on the origin of illusory correlations

European Journal of Social Psychology, Vol. 14, 191 -201 (1 984)

On the origin of illusory correlations

KLAUS FIEDLER*, ULI HEMMETER and CAROLIN HOFMANN Fachbereich Psychologie der Universitat Giessen I

Otto-Behaghel-Strasse 70, 0-6300 Giessen. W. Germany

Abstract

Empirical attempts to explain the genesis of illusory correlations have been largely confined to the demonstration of biased recall processes, although it has been acknowledged that perception and encoding processes may also contribute to the illusion. In the present research, illusory correlations between person types (a student versus a clerk) and educational attitudes (liberal versus authoritarian statements) are demonstrated under conditions where selective recall processes are highly unlikely. The cognitive bias that gives rise to the illusion is shown to already be effective when the stimulus in formation is perceived. Interestingly, there are marked interindividual differences between experimental participants. The results are discussed in the context of the literature on illusory correlations.

INTRODUCTION

The term ‘illusory correlation’ refers to the erroneous report of a correlation within a series of observations where in fact none exists. Two factors have been investi- gated which give rise to such an illusion: semantic associations (Chapman and Chapman, 1967,1969; Golding and Rorer, 1972; Shweder, 1975,1977; Starr and Katkin, 1969) and distinctiveness (Chapman, 1967; Hamilton and Gifford, 1976; McArthur and Friedman, 1980). The former can best be demonstrated by Chap man and Chapman’s (1967) original experiments. They presented their subjects with a series of Draw-a-Person Test pictures along with an indication of the drawer’s diagnostic category. Illusory correlations were found to be due to semantic associations between certain diagnoses and certain pictorial features (e.g. patients who worry about their intelligence would emphasize the head in their drawings). The co-occurrence of these semantically tied diagnoses and features was systemati- cally overestimated. The second factor, distinctiveness, can be exemplified by Hamilton and Gifford’s (1976) work. Behaviour descriptions pertaining to mem- bers of two different social groups served as stimuli. Although the proportion of

*Addressee for reprints.

0046-2772/84/020191-11$01.10 0 1984 by John Wiley & Sons, Ltd.

Received 13 March 1983 Revised 8 August 1983

192 K . Fiedler, U. Hemmeter and C. Hofmann

desirable and undesirable behaviours was always the same for both groups, the absolute frequencies of group-behaviour combinations was varied. Illusory correlations between group membership and behaviour valence reflected the overestima- tion of the most distinctive combination, that is, the less frequent behaviour of the minority group. Parenthetically, Hamilton and Gifford illustrated how illusory correlations can serve as a useful paradigm for studying stereotypes and social minorities.

Both kinds of illusory correlations, although inherently different, have been confounded not only by their common name but have also, and more importantly, been explained on the same theoretical grounds. There seems to be wide agreement that illusory correlation judgments originate in selective recall processes. Accord- ing to Tversky and Kahneman’s (1973) availability hypothesis, the frequency of semantically related or highly distinctive stimulus combinations is overestimated because these stimuli come to mind more easily. Those pieces of information which support the illusion are assumed to be more recallable at the time when the correlation judgments are made.

On the theoretical level, of course, the possibility has been mentioned that attentional, perceptual, and encoding factors might also contribute to the illusion (cf. McArthur, 1980; Rothbart, 198 1). On the operational level, however, experimental attempts to empirically demonstrate the origins of illusory correlations have. been typically confined to the inclusion of some recall measure (Tversky and Kahneman, 1973; Hamilton and Gifford, 1976; Jones et a[., 1977). One is left with the impression that even if attentional, perceptual, or encoding influences are operating, these influences will be mediated by selective recall.

The present research starts from the premise that explaining memory-based judgments by selective recall is theoretically unsatisfactory anyhow, for, as Mc- Arthur (1980) correctly noted, biased recall may be an epiphenomenon rather than a cause of biased judgments’. Hence, we attempted to demonstrate that the cognitive forces which give rise to illusory correlations are also effective when (a) recall- independent measures are considered and (b) when availability differences are eliminated. To clarify this, consider the task situation of the experiment to be reported. The stimulus material consisted of a series of attitude statements produced by two persons, a student and a clerk. Each statement expressed either a liberal or an authoritarian attitude towards educational practices. Hence, the correlation between statement direction (liberal versus authoritarian) and person types (student versus clerk) was to be observed. It was expected that the proportion of authoritarian statements would be overestimated for the clerk and underestimated for the student, in accordance with stereotypical semantic relations. This standard arrangement for producing an illusory correlation effect was elaborated, however, in several respects in order to test the viability of the selective recall explanation.

First, we attempted to demonstrate that the same stereotypical influence that leads to an illusory correlation would be already present during the perception of the stimulus information, that is, prior to any recall operations. Thus, when the stimuli were presented, participants were asked to categorize each attitude statement on a rating scale ranging from ‘extremely authoritarian’ to ‘extremely liberal’. It was expected that the same statements would tend to be perceived in a more

‘It should be noted that the empirical evidence that seems to support the availability hypothesis is ‘corretational in nature.

Illusory correlations 193

liberal light when produced by the student than when produced by the clerk. If so, one factor would be identified that may contribute to the illusion although it is independent of any recall operations. The conclusion would be, at least, that selective recall is not necessary but, rather, that the illusion occurs probably at different stages of the cognitive process where some uncertainty is reduced.

Second, apart from the percentage judgments of the proportion of authoritarian statements produced by the student and the clerk, a cued-recall test was included as another dependent measure. That is, at the end of the experimental session, all the attitude statements were presented once more and the participants had to repro- duce the person label with which the statements had been associated. We expected that the illusion would also show up on this measure in that recall errors would tend to confirm the stereotype (i.e. liberal items falsely attributed to the student and authoritarian items falsely attributed to the clerk). However, the crucial point with this recall test is that it makes ail information completely available, thus eliminating any differences in availability. Because the whole wording of the attitude statements as well as the two response alternatives, ‘student’ and ‘clerk’, appear on the test format, differential recall errors cannot reflect the fact that some information fails to come to the participant’s mind. Such a finding, therefore, would be inconsistent with the usual availability account. One might argue in return that it is the association of a liberal (authoritarian) statement with a student (clerk) which is more available, rather than the informational constituents. however, this is the point where the availability concept becomes circular, for the association between liberal (authoritarian) statements and the student (clerk) is to be explained eventually. In any case, maintaining an availability explanation in spite of perfect availability of all pieces of information would be difficult to justify.

Third, the opportunity to learn the information was also manipulated. The stimulus series was presented either once or three times to two different groups of participants. A selective recall explanation might suggest-even though it does not necessarily imply-that the illusion reflects imperfect learning and should vanish or decrease if memory performance is maximized. Hence, an opportunity to study the series three times might reduce the predicted illusory correlations.

Finally, the absolute frequency of the four attitude-person combinations was manipulated. While the relative proportion of liberal and authoritarian statements was always the same for both persons (i.e. always zero correlations), the absolute frequencies were equal for only one half of the participants. The other half saw fewer authoritarian than liberal statements and fewer statements of the clerk than of the student, thus making authoritarian statements by the clerk the rarest and most distinctive combination. The greater distinctiveness of this information should further enhance the selective recall bias and result in an increased illusory correlation effect, according to Hamilton and Gifford (1976); see also Jones et al. (1977) and McArthur and Friedman (1980).

METHOD

Participants

Forty-eight students of psychology (23 male and 25 female) took part in the experiment in partial fulfillment of their study requirements. Male and female

194 K. Fiedler, U. Hemmeter and C. Hofmann

students were approximately equally distributed across the four independent groups of twelve persons. All participants were naive with regard to the illusory correlation phenomenon.

Design

As already outlined, the number of presentations of the stimulus series (one versus three) and the distribution of attitude statements and person labels (equal versus skewed) were the two between-subjects factors of the design.

Stimuli

Based on preliminary testing, a set of 42 statements expressing different degrees of liberal and authoritarian attitudes towards educational practices were selected. These had been categorized as extremely liberal (12), moderately liberal (12), moderately authoritarian (9), or extremely authoritarian (9). An example of an extremely liberal item is: ‘Children should not be prohibited to act out their aggres- sions’. An example of a moderately authoritarian item is: ‘I’m always informed about my children’s performance at school’2. All individual participants received a different stimulus series in a different random order; each series was always com- posed of 36 items. The proportion of liberal and authoritarian statements for those items associated with one person type was always the same as the proportion of those items associated with the other person type, yielding zero correlations in each case. Across all participants, statement content and person type were made orthogonal that is, each statement appeared about equally often with the student and the clerk. In the equal distribution condition, a series consisted of 9 liberal statements (5 extreme/4 moderate) paired with the clerk, 9 liberal statements (4/5) paired with the student, 9 authoritarian statements (4/5) paired with the clerk, and 9 authoritarian statements (5/4) paired with the student? Hence, three of the extremely liberal and three of the moderately liberal items had to be discarded; overall, each liberal item was discarded about equally often. In the skewed distribution condition, a series consisted of 8 liberal statements (4 extreme/4 moderate) paired with the clerk, 16 liberal statements (8/8) paired with the student, 4 authoritarian statements (2/2) paired with the clerk, and 8 authoritarian statements (4/4) paired with the student. Here all of the 2 x 12 liberal items were used in constructing the stimulus series, and three of the extremely and moderately authoritarian items had to be eliminated; all items were eliminated equally often.

Procedure

An experimental session lasted between 30 and 60 minutes depending on the number of repetitions of the stimulus series. All participants appeared individually. After being told by the experimenters (one male and one female) that the experiment would be concerned with statements about educational affairs, they read the

*All literal descriptions concerning the stimulus material and the dependent measures are translated from German. 3Due to the odd number of 9 statements of each type, the ratio of moderate to extreme items was 4/5 or 5/4. The ratios were chosen such that any bias would act against the stereotype.


written instructions which provided a justification for the fact that the statements were paired with a person label. It was argued in the instructions that while isolated attitude statements were used in many experiments, this would be quite an unrealis- tic situation. Therefore, in the present experiment, attitude statements were presented along with an indication of the person who produced the statement, either a student or a clerk. Hence, the single statements were interrelated by their association either to the same person or to different persons. (In constructing the stimulus series an attempt was made to avoid obvious contradictions between the statements expressed by the same person.) Participants were told that their task would be to rate the attitude positions advocated by various statements; they were not instructed to attend to the correlation inherent in the stimulus series.

A deck of 36 cards had been prepared each containing a person label, colon, and an attitude statement below. Participants were given one card at a time, gave their ratings on a separate answer sheet without time pressure, and received the next card until the series of 36 stimuli was finished. Participants in the three- presentations condition saw the same series a second time without the rating task and a third time again with the rating instruction. Immediately afterwards, the dependent measures were applied.

Dependent measures

Two criteria1 questions included in an answer sheet pertained to the measurement of illusory correlations: ‘What percentage of the clerk’s statements did you consider to be authoritarian?’ and ‘What percentage of the student’s statements did you consider to be authoritarian?’ Next the participants were asked to give their impression of the student and the clerk on a semantic differential. The differential consisted of ten five-point scales whose endpoints were labelled by the following adjective pairs: hardlsoft, persistentfcompliant, likeable/unlikeable, calm/hec- tic, democratjc/dictatorial, credulous/sceptical, mature/immature, wisefnaive, unimaginative/creative, open-mindedlpetty-bourgeois. While half of the adjective scales, appearing in italics here, are directly related to the liberal versus authoritarian distinction, the other half of the scales bear no denotative connection with this dimension but are only characterized by positive versus negative connota- tions. Finally, the complete list of 42 items, in a constant random order, was used for the cued-recall test4.

RESULTS AND DISCUSSION

An illusory correlation score was computed for each participant as the estimated percentage of authoritarian statements by the clerk minus the estimated percentage of authoritarian statements by the student. As Table 1 reveals, the positive means of this score support the expected illusory correlation. However, there is no effect of the two independent variables. Neither the number of repetitions (1 or 3) nor the distribution of event frequencies (equal or skewed) affected the degree of the

%ose six items which had been eliminated from the individual stimulus series served as distractors in the recall test. Thus, there were three response alternatives: ‘clerk’, ‘student’, and ‘not included in the list’.

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Table 1. Mean scores by experimental conditions

K . Fiedler, U. Hemmeter and C. Hofmann

Score

Experimental condition

Stimulus series Stimulus series presented once presented 3 times

Distribution Distribution skewed equal skewed equal Total

~~ ~~~

Illusory correlation score (Judged 6.8 13.3 6.9 5.4 8.1 per cent authoritarian statements clerk minus student)

(student minus clerk)

confirming minus disconfirming errors)

rating of student’s minus clerk’s statements, averaged per judge)

given by student versus clerk, averaged per statement)

Semantic differential liberalism score 1.50 3.33 2 .oo 1.75 2.15

Constructive error score (Proportion of 0.09 0.31 0.20 0.34 0.22

Attitude rating score (Mean liberalism -0.03 +0.03 +0.18 +0.05 +0.06

Differential rating of same statements (if -0.06 +0.22 +0.24 +0.19 +0.15

Positive values always point in the expected direction.

illusion, F( 1,44) < 1, n.s. and F( 1,44) < 1, n.s., respectively. Thus, increasing the amount of learning, from one to three presentations, does not reduce the correlation bias’. This is consistent with Chapman and Chapman’s (1967) finding that reduction of time pressure has no influence. Apparently, deficient memory is no pre-condition for illusory correlations to occur. On the other hand, the failure of the frequency manipulation is clearly inconsistent with Hamilton and Gifford’s (1 976) finding, although their distinctiveness manipulation was exactly replicated in the present experiment. We shall return to this inconsistency in our concluding remarks.

Since the two independent variables also had no effect on any of the other dependent variables, the data of all four groups were collapsed for further analyses. Overall, the illusory correlation scores were significantly greater than zero, z = 2 . 3 7 , ~ < 0.02, according to a Wilcoxon signed-ranks test. On the average, the percentage estimate of authoritarian statements for the clerk was 8.08 per cent higher than for the student. In any case, the phenomenon under consideration is evident in the context of the present experiment. The stereotypical image of a student and a clerk was able to produce illusory correlations.

That stereotypical knowledge was in fact the source of the illusion becomes plausible from the semantic differential data. A semantic differential total score was computed after inverting adjective scales so that higher scores would represent

’As a check on the amount-of-learning manipulation, we might consider the number of errors on the recall test, excluding those constructive errors which are confounded with the biasing influence of the stereotype. Thus, we took the number of intrusion errors, that is, of erroneous attributions of distractor items to the student or the clerk, as an index of the amount of learning. The effect of the manipulation on this index amounts to z = 3.43, p -= 0.001, according to an U-test.


higher liberalism (5 scales) and higher likeability (5 scales). The difference of this total score for the student minus that for the clerk was reliably positive, z = 2.07, p < 0.05, reflecting a more liberal/likeable impression of the student. This tendency is highly correlated, across participants, with the illusory correlation scores (r = 0.84). Of more importance, however, is the fact that the differential impressions of the student and the clerk are exclusively due to those adjective scales which are denotatively relevant to the liberal versus authoritarian dimension, while there is no difference in genera1 likeability. The relevant interaction in a separate ANOVA with stimulus persons and scale types as repeated measures amounts to F(1,47) = 10.65, p < 0.01. Inspection of the means shows that the student (3 = 15.5) appeared more liberal than the clerk (2 = 13.3)-which is a reliable difference, z = 2.45, p < 0.05-while there was no difference with regard to general likeability (Z = 15.6 versus% = 15.4). Hence, the differential impression effect is confined to semantically specific and stereotypically relevant adjective scales and cannot be interpreted as a simple halo effect or likeability effect due to the fact that the participants themselves were students and preferred a liberal attitude. Conse- quently, we decided to use the liberalism score (based on 5 scales) instead of the total score (based on 10 scales) for further analyses (see Tables 1, 2, and 3).

To analyse the recall test data, a constructive error score was defined as the number of stereotype-confirming errors (liberal statements falsely attributed to the student and authoritarian statements falsely attributed to the clerk) minus the number of stereotype-disconfirming errors (liberal statements falsely attributed to the clerk and authoritarian statements falsely attributed to the student). Although the cued-recall test was designed so as to make all information completely available, the illusion is nevertheless present. Recall errors tend to confirm the stereotype; that is, the constructive error scores tend to be positive, z = 2.40, p < 0.02. This effect which occurs when the attitude statements and the two person labels are presented entirely, simultaneously, and enduringly, can hardly be explained by assuming that some information is less available. Recall errors are substantially correlated, across participants, with the illusory correlation score (r = 0.60) and the semantic differential liberalism score (r = 0.61), as shown in Table 2.

Now, if selective recall is not necessarily involved, the bias may be already visible when the stimulus series is perceived and encoded with respect to liberalism versus authoritarianism. Based on the participants’ ratings of the attitude statements during stimulus presentation, an attitude rating score was defined as a judge’s mean rating of the student’s statements minus his/her mean rating of the clerk’s statements. Positive scores would indicate that the student’s statements are interpreted in a more liberal light. Although the mean attitude rating score turns out to be slightly positive (it = +0.06), indeed, this tendency does not reach statistical significance, z = 0.86. This is no surprise, however, since the attitude rating score is confounded with much error variance that is due to the balancing procedure. (Dif- ferent statements had been paired with the student and the clerk for each participant.) Hence, a more powerful test was performed that eliminates part of the error variance. The mean rating per attimde statement was calculated separately for those participants who saw the statement paired with the student and for those who saw it paired with the clerk. This time the difference was reliable; the same statements were rated to be relatively more liberal when paired with the student and relatively

198

Table 2. Intercorrelations of several scores across judges


1 2 3 4

1. Illusory correlation score 1 0.81 0.60 0.23 2. Semantic differential liberalism score 1 0.61 0.24 3. Constructive error score* 1 0.10 4. Encoding score? 1

‘Correlations involving this score are based on 47 judges only, due to the refusal of one judge to perform the recall test. tNote the difficulties with this score discussed in the text.

more authoritarian when paired with the clerk, z = 2.07, p < 0.05. This last finding-which reminds us of the well-known accentuation effects ( c j Tajfel, 1959; Eiser and Stroebe, 1972)-suggests that the origin of the illusion is already apparent at the early stage of information encoding.

Intercorrelations between the different manifestations of the illusion, computed across participants, are summarized in Table 2. Obviously, these correlations are all positive and most of them are statistically reliable, indicating that the same individual participants who show the illusion on one measure also tend to show it on the other measures. Only correlations which involve the encoding score are markedly reduced. This could be expected because the encoding effect was only visible in a more sensitive per-statement analysis (see above), while the per-subject scores (i.e. the extent to which each participant rated the student’s statements more liberal than the clerk’s statements) suffered from too much extranous variance: The student and the clerk were associated with different subsets of statements for different participants so that the per-subject scores are not based on differential ratings of the same statements as a function of the two person labels but on the ratings of different sets of statements. To partly overcome this difficulty, we attempted to improve the scores in the following way: We compared each participant with each other participant for the degree of the encoding bias, considering only those statement-person pairings that were common to a couple of participants. The average of all comparisons involving the same individual yields a measure of the relative degree of his/her encoding bias. Unfortunately, however, the reliability of this encoding score, which was used in computing the correlations in Table 2, is still reduced because many of the underIying comparisons are based on too few cases. Therefore, the correlations reported in the table presumably underestimate the relationship between the encoding bias and the other measures of illusory correlations. Nevertheless, even these lowered values (r = 0.24 and r = 0 . 2 3 , ~ - 0.10) approximate the conventional level of statistical significance.

In principle, the correlational analysis could have been extended to test structural assumptions about the possible causal paths between the variables of Table 2. In this way, one might try to identify the specific cognitive stages at which significant influences arise. It should be acknowledged, however, that conclusions from such an analysis would have been ill-founded since the number of subjects is too small relative to the homogenous pattern of positive correlations and since the only deviating correlations (involving the encoding score) may be underestimated. Hence, we contend ourselves with demonstrating that an effect exists at all cogni-


tive stages. Whether the effect is stronger at one stage or another remains to be shown by future research.

CONCLUDING REMARKS

To summarize, the present experiment demonstrates that the stereotypical influence which gives rise to an illusory correlation effect is effective at all stages of information processing where some uncertainty has to be reduced: When the stimulus series is perceived and encoded, when the information is reconstructed on the cued-recall test, when statistical properties of the series are estimated, and when the impressions of the target persons are expressed within an adjective space. There is no reason to doubt that all these influences, which are substantially inter- correlated, reflect the same psychological forces. We have to conclude, therefore, that illusory correlations are probably not the product of a single stage of cognitive functioning, and that selective recall is not a necessary condition for the phenomenon to occur. Rather, the illusion seems to reflect the filling of informational gaps with stereotypical knowledge at all stages, from initial encoding to the remote semantic differential measure. Further research will have to find out whether this filling of informational gaps must be understood as a simple guessing effect or whether it truly reflects the generative activity of constructive memory and thought (cf. Upmeyer, 1981; Bransford, Barclay and Franks, 1972).

It is worth noting that the statistical analysis of group data conceals marked differences between individual participants. In fact, the group effect is essentially due to the overly biased responses of a dozen of participants, as shown in Table 3. This suggests that illusory correlations, even though universally observed, may not be enforced by the inherent laws of cognitive processing but may be the product of arbitrarily chosen or learned strategies. In any case, analysing illusory correlation experiments for inter-individual differences would be of much interest.

A final remark on the failure to replicate Hamilton and Gifford’s often cited finding is in order. That is, illusory correlations were not more pronounced in the skewed distribution condition where the most distinctive (Le. rarest) combination (viz. authoritarian statements by the clerk) ought to have been over-represented. One reason may lie in the use of meaningful, stereotypically relevant person labels instead of the meaningless group labels used by Hamilton and Gifford. How- ever, as McArthur and Friedman (1980) have shown, meaningfulness does not

Table 3. Interindividual variations in two measures of illusory correlation ~ ~~

Distribution of illusory correlation scores

Category boundaries -30 -15 -1 +1 +15 +30 Frequencies 2 4 7 16 1 6 12

Distribution of semantic differential liberalism scores

Category boundaries -6.5 -3.5 -0.05 +0.05 +3.5 +6.5 Frequencies 4 4 2 10 9 7 12

~~ ~~~

The boundaries of the middle category are made extremely narrow to include only those judges who obviously wanted to express that there was no correlation whatsoever.

200

interfere with Hamilton and Gifford’s effect when the distinctiveness manipulation and the influence of the stereotype act in the same direction, which is the case here. Alternatively, one might argue that Hamilton and Gifford‘s stimulus material consisted of diverse descriptions of manifest behaviours whereas the present material consists of a thematically homogenous set of attitude statements. A third difference is due to the fact that Hamilton and Gifford’s behaviour descriptions pertained to different individuals from one of two groups while the present information pertains to only two individuals or characters. Actually, there is some evidence (Rothbart et al., 1978) for the impact of this factor on the organization of memory6.

Whatever the validity of these arguments may be, however, there is another possibility which entails a more fundamental criticism suggesting that Hamilton and Gifford’s finding may reflect a somewhat artificial mechanism. That is, the overes- timation or rare events may be due to a simple regression effect. If information transmission is imperfect, any information loss will result in a regression of frequency estimates toward some central value. This may appear as if the smallest frequency were over-represented, psychologically. That Hamilton and Gifford found a similar effect in a cued-recall test could be explained by assuming that cued-recall responses often follow a probability matching or frequency matching strategy. Thus, whenever the participants have to guess on the recall test, they might try to match their responses with their general memory for frequency. The present experiment may have not been subject to such a regression effect because participants were not asked for the absolute frequency of the four combinations but for the relative proport ions of authoritarian statements produced by the two persons. To our knowledge, this possibility has not been seriously considered and should be tested in an adequately designed experiment.


REFERENCES

Bransford, J. D., Barclay, J. R. and Franks, J. J. (1972). ‘Sentence memory: A constructive versus interpretive approach’, Cognitive Psychology, 3: 193-209.

Chapman, L. J. (1967). ‘Illusory correlation in observational report’, Journal of Verbal Learning and Verbal Behavior, 6: 151-155.

Chapman, L. J. and Chapman, J. P. (1967). ‘Genesis of popular but erroneous psychodiagnostic observations’, Journal of Abnormal Psychology, 72: 193-204.

Chapman, L. J. and Chapman, J. P. (1969). ‘Illusory correlations as an obstacle to the use of valid psychodiagnostic signs’, Journal of Abnormal Psychology, 74: 271-280.

Eiser, J. R. and Stroebe, W. (1972). Categorization and Social Judgment, Academic Press, New York.

Golding, S. L. and Rorer, L. G. (1972). ‘Illusory correlation and subjective judgment’, Journal of Abnormul Psychology, 80: 249-260.

Hamilton, D. L. and Gifford, R. K. (1976). ‘Illusory correlation in interpersonal perception: A cognitive basis of stereotypical judgment’, Journal of Experimental Social Psychology,

Jones, R. A., Scott, J., Solernou, J., Noble, A., Fiala, J. and Miller, K. (1977). ‘Availability

McArthur, L. Z. (1980). ‘Illusory causation and illusory correlation: Two epistemological

12: 392-407.

and formation of stereotypes’, Perceptual and Motor Skills, 44: 631-638.

accounts’, Personality and Social psychology Bulletin, 6: 507-5 19.

6We have to thank an unknown reviewer for his/her suggestions about some of these alternative explanations.


McArthur, L. Z. and Friedman, S. A. (1980). ‘Illusory correlation in impression formation: Variations in the shared distinctiveness effect as a function of the distinctive person’s age, race, and sex’, Journal of Personality and Social Psychology, 39: 615-624.

Rothbart, M. (1981). ‘Memory processes and social beliefs’. In: Hamilton, D. L. (Ed) Cognitive Processes in Stereotyping and Intergroup Behavior, Erlbaum, Hillsdale, N.J.

Rothbart, M., Fulero, S., Jensen, C., Howard, J. and Birrell, P. (1978). ‘From individual to group impressions: Availability heuristics in stereotype formation’, Journal of Experimen- tal Social Psychology, 14: 237-255.

Shweder, R. A. (1975). ‘How relevant is an individual difference theory of personality’, Journal of Personality, 43: 455-484.

Shweder, R. A. (1977). ‘Likeness and likelihood in everyday thought: Magical thinking in judgment about personality’. Current Anthropology, 18, 637-648.

Starr, B. J. and Katkin, E. S. (1969). ‘The clinician as an aberrant actuary: Illusory correlation and the Incomplete Sentence Blank’, Journal of Abnormal Psychology, 74: 670-675.

Tajfel, H. (1959). ‘Quantitative judgement in social perception’, British Journal of Psychol- ogy, 25: 79-97.

Tversky, A. and Kahneman, D. (1973). ‘Availability: A heuristic for judging frequency and probability’, Cognitive Psychology, 5: 203-232.

Upmeyer, A. (1981). ‘Perceptual and judgmental processes in social contexts’. In: Ber- kowitz, L. (Ed) Advances in Experimental Social Psychology, Academic Press, New York.

Les recherches visant B expliquer I’origine du phtnomene ‘d‘illusion de corrtlation’ se sont en gCnCral efforcCes de mettre en Cvidence un biais au niveau des processus responsables du rappel. On sait pourtant que les processus perceptifs et d’encodage peuvent Cgalement con- tribuer a I’illusion.

Cette recherche pr6sente un phCnomkne d’illusion de corrtlation entre des types d’indi- vidus (Ctudiants ou fonctionnaires) et des attitudes Cducatives (progressisme vs auto- ritarisme) dans des situations OG des processus de rappel sClectif sont hautement improb- ables. On montre que le biais cognitif responsable du phCnomene est dCja prtsent au moment de la perception du stimulus. D’importantes differences interindividuelles sont observkes. Ces rCsultats sont discutes i la lumibre de la IittCrature sur les illusions de corrklation.

ZUSAMMENFASSUNG

Empirische Versuche, die Entstehung von illusionaren Korrelation zu erklaren, waren bis- lang groBtenteils auf die Demonstration von verzerrten Erinnerungsprozessen beschrankt, wenngleich zur Kenntnis genommen wurde, dal3 Wahrnehmungs- und Encodierprozesse ebenfalls zu der Illusion beitragen konnen. In der vorliegenden Untersuchung werden illusionare Korrelationen zwischen Persontypen (Student vs. Beamter) und erziehungs- bezogenen Einstellungen (liberale vs. autoritare AuBerungen) demonstriert, und zwar unter Bedingungen, die selektive Erinnerungsprozesse sehr unwahrscheinlich machen. Hingegen wird gezeigt, daB die kognitive Tendenz, die zu der Illusion fuhrt, schon wahrend der Wahr- nehmung der Information wirksam sein muB. Bemerkenswert sind die deutlichen interin- dividuellen Unterschiede zwischen den Versuchsteilnehmern. Die Ergebnisse werden im Kontext der Literatur uber illusionare Korrelationen diskutiert.

on the origin of illusory correlations

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