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O n the M en tal Represen tation of Conditional Sen tencesJonathan S t. B. T. E vans, Charles E . E llis, and S tephen E . N ewstead U niversity of P lymouth, P lymouth, U.K .Fou r exp erim en ts are repo r ted w h ic h attem p t to exter n aliz e su bjects' m en tal rep resentation of con dition al sen tences, u sin g no vel research m eth od s. In E xp erim en t 1, subjects w ere sh ow n ar ra ys of colou red sh ap es an d asked to rate th e de gr ee to w h ich the y app eared to be tr u e of con d ition al statem en ts su ch as``If th e ® gu re is g reen then it is a trian gle ' ' . T h e ar rays c on tain ed d ifferent distrib ution s of th e fou r logically po ssible cases in w h ich th e an teced en t or con sequ en t is tru e or false: T T, T F, F T, and FF. For exam p le, a blue trian gle wo u ld be F T for the co n ditio na l qu oted above. In E xp erim en ts 2 to 4, su bjects w ere able to con str uct th eir ow n ar rays to m ake c on dition als eith er tr u e or false w ith any d istribu tion of th e four cases th ey w ishe d to ch oose. T h e p resen ce an d absen ce of n eg ative com p on en ts w as varied , as w as th e for m of the co nd ition al, being eith er``if th en ' ' as above or``o nly if ' ' :``T h e ® gu re is green o n ly if it is a triang le' ' . T h e ® rst ® n d ing w as th at su bjects rep resen t con d ition als in fu zzy w ay: con d ition als th at includ e so m e cou nter-exam p le T F cases (E xp erim en t 1) m ay be rated as tru e, an d su ch cases are often includ ed w h en su bjects con struc t an ar ray to m ake th e r u le tru e (E xp erim ents 2 to 4). O th er ® n din gs includ ed a stron g ten d en cy to includ e p sy ch ologically irrelevan t F T an d FF cases in con str u cted ar rays, pr esu m ably to sh ow th at con d itio n al statem en ts on ly app ly so m e of th e tim e. A ten den cy to con s tru ct cases in lin e w ith th e``m atch ing bias' ' rep orted on an alogou s tasks in th e liter atu re w as fou nd , bu t o n ly in E xp erim ent 4, w h ere the nu m ber of sy m bo ls available to co nstru ct each case w as co n trolled. T h e ® n din gs are d iscu ssed in relation to th e m ajor co ntem p orar y th eor ies of con d ition al reason ing based u p on inferen ce ru les an d m en tal m od els, n either of w h ich can accou n t for all th e resu lts.T he study of co nd ition al sentences has been central to m uch of th e research in the psycholog y of deductive reason ing. For exam ple, the sin gle m ost investigated problem in this literature, the Waso n selectio n task (Wason, 1966), involves asking subjects to test the truth of a sentence such as``If there is a vow el o n on e side of a card then there is an even num b er on the other side of the card ' ' (see E van s, N ew stead , & B yr ne, 1993, C hap ter 4, for a review of studies w ith this task). O ther popular m ethod s are (a) condiRequests for reprints should be sent to Jonathan St. B.T. E vans, D epartm ent of Psycho logy, U niversity of Plymo uth, P lym outh P L1 5R R, U.K .The au thors would lik e...

Four experiments are reported which attempt to externalize subjects' mental representation of conditional sentences, using novel research methods. In Experiment 1, subjects were shown arrays of coloured shapes and asked to rate the degree to which they appeared to be true of conditional statements such as "If the figure is green then it is a triangle". The arrays contained different distributions of the four logically possible cases in which the antecedent or consequent is true or false: TT, TF, FT, and FF. For example, a blue triangle would be FT for the conditional quoted above. In Experiments 2 to 4, subjects were able to construct their own arrays to make conditional either true or false with any distribution of the four cases they wished to choose. The presence and absence of negative components was varied, as was the form of the conditional, being either "if then" as above or "only if": "The figure is green only if it is a triangle". The first findings was that subjects represent conditional in fuzzy way: conditional that include some counter-example TF cases (Experiment 1) may be rated as true, and such cases are often included when subjects construct an array to make the rule true (Experiments 2 to 4). Other findings included a strong tendency to include psychologically irrelevant FT and FF cases in constructed arrays, presumably to show that conditional statements only apply some of the time. A tendency to construct cases in line with the "matching bias" reported on analogous tasks in the literature was found, but only in Experiment 4, where the number of symbols available to construct each case was controlled. The findings are discussed in relation to the major contemporary theories of conditional reasoning based upon inference rules and mental models, neither of which can account for all the results.

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A novel process to selectively deposit polycrystalline diamond on a silicon surface was developed, establishing the capability to fabricate polycrystalline diamond microstructures using anisotropic etching of silicon. Micro-mechanical beams, cantilevers, and optically transparent membranes/windows of polycrystalline synthetic diamond were fabricated on single-crystal silicon <100> wafers. These diamond films were deposited by high-pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen. The Young's modulus of polycrystalline diamond thin film was estimated using the elastic deformation cantilever beam formulation. The fabrication procedure, optical and scanning electron microscopy views of various designs, and the evaluation of the elastic properties are reported.