not be discussed here; there is a full discussion in chapter 2 of Social Empiricism (2001). Empirical decision vectors are causes of preference for theories with empirical success, either a kind of empirical success in general or one empirical success in particular (e.g., a preference for theories with novel empirical success or a particular salient empirical success). Nonempirical decision vectors are other reasons or causes for success (e.g., preference for theories with hierarchical ideology, preference for simpler theories, holding onto a theory because of pride). Decision vectors include anything that influences the outcome of a decision, including those influences typically considered as “biasing factors.” These concepts are discussed at length in my book Social Empiricism. * Philip Pettit and Christian List’s recent result, which they call “the impossibility theorem” (List and Pettit 20021, argues that there is no aggregation procedure yielding consistent collective judgments that satisfies their four reasonable constraints (universal domain, completeness, anonymity, systematicity). Bibliography Chisholm, Roderick. 1989. Theory of knowledge. 3rd ed. Englewood Cliffs, NJ: Prentice Hall. Frawley, W., G. Piatetsky-Shapiro, and C. Matheus. 1992. Knowledge discovery in databases: An overview. AZ Magazine (Fall): 213-28. Gladwell, Malcolm. 2000. The tipping point: How little things can make a big difference. New York: Little, Brown and Co. . Goldman, Alvin. 2002. Pathways to knowledge: Private and public. New York: Oxford University Press. . 2004. Group knowledge versus group rationality: Two approaches to social epistemology. Episteme l(1): 11-22. Goldman, Alvin, and Moshe Shaked. 1992. An economic model of scientific activity and truth acquisition. In Liaisons: Philosophy meets the cognitive and social sciences, ed. A. I. Goldman, 227-54. Cambridge, MA: MIT Press. Janis, Irving. 1982. Groupthink. 2nd ed. Boston: Houghton Mifflin Co. Kitcher, Philip. 1993. The advancement of science. Oxford and New York: Oxford University Press. Kornblith, Hilary. 1994. A conservative approach to social epistemology. In Socializing epistemology: The social dimensions of knowledge, ed. Fred Schmitt, 217-33. Lanham, MD: Roman and Littlefield. List, Christian, and Philip Pettit. 2002. Aggregating sets of judgments: An impossibility result. Economics and Philosophy 18:89- 110. Longino, Helen. 1990. Science as social knowledge: Values and objectivity in scientific inquiry. Princeton, NJ: Princeton University Press.

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Longino, Helen. 2002. The fate of knowledge. Princeton, NJ: Princeton University Press. Solomon, Miriam. 2001. Social empiricism. Cambridge, MA: MIT Press. Sunstein, Cass. 2003. Why societies need dissent. Cambridge, MA: Harvard University Press. Surowiecki, James. 2004. The wisdom of crowds: Why the many are smarter than the few and how collective wisdom shapes business, economies, societies and nations. New York: Random House, Doubleday Books.