A study of the Cognitive Structure of Conflict over Disaster Mitigation Projects

Transcription

1 Journal of Natural Dsaster Scence, Volume 6, Number,, -7 A study of the Cogntve Structure of Conflct over Dsaster Mtgaton Projects Hroyuk SAKAKIBARA, Hsanor KAKU and Kazush KIDERA Deartment of Cvl and Envronmental Engneerng, Yamaguch Unversty -6- Tokwada, Ube, Yamaguch, , Jaan Ohash Archtecture Offce TVQ Kyushu Broadcastng CO. LTD. (Receved for Jun., and n revsed from 7 Jan., 5 ABSTRACT Projects for dsaster mtgaton such as reservors often change the natural and socal envronments of a regon. If eole have dfferent onons on such changes, these rojects may cause conflcts. Partcatory dsaster mtgaton requres a mechansm for managng such conflcts. To romote stakeholders nvolved n a conflct to a comromse, t s necessary to understand the structure of the conflct. Ths study focuses on the relatonsh between eole s recognton about a conflct and fnal outcome of the conflct. Frst, a model nvolvng layers game-makng rocess s constructed, and t s shown that onon-summarzng rules can affect the outcome of a conflct. Second, a survey of eole s cogntve structure of a conflct was made, and the results show the ossblty of olarzaton between eole s recognton and game theoretc model.. INTRODUCTION Projects for dsaster mtgaton, such as reservors, often change the natural and socal envronments of a regon. When eole have dfferent onons on such changes, rojects may cause conflct. Partcatory dsaster mtgaton requres a mechansm for managng such conflcts. To get stakeholders nvolved n a conflct to comromse, t s necessary to understand the structure of that conflct. Game theory s often used for to analyze conflct. The non-cooeratve game model conssts of layers (stakeholders nvolved n a conflct, strateges (actons whch a layer can take, and ayoffs (layers numercal evaluatons of the outcomes of conflct. In game theory, t s assumed that combnaton of layers strateges and an outcome have one-to-one corresondence. In an actual conflct, however, stakeholders may erceve the same conflct dfferently. Addtonally, eole s cogntve structures may dffer from the standard game theoretc model, and narorate recognton may lead to an neffcent outcome. Conflct management needs to ncororate a rocess for sharng knowledge about a conflct. Ths study focuses on the relatonsh between eole s recognton of a conflct and the fnal outcome of that conflct. The study conssts of two arts, model analyss and survey analyss. In the frst art (Secton, a model nvolvng layers gamemakng rocess s constructed. It shows that onon summarzng rules can affect the outcome of a conflct. In the second art (Secton, a survey of eole s cogntve structures of a conflct s made. Results show the ossblty of olarzaton between eole s recognton and game theoretc model.. GAME THEORY BASED CONFLICT MODELING. Non-Cooeratve Strategc Form Game Game theory s often used for modelng an nteractve decson-makng stuaton. Game theory s classfed nto cooeratve and non-cooeratve game, deendng on whether a bndng agreement exsts. The non-cooeratve strategc form game s defned hereafter. Defnton. (Myerson, 99 A strategc-form game s any of the form G = ( N,( Q ŒN,( P ŒN (. Where N s a nonemty set and, for each n N, Q s a nonemty set and P a functon from P Qj nto the set of real numbers R. jœn N s a set of layers who corresond to stakeholders n a conflct. Each layer n N has the set of strateges Q. Q = P Q j s jœn the set of strategy rofle. For any strategy rofle, the number P ( reresents the ayoff that layer can obtan f strategy rofle c s realzed. Strategy rofle * s the Nash equlbrum f the followng nequalty s satsfed; * * P( q P( q, q," Œ N, " q Œ - Q (. (, * s the strategy rofle by whch layer chooses strategy and the other layers choose the same strateges wth *. The equlbrum of a game s usually nterreted as the outcome of a conflct. KEY WORDS: Dsaster Mtgaton, Partcatory Plannng, Conflcts, Exermental Game

2 H. SAKAKIBARA, H. KAKU AND K. KIDERA. Players Recognton on the Structure of a Game As stated n, the stakeholders n a conflct about dsaster mtgaton often have dfferent recognton on the conflct. Examles of non-cooeratve game models that descrbe behavors of layers who do not share the knowledge about the structure of a conflct are, ncomlete nformaton game of Harsany (967, 968 and learnng model (ex. Fudenberg and Levne, 998 and Young, 998. In the ncomlete nformaton game, the robablty dstrbutons of elements of the game are common knowledge of the layers. In contrast, n the learnng model, exectatons of other layers behavor are formed by reettve lays of the same game..e., the learnng model assumes that tral and error s ermtted n the model. Addtonally, as Oechssler and Scher ( mentoned, layers n the learnng model learn about How should we lay?, but not about the structure of the game. Whereas Bayesan equlbrum n the ncomlete nformaton game s determned by the objectve robablty dstrbutons of the elements of the game, for subjectve equlbrum by Kala and Lehrer (995, layers own subjectve exectatons on robablty dstrbutons of elements of a game, and decsons are made based on those exectatons. If subjectve and objectve exectatons accdentally are consstent, then subjectve and objectve equlbrum also are consstent. Even f exectatons are not same, subjectve and objectve equlbrum can exst smultaneously wthout correct recognton of the structure of the game. From the vewont of exermental game, Oechssler and Scher ( showed that layers may not recognze the structure of a game even after reettve lay. They also showed that the layer wth wrong recognton may be able to behave the way as the layer wth correct recognton. In conflcts on dsaster mtgaton, the structure of conflct vares deendng on each case, and t s dffcult to form exectaton by reettve lay. In each conflct, layers need to form game structure and share the recognton about t. In the followng sectons, the nteractve decson makng stuatons n whch layers do not share the knowledge on the structure of a conflct are analyzed. In secton, a model ncororatng layers onon summarzng rocess s descrbed. When layers need to reflect ther suorters references for ther behavors, they summarze the suorters onons n order to construct a game. In that case, dfferences of onon-summarzng rules can affect the outcome of a conflct. Secton reorts a survey of eole s recognton of a conflct. The survey focuses on corresondence between the strategy rofle and the outcome of conflct.. DECISION MODEL INVOLVING OPINION SUMMARIZING PROCESS. Modelng Agent Game A model that descrbes a game n whch layers behave as the agents of suorters s shown. The relatonsh between layers and suorters s dagrammed n Fg... Suorters and have ther own references for the outcomes of a conflct. The layers as agents behave accordng to rorty orders, whch reflect suorters reference orders ndrectly. Suorter s evaluaton of outcome j s reresented by the ayoff j. Suorter s ayoff rofle s; Fg.. P = (,,..., (. The layer summarzes suorter s onons and derves a rorty order. Player s rorty for outcome j s reresented by j. Snce j s determned by ayoff rofle and outcome j, we can defne the followng functon. = f ( P, j j (. Hereafter, s called the onon summarzng rule. Players take actons to obtan the outcome that has the maxmum j. Even f suorters references are the same, j may dffer, deendng on the onon summarzng rule.. Modelng a Conflct In ths secton, the Grah Model for Conflct Resoluton (GMCR by Fang, et al. (99 s emloyed to descrbe a conflct. Let N = {,,,n} be the set of layers and K={k,k,,k u } the set of states of the conflct. In ths aer, only two layer conflcts (N = {,} are dscussed. Two-tule {D }(=, s defned as the set of drected grahs such that D = (K,V. The set of arcs, V, denotes layer s ossble move between states. Let k l k m be the arc from state k l to state k m. k l k m V mles that layer can move from state k l to state k m, unlaterally. To formulate a conflct by the GMCR, ayoff functons are also necessary to be defned. Payoff functon P secfes the layer s reference order. If P (k l > P (k m, then layer refers state k l to state k m. In the general defnton of GMCR, the states can be referred equally. However, n ths aer, t s assumed that each ar of states s ordered strctly (.e., there are no equally referred states. The GMCR for a -layer conflct s reresented by -tule {N,K,V,P}, n whch N={,}, K={k,k,,k u }, V = {V,V } and P={P N}. Here are other defntons used n GMCR. a State k s reachable lst: S (k (k K kk' Œ V k' ŒS ( k Relatonsh between Players as Agents and Suorters u b State k s unlateral mrovement (UI: S + (k k' Œ S( k and P( k' > P( k k' Œ S + ( k (. (. By means of the GMCR, the conflct over reservor roject s

3 A STUDY OF THE COGNITIVE STRUCTURE OF CONFLICT OVER DISASTER MITIGATION PROJECTS modeled. Player s called the ooston grou, layer the government. For smlcty, ossble outcomes are lmted to followng the four states (K={k,k, k, k }. State (k : Ooston escalates and the roject s modfed. State (k : Ooston escalates and the roject s carred out as lanned. State (k : The ooston grou communcates wth the government and the roject s modfed. State (k : The ooston grou communcates wth the government and the roject s carred out as t lanned. Possble layers actons are takng aggressve behavor and accetng dalogue wth the government for layer, and modfyng the roject and carryng out the roject as lanned for layer. The set of ossble actons for layer s defned as A. The state where layer chooses a l A and layer chooses a m A s reresented by k(a l,a m. Players can change the state by varyng ther actons. Player can change the state between k and k and between k and k, whereas, layer can change the state between k and k and between k and k. Fg.. shows layers ossble transtons. In ths study, the above four states are nterreted as the hases of the conflct, and the set of layer s reactons n each state s defned as statonary strategy. Player s statonary strategy s formulated as follows. q : k Æ k', k' Œ [ S( k»{ k}] (.5 Under statonary strategy, layer s reacton at each state s determned n advance. The set of layer s statonary strateges s defned as Q. Fg.. and Fg.. show the feasble statonary strateges of layers and. The combnaton of layers statonary strateges, the strategy rofle, s reresented by. The outcome of conflct under strategy rofle s defned as follows. Defnton. Under strategy rofle, state k that satsfes the followng equaton s called the outcome of conflct under and s reresented by O( ; q ( k = k " ŒN (.6 Snce each layer has four statonary strateges (Fgs.. and., the modeled conflct can be formulated as a strategc-form game wth 6 strategy rofles. Table. shows the relatonshs between the statonary strateges and outcomes. In the strategy rofles reresented by -, the outcome defned by (.6 does not exst. Players choose a statonary strategy that maxmzes ts own ayoffs. Nash equlbrum can be formulated as t defned n ordnary strategc form game. Defnton. Strategy rofle * s Nash equlbrum f and only f the followng relatonsh s satsfed for each layer; * * PO ( ( q PO ( ( q, q " q Œ - Q (.7. Onon Summarzng Rules In ths aer, two tyes of onon summarzng rules are suosed. (a Outcome-Based Onon Summarzng f ( P, j = j (.8 Fg.. D (Left and D (Rght Fg.. Player s Statonary Strateges Table. Relatonsh between Statonary Strateges and Outcomes Fg.. Player s Statonary Strateges

4 H. SAKAKIBARA, H. KAKU AND K. KIDERA (b Acton-Based Onon Summarzng Under the outcome-based onon-summarzng rule, layers ask suorters to reveal the ayoff for each outcome (.e., layers say Please let me know your ayoffs for outcomes.. As a result, j = j s satsfed for each layer and outcome j. In contrast, layers under the acton-based onon-summarzng rule ask suorters to reveal dfferences n the desrablty of each acton (Players ask suorters, Whch acton do you refer?. Suorter s dfference of desrablty for layer l s actons and s defned as l. When l >, suorter hoes that layer l wll choose acton rather than acton. Player determnes behavor based on the revealed (,. The Onon-summarzng rule must satsfy the followng condtons. ( Consstency wth suorter s reference P > P and P > P f s > (.9 P > P and P > P f > and > P < P and P < P f < and < P > P and P > P f > and > P < P and P < P f < and < (.7 (.8 (.9 (. Obvously, outcome-based onon-summarzng rule satsfes the rorty of the suorter s domnant acton. Note that equatons (.7 (. are not necessary and suffcent condtons. The acton s domnant n layer s rorty, the acton s not necessarly domnant n suorter s reference order. In the followng art, acton-based onon-summarzng rule that satsfes the rorty of suorter s domnant acton s formulated. Suorter s assumed to determne lk accordng to the followng equatons. P < P and P < P f s < (. s = ( P - P b + ( P -P ( - b (. P > P and P > P f s > (. s = ( P - P a + ( P -P ( -a (. P < P and P < P f s < ( Consstency wth revealed nformaton s > f > and > s < f < and < s > f > and > s < f < and < (. (. (. (.5 (.6 Consstency wth suorter s reference means that f the suorter refers outcomes lead from one layer s acton domnantly, suorter reveals that the acton s more desrable. Consstency wth revealed nformaton means that layer gves rorty to the acton whch s desrable for the layer s suorter. From condtons ( and (, the followng roerty can be derved. Prorty of the suorter s domnant acton s = ( P - P b + ( P -P ( - b s = ( P - P a + ( P -P ( -a (. (. Here, a and b. a( - a and b( - b resectvely are nterreted as subjectve robabltes for layer s strateges and layer s strateges. A layer determnes the rorty j, based on the revealed l by the followng equatons. = s + s, = s - s, = - s + s, = -s -s (.5 By equatons (. (.5, the acton-based onon-summarzng rule s, f ( P, = ( a + b + (-a - b + + (-a - b + + ( a + b - f ( P, = (- a + b + ( a - b + + ( a - b - + (- a + b f ( P, = ( a - b + (- a + b - + (- a + b + + ( a - b f ( P, = (-a - b + ( a + b - + ( a + b - + (-a - b + (.6 Table. Relatonsh between l and Outcomes

5 A STUDY OF THE COGNITIVE STRUCTURE OF CONFLICT OVER DISASTER MITIGATION PROJECTS 5 The acton-based onon-summarzng rule formulated n equaton (.6 satsfes the rorty of the suorter s domnant acton.. Nash Equlbrum n Agent Game The equlbrum under the two onon-summarzng rules defned n. s comared n the case defned as follows. Suorters : P > P > P > P Suorters : P > P > P > P (.7 Whereas suorters of the government refer that roject s carred out as lanned (P > P, P > P, suorters of the ooston grou refer that the roject s modfed (P > P, P > P. If the roject s modfed, suorters of the ooston grou refer dalogue wth the government (P > P. However, f the roject s carred out as t lanned, they refer escalatng the conflct. In the reference of the suorters of governments, the states where the ooston grou accets dalogue are domnant to the states where the ooston grou s for escalatng a conflct (P > P, P > P. Ths mles that the rorty of the suorters of government s for dalogue wth the ooston grou. When the outcome-based onon-summarzng rule s emloyed, Nash equlbrum strategy rofles are IV and I. Consequently, from Table., the realzed outcomes are the states (Ooston escalates and roject s carred out as t lanned or (Ooston grou communcates wth government and roject s modfed. Equaton (.6 shows that the state s domnant to the state. When acton-based onon-summarzng rule s emloyed, >, < and < are derved from (.6. From Table., state may be unque outcome of the conflct,.e., only the Pareto nferor outcome can be realzed.. SURVEY OF THE COGNITIVE STRUCTURE OF A CONFLICT. Survey In secton, a model ncludng onon-summarzng rules was constructed. It showed that the result of conflct mght change deendng on the rules. In actual conflcts, onon-summarzng rules are based on eole s recognton of the structure of conflct. Here, a questonnare s used to survey eole s cogntve structures of conflcts over dsaster mtgaton rojects. Frst, a resondent was nstructed on the background of a hyothetcal conflct over a reservor roject. For smlfcaton, only two layers, government and ooston grou, are assumed. The government lans and roceeds wth the reservor roject. In contrast, the ooston grou s concerned about damage to natural envronment and ooses the roject. Both the government and ooston grou have lural acton choces. Although the conflct s hyothetcal, smlar stuatons occur n a real world. Gven nstructons on the conflct, the resondent s asked to choose actons whch he or she recognzes as beng ossble to take on the conflct, and outcomes whch he or she recognzes as beng ossble to be realzed. If eole s cogntve structure of a conflct s smlar to game theoretc model, the choces n and should be consstent. We formulated an nstructon to exlan ths hyothetcal conflct. Resondents were asked to read the nstructon and answer the followng questons: Q: From your subjectve vewont, choose the set of ossble actons of the ooston grou from the followng three actons. (Choose more than one acton. A. Takng aggressve behavor B. Askng for a referendum C. Communcatng wth the government Q: From your subjectve vewont, choose the set of ossble actons of the government from the followng three actons. (Choose more than one acton. A. Communcatng wth the ooston grou B. Susenson of the roject C. No communcaton and roceedng wth the roject Q: From the set of ossble actons secfed n Q and Q, choose one acton as the most desrable acton. Q: From your objectve vewont, choose the set of ossble outcomes of a conflct from the followng nne outcomes. (The number of choces s not lmted. The ooston grou takes aggressve behavor, and the government tres to communcate wth the grou (AA. The ooston grou takes aggressve behavor, and the government susends the roject (AB. The ooston grou takes aggressve behavor, but the government does not try to communcate wth the grou and roceeds wth the roject (AC. The ooston grou asks for a referendum, and the government tres to communcate wth the grou (BA. The ooston grou asks for a referendum, and the government susends the roject (BB. The ooston grou asks for a referendum, but the government does not try to communcate wth the grou and roceeds wth the roject (BC. The ooston grou tres to communcate wth the government, and the government tres to communcate wth the grou (CA. The ooston grou tres to communcate wth the government, and the government susends the roject (CB. The ooston grou tres to communcate wth the government, but the government does not try to communcate wth the grou and roceeds wth the roject (CC. Two characters n arentheses n Q reresent actons that lead a conflct to the corresondng outcome. In the actual questonnare, these characters are not shown, and the order of outcomes n Q s randomzed. As the urose of ths survey was to detect the general roertes of cogntve structure of a conflct, the resondent was not necessarly a stakeholder nvolved n a secfc conflct. There were 9 resondents, 99 unversty students and engneers. Note that all the students belonged to the deartment of cvl engneerng, and most of the engneers were cvl ones. Table. shows the relatonsh between the set of layers ossble actons and the corresondng outcomes. As defned n, the combnaton of layers actons s the strategy rofle. Shaded areas n Table. reresent the strategy rofles when the ooston grou chooses actons A and B as ossble and the government actons B and C. If the resondent chooses outcomes outsde of the shaded areas or does not choose outcomes ncluded n

6 6 H. SAKAKIBARA, H. KAKU AND K. KIDERA Table. Relatonsh between the Set of Players Possble Actons and Corresondng Outcomes Table. Results of Test I *: 5% sgnfcant (null hyothess s rejected SUM (. SUM SUM - SUM =, = N - SUM SUM: The number of resondents who chose the corresondng strategy rofle derved from Q and Q. SUM: The number of resondents who chose the corresondng outcome n Q. SUM: The number of resondents who chose the corresondng strategy rofle derved from Q and Q, and chose the corresondng outcome n Q. N: Total number of resondents s the rato of the resondents who chose the corresondng strategy rofle and outcome smultaneously, and the rato of resondents who chose the corresondng outcome out of those who dd not choose the corresondng strategy rofle. When the dfference between and s sgnfcant, the choce of outcomes deends on the choce of strategy rofles. Ths means that the strategy rofle and outcome are related to the resondent s cogntve structure of a conflct and that non-cooeratve game model s arorate to descrbe that conflct. If, however, the dfference between and s not sgnfcant, olarzaton between recogntons of strategy rofles and outcomes exsts. Table. shows the results of Test I. The sgnfcance level a s.5. In some outcomes, such as AC and BC, the dfference between and s not sgnfcant. Ths result shows that eole s cogntve structure of a conflct s olarzed n at least for some outcomes. those areas, t sgnfes that resondent s cogntve structure s olarzed from non-cooeratve game model.. Survey Result A statstcal test on ratos was carred out to detect eole s cogntve structures. The oulaton ratos of the two sets are defned as and. The null hyothess s = (=. The samle ratos of two samles from the two sets are defned as and (Samle szes are n and n. Statstc Z s formulated as follows. Z = - n + n, = n+ n ( - ( + n n (. When the samle sze s large enough, Z follows normal dstrbuton. If Z s larger than the threshold, the null hyothess s rejected and and dffer statstcally. Results of three statstcal tests are gven below. Test I: Dfference between choces of strategy rofles and outcomes In ths test, samle ratos and were defned as follows. Test II: Consstency between the Subjectve and Objectve Recogntons of Actons Possble reasons for the olarzaton seen n Test I are as follows.. Havng heard or seen about conflcts over reservor rojects, resondents may already have knowledge about the structure of such conflcts. Ths ror knowledge mght affect ther answers.. Resondents may have answered dfferently from the subjectve (Q and Q and objectve (Q vewont. Test II was done to examne the second reason. Frst, the objectve recognton of actons was defned. If a resondent chose at least one outcome caused by an acton n Q, t was judged that the resondent recognzed the exstence of the corresondng acton objectvely. In Test II, objectve and subjectve recognton of actons derved from Q and Q are comared. The samle ratos, and, are defned as follows. SUM 6 (. SUM SUM 5 - SUM 6 =, = N - SUM SUM: The number of resondents who chose the corresondng acton a n Q or Q. SUM5: The number of resondents who chose at least one outcome caused by the acton a n Q. SUM6: The number of resondents who chose the corresondng acton a n Q or Q and at least one outcome caused by the acton a n Q. s the rato of resondents recognzng acton a objectvely to those recognzng a subjectvely, and s the rato of resondents recognzng acton a objectvely to those not recognzng a subjectvely. When the dfference between and s sgnfcant, subjectve and objectve recogntons of the acton a are consstent. Table. gves the results of Test II. In the ooston grou s actons (Q, olarzaton between subjectve and objectve recognton was relatvely sgnfcant. Ths s artly because the survey resondents conssted of eole famlar wth ublc works rojects. Test III: Dfference between choces of objectve strategy rofles and outcomes The samle ratos and are defned as follows. SUM 8 (. SUM SUM - SUM 8 =, = 7 SUM 5 - SUM 7 SUM7: The number of resondents who chose at least one outcome caused by the ooston grou s acton a and the government s acton a n Q. SUM8: The number of resondents who chose at least one out-

7 A STUDY OF THE COGNITIVE STRUCTURE OF CONFLICT OVER DISASTER MITIGATION PROJECTS 7 Table. Table. Results of Test II Results of Test III a conflct wthout examnng the nteracton of decsons. However, such knowledge may sometmes revent them from behavng strategcally. In the case of the conflct over a reservor roject, the ooston grou may hoe for dalogue wth the governmental agency. If, however, government s knowledge suggests that ooston grou refers aggressve actons, government may not try to talk wth ooston grou, and the ossblty of comromse s lost. 5. CONCLUSION come caused by the ooston grou s acton a, the government s acton a n Q, and the corresondng outcome n Q. As n Test I, the urose of Test III was to confrm dfferences between recognton of actons and outcomes. Based on results of Test II, choces of the ooston grou s acton n Q were relaced by the objectve recognton of actons derved from Q. When the dfference between and s sgnfcant, the strategy rofle based on subjectve recognton of ooston grou s actons and outcome are related n resondent s cogntve structure of a conflct. Table. shows the results of Test III. Comarson wth Table. shows that the dfferences between and are not necessarly ncreased. That s, olarzaton between recognton of strategy rofle and outcome s not decreased by removng the dfference between the subjectve and objectve recognton of acton. Polarzaton may be due to resondents knowledge of conflcts n the ast, or ther ablty to estmate results from context.. Interretaton of Survey Results Results of the statstcal test show that olarzaton exsts for some questons between recognton of actons and outcomes, whereas recogntons have consstency n other. Ths suggests that there were eole who had ror knowledge of a smlar tye of conflct. Such knowledge s suosed to affect eole s cogntve structure of a conflct. In some cases, ror knowledge s useful for understandng a stuaton. For examle, eole may be able to fnd equlbrum of In ths study, eole s recognton about a conflct was analyzed. Frst, a model nvolvng layers game-makng rocess was constructed. Next, a survey of eole s cogntve structure on a conflct was made. Results of both suggested that the cogntve structure of a conflct may affect outcome of the conflct. In artcatory lannng, the mortance of a coordnator s often emhaszed. One role of a coordnator s to create the stage for dscusson. Ths role can be nterreted as romotng communcaton between stakeholders. Our fndngs ndcate the mortance of such communcaton n order to acheve a better outcome. REFERENCES Fudenberg, D. & D. Levne, 998. The Theory of Learnng n Games, MIT Press, Cambrdge. Harsany, J. C., Games wth Incomlete Informaton Played by Bayesan Players, arts I, II, and III, Management Scence,, 59-8, -, Kala, E. & E. Lehrer, 995. Subjectve Games and Equlbra, Games and Economc Behavor, 8, -6. Myerson, R. B., 99. Game Theory -Analyss of Conflct-, Harvard Unversty Press, Cambrdge. Oechssler, J. & B. Scher,. Can You Guess the Game You re Playng?, Games and Economc Behavor,,, 7-5. Young, P., 998. Indvdual Strategy and Socal Structure, Prnceton Unversty Press, Prnceton.