Introduction

Reasoning and argumentation: Towards an integrated

psychology of argumentation

Jos Hornikx1and Ulrike Hahn

2

1Department of Business Communication, Radboud University Nijmegen,Nijmegen, The Netherlands2School of Psychology, Cardiff University, Cardiff, UK

Although argumentation plays an essential role in our lives, there is nointegrated area of research on the psychology of argumentation. Insteadresearch on argumentation is conducted in a number of separate researchcommunities that are spread across disciplines and have only limited interaction.With a view to bridging these different strands, we first distinguish between threemeanings of the word ‘‘argument’’: argument as a reason, argument as astructured sequence of reasons and claims, and argument as a social exchange.All threemeanings are integral to a complete understanding of human reasoningand cognition. Cognitive psychological research on argumentation has focusedmostly on the first and second of these meanings, so we present perspectives onargumentation from outside of cognitive psychology, which focus on the secondand third. Specifically, we give an overview of the methods, goals, anddisciplinary backgrounds of research on the production, the analysis, and theevaluation of arguments. Finally, in introducing the experimental studiesincluded in this special issue, which were conducted by researchers from a rangeof theoretical backgrounds, we underline the breadth of argumentation researchas well as stress opportunities for mutual awareness and integration.

Keywords: Argumentation; Argument quality; Fallacies; Persuasion;Reasoning.

Given the importance of argumentation to our lives, it seems surprisingthat there is no established core area within cognitive psychology of thatname. What there has been, of course, is a long tradition of research on

Correspondence should be addressed to Jos Hornikx, Department of Business Commu-

nication, Centre for Language Studies, Radboud University Nijmegen, P.O. Box 9103, 6500

HD Nijmegen, The Netherlands. E-mail: j.hornikx@let.ru.nl

THINKING & REASONING, 2012, 18 (3), 225–243

� 2012 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business

http://www.psypress.com/tar http://dx.doi.org/10.1080/13546783.2012.674715

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‘‘reasoning’’; but it has become increasingly clear that reasoning research astraditionally conceived has been too narrow in its focus in a number ofways. These may be traced by considering the different, interrelatedmeanings that the term ‘‘argument’’ has—a term that has been central toreasoning research.

The first sense of the term ‘‘argument’’ to be distinguished here is anargument as a ‘‘reason’’. Giving an argument for something is providing areason for it. The strongest such reason possible is one from which the claimor conclusion in question follows by necessity.

This leads on to the second, closely related, sense of the term argument.Here the term is used not just to refer to the reason itself but to the core unitof reason and claim. It is in this sense that the term ‘‘logical argument’’ isunderstood: namely as a structured unit comprising one or more premisesand a conclusion. Probably the most well-known example of such anargument is the conditional argument modus ponens:

If daffodils are red, the moon is made of cheeseDaffodils are red. . . . . . . . .

The moon is made of cheese.

For much of the last 50 years, ‘‘argument’’ within cognitive psychologyhas been largely synonymous with ‘‘logical argument’’ in this sense.Likewise, ‘‘reasoning’’, as a cognitive activity, to a great extent has simplymeant ‘‘logical reasoning’’. From a logical perspective, the crucial aspect ofinterest in arguments is the presence or absence of a logical consequencerelation between premises and conclusion. Consequently the focus ofpsychological research on logical reasoning has been on people’s ability todistinguish logically valid from invalid arguments.

However, as has become abundantly clear, most of our everyday thoughtdoes not involve deduction (see e.g., Evans, 2002; Oaksford & Chater,1991), not just because we might be ‘‘poor’’ logical reasoners, but becausemuch of our everyday reasoning involves uncertain information andrelevance relations between pieces of information that are beyond the remitof (classical) logic. Consequently, a number of other ‘reasoning’ literaturesemerged within cognitive psychology. For example, a literature emerged on‘‘inductive reasoning’’ which, following on from the seminal work of Rips(1975) and Osherson, Smith, Wilkie and Lopez (1990), centred around‘‘category-based induction’’; that is, a type of inductive argument thatinvolves inferences about members of a category on the basis of informationabout other categories. A standard example here is given by the followingtwo arguments, of which the second is typically perceived to be strongerthan the first (a phenomenon known as the ‘‘typicality effect’’ in category-based induction):

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Penguins have ulnar arteries. . . . . . . . .

All birds have ulnar arteries

versus

Robins have ulnar arteries. . . . . . . . .

All birds have ulnar arteries

Although the literature on category-based induction has remained largelyseparate from the logical reasoning literature (for some exceptions see Heit& Rotello, 2010, 2012 this issue), it too has focused on ‘‘arguments’’ in thesense of one (or more) premises and a conclusion.

In short, the resultant psychology of reasoning has been very selectivegiven the breadth of everyday reasoning activities. Much is to be gained herefrom the general realisation that there are many distinct types of premise–conclusion schemes that are every bit as prevalent and practically important(if not more so) as the narrow range of logical (e.g., modus ponens, modustollens etc.) or inductive arguments (e.g., category-based induction) thathave been studied so extensively in the past. Furthermore, these manydistinct types of premise–conclusion schemes may be amenable totheoretically unified treatment. Much of the most recent literature onreasoning and argument that has examined, for example, other forms ofconditionals such as persuasions, dissuasions, or slippery slope arguments(e.g., Beller, Bender, & Kuhnmunch, 2005; Bonnefon, 2009; Bonnefon &Hilton, 2004; Corner, Hahn, & Oaksford, 2011; Hahn & Oaksford, 2007a;Ohm & Thompson, 2004; Thompson, Evans, & Handley, 2005) may be seenas attempts to redress the theoretical imbalance and broaden out reasoningresearch in this way.

A further limitation in the focus of reasoning research has been thatarguments as structured units need not be restricted to a single claim andreason. Although many logical arguments involve multiple premises (as inthe modus ponens example above), these multiple premises typicallycombine in such a way as to jointly constitute only a single reason.However, the term argument in the structural sense can also readily refer tolonger sequences of individual claims, counter-claims, and supportingstatements. For example, something that constitutes a ‘‘well-developed’’argument will typically involve more than a simple, single reason, even if thetopic itself is trivial. Consider, for example, the following case for picking upthe milk before lunch:

It would be good to pick up the milk before lunch, because there would besome in the house for a cappuccino with dessert, but going to the shopsnow will mean not being able to finish the paper. However, it looks like that

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really might not be finished anyway. On the other hand, maybe now would bea good time to stop having dessert, after all, it has become clear that there is abit too much sugar in my diet. So then the cappuccino is also not really apriority.

So skip the milk.

This overall ‘‘argument’’ for (not) picking up the milk for lunch involvesnot just a single, overall conclusion, but also intermediate conclusions(‘‘stop having dessert’’), as well as a variety of supporting reasons (‘‘going tothe shops will mean not finishing the paper’’) and counter reasons (‘‘but thatit won’t get finished anyway’’) which individually constitute ‘‘arguments’’ inthe first sense.

In fact, the realisation that much of ‘‘everyday’’ argument takes this morecomplex form was arguably one of the reasons philosophers such asToulmin (1958) came to the conclusion that there is much more to argumentand argumentation than logic, and that a different framework for dealingwith argument was required. According to Toulmin an overall argument canbe broken down into distinct types of components: a claim (that is, theconclusion whose merits are to be established); data (that is, the facts thatare used to support the claim); and warrants (that is, the reasons that areused to justify the connections). Toulmin’s framework (and others like it)has been influential in education and developmental research on argumen-tation (e.g., Brem, Russell, & Weems, 2001; Kelly, Druker, & Chen, 1998).However, treatment of interconnected sequences of claims and counter-claims has been virtually absent from mainstream cognitive psychology(for exceptions see Bailenson & Rips, 1996; McKenzie, Lee, & Chen, 2002;Rips, 1998).

Finally, it is only when one considers more complex arguments asstructured units, such as the preceding example, that a third and finaldistinct sense of the term argument comes into view. Specifically, the termargument can be used not just to refer to information content—whether thisbe a single premise and conclusion pair or a sequence interconnected claimsand counter-claims—but also to the dialogical, social activity that may begiving rise to these claims. So, for example, the above sequence of claims,supporting reasons, and counter-claims might reflect not the thoughts of asingle reasoner, but actually form the information content of an adversarialdialogue with distinct proponents:

John: It would be good to pick up the milk before lunchJoan: Why?John: Because there would be some in the house for a cappuccino with dessertJoan: But going to the shops now will mean not being able to finish the paperJohn: But it looks like that really might not be finished anyway!. . . etc.

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At the level of social activity, philosophers have distinguished differentkinds of argument, ranging from ‘‘quarrels’’ through to rational debate (see,e.g., Van Eemeren & Grootendorst, 2004). A specific type, such as rationaldebate, is characterised by procedural rules or norms that must be respectedin order for an argument to qualify as being of this type. Again there hasbeen not just theoretical work within philosophy, but also empirical, andoften experimental work on people’s appreciation of these procedural norms(Christmann, Mischo, & Groeben, 2000; Mischo, 2003; Schreier, Groeben,& Christmann, 1995; Van Eemeren, Garssen, & Meuffels, 2009, 2012 thisissue). However, this work too has been largely absent from mainstreamcognitive psychology.

It is the contention of this special issue of Thinking & Reasoning that thesedifferent senses of the word ‘‘argument’’—argument as reason, argument asstructured sequence of reasons and claims, and argument as a socialexchange—need to be brought together.1 All three are integral to thecomplex phenomenon that is argument, which itself seems central to ourunderstanding of higher-level cognition. Moreover, we believe that under-standing, both theoretically and empirically, even any single one of thethree different senses of argument distinguished here requires attention tothe others.

There is ample evidence, for example, that attempts to understand our‘‘reasoning’’ ability—that is, our ability to evaluate individual premise–conclusion connections—must take into account that, in our everyday lives,such reasoning is typically embedded in broader argumentative contexts(of the second and third sense; Hahn & Oaksford, 2007a). The presence orabsence of such wider argumentative context may influence profoundly theseeming levels of competence observed, a point that has recently beendeveloped extensively within Mercier and Sperber’s argumentative theoryof reasoning (2011). At the same time reasoning experiments, like otherpsychological experiments, are themselves communicative situations, andthe way participants interpret those communicative situations will beinfluenced by pragmatic rules of communication outside the laboratory.This can give rise to systematic differences in interpretation between

1The three senses of argument as (1) reason, as (2) a structured unit of reason(s) and

claims(s), and (3) as a dialogical, social exchange distinguished here are related to a distinction

by O’Keefe (1977). O’Keefe distinguishes two sense of argument: the first is a particular kind of

utterance or communicative act (as in ‘‘he made an argument’’), and the second a particular

kind of interaction; that is, an argument in the first sense is something a person makes, whereas

in the second sense it is something two or more people have. This second sense corresponds to

arguments as dialogical, social exchange. In contrast to O’Keefe’s first sense of argument,

arguments as reasons or structured units of reasons and claims as we conceive of them, can, but

need not be, expressed in ‘‘utterances’’ or ‘‘communicative acts’’, in the same way that standard

logical derivations do not consider premise material to be conversational.

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experimenters and participants of what the task is actually about—much tothe detriment of the experimental finding (see Hilton, 1995). To provide justone example, Nisbett, Zukier and Lemley (1981) found evidence of seemingirrationality in people’s evaluation of reasons in that the addition of non-diagnostic information lessened the impact of a diagnostic reason lessened(the so-called ‘‘dilution effect’’), However, Gricean conversational norms(Grice, 1975) mean that information presented in communication has thepresumption of relevance. Hence participants seek to incorporate the non-diagnostic information, because they assume they have been given it withgood cause (Peters & Rothbart, 2000; Tetlock, Lerner, & Boettger, 1996);they actively try to make relevant what the experimenter deemed irrelevantbecause their reasoning is set in the communicative context of theexperiment.

Conversely, those researchers studying complex sequences of claims andcounter-claims or those focusing on procedural rules of debate still requireinsight into the normative relationship between individual premises andconclusions, and the extent to which premise material does or does notsupport a particular inference (see for discussion also Hahn & Oaksford,2007b, 2012).

In light of this, the aim of this special issue is to bring togetherpsychological, experimental research originating in what are presentlydistinct and very much separate communities (cognitive psychologists,communication researchers, and philosophers) that highlights some of thesedifferent aspects. It is our hope that bringing together research (andresearchers) in this way will increase mutual awareness of the many facets ofargument and provide a step towards a broad and integrated psychology ofargumentation, which (in our view) should be a cornerstone of cognitivepsychology.

RESEARCH ON ARGUMENT: WHO DOES WHAT(AND WHERE)?

If there are many ways to think about the term ‘‘argument’’, it should comeas no surprise that research on argumentation is diverse in its methods(e.g., analytical, empirical), its goals (e.g., the analysis or evaluation ofarguments), and its disciplinary backgrounds (e.g., philosophy, linguistics,psychology, computer science). As a consequence, there is no common,accepted theory of what constitutes argumentation.

However, scholars appear to agree that the study of argumentationcentres around (at least) three different, but interrelated, topics: theproduction, the analysis, and the evaluation of arguments (Van Eemeren,Grootendorst, & Snoeck Henkemans, 1996). In the following we introducedifferent perspectives on argumentation. We focus in particular on research

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that is from outside cognitive psychology and hence is complementary to thereasoning and argumentation work discussed so far.

This overview is organised around the three central topics of production,analysis, and evaluation. For each of these topics we explain the specificresearch goals involved, and situate research relative to the three sensesof ‘‘argument’’ distinguished above. We also identify the main methodsthat are used, the disciplines within which that research typically takesplace, and the key journals in which it is published. It should be noted thateven research grouped here under the same header (e.g., production,analysis, or evaluation), may be very heterogeneous in detail, with respectto both methodology and theoretical background or perspective. Inproviding this overview our aim is not to be exhaustive, but to give abroad sense of what kinds of research on argumentation have beenconducted.2 Interested readers who want a more complete overview ofapproaches may consult, for instance, Van Eemeren et al. (1996, 2012) andHahn and Oaksford (2012).

PRODUCTION OF ARGUMENTS

The study of argument production aims to investigate how ordinarylanguage users employ arguments. Questions that have been addressed are,among others: What kinds of arguments are used in professional persuasivedocuments (Schellens & De Jong, 2004) or in students’ speeches (Kline,1971)? What kinds of evidence are employed in presidential debates(Levasseur & Dean, 1996)? What kinds of arguments or evidence wouldpeople prefer to use if they had to persuade another person (Hornikx, 2008),and why (Hample & Dallinger, 2006)? Does mood affect the kinds ofarguments people produce to oppose or favour a standpoint (Bohner &Schwarz, 1993)? How do students write an argumentative text (Wolfe, Britt,& Butler, 2009)?

2Readers should also note that we have largely neglected research on argumentation within

computer science and artificial intelligence (AI) in the following. While there has been a

burgeoning interest in argumentation (for an overview see, e.g., Bench-Capon & Dunne, 2007;

Rahwan & Simari, 2009), and there has been work on production (Carenini & Moore, 2006;

Green, Dwight, Navoraphan & Stadler, 2011; Zukerman, 2009) or assisted production (see

Verheij, 2003), analysis (e.g., Rahwan, Zablith & Reed, 2007; Reed & Rowe, 2004), and

evaluation (in particular in the context of non-classical logics, e.g., Amgoud & Cayrol, 2002;

Dung, 1995; for a review of non-classical logics for argumentation see Prakken & Vreeswijk,

2002; for other approaches see, e.g., Pollock, 2001), there have been fewer links with empirical

psychological work to date (for an exception see Rahwan, Madakkatel, Bonnefon, Awan &

Abdallah, 2010), and there is no research from these communities represented in the present

special issue.

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These kinds of questions relate to our first meaning of the term‘‘argument’’: an argument as a reason that you give for a standpoint. Studieson argument production are generally descriptive, and usually empiricallyoriented. They are often conducted by scholars working in (speech)communication and rhetoric, and are published in journals such asArgumentation, Argumentation and Advocacy, and Communication Mono-graphs.

ANALYSIS OF ARGUMENTS

This second group of argument research focuses on detailed analysis ofarguments or argumentative discourse. Researchers aim to best describe atext, film, or debate from an argumentative perspective. Importantquestions are: What is the argumentative structure of (complex) argumen-tative discourse (Snoeck Henkemans, 2000, 2003)? What exactly is astandpoint (Houtlosser, 1998), and how do people use discourse markers toexpress standpoints (Craig & Sanusi, 2000)? How do people use language toindicate different ‘‘moves’’ in argumentative discourse (Van Eemeren,Houtlosser, & Snoeck Henkemans, 2008)? Which kinds of argumentationschemes (generalised types of argument) can be distinguished (e.g., Godden& Walton, 2007; Kienpointner, 1992)? How are discussions moderated(Weger & Aakhus, 2005)? And, from a methodological point of view, whatmeans are available for analysing discourse (e.g., Pallotta & Delmonte,2011; Reznitskaya & Anderson, 2006)?

Such analysis of arguments relates to our second and third meanings of‘‘argument’’. Argument as a unit that consists of a claim and a reason(second meaning) is relevant when analysis is conducted on extant concretesamples of argumentative discourse (e.g., Zenker, 2010). For genres such asfilms and debates, the third meaning comes into play: the dialogical, socialactivity in which people argue. Research on argument analysis is descriptive,and empirical. It is often conducted by scholars working in (speech)communication, rhetoric, informal logic, and pragma-dialectics. Readingscan be found in edited books (e.g., Van Eemeren & Houtlosser, 2005;Van Haaften, Jansen, De Jong, & Koetsenruijter, 2011), and outlets such asArgumentation, Argumentation and Advocacy, Argument and Computation,Cogency, Informal Logic, and Rhetoric Society Quarterly.

EVALUATION OF ARGUMENTS

Research concerned with the analysis of argumentative discourse is often(though by no means necessarily) followed by evaluation of arguments as anatural, second step. Whereas the analysis of arguments is relatively non-judgmental in that it does not judge whether, for instance, the underlying

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argumentative structure found in the text is correct, studies on argumentevaluation judge the quality of arguments and argumentative discourse.Central questions are: What is good argumentative practice, and what arestrong and weak arguments? These questions can be formulated moreconcretely, such as in: What distinguishes fallacies from reasonablearguments (e.g., Hahn & Oaksford, 2006; Tindale, 2007; Van Eemerenet al., 2009; Walton, 1995)? What rules and norms are important forreasonable argumentation (e.g., Godden & Walton, 2007; Kienpointner,1992)?

Like research on the analysis of arguments, argument evaluation researchrelates to our second and third meaning of ‘‘argument’’—arguments asstructured units comprising reasons and claims, and arguments as dialogues.In contrast with research on production and analysis, research on argumentevaluation is largely normative, and analytically oriented: what should‘‘good’’ argumentation be like? The specific tools for argument evaluationdiffer depending on the theoretical paradigm chosen. Theoretical frame-works include so-called informal logic (e.g., Govier, 2005; Johnson, 2000;Walton, 1997) and pragma-dialectics (e.g., Van Eemeren & Grootendorst,2004), along with the more familiar standards of logic, probability theoryand statistics that are used also in the related study of ‘‘evidence’’, be it inphilosophy of science (e.g., Howson & Urbach, 1996), epistemology (e.g.,Bovens & Hartmann, 2003), or law (see, e.g., Schum, 1994). Finally, manyempirical studies have relied on intuitive criteria, or special purposeevaluation schemes tailored to the specific aspect or domain of argumenta-tion at hand (see e.g., Driver, Newton, & Osborne, 2000; Kuhn, Shaw, &Felton, 1997).

At the same time there are descriptive, empirical, approaches toevaluating arguments that equate argument quality with persuasive success.These approaches focus on the effects of arguments on receivers, and aretypically taken by scholars in communication (working on persuasion anddecision making; see O’Keefe, 2002, for an introduction), by scholars insocial psychology (working on persuasion and attitude change; see, e.g.,Eagly & Chaiken, 1993; Maio & Haddock, 2010, for introductions), and byresearchers in the field of rhetoric (for an overview see Lunsford, Wilson &Eberly, 2009). Among the questions are: Does making an explicit standpoint(O’Keefe, 1997) or explicit justification (O’Keefe, 1998) an argument morepersuasive? Is evidence that respects normative criteria for good argumenta-tion more persuasive than evidence that does not respect such criteria(Hoeken & Hustinx, 2009; Hornikx & De Best, 2011; Hornikx & Hoeken,2007)? Under which conditions are strong arguments more effective thanweak arguments in persuasive texts (Park, Levine, Kingsley Westerman,Orfgen, & Foregger, 2007)? Research on argument evaluation can be foundin all the journals mentioned above.

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OVERVIEW OF THIS SPECIAL ISSUE

Having set the stage, we now turn to the individual papers in this specialissue of Thinking & Reasoning. Our aim has been to bring togetherresearchers from the different strands of argumentation research that wehave described in the context of a journal aimed traditionally at a cognitivepsychology audience. It is hoped not only that this has led to an interestingset of articles, but also that this diversity will serve to consolidateargumentation research and raise overall awareness and interest in thefield. The breadth of the topic ‘‘argumentation’’ is reflected in the fact thatthe contributors to this issue are drawn from psychology, philosophy,communications, and cognitive science departments, and business pro-grammes. Nevertheless, all papers constitute ‘‘experimental psychology’’,and report the outcomes of novel, experimental studies.

The paper by Heit and Rotello on The pervasive effects of argument lengthon inductive reasoning deals with the question of how the amount of evidenceis balanced against the strength of the evidence in one specific context inwhich the two can dissociate, namely where short, but logically valid,arguments may be contrasted with longer, but only inductively probable,arguments. Heit and Rotello experimentally address the question of whetherargument length is so compelling that people cannot help being influencedby it. Materials and format of these experiments are paradigmatic ofreasoning research within cognitive psychology. At the same time, however,Heit and Rotello set their question in the context of an extensive review ofrelevant literature drawn from a wide range of research areas. These includenot just core cognitive topics such as category-based inductive reasoningand causal reasoning, but also argumentation and persuasion research, thusexemplifying the way in which these areas may be linked to mutual benefit.

The second contribution in this special issue, Belief bias in informalreasoning by Thompson and Evans, also has the reasoning literature as itspoint of departure. Specifically, it starts with a standard phenomenon withinthe logical reasoning literature, namely that judgements of logical validityare influenced both by actual validity and the believability of theconclusions, and show an interaction between the two. Apparentlyanalogous effects of belief and argument strength have been observed ininformal reasoning; however, the design of those studies has not made itpossible to examine directly whether belief bias in formal and informalreasoning is a unitary phenomenon. Thompson and Evans paper redesignstwo familiar, informal reasoning tasks—the Argument Evaluation Task(AET, Stanovich & West, 1997) and a Law of Large Numbers (LLN,Klaczynski & Robinson, 2000) task—in order to test the similarity of thebelief bias in informal reasoning tasks. Thompson and Evans find littlesupport for the idea of a unitary phenomenon. Their studies underline the

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fact that findings reported in formal reasoning tasks do not always translateto results in more informal reasoning tasks, which are more close toeveryday argumentation.

Harris, Hsu and Madsen’s paper Because Hitler did it! Quantitative testsof Bayesian argumentation using ad hominem is a contribution to theemerging Bayesian approach to argumentation. ‘‘Ad hominem’’ arguments(see e.g., Walton, 1998) are arguments that target the proponent of a claiminstead of the claim itself. Ad hominem arguments have often been viewedas fallacious, on the grounds that a statement may be sound even if theperson uttering it is not. However, it is also clear that characteristics of thesource may be informative in considering a claim. For example, when welack sufficient expertise to evaluate it ourselves, we may rely on an expert(e.g., Walton, 1997). In light of this, argumentation researchers have soughtto characterise the circumstances under which the nature of the sourceshould or should not be taken into account (e.g., Walton, 1997, 1998, 2008)and how source considerations should be integrated with other criteria inevaluating how convinced we should be by a given argument (Hahn, Harris,& Corner, 2009; Hahn, Oaksford, & Harris, in press). In this special issueHarris et al. examine a specific type of argument found in many real-worldargumentation contexts which appeals to the fact that Hitler might haveendorsed a particular policy as sufficient grounds for rejecting that policy.Harris et al. provide a Bayesian (probabilistic) formalisation of the‘‘ad Hitlerum’’ argument, as a special case of the ad hominem argument.They then demonstrate, across three experiments, how people’s evaluationof this argument is sensitive to probabilistic factors deemed relevant on thisBayesian formalisation. Importantly, they also go beyond past researchwithin this framework by providing direct quantitative evidence in favour ofthe Bayesian approach to argumentation from a priori, parameter-free,model fits.

Ad hominem arguments are also the focus of Van Eemeren, Garssen, andMeuffels’ paper The disguised abusive ad hominem empirically investigated:Strategic manoeuvring with direct personal attacks. However, the adhominem argument is viewed from a very different theoretical perspectivein this paper. Van Eemeren et al.’s contribution stems from a researchtradition focusing on the kinds of procedural rules that define reasonableargumentation (Van Eemeren & Grootendorst, 2004). While much of thatresearch tradition has been concerned solely with normative issues, morerecent work has also started to examine empirically the descriptive,psychological question of the extent to which lay people are sensitive toprocedural norms for rational argument (Van Eemeren et al., 2009; forstudies beyond pragma-dialectics, see also O’Keefe, 2007). This has directbearing on putative fallacies of argumentation such as the ad hominemargument, because authors such as Van Eemeren and colleagues have

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argued specifically for a procedural treatment of the traditional catalogue offallacies, whereby arguments such as the ad hominem argument are viewedas fallacious specifically because they violate fundamental procedural normsof rational arguments (specifically, it is an attempt to eliminate the opponentas a serious partner in a discussion by undermining his or her right toadvance a standpoint or to cast doubt on a standpoint, see, e.g., VanEemeren & Grootendorst, 2004; see also Walton, 1997, for a relatedposition). Van Eemeren, Garssen, and Meuffels’ contribution to this specialissue takes on the ad hominem argument, outlining how and why it may befallacious from a pragma-dialectical perspective. At the same time, the paperseeks to address a puzzle that has emerged from recent empirical researchwithin the pragma-dialectical tradition. Specifically, Van Eemeren et al.(2009) found that ordinary language users judge to be unreasonablediscussion moves that are considered fallacious from a pragma-dialecticalperspective. In light of this it may seem surprising that fallacies such as thead hominem argument occur and often seem not to be noticed by theparticipants in the discourse. Van Eemeren and colleagues argue that thistension may be resolved by the fact that fallacious instances of ad hominemarguments may be masked or disguised as instances of non-fallaciousversions of this argument form. Specifically, Van Eemeren et al. analyse so-called abusive ad hominem attacks (which are clearly fallacious) as a mode ofstrategic manoeuvring which takes on a reasonable appearance in real-lifesituations when it mimics legitimate critical reactions to authorityargumentation. This explanation is then tested in two experiments. Resultsshow that, indeed, when the ad hominem arguments are presented ascriticising arguments by authority, they are seen to be more reasonable.

It should be clear from the preceding discussion that, while classicfallacies such as the ad hominem argument or the appeal to authority aretopics that have only fairly recently started to attract experimental,psychological research (see e.g., Corner et al., 2011; Hahn & Oaksford,2007a; Neuman, Glassner, & Weinstock, 2004; Neuman, Weinstock, &Glasner, 2006; Neuman & Weitzman, 2003; Rips, 2002; Weinstock,Neuman, & Tabak, 2004), they have been the long-standing focus oftheoretical inquiry, in particular within philosophy. One might assume thata long history of research on argumentation across a range of differentdisciplines (as outlined above) would have identified all the basic topics orissues that psychological research should address if we are to gain anunderstanding of how it is that people generate and evaluate arguments.

However, such an assumption would be mistaken. Mercier and Strick-land’s paper Evaluating arguments from the reaction of the audience drawsattention to a probabilistic cue to argument evaluation that has beenoverlooked. Specifically, observers might evaluate arguments by the reactionthey evoke in an audience—a type of evaluation that is likely to occur when

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people are not privy to the actual content of the argument or when they arenot expert enough to appropriately evaluate it. Mercier and Strickland’spaper presents a series of four experiments providing a first empiricalexamination of this important social cue.

Similarly, Bonnefon’s paper Utility conditionals as consequential argu-ments: A random sampling experiment draws attention to the fact that peoplemust not only have a capacity for evaluating arguments, but often they firstneed to work out what the argument is. Orthogonal to much of the workpresented in this special issue, which concerns itself with the question ofwhen and why an argument might be considered to be weak or strong,Bonnefon’s paper focuses on one how we generate interpretations forcertain kinds of arguments, namely arguments involving consequentialarguments, such as ‘‘if you do this, I will hurt you’’. Researchers havesought to characterise formally the circumstance under which sucharguments should be viewed as convincing or not (Thompson et al., 2005;Hoeken, Timmers, & Schellens, 2012 this issue). Bonnefon’s concern, bycontrast, is how it is that we work out, in the absence of any othercontextual information, that the speaker of this argument is seeking toprovide support for the claim that ‘‘this’’ (whatever it may be) should not bedone. Bonnefon’s recent (2009) theory of utility conditionals provides aframework for generating such arguments and a simple ‘‘inference engine’’that reasoner’s may draw on when inferring a default interpretation.Although not cast explicitly in this way, one might view this interpretationprocess as guided by generic assumptions about behaviour that mean thatthose interpretations are preferred on which the statement would seem likethe stronger argument. Hence this paper too emphasises the close linksbetween reasoning and argumentation and the benefits that arise fromconsidering the two together.

The last paper in the issue, Hoeken, Timmers, and Schellens’ Arguingabout desirable consequences: What constitutes a convincing argument? drawstogether many of the themes that run through the other papers. Their paperreports on a study in which participants without training in argumentationtheory rated the acceptance of claims about the desirability of a consequencethat were supported by either an inductive argument from analogy, anargument from authority, or an argument from consequences. Thesesupporting arguments were systematically manipulated so as to includeviolations of criteria that theorists have proposed as integral to normativeevaluation of such arguments. Like Heit and Rotello (2012 this issue), theirpaper takes great care to set these experiments in a broader context of notjust argumentation, but also persuasion research.

In our opinion the most important contribution this special issue ofThinking & Reasoning could make would be for the kind of integrationacross reasoning, argumentation, and persuasion research that Hoeken

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et al., and Heit and Rotello provide to become commonplace. The synergythat comes from such integration can be seen nowhere better than in themany different ways the papers in this special issue could be grouped andthe many links that exist between them, even though each of them reflectsa specific project, within a specific research tradition.

In particular, the different senses of argument outlined in the introduc-tion are reflected in different ways across the papers in this special issue. Thepapers by Heit and Rotello, by Harris et al., and by Thompson and Evansfocus on arguments as reasons, and hence are relevant even to the lonereasoner. By contrast, the contributions by Van Eemeren et al., by Hoekenet al., by Mercier and Strickland, and by Bonnefon deal intrinsically withsituations where there are multiple protagonists in a communicativeexchange. At the same time, all but the experiments of Heit and Rotelloand that of Bonnefon use experimental materials that involve dialogues.This illustrates the fact that such methodological use of dialogue is distinctfrom the question of whether the unit of theoretical and experimentalevaluation is a single reason or a broader communicative exchange.Moreover, even for a single reason, different theoretical frameworksrepresented in the issue diverge with regard to the question of whether ornot the normative judgement on that reason would be different if it werebeing evaluated in the head of a single person, or as a move in a widerdialectic exchange. Specifically, the contributions in this special issue mayalso be grouped by the normative frameworks to which they appeal. ForHeit and Rotello, for Harris et al., and for Thompson and Evans, thatframework is logic and probability theory, which, as classic epistemicstandards for deduction and induction respectively, are concerned withtruth and make no reference to dialogue. By contrast, for Van Eemerenet al. norms derive from pragmatic rules and social conventions, andconsequently it matters whether reasons are considered in isolation or in adialogical exchange. For Hoeken et al., standards for evaluation originatefrom normative criteria for argumentation schemes. Finally, Bonnefon, onthe one hand, and Mercier and Strickland, on the other, are agnostic aboutnorms, although it seems clear that both rely on a likely or ‘‘normal’’ courseof affairs.

In short, the different senses of argument, and with them differentperspectives on argumentation, weave through these papers on many levelsand in a variety of ways.

CONCLUDING REMARK

Argumentation is an essential component of our lives. Our legal system,our political system, and science itself, are unimaginable without rationaldebate. Moreover, much of the reasoning we do in our day to day lives

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arguably takes place in the context of exchanges about what to believe andwhat to do (see also Mercier & Sperber, 2011). It would seem time forcognitive psychology to follow other disciplines in giving argumentation theattention it deserves.

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