Ajzen - Attribution of Disposition to an Actor

8/2/2019 Ajzen - Attribution of Disposition to an Actor

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Journal 0 ' Personality and Social Psychology1971, Vol. 18, No.2, 144-156ATTRIBUTION OF DISPOSITIONS TO AN ACTOR:

EFFECTS OF PERCEIVED DECISION FREEDOM ANDBEHAVIORAL UTILITIES 1

ICEK AJZEN2University oj Illinois

Situations in which a hypothetical actor was faced with a choice betweenalternative behaviors are described. Each situation varied along two dimen-sions: the actor's perceived decision freedom (high versus low) and the utili-ties of the behavioral alternatives (high versus low). Estimates were obtainedof the perceived probability that the actor would engage in each of the behav-ioral alternatives. Subjects were told which alternative the actor had chosenand were then asked to attribute attitudes or personality traits to the actoron the basis of his choice. Perceived behavior probabilities were shown to beinfluenced by the actor's decision freedom and by the utilities of the availablealternatives. Also, consistent with expectations, the strength of an attributionwas a negative function of behavior probabilities. The effects of decision free-dom and of behavioral utilities on attribution strength could be predictedfrom the influence of these variables on behavior probabilities and from theinverse relation between behavior probabilities and attribution strength. Fi-nally, evidence is presented for the utility of a Bayesian approach to theprediction of attribution.

Research on the processes underlying in-ference of traits as the result of observed be-havior has centered around two variables:the perceived decision freedom of the actorand the desirability or utility of the act.Steiner (1970) has emphasized perceived de-cision freedom. In an empirical investigation(Steiner & Field, 1960), perceived decisionfreedom was found to be positively relatedto the degree of confidence in the attributionof a trait to the actor. The degree of con-fidence with which an accomplice of the ex-perimenter was rated to be a segregationistwas higher when the accomplice was per-ceived to have freely chosen a prosegregationstand than when he was assigned a prosegre-gationist role by the experimenter. In theirtheory of the attribution process, Jones andDavis (1965) stress the importance of theact's utility, that is, the favorableness of theeffects produced by the act. Jones, Davis, andGergen (1961) reported a study that bears1This research was supported in part by Grant

00-26-10-300 from the University of Illinois ResearchBoard. The author is grateful to Martin Fishbein,Ivan D. Steiner, and Allan W. Wicker for criticalreadings of an earlier draft.2Requests for reprints should be sent to the au-thor, Department of Psychology, University of Illi-nois, Champaign, Illinois 61820.

on the effect of behavioral utility on the at-tribution process. Out-of-role behavior (withlow utility) was found to permit stronger in-ferences about the actor's disposition towardextraversion or introversion than did in-rolebehavior (with high utility). In a more re-cent study (Jones & Harris, 1967), an at-tempt was made to examine the simultaneouseffects of perceived decision freedom and be-havioral utilities. A short essay on "Castro'sCuba" was read by the subjects, Itwas eitherpro-Castro (low utility) or anti-Castro (highutility), and it was alleged to have beenwritten either under conditions of free choice(high decision freedom) or by assignment ofa course instructor (low decision freedom).The results demonstrated that high decisionfreedom permitted stronger inferences aboutthe writer's attitude toward Castro than didlow decision freedom. Beyond this, however,the findings must be regarded as inconclu-sive. While most studies on the attributionprocess have used certainty of attribution astheir major dependent variable (de Charms,1968), Jones and Harris simply measured theactor's perceived attitude. Although attitudesattributed to the actor were in line with theessay he was believed to have written (eitherpro- or anti-Castro), it is impossible to say

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145 Iczx AJZENwhich of the two essays allowed a morepowerful inference. In other words, no clearconclusions can be reached about the maineffect of behavioral utility or about its inter-action with perceived decision freedom.One means of avoiding this problem is to

obtain an estimate of change in attributeddisposition (e.g., attitude) that results frominformation about the actor's behavior. Thatis, the disposition or trait attributed to theactor after information about his behaviorhas been obtained must be compared withthe disposition that is attributed to him priorto obtaining the information. Attribution,then, may be viewed as a process by whichthe probability that the actor possesses agiven trait is revised in the light of informa-tion about his behavior. The term "inferencemagnitude" is used to denote this revision inperceived trait probabilities. The greater thechange in trait probabilities, the greater theinference magnitude.The most fundamental proposition of

the present paper is based on informationtheory notions (d. Reza, 1961) and can bestated as follows: Inference magnitude is adirect function of the amount of informationentailed in the actor's behavior. In informa-tion theory terms, hi = -IOg2Pi, where hi isthe information value or uncertainty of eventiand Pi is its prior probability. For our pur-poses, event iis the occurrence of an actor'sbehavior. The information value of an act,thus, is an inverse function of its prior proba-bility of occurrence."Behavioral utility and perceived decision

freedom should both influence the prior prob-abilities of alternative behaviors available tothe actor. The assumption has frequentlybeen made that the expected utility of analternative is closely related to the probabil-ity that it will be taken. Behavioral decisiontheory (d. Edwards, 1954, 1961) is clearlybased on this assumption. Some empirical evi-dence for this proposition has been summar-ized by Edwards and can also be found inAjzen and Fishbein (1970). Thus, we mayexpect that an available act's utility will havea direct influence on its perceived probability.Similarly, perceived decision freedom3Similar notions have been discussed by Jones and

Harris (1967) and by Jones and Gerard (1967).

should also influence prior behavioral prob-abilities. External pressures, social norms, theperceived consequences of the available al-ternatives, and other factors that restrict anactor's decision freedom tend to result in theincreased likelihood of one of the availablealternatives at the expense of all others. Ahigh degree of decision freedom is indicatedby the availability of equally probable alter-natives. The more equiprobable the availableoptions, the higher the actor's decisionfreedom. A convenient index for the equi-probability of a set of alternative acts isprovided by the information theory measureof expected uncertainty: H = -~Ptlog2p;,where H is the average uncertainty or, in thepresent case, the degree of decision freedom,and Pi is the prior probability of alternative i.Since present concern is with perceived de-cision freedom, this formula can be rewrittenas follows: PDF = -~SPilog2SPi' wherePDF is perceived decision freedom and SPi isthe subjective prior probability of alterna-tive i.These notions are closely related toSteiner's (1970) conceptualization of decisionfreedom. According to Steiner, "whenever anindividual must choose between two or moreavailable alternatives, decision freedom shouldbe a negative function of the discrepanciesbetween the gains offered by the availableoptions [p, 195]." Under the above proposi-tion that the expected utility of an availablealternative is closely related to the subjectiveprobability of its being chosen, this argumentbecomes equivalent to the definition of de-cision freedom in terms of equiprobability.The above considerations also lead to theexpectation that behavioral utility and per-ceived decision freedom interact in their ef-fects on prior probabilities of available be-havioral alternatives. Given that an actorfaces a choice between alternatives varyingin expected utility, the existance of few posi-tive (i.e., high utility) and many negative(i.e., low utility) behaviors creates a situa-tion of low decision freedom for the actor,since he has only a few reasonable options.By definition, increasing decision freedom in-volves greater equalization of the behavioralutilities, and hence probabilities, of the alter-natives. This can be achieved by raising the


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ATTRIBUTION OF DISPOSITIONS TO AN ACTOR

attractiveness of the negative behaviors, bydecreasing that of the positive behaviors, orby adding new positive alternatives. What-ever the method used, however, under highdecision freedom, the differences between per-ceived probabilities of positive and negativealternatives will tend to be smaller than un-der low decision freedom. That is, the effectof behavioral utility on prior behavior proba-bilities depends on the overall decision free-dom: differences in utilities are associatedwith greater differences in perecived behaviorprobabilities under low than under high de-cision freedom.Assuming that behavioral utility and per-ceived decision freedom display the describedeffects on prior probabilities of the alterna-tives, a number of hypotheses concerning theattribution process can be formulated. First,however, it should be noted that the stipula-tion, based on information theory, of an in-verse relation between prior behavior proba-bilities and inference magnitude has thefollowing implications: Inference magnitudeis high when the actor performs a behaviorof low prior probability and when he rejectsan alternative of high prior probability. Bothof these actions should facilitate the attri-bution of traits to the actor since they areboth unanticipated choices with high infor-mation value. On the other hand, perform-ance of a high-probability behavior and rejec-tion of a low-probability behavior shouldhave little information value, and thus in-ference magnitude should be low.The kinds of inferences that can be made,that is, the specific disposition that can beattributed will of course depend on the par-ticular alternative performed or rejected.The following predictions were made re-garding the effects of behavioral utility andof perceived decision freedom on inferencemagnitude.1. Assuming a direct relationship betweenutilities and prior probabilities of behaviors,and an inverse relationship between priorprobabilities and inference magnitude, it waspredicted that inference magnitude is greaterwhen the chosen alternative has low utilitythan when it has high utility. Conversely,with respect to a rejected option, inferencemagnitude is greater when the rejected alter-

1 4 6

native has high utility than when it has lowutility.2. It should be recalled that the discrep-ancy between prior probabilities of positiveand negative acts is expected to be greaterunder low than under high decision freedom.Behavioral utility is therefore expected to in-teract with perceived decision freedom. Theeffects of behavioral utility on inference mag-nitude specified above are predicted to bestronger under low decision freedom than un-der high decision freedom. That is, differ-ences in inference magnitude resulting fromperformance or rejection of positive as op-posed to negative alternatives should begreater under low decision freedom than un-der conditions of high decision freedom.3. It is difficult to make unequivocal pre-dictions about the main effect of perceiveddecision freedom in general. The hypothesesdescribed below are specific to the presentmanipulation of the actor's perceived decisionfreedom. Specifically, the actor chooses eithera high-utility or a low-utility alternative.Under high decision freedom, two additionalpositive options are available, while underlow decision freedom the two additional op-tions are negative.This implies that the choice of a positiveoption (i.e., of a high-utility alternative) willprovide more information about the actor'sdisposition under high decision freedom(where other positive options are available)than under low decision freedom (where thisis the only available option of high utility).Choice of a negative alternative, however, haslow prior probability, regardless of the de-gree of decision freedom. In both conditionsof decision freedom, more positive and thusmore likely alternatives are available. Hence,inference magnitude should be high in bothconditions. The overall effect of perceived de-cision freedom on inference magnitude, there-fore, should be in favor of high decision free-dom for inferences based on chosen options.Rejection of a positive alternative shouldresult in considerable inference magnitudeunder conditions of low perceived decisionfreedom (where it is the most likely option),but less so under high decision freedom(where it is only one of the attractive op-tions available). Rejection of a negative al-


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147 Icsx AJZENternative, however, has high prior probabilityin both conditions of decision freedom, be-cause more attractive alternatives are avail-able. Such a rejection should thus providerelatively little information about the actor,regardless of the degree of decision freedom.The overall effect, then, of perceived decisionfreedom on inference magnitude based on re-jected options should tend to favor the low-decision-freedom condition.4. Finally, it was predicted that the over-

all level of inference magnitude is lower foran inference based on a rejected alternativethan it is for an inference based on the chosenoption. That is, knowledge that the actor haschosen a given alternative is expected to re-veal a great deal about his traits implied bythe chosen alternative, but much less abouttraits implied by other options that wereavailable, but were not chosen.One major purpose, then, of the present

study was to test the above hypotheses aboutinference magnitude in person perception. Tosummarize briefly, inference magnitude ismeasured in terms of revision in the perceivedprobability that an actor has a given traitas a result of information about his behavior.Magnitude of inference about an actor's dis-positions was expected to be related to theutilities of the chosen and rejected options, andthese effects of behavioral utilities on infer-ence magnitude are predicted to interact withperceived decision freedom. Further, greaterinference magnitude is expected for attribu-tions based on chosen options than for attri-butions based on rejected alternatives.Another purpose of the present study was

to examine an alternative approach to theprediction of posterior trait probabilities,based on Bayesian analysis (d. Morgan,1968). In its simplest form, and adapted tothe present purposes, Bayes's theorem canbe presented as follows:

SP(T\B) SP(B I T)SP(T)SP(B)SP(TIB) is the subjective posterior traitprobability, that is, the subjective probabilitythat the actor has Trait T, given that he hasengaged in Behavior B; SP(BIT) is the sub-jective probability that Behavior B will oc-

cur, given that the actor possesses Trait T;SP(T) is the subjective prior trait probabil-ity; and SP(B) is the subjective prior be-havior probability.It is interesting to note that Bayes'stheorem is quite consistent with some of the

notions in the preceding discussion of theattribution process. First, the prior trait prob-ability is taken into account in predictingthe level of posterior probability, and second,the posterior trait probability is an inversefunction of the prior behavior probability.The conditional probability SP(BiT) is anadditional variable not previously considered.Itreflects the perceived degree of relationshipbetween the trait and the behavior.Itwas predicted that a significant correla-tion would be obtained between the observed

posterior trait probability and the estimateof that probability by Bayes's theorem.METHOD

Four hypothetical situations were formulated foruse in the present experiment. In each of the situa-tions, a hypothetical person (the actor) was con-fronted with a choice between 4 alternatives. Eachof the alternatives had different implications for theactor's dispositions in three of the situations and foranother person's characteristics in the fourth. A pilotstudy was designed to select 3 high-utility and 3low-utility alternatives for each situation. For thispurpose, 37 undergraduate students enrolled in anintroductory psychology course were presented withthe four hypothetical situations. The order of pres-entation was randomized. The actors in these situa-tions had a choice between 12 different alternativesvarying in utility. The subjects were asked to indi-cate their beliefs about the actor's evaluation of eachalternative on a 7-point bipolar scale ranging from"good" to "bad."Based on the rank orders of these utility measures,

the three highest and the three lowest alternativesin each situation were selected for use in the experi-ment. The second highest and the second lowest al-ternatives were designated as "crucial"; that is, thehypothetical actor was later described to have chosenone or the other of these two alternatives. In theexperiment, conditions of high and low decision free-dom were created by differentially combining fourof the six alternatives selected in the pilot study.In the high-decision-freedom conditions, the actorwas confronted with a choice between four optionsincluding the three high-utility alternatives, as wellas the crucial low-utility alternative. That is, threeof the actor's available alternatives were reasonableoptions. In the low-decision-freedom conditions, theactor was again given four options, but here hischoice was between the three low-utility alternatives


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ATTRIBUTION OF DISPOSITIONS TO AN ACTOR 148and the crucial alternative with high utility. Thus,in the low-decision-freedom conditions, only one al-ternative was a reasonable option.The following are the four hypothetical situations

Situation 1

and the two sets of four alternatives, one set forhigh and the other for low decision freedom. Thefour alternatives were presented to the subjects inthe order given below.

On a Friday night, Student L could engage in on e of the following activities:HIGH DECISION FREEDOM

1. Go to a party**2. Inspect a friend's stamp collection*3. Have dinner with a date4. Listen to some new record albums at a friend'splace

Situation 2

LOW DECISION FREEDOM1. Read assignments for next week's classes

**2. Inspect a friend's stamp collection*3. Have dinner with a date4. Attend an optional evening quiz section

Student B is a member of a group that prepares discussions before a general student audience. From among anumber of alternatives, Student B had to select on e position, present it to the audience, and defend it as his positionin the discussion. The followingis the list of positions from which Student B had to choose one to present as hisown opinion before the audience:

HIGH DECISION FREEDOM**1. The desirability of increasing tuition at the Uni-

versity of Illinois2. The need for peaceful coexistence in today's world*3. The urgent need for an end to the nuclear arms

race4. The necessity of improving education for the poor

Situation 3

LOW DECISION FREEDOM**1. The desirability of increasing tuition at the Uni-

versity of Illinois2. The student revolt: Traitors in American society*3. The urgent need for an end to the nuclear arms

race4. The need for drafting large numbers of college stu-dents into the Armed Forces

A national company is considering Mr. K for a job. As part of the screening process, a few friends of Mr. K whohave known him for some time were asked to select the on e most fitting description of Mr. K from the followinglist:

HIGH DECISION FREEDOM1. intelligent*2. reliable3. honest

**4. lazySituation 4

LOW DECISION FREEDOM1. deceitful*2. reliable3. rude

**4. lazy

A university is offering a number of general interest courses on various topics; these courses are given for credit,but are not required. Student P wanted to take one of these courses, but he was not sure which one would bethe most valuable. In addition to the coursedescriptions, he therefore looked at student evaluations of these coursesthat were collected in previous semesters. The followingare the percentage of students who expressed satisfactionwith a given general interest course:

HIGH DECISION FREEDOM*Course 1. 81% satisfactionCourse 2. 79% satisfactionCourse 3. 84% satisfaction

**Course4. 14% satisfactionAsterisked items are the critical alternatives. One

asterisk indicates high utility, two asterisks indicatelow utility. In each situation the actor was said tohave chosen either the high- or the low-utility al-ternative. There were thus four conditions for each

LOW DECISION FREEDOM*Course 1. 81% satisfactionCourse 2. 11% satisfactionCourse 3. 16% satisfaction

**Course4. 14% satisfactionsituation: decision freedom was either high or low(depending on the set of alternatives), and behavioralutility was either high or low (depending on thechoice attributed to the actor). It should be notedthat when the chosen alternative had high utility,


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149 Icsx AJZENthen the critical rejected alternative had low utility,and vice versa.QuestionnairesIn a session that lasted approximately 30 minutes,

the subjects, in groups of about 3S each, completedquestionnaires related to the hypothetical situations.The description of each situation was followed by astatement of the actor's choice. For example, in Situ-ation 1 the subjects in the condition of high behav-ioral utility were told: "In this situation, Student Lchose to have dinner with a date." Under low behav-ioral utility, they were told: "In this situation, Stu-dent L chose to inspect a friend's stamp collection."The subjects then answered two questions regard-ing dispositions of the focal person in each of thehypothetical situations. Responses to these questionsconstitute measures of SP(TiB), that is, posterior

trait probabilities. In Situation 1 these two questionsread as follows:1. In view of his choice, do you think that Stu-dent L enjoys eating out? What are the chancesthat Student L enjoys eating out? The chances are_ in 100 that Student L enjoys eating out+2. In view of his choice, do you think that Stu-dent L is interested in stamp collections? Whatare the chances that Student L is interested instamp collections? The chances are _ in 100that Student L is interested in stamp collections.

The remaining three situations were dealt with ina similar manner. In Situation 2, the inferences madewere about Student B's positions toward "endingthe nuclear arms race" and "increasing tuition at theUniversity of Illinois." In Situation 3, the inferencesconcerned Mr. K's being "reliable" and "lazy." Thetraits inferred in Situation 4 were Student P's in-terests in "the topic of Course 1" and "the topic ofCourse 4."Each subject was thus requested to make infer-ences about the focal person in each situation; oneinference was directly related to the chosen alterna-tive, and the other was related to the crucial rejected

alternative.The subjects then turned to the second part of thequestionnaire which contained measures of priorprobabilities. First, they again read the descriptionsof the four hypothetical situations. They were thenasked to provide estimates of prior probabilities, thatis, of behavior and trait probabilities, without ref-erence to the actor's actual choice. However, theseprobability estimates might be influenced by the pre-ceding information about the actor's choice and bythe subject's earlier replies to the questionnaire items.Therefore, control subjects who responded only tothis part of the questionnaire were also used. The4 Selection of the trait that was to be inferredfrom the behavioral choice was arbitrary. The sub-jects could have been asked to make inferences aboutStudent L's liking for good food or about any of anumber of other traits.

items of Situation 1 exemplify the questionnaireitems.1. Subjective prior behavior probabilities

SP(B)Imagine that you observe 100 typical students,each of whom can engage in one of the above ac-tivities on a Friday night. Out of the 100 students,how many do you think would engage in each ofthe four Friday night activities?In front of each activity above, place the num-ber of students who would engage in that activityon a Friday night. Please make sure that your es-timates sum to 100, so that you have accountedfor all 100 students.

2. Subjective prior trait probabilities SP(T)a. Subjective probability of the trait related to

the high-utility behavior: "Out of 100 typicalstudents, how many do you think enjoy eatingout?Out of 100 typical students, _ studentsenjoy eating out."b. Subjective probability of the trait related tothe low-utility behavior: "Out of 100 typicalstudents, how many do you think are interestedin stamp collections?Out of 100 typical students, _ studentsare interested in stamp collections."

3. Subjective prior conditional probabilitiesSP(BIT)a. Trait corresponding to the high-utility be-

havior-SP(BiT+) :"Out of 100 students who enjoy eating out,how many do you think would engage in eachof the four Friday night activities?In front of each activity below, place thenumber of these students who would engage inthat activity on a Friday night. Again, pleasemake sure that your estimates sum to 100, sothat you have accounted for all 100 students."b. Trait corresponding to the low-utility be-

havior-SP(BiL) :"Out of 100 students who are interested instamp collections, how many do you thinkwould engage in each of the four Fridaynight activities?"The remainder of the question followed the for-mat of 3a above.The order of the four hypothetical situations andof the related measures within both parts of thequestionnaire was randomized.

SubjectsA total of 201 subjects participated in the exneri-ment, 100 males and 101 females. The subjects wereundergraduates enrolled in an introductory psychol-ogy course, who participated in the experiment aspart of their course requirements. Of the 201 stu-dents, 147 served as experimental and S4 as control


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subjects. In order to obtain equal cell frequencies inthe four experimental groups, 7 of the experimentalsubjects were eliminated at random, within the con-straints of the design to be described below. Thisleft a total of 140 experimental subjects, 72 males and68 females, and 54 control subjects, 25 males and 29females, who were assigned to the experimental andcontrol treatments at random.Experimental DesignThe 140 experimental subjects were assigned to thefour experimental conditions (high versus low deci-sion freedom and high versus low behavioral utility)on the basis of a balanced Latin square design. Eachsubject responded once, and only once, to each situ-ation and to each condition. Subjects were divided inequal numbers into the possible situation-conditioncombinations under the constraints of the Latin

square. There were thus a total of 35 subjects ineach of the four conditions in every situation.The 54 control subjects were assigned in equalnumbers to the two conditions of decision freedom;behavioral utility was irrelevant since no action wasattributed to the actor. Each subject responded toall four situations, two with high and two with lowdecision freedom; responses were obtained only onthe second part of the questionnaire. A total of 27control subjects were thus available in each conditionof decision freedom in every situation.In sum, four experimental conditions were createdwithin each of the four hypothetical situations, 2levels of decision freedom X 2 levels of behavioralutility. Decision freedom was manipulated by varyingthe available alternatives of the actor, while behav-ioral utility was a function of the choice attributedto the actor. Measures were obtained of posteriortrait probabilities; both the probability of thechoice-related trait as well as that of the trait re-lated to the crucial rejected alternative were consid-ered. In addition, measures were taken of prior traitprobabilities, prior behavior probabilities, and priorconditional probabilities. Subjects were assigned tothe experimental conditions on the basis of a Latinsquare design. In order to avoid possible contamina-tion of the prior probability measures, control sub-jects were used to measure these prior probabilitiesonly.

RESULTSPrior probabilities of behaviors and traits

were assessed both in the experimental andcontrol groups. As noted above, since in theexperimental groups this measurement waspreceded by the attribution phase, it mayhave been influenced by the latter. In order toexamine this possibility, two-way analyses ofvariance were computed for each of the fourhypothetical situations. The main effects weredecision freedom (high versus low) and ex-perimental condition (high behavioral utility,

150low behavioral utility, or control, i.e., no be-havior by the actor). Only the main effect ofexperimental condition was of importance forpresent purposes. The dependent variableswere the prior probabilities of the four be-havioral alternatives, the two prior trait prob-abilities, and the two sets of four conditionalprobabilities, a total of 14 variables." Theresults indicate that although of small mag-nitude, the attribution phase of the question-naire in the experimental groups tended toinfluence subsequent responses to the priorprobability items. In particular, the perceivedprior probability of a behavior, and of thecorresponding trait, tended to increase whenthe actor was described to have chosen thatbehavior, and to decrease when he had rejectedit. These effects, however, were not verystrong. The mean levels of responses in theexperimental groups differed only slightlyfrom the control groups, and relatively few ofthese differences reached statistical signifi-cance. In Situation 1, 3 of the 14 variableswere significant beyond the .05 level. In Situ-ation 2, only one comparison was significant.In Situations 3 and 4, the number of variablesreaching statistical significance were 6 and 2,respectively.These results indicate that the measures ofprior probabilities obtained from the experi-

mental subjects were to some extent influ-enced by the experimental manipulations, andthat care has to be taken, therefore, in in-terpreting results based on these measures. Inorder to avoid such problems of interpretation,the control group estimates of prior probabil-ities were used in all analyses where this wasfeasible.Prior Behavior ProbabilitiesMost hypotheses of the present paper rest

on the expectations that subjective prior prob-abilities of behaviors are influenced by theirutilities and by the actor's perceived decisionfreedom. Further, perceived decision freedomwas itself expected to be related to the partic-ular combination of available alternatives dif-fering in utility. The results presented in Ta-ble 1 confirm these expectations. Mean sub-jective prior probabilities of the two crucial

5 See the Method section for a detailed description.


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151 Icsx AJZENTABLE 1

SUBJECTIVE PRIOR BEHAVIOR PROBABILITIES AND RELATIVE PERCEIVED DECISION FREEDOM:MEANS AND t TESTS FOR CONTROL GROUPS

Situation 1 Situation 2 Situation 3 Situation 4

High I Low High Low High Low High Lowdecision decision t decision decision t decision decision t decision decision tfreedom freedom freedom freedom freedom freedom freedom freedom--- --- --- --- --- --- --- --- --- --- ---SP(B+l .297 .647 8.192.... .247 .556 5.554.... .334 .849 12.679** .309 .721 8.592**SP(B_l .051 .102 2.889.... .077 .105 .990 .043 .061 1.011 .040 .089 3.048**SP(B+l - SP(B_l .246 .545 5.608** .170 .451 3.941** .291 .788 9.586** .269 .632 6.052**Rei. perceived de- 3.135** .787 .658 2.361* .808 .368 8.672** .786 3.600**ision freedom .798 .658 .573* p < .05, dj =52, two-tailed.

** p < .01, dj =52, two-tailed.behaviors, one with high utility [SP(B+)]and the other with low utility [SP(BJ]' aregiven for the control groups under high andlow decision freedom. Mean differences be-tween SP(B+) and SP(BJ are also presented.In addition, perceived decision freedom hasbeen estimated for each subject on the basis ofhis subjective prior probabilities for the fouralternative acts," as indicated by the informa-tion theory index, PDF = -~SPilog2SP"Since the maximum perceived decision free-dom in the case of four alternatives is 2.0, anindex of relative perceived decision freedomis obtained as follows: ReI. PDF = PDF/2.This index can range from 0 to 1.As anticipated, the prior probabilities of the

positive alternatives in the hypothetical situ-ations were considerably higher than those ofthe negative alternatives. These differenceswere significant (p < .01) in all four situa-tions under both high and low decision free-dom. More importantly, the expectation of aDecision Freedom X Utility interaction wasalso confirmed. It can be seen that the dif-ferences between prior probabilities of positiveand negative behaviors were always signifi-cantly greater under low than under high de-cision freedom. The results of t tests for thesedifferences are given in Table 1.The information theory estimates of per-ceived decision freedom proved reasonablysuccessful. In all four situations, these esti-mates were significantly higher under highthan under low decision freedom. These re-sults thus provide some evidence for the valid-ity of the information theory measure of per-6 As log.G is undefined, behavior probabilities equalto 0 were set at .01.

ceived decision freedom. It is worth notingthat the estimates of decision freedom pre-sented in Table 1 indicate that even in thelow-decision-freedom conditions, the perceiveddecision freedom of the actor was still farfrom zero. That is, even when only one alter-native was of high utility, the actor wasusually perceived to have a considerableamount of decision freedom.Inference MagnitudeAfter confirming the expected effects of the

experimental manipulations on perceived be-havioral probabilities and on perceived deci-sion freedom, it is now possible to test thehypotheses concerning inference magnitudewhich were based on these anticipated effects.A measure of inference magnitude was ob-tained by subtracting a subject's posteriortrait probability, that is, SP( TIB), from theaverage prior trait probability, SP( T), of thecorresponding control group. That is, for eachof the two traits that were inferred in eachhypothetical situation, the difference was com-puted between the posterior probability ofthe trait as supplied by the experimental sub-ject and the prior probability of the sametrait for which the control group mean wastaken as an estimate. For subjects who madetheir inferences in a high-decision-freedomcondition, the estimate of the prior trait prob-ability was based on the high-decision-freedomcontrol group. Similarly, low-decision-freedominferences were paired with the average of thelow-decision-freedom control group. Devia-tions of posterior from estimated prior traitprobabilities were scored positively if theyconformed to expectations; deviations con-


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ATTRffiUTION OF DISPOSITIONS TO AN ACTOR

TABLE 2INFERENCE MAGNITUDEFOR ACHOICE-RELATED TRAIT:

MEAN DEVIATIONS OF POSTERIOR TRAITPROBABILITIES FROM CONTROL GROUP

ESTIMATES OF PRIOR TRAITPROBABILITIES

Decision freedomUtility of chosen

alternativeHigh Low M

High .137 -.033 .052Low .573 .565 .569M .355 .266 .311

trary to expectations were scored negatively.(Choice of an act was expected to increase thesubjective trait probability, while its rejectionwas expected to decrease this probability.)Thus, the higher the resulting score, thestronger the inference made by the subject.Table 2 presents the average inference mag-

nitudes under the four experimental conditions(high versus low decision freedom and highversus low behavioral utility) for the traitcorresponding to the chosen alternative,summed over all four hypothetical situations.'These data were submitted to an analysis ofvariance, and the results are presented in Ta-ble 3. The main effects were decision freedomand behavioral utility, both "within-subjects"factors."Looking at Table 2 it can be seen that thehypotheses concerning inferences about choice-

7 Separate analyses were also performed for eachindividual situation. The results were essentiallyequivalent to those using the pooled data and willnot be presented due to lack of space.S Sex was included as a third factor. Neither themain effect of sex nor any of its interactions withthe other factors reached statistical significance.Therefore, sex was omitted in reporting the analysesof variance.

TABLE 3ANALYSIS OF VARIANCE SUMMARYTABLE OF

INFERENCE MAGNITUDE FOR ACHOICE-RELATED TRAIT

Source df Error term MS F---Decision freedom (A) 1 AXe 1.118 27.781*Behavioral utility (B) 1 BXe 37.377 787.420*Ss within groups (C) 138 .071A XB 1 AXBXC .909 18.654*A x c 138 .040BXC 138 .047A XB XC 138 .049* p < .01.

152

TABLE 4INFERENCE MAGNITUDE OF A REJECTION-RELATED

TRAIT: MEAN DEVIATIONS OF POSTERIORTRAIT PROBABILITIES FROM CONTROL

GROUP ESTIMATES OF PRIORTRAIT PROBABILITIES

Decision freedomUtility of rejectedalternative High Low MHigh .288 .355 .321Low -.062 -.066 -.064M .113 .145 .129

related traits were strongly supported. First,low choice utility permitted considerablystronger inferences than did high choice util-ity. Individual comparisons between cellmeans revealed that the differences betweenhigh and low utility choices were significantboth under high decision freedom (F =271.428, dj = 1/138, P < .01) and under lowdecision freedom (F =505.714, dj =1/138,P < .01).Second, a highly significant interaction ef-

fect was found between decision freedom andchoice utility. As expected, the impact ofchoice utility was greater under low than un-der high decision freedom.Third, it was found that inference magni-

tude under high decision freedom was signifi-cantly greater than under low decision free-dom. Comparisons between the means showedthat the difference between high and low de-cision freedom was significant (F = 41.428,dj = 1/138, P < .01) only when the chosenalternative had high utility. The differencebetween the effects of high and low decisionfreedom was not significant when the chosenact had low utility. Thus, increasing the ac-

TABLE 5ANALYSIS OF VARIANCE SUMMARYTABLE FOR

INFERENCE MAGNITUDE OF A REJECTION-RELATED TRAIT

Source df Error term MS F--Decision freedom (A) 1 AXe .143 4.115*Behavioral utility (B) 1 B XC 20.792 588.896**Sswithin groups (C) 138 .068AXB 1 AXBXC .175 3.942*A XC 138 .035B XC 138 .035AXBXC 138 .044

* p < .05.** P < .01.


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153 Icsx AJZENtor's perceived decision freedom does notalways enhance inference magnitude.Results confirming the hypotheses with

respect to inferences about traits related torejected alternatives are presented in Tables4 and 5. Again, in Table 4 the average infer-ence magnitudes under the four experimentalconditions are given, and Table 5 shows theresults of the analysis of variance with themain effects of decision freedom and behav-ioral utility (i.e., utility of the rejected alter-native; see Footnotes 7 and 8). Computationsof inference magnitude and of the analysis ofvariance were identical to those for the resultspresented in Table 3.The findings given in Tables 4 and 5clearly support the hypotheses. For traits re-

lated to rejected alternatives, the followingconclusions can be drawn. First, rejection ofa positive alternative permitted stronger in-ferences than rejection of a negative alterna-tive. Individual mean comparisons showedthese differences to be significant for highdecision freedom (F = 81.080, df = 1/138, P< .01), as well as for low decision freedom(F =281.333, df = 1/138, P < .01).Second, the effect of rejection utility was

stronger under low than under high decisionfreedom, as indicated by the significant Deci-sion Freedom X Utility interaction.Third, with respect to the main effect of

perceived decision freedom, inference magni-tude was found to be greater under low thanunder high decision freedom. Mean compari-sons show that only for the rejection of anoption with high utility was the differencebetween high and low decision freedom sta-tistically significant (F = 7.127, df = 1/138,P < .01).A final comparison was made between in-

ference directions, that is, between the overalllevels of inference magnitudes for choice-related traits and rejection-related traits. Asanticipated, this overall level was higher fora choice-related trait (.311) than for a traitcorresponding to a rejected alternative (.129).In an additional analysis of variance, in-ference direction was included as a third fac-tor (together with decision freedom and be-havioral utility). Of interest here is that themain effect of inference direction was highly

TABLE 6CORRELATIONS BETWEEN PRIOR BEHAVIOR PROB-

ABILITIES AND INFERENCE MAGNITUDE

Situation

.643.492.258.642

Inferences aboutchosen traits Inferences aboutrejected traits-.774-.570-.387-.750

1234

Note.-All correlations are significant (p < .01); N = 140.significant (F = 186.418, df = 1/138, P


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TABLE 7CORRELATIONS BETWEEN OBSERVED POSTERIOR TRAIT

PROBABILITIES AND BAYES'STHEOREM ESTIMATES

Situation

.697.577.725.650

Inferences abouthigh-utility traits Inferences aboutlow-utility traits1224

.478.442.680.526Note.-All correlations are significant (p < .01); N = 140.

beyond the .01 level and had the expectedsigns.Ithas been implicit in the present paper

that the effects of decision freedom and be-havioral utility on inference magnitude aremediated by prior behavior probabilities.Some support for this notion has been pre-sented earlier. Decision freedom and behav-ioral utility were shown to affect prior be-havior probabilities (Table 1), and the latterwere in turn found to be related to inferencemagnitude (Table 6). However, more directevidence is needed before it can be concludedthat the effects of decision freedom and be-havioral utility on inference magnitude areindeed mediated by, and dependent upon, theinfluence they exert on prior behavior prob-abilities.Prediction oj Posterior Trait Probabilities:Bayes's TheoremEstimates of the subjective posterior prob-

abilities of the positive (high utility) andnegative (low utility) traits were computedon the basis of Bayes's theorem, for eachsubject." These estimates were correlated11Bayes's theorem estimates above unity were set

equal to 1.

154with the posterior trait probabilities suppliedby the subjects. The correlation coefficientscan be inspected in Table 7, where it can beseen that the relationships obtained were gen-erally high and significant, for all four situa-tions. Bayes's theorem thus appears to be areasonably good predictor of trait inferences.However, in order to evaluate Bayes's the-

orem as an estimator of posterior trait prob-abilities, it is not sufficient to demonstratesignificant correlations. Itis also necessary toexamine the accuracy of the predicted scores.One possible approach is to compare the pre-dicted and observed scores. In Table 8 it canbe seen that although the mean levels of ob-served and estimated scores were relativelyclose, the differences were mostly significant.Thus, the attribution of a trait to an actorafter observing his behavior differs somewhatfrom the prescription provided by Bayes'stheorem. Consistent with findings in differentcontexts (d. Edwards, 1965), the subjects'estimates of posterior trait probabilitiestended to be more conservative than the pre-scribed optimal levels. That is, the subjects'posterior trait probabilities tended to be lessextreme than the estimates based on Bayes'stheorem.Overall, then, estimates of posterior trait

probabilities based on a Bayesian approachwere highly related to the subjects' actualposterior trait probabilities. However, thesubjects tended to be more conservative inmaking use of the information about the ac-tor's behavior than would be considered opti-mal by Bayes's theorem.P12Itmight be argued that the previously reportedinfluence of the actor's choice on measures of prior

probabilities may have contributed to this effect.TABLE 8

OBSERVED POSTERIOR TRAIT PROBABILITIES AND BAx'ES'S THEOREMESTIMATES: MEANS AND t TESTS

High-utility trait Low-utility traitSituation

Observed Estimated t Observed Estimated t1 .557 .652 -3.770-- .525 .372 6.145--2 .636 .698 -2.255* .417 .301 3.854*-3 .522 .443 3.376-- .493 .450 1.8144 .410 .576 -5.845-- .558 .442 4.280--

* p < .05. two-tailed, df = 139.**P < .01, two-tailed, df = 139.


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1 5 5 ICEK AJZEN

DISCUSSION. In view of the present findings, the follow-mg picture of the attribution process in per-son perception seems to emerge. Attributionof a disposition to an actor appears to be in-fluenced by at least two factors: the priorprobability that the actor has the dispositionin question and the prior probability of hisbehavior. Prior behavioral probabilities maybe a function of the subject's general knowl-edge about peoples' behavior in the givensituation and of the perceived consequencesof the available alternatives. Prior trait prob-abilities may be based either on actual ac-quaintance with the actor or on a generalfamiliarity with his background (occupation,sex, age, etc.). Inference magnitude may bedefined as the degree to which posterior traitprobabilities deviate from their prior counter-parts as the result of intervening behavior bythe actor. The actor's behavior may be either(a ) observed, (b ) inferred from some of itseffects, or (c ) communicated to the subjectby some source of information.The importance of defining inference mag-

nitude in terms of revision in attributed prob-abilities of dispositions lies in the fact thatsuch a definition takes prior trait probabilitiesinto account. Clearly, the final probabilitythat the actor possesses a given trait (afterobserving his behavior) will depend, amongother things, on the level of initial probabil-ity. As suggested by Bayes's theorem, the in-ference process must be viewed as a revisionof probabilities in the light of new informa-tion. When prior trait probabilities are al-ready high, only relatively small increases canbe expected. Nor can decreases in trait proba-bilities be very great when the initial levelsare already low.Some evidence for these notions is obtained

by looking at the means for subjective priortrait probabilities in the control groups,pooled over the four situations. The priorprobabilities of traits corresponding to thepositive alternatives were .626 under high de-However, Bayes's theorem estimates of attributionsbased on probability measures obtained in the con-trol groups did not support this explanation. Theseestimates differed from the observed attributions ap-proximately as much as did the estimates for theexperimental groups.

cision freedom and .705 under low decisionfreedom. For traits corresponding to the nega-tive alternatives, prior trait probabilities were.180 and .182 under high and low decisionfreedom, respectively.P Thus, changes fromprior to posterior trait probabilities (i.e., in-ference magnitude) may depend at least inpart on the levels of prior trait probabilities.The role of prior trait probabilities in the

attribution process becomes apparent whenone compares the relations of behavior prob-abilities to inference magnitude with their~elations to posterior trait probabilities, thatIS, by comparing effects of prior behaviorprobabilities on revisions in perceived traitprobabilities (inference magnitude) with theireffects on the final, absolute level of posteriortrait probabilities. The correlations with in-ference magnitude were reported in Table 6,where it was shown that prior behavior prob-abilities provided high and consistent predic-tions of trait attributions. When the depend-ent variables were posterior trait probabilities,the obtained correlations were much lower. 'rangmg from -.470 to .390. The signs ofthese correlations were not always in the ex-pected directions, and the coefficients wereoften nonsignificant.Measurement of inference magnitude in

terms of prior-to-posterior revisions in attrib-uted trait probabilities permitted tests ofhypotheses about the effects of the utility ofa choice or rejection and of perceived decisionfreedom. Inference magnitude decreased withbehavioral utility for a choice-related infer-ence and increased with utility for a rejec-tion-related inference. Also consistent withexpectations was the interaction effect be-tween utility and decision freedom' the effectsof behavioral utility were greater' under lowthan under high decision freedom.The influence of decision freedom on in-

ference magnitude is of particular interest.Contrary to common theorizing, behavior un-der greater decision freedom did not always13 t tests of significance performed within each

hypothetical situation yielded highly significant re-sults for the comparisons of trait probabilities corre-sponding to high and low behavioral utilities. Dif-ferences in trait probabilities between high and lowdecision freedom were nonsignificant except forSP(T+) in Situation 4, where t=2.523, dj =52,p< .05.


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ATTRIBUTION OF DISPOSITIONS TO AN ACTOR 156

increase inference magnitude. Specifically, in-ference magnitude was greater under highthan under low decision freedom when thechosen alternative was positive. There wasno significant difference between high andlow decision freedom when the performed be-havior was negative.It should be recalled, however, that differ-

ent results might have been obtained if adifferent manipulation of perceived decisionfreedom had been utilized. Itshould furtherbe noted that in contrast to frequent concep-tualizations, decision freedom was definedhere not as absence of external pressure, butrather in terms of the relative attractivenessof the available alternatives. External pres-sure may reduce decision freedom by increas-ing the likelihood of one alternative at theexpense of all others. However, it may alsoincrease decision freedom, as defined in thepresent study, by producing more equallyprobable alternatives.Finally, support was presented for the pos-

sibility of using Bayes's theorem for theprediction of trait inferences. High and sig-nificant correlations were obtained in thesepredictions. In comparison with the relativelycomplex reasoning behind the predictionsbased on decision freedom, behavioral utility,and prior behavior probabilities, Bayes's the-orem provided a simpler and more directapproach to the prediction of trait inferences.Another advantage of the Bayesian ap-

proach is that it can be directly applied tomultiple inferences, that is, to inferencesabout more than one trait, and that it takesprior knowledge about the actor (i.e., priortrait probabilities) into explicit consideration.These findings in support of all major hy-

potheses lend credence not only to the the-orizing behind the predictions but also to themeasurement procedures of the present ex-periment. While it is realized that the presentmeasures of probabilities are relatively crude,they have been shown to be accurate enoughfor purposes of testing hypotheses concerningthe attribution process.

A final word needs to be said about theuse of hypothetical situations. While thistechnique may at times be inappropriate (d.Freedman, 1969), it appears justifiable in thepresent circumstances. It stands to reasonthat inferences about another person's dispo-sitions are frequently made on the basis ofhearsay information about the actor's be-havior, about his available alternatives, andabout the situation in which the behavioroccurred. The techniques of the present studymay thus be quite representative of manyreal-life situations.

REFERENCESAJZEN, I., & FISHBEIN, M. The prediction of be-havior from attitudinal and normative variables.Journal of Experimental Social Psychology, 1970,6, 466-487.DECHARMS,R. Personal causation. New York: Aca-demic Press, 1968.EDWARDS,W. The theory of decision making. Psycho-logical soueu, 1954, 51, 380-418.EDWARDS,W. Behavioral decision theory. Annual Re-view of Psychology, 1961, 12, 473-498.EDWARDS,W. Emerging technologies for decisionmaking. In, New directions in psychology. Vol. 2.New York: Holt, 1965.

FREEDMAN,. L. Role playing: Psychology by con-sensus. Journal of Personality and Social Psychol-ogy, 1969, 13, 107-114.JONES,E. E., & DAVIS,K. E. From acts to disposi-tions. In L. Berkowitz (Ed.), Advances in experi-mental social psychology. Vol. 2. New York: Aca-demic Press, 1965.JONES, E. E., DAVIS,K. E., & GERGEN,K. J. Roleplaying variations and their informational valuefor person perception. Journal of Abnormal andSocial Psychology, 1961, 63, 302-310.JONES,E. E., & GERARD,H. B. Foundations of socialpsychology. New York: Wiley, 1967.JONES, E. E., & HARRIS,V. A. The attribution ofattitudes. Journal of Experimental Social Psychol-ogy, 1967, 3, 1-24.MORGAN,B. W. An introduction to Bayesian sta-tistical decision processes. Englewood Cliffs, N. J.:Prentice-Hall, 1968.REZA,F. M. An introduction to information theory.New York: McGraw-Hill, 1961.STEINER,I. D. Perceived freedom. In L. Berkowitz(Ed.), Advances in experimental social psychology.Vol. 5. New York: Academic Press, 1970.STEINER,I. D., & FIELD,W. L. Role assignment andinterpersonal influence. Journal of Abnormal andSocial Psychology, 1960, 61, 239-246.

(Received March 13, 1970)

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Ajzen - Attribution of Disposition to an Actor