of a painting illustrates a text, and a cartoon a political article, a citationenables the reader to grasp the overallpoint of the discussion withoutnecessarily being an exact reflection ofthe point being illustrated. For example, a recurring theme in the research intoexpertise, already present in the seminalwork of De Groot (1965), is that the keydifference between experts and noviceslies in the amount and organisation oftheir knowledge rather than in theircomputational abilities (see Gobet, 1998,for a literature review). Sherlock Holmesis no exception to this rule, and is awareof the importance that the organisation of his knowledge in criminology plays.

Whilesuggestive, theextract from A Study inScarlet (see boxopposite) doesnot howeverreflect the trueorganisation ofexpert memory.

Whileresearch hasfocused onexperts’knowledgeorganisation inmemory, otheraspects ofexperts’cognitivefunctioning ingeneral, and ofHolmes in

particular, seem tohave been so far less

investigated. The study of SherlockHolmes allowed us to illustrate not onlycurrent models but also to point topossible ways in which they coulddevelop in the future. Thus, Holmes givesmuch importance to emotional control,whilst this dimension has attracted onlyscarce attention in the cognitivepsychology of expertise:

‘But love is an emotional thing, andwhatever is emotional is opposed tothat true cold reason which I placeabove all things. I should never marrymyself, lest I bias my judgment.’

The Sign of Four (1890)

Whilst this citation illustrates the linksbetween expertise and emotion, and isalso likely to attract the reader’s attentionon the importance of future research onthis question, it probably does not reflectthe role actually played by emotions inexpert performance. Expertise is notnecessarily inconsistent with marital life,

The development of cognitivepsychology is typically fosteredthrough the study of groups of

participants placed in varied,and often imaginative,experimental situations. Morerarely, some research topicsrequire a single subject. Thistype of study can be found inresearch on specific cognitivedysfunctions, or in the studyof individuals having a type of functioning exceptional in some respects. This articleaddresses the latter case: thestudy of the cognitivecharacteristics underpinningexpertise in one domain. Thefield of cognitive expertise hasa certain tradition of usingcase studies of experts, but ina recent article we went onestep further: we analysed afamous but fictional expert –Sherlock Holmes (Didierjean& Gobet, 2008).

The use of citations takenfrom Conan Doyle’s worksmade it possible not only to present thelatest advances in the field of cognitiveexpertise, but also to suggest avenues of research that we believe should beexplored with more attention. WhileConan Doyle’s works offer a seductivemeans of presenting current research oncognitive expertise, the use that can bemade of literary citations is rather varied.The aim of this short article is twofold: to

offer some thoughts on the different waysin which literary citations can be used,and to illustrate the extent to which the

study of Sherlock Holmes can help usmake progress in the understanding ofexperts’ cognitive mechanisms.

The citation as a tongue-in-cheek illustration A first usage of literary citations consistsof illustrating a serious discussion withsome humour. Just like the reproduction

2 vol 21 no 10 october 2008

De Groot, A.D. (1965). Thought and choicein chess (first Dutch edition in 1946).The Hague: Mouton Publishers.

Didierjean, A. & Gobet, F. (2008).Sherlock Holmes – An expert’s viewof expertise. British Journal ofPsychology, 99, 109–125.

Gobet, F. (1998). Expert memory: Acomparison of four theories.Cognition, 66, 115–152.

Hanson, N.R. (1958). Patterns of

discovery. Cambridge, MA:Cambridge University Press.

Kolodner, J. (1993). Case-basedreasoning. San Francisco, CA:Morgan Kaufman.

Van Merriënboer, J.J.G., & Sweller, J.(2005). Cognitive load theory andcomplex learning: Recentdevelopments and future directions.Educational Psychology Review, 17,147–177.

Can Sherlock Holmes help cognitive psychology?André Didierjean and Fernand Gobet with the latest in our series on therelationship between psychology and the world of fiction

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with the possible exception of a Catholicpriest’s expertise in theology.

The citation as a means to illustrate a mechanismThe explanation of the mechanismsunderlying a complex phenomenon isoften made easier by the presentation ofan example involving this phenomenon.Watching a movie showing a cyclonefacilitates the understanding ofexplanations of the physical mechanismsproducing it. Among other reasons,examples facilitate learning because theydecrease the learner’s ‘cognitive load’ (VanMerriënboer & Sweller, 2005). Similarly,literary citations can offer an illustrationof a phenomenon and allow a betterunderstanding of the mechanismsinvolved.

Observing Sherlock Holmes in hisadventures no doubt facilitates theunderstanding of the phenomenon ofcase-based reasoning (e.g. Kolodner,1993), where one refers to a previoussituation in order to adapt it to a newsituation. Sherlock Holmes takes thestandpoint that ‘there is a strong familyresemblance about misdeeds, and if youhave all the detail of a thousand at yourfinger ends, it is odd if you can’t unravelthe thousand and first,’ and thus oftentackles cases by remembering andadapting past inquiries:

‘It reminds me of the circumstancesattendant on the death of Van Jansen,in Utrecht, in the year ‘34.’

A Study in Scarlet (1887)

Thus, Holmes beautifully illustrates thisaspect of experts’ cognitive functioning:the recourse to episodes stored in long-term memory.

The citation as a means to explain a mechanismA last use of citations is in presentingexcerpts with the goal of providing aprecise description of a psychologicalmechanism. Cognitive psychology aims to understand the mechanismsunderpinning general human behaviours,and a literary character can describe withprecision, although possibly with adifferent vocabulary, a cognitive

mechanism. To this day, research onexpertise has devoted little attention toexpert reasoning, and the few availablestudies on this theme mostly deal withinductive reasoning. However, experts use abductive reasoning in manysituations. Abductive reasoning consistsof starting from observed data andderiving from these data the most likelyexplanation or hypothesis. From thisexplanation, the data can be deduced byimplication (e.g. Hanson, 1958). Holmesclearly explains the method of reasoningto Watson in A Study in Scarlet (1887):

‘In solving a problem of this sort, thegrand thing is to be able to reasonbackward. That is a very usefulaccomplishment, and a very easy one,but people do not practise it much. Inthe everyday affairs of life it is moreuseful to reason forward, and so theother comes to be neglected. Thereare fifty who can reason syntheticallyfor one who can reason analytically.’

‘I confess’, said I, ‘that I do notquite follow you.’

‘I hardly expected that you would.Let me see if I can make it clearer.Most people, if you describe a train ofevents to them, will tell you what theresult would be. They can put thoseevents together in their minds, andargue from them that something willcome to pass. There are few people,however, who, if you told them aresult, would be able to evolve fromtheir own inner consciousness whatthe steps were which led up to thatresult. This power is what I meanwhen I talk of reasoning backward, oranalytically.’

In this example, Holmes describes in hiswords, but also with precision, the natureof abductive reasoning.

Find your own HolmesNearly 125 years old, Conan Doyle’sbooks show remarkable illustrations ofexpert behaviour, including the coverageof themes that have mostly beenoverlooked by current research. Wesuspect that other fields of psychologyhave their own Sherlock Holmes and can benefit from the study of fictionalcharacters.

read discuss contribute at www.thepsychologist.org.uk 3

eye on fiction

I André Didierjean is at theLaboratoire de Psychologie,Université de Franche-Comté.Andre.Didierjean@univ-fcomte.fr

I Fernand Gobet is at theSchool of Social Sciences,Brunel University.fernand.gobet@brunel.ac.uk

The brain as atticHis ignorance was as remarkable as hisknowledge. Of contemporary literature,philosophy and politics he appeared to knownext to nothing. … My surprise reached aclimax, however, when I found incidentallythat he was ignorant of the CopernicanTheory and of the composition of the SolarSystem. That any civilized human being inthis nineteenth century should not be awarethat the earth travelled round the sunappeared to be to me such an extraordinaryfact that I could hardly realize it.

‘You appear to be astonished,’ he said,smiling at my expression of surprise. ‘Nowthat I do know it I shall do my best to forgetit.’

‘To forget it!’‘You see,’ he explained, ‘I consider that

a man’s brain originally is like a little emptyattic, and you have to stock it with suchfurniture as youchoose. A fooltakes in all thelumber of everysort that hecomes across,so that theknowledgewhich might beuseful to himgets crowdedout, or at best isjumbled up witha lot of otherthings so that hehas a difficultyin laying hishands upon it.Now the skilfulworkman is verycareful indeedas to what hetakes into his brain-attic. He will havenothing but the tools which may help him indoing his work, but of these he has a largeassortment, and all in the most perfect order.It is a mistake to think that that little roomhas elastic walls and can distend to anyextent. Depend upon it there comes a timewhen for every addition of knowledge youforget something that you knew before. It isof the highest importance, therefore, not tohave useless facts elbowing out the usefulones.’

‘But the Solar System!’ I protested.‘What the deuce is it to me?’ he

interrupted impatiently; ‘you say that we goround the sun. If we went round the moon itwould not make a pennyworth of differenceto me or to my work.’

A Study in Scarlet (1887)

‘But the Solar System!’