Reduction of hindsight bias by restoration of foresight perspective: Effectiveness of foresight-encoding and hindsight-retrieval strategies

ORGANIZATIONAL

BEHAVIOR

AND

HUMAN

DECISION

PROCESSES

40, 50-68 (1987)

Reduction of Hindsight Bias by Restoration of Foresight Perspective: Effectiveness of Foresight-Encoding and Hindsight-Retrieval Strategies MARTIN E DAVIES University

of London,

Goldsmiths’

College

Reduction of hindsight bias in judgments of outcomes of psychology experiments was examined in three studies designed to manipulate the availability of foresight cognitions in hindsight. In Experiment 1, subjects provided with a written record of their cognitions, thoughts, and reasons generated in foresight showed less hindsight bias than subjects who were not provided with such a record of their foresight cognitions. Experiment 2 investigated the role of foresight encoding elaboration by comparing hindsight judgments of subjects who had produced a written record of their foresight cognitions with those of subjects who had not produced a written record of their foresight cognitions. Hindsight bias was not significantly reduced by this manipulation of foresight encoding-elaboration. Experiment 3 compared the review-of-foresight-cognitions manipulation of Experiment 1 with a hindsight generation-of-reasons manipulation previously found to be effective in reducing hindsight bias. The foresight-review manipulation was not found to be superior to the hindsightgeneration manipulation in reducing hindsight bias. The findings were discussed in terms of memory mechanisms involved in hindsight bias, foresight encoding strategies, and real-world constraints on the use of such strategies. 0 1987 Academic Press, Inc.

“Learning from the past-as opposed to merely learning about the past-is one of the main benefits of historical inquiry.” “Knowledge of the successes and failures of our ancestors serves to enlighten the present generation. ” “ Those who do not study the past are condemned to repeat it.” Contrary to the apparent wisdom of such maxims, recent psychological research suggests that the benefits of hindsight may be overrated. In hindsight, people exaggerate what could or should have been foreseen in foresight. They tend to overestimate how well they would have predicted events in foresight once they know how events turned out. Not only do hindsightful judges overestimate how much other people knew (or should have known) before the event, they even misremember their own foresight state of ignorance, recalling that they were wiser before the event than was actually the case. Such results have been demonstrated for judgments of historical events (Fischhoff, 1973, contemporary social and Requests for reprints should be sent to Martin E Davies, Department of Psychology, Goldsmiths’ College, Lewisham Way, New Cross, London SE14 6NW, England. 50 0749-5978/87$3.00 Copyright Q 1987 by Academic Press, Inc. All rights of reproduction in any form reserved.

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political events (Fischhoff & Beyth, 1975; Leary, 1981; Pennington. 1981), outcomes of scientific experiments (Slavic & Fischhoff, 1977), and factual knowledge (Fischhoff, 1977; Hasher, Attig, & Alba, 1981; Wood, 1978). On one hand, hindsight bias has certain social and public consequences. Those who did not foresee a particular turn of events or who were caught unprepared by the tide of events will tend to be blamed by hindsightful judges for their lack of perspicacity. To avoid being cast in the role of a buffoon, protagonists in public dramas use a number of devices for forestalling such criticism, including justifications, rationalizations, and reinterpretations of the events. On the other hand, hindsight bias has important intrapersonal consequences. If we overestimate how much we knew, then we have less need to reevaluate and improve our decision-making processes and evidence-gathering strategies. As stated by Fischhoff (1982a), “The very outcome knowledge which gives us the feeling that we understand what the past was all about may prevent us from learning anything about it” (p. 343). It is important, therefore, to understand the processes which lead to hindsight bias and to devise methods of reducing or preventing such bias. According to Fischhoff (1977), hindsight bias is a product of the human memory system. Upon receipt of outcome knowledge, we immediately assimilate this information with existing information about the event; old information is updated by new outcome information. In their general model of memory storage, Loftus and Loftus (1980) maintain that, under certain circumstances, updating of memories by new information results in the erasure of old information such that no trace remains in memory of the original event or foresight state of mind. Updating and erasing occurs when it is inefficient or inconsistent to retain two different memories for an event. Such circumstances are present in the hindsight paradigm. After learning the outcome of an event, it is not only inefficient to retain the foresight state of uncertainty along with the hindsight state of certainty, but is inconsistent-and possibly confusing-to maintain some belief in the outcome that did not occur. Moreover, the automatic nature of updating means that instructional manipulations designed to inhibit or prevent updating are bound to fail. Exhorting people to work harder or warning them of the operation of hindsight bias leaves the effect relatively untouched (Fischhoff, 1977). The update-and-erase view of memory therefore holds that the foresight state cannot be recovered in hindsight. When asked to judge the likelihood of event outcomes as if they had not known or been told the actual outcome, hindsight judges have no memory of their original foresightful state of knowledge or uncertainty. Lacking any direct means of accessing their foresight state, judges may adopt a number of heuristic strategies in generating likelihood

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estimates. Fischhoff (1975) suggests three possibilities derived from Tversky and Kahneman’s (1974) heuristics. The “representativeness” heuristic leads judges to estimate an outcome as more or less likely according to the extent to which its features match the salient features of the event. The integration or assimilation of the outcome into the event scenario as a result of memory updating produces a natural “fit” between the reported outcome and the event which produced it. Using the “anchoring and adjustment” heuristic, the hindsight judge assigns an initial probability of 1.00 to the reported outcome (the anchor) and then looks for reasons to adjust the initial value downward. This adjustment is typically insufficient (Slavic & Lichtenstein, 1971) and biased toward the initial value. Finally, using the “availability” heuristic, the hindsight judge estimates the probability of an outcome based on the ease with which the outcome can be generated or imagined from the event scenario. Given the updating of memory after receipt of outcome knowledge, it is easier to generate or imagine the reported outcome than the nonreported outcome. Recent studies, however, suggest some modification to the updateand-erase idea. For example, Wood (1978) found reduced hindsight bias for answers to general knowledge statements when subjects were instructed to try to remember their earlier foresight judgments. Hasher et al. (1981) eliminated hindsight bias in a similar general knowledge task by informing subjects that the answers they had been given were in fact wrong. If no trace of the original foresight state of knowledge is left in memory after receipt of outcome knowledge, then subjects would not be able in hindsight to recall their previous judgments. By discrediting the validity of the outcome feedback, Hasher et al. succeeded not only in almost entirely eliminating hindsight bias, but also in allowing judges to recover their original foresight perspective. Hasher e? al. suggest that, although original preoutcome knowledge may be difficult to access in hindsight, it is nevertheless “available” (Tulving & Pearlstone, 1966). Access to old information requires that retrieval follow a route it would not ordinarily follow. Of course, the discrediting manipulation used by Hasher ef al. to improve access to foresight information is somewhat unusual. In terms of mundane realism, suspending people’s beliefs about the actual outcome of a real-life event would not seem a very practical means of reducing hindsight bias, although at least one historian has tried to avoid hindsight bias in writing a biography of Robert E. Lee by attempting to ignore the outcome of events in the American Civil War (reported in Commager, 1965). One frequently cited precept in historical and investigative analysis is that the researcher seek out original records, preferably contemporaneous accounts of events, in order to arrive at a more veridical understanding of the relevant forces, actions, and circumstances. However,

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from the viewpoint of hindsight, it may not be the details of the events which are of most interest to the historical researcher, but the perceptions, feelings, and intentions of the participants. Records of such thoughts, reactions, and feelings prior to an event may provide a valuable guide for the hindsightful judge attempting to recapture foresightful states of mind. Experiment 1 examined the effects of presenting subjects in hindsight with a record of their thoughts about an event that had been written before receiving outcome knowledge. This foresight record could provide subjects with cues to their original state of knowledge-such as feelings of doubt or confidence about possible outcomes, arguments, and reasoning about how events could turn out. The process model adopted (but not tested) here was based on the assumption that hindsight judges can retrieve their old foresight state of knowledge given favorable circumstances. Armed with their foresight record, hindsight judges should be better equipped to recover their foresight perspective. Using an anchoring and adjustment strategy, judges in receipt of outcome knowledge might start with the reported outcome as the anchor (p = 1.OO)and adjust downward according to how much they can recall of their foresight state of uncertainty. Having their original foresight records available in hindsight would then allow judges to adjust their probability estimates further from the initial anchor, thus reducing hindsight bias. EXPERIMENT

1

Method Design and subjects. Subjects were required to record their thoughts while reading descriptions of four psychology experiments. After a 2week interval, subjects returned and judged the likelihood of possible experimental outcomes under one of four conditions derived from a 2 (outcome knowledge/no outcome knowledge) x 2 (review/no review of foresight cognitions) between-subjects design (with case study as a third. within-subjects factor). Subjects were 35 male and 46 female undergraduates aged between 18 and 29, recruited for a study on people’s perceptions of psychological research. No subject was familiar with the experimental case studies employed, nor with the research areas involved. Materials. The stimulus materials were brief case studies (approximately 350 words) describing four simple psychology experiments. The experiments were prototypes of actual psychology experiments constructed such that after pilot testing the alternative outcomes of each experiment were similar in plausibility. The descriptions covered methods used (subjects, procedure, setting), and for each experiment two possible

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outcomes were described: condition X < condition Y, condition X > condition Y. The experiments were (1) Forbidden Toy; children’s preferences for toys were investigated as a function of a prohibition on play (cf. Aronson & Carlsmith, 1963), (2) Observer Effects; performance on a spatial coordination task was investigated as a function of being observed by others (cf. Manstead & Semin, 1980), (3) Emergency Helping; passersby were observed giving or not giving aid to a person in apparent need (cf. Piliavin & Piliavin, 1972), (4) Discredited Eyewitness; jurors’ judgments of a defendant’s guilt were investigated as a function of the discrediting of eyewitness testimony (cf. Hatvany & Strack, 1980). The following is the description of one of the experiments. The Forbidden Toy This experiment examined the effect of a prohibition on object attraction in children. Participants were 6- to 7-year-old children from a number of state schools in a large city. The children had an average IQ of 102, and showed no indication of behavior problems (according to school reports and psychological tests). The experiment was carried out in a schoolroom during the early afternoon between the months of February and May. Each child was brought to the experimental room by one of the school teachers who had previously explained that the experimenter was a teacher from another school. The experimenter ushered the child to a play area in the room where there were five attractive looking toys. The child was invited to play with the toys. After 5 min of play, the experimenter obtained a measure of the relative attractiveness of the toys. The child was shown a pair of toys and asked to point to the one that was preferred. By presenting all possible pairs of toys, the experimenter was able to obtain a preference ranking of the five toys. The toy that was ranked second most attractive to the child was left on the table while the other toys were spread out on the floor. The experimenter then said that he was leaving and would return in 10 min. At this point, the experimental manipulation of prohibition vs no prohibition was introduced into the proceedings. In the no threat condition, the experimenter simply took the secondranked toy from the table and left the room, so that the child did not have an opportunity to play with it. In the threat condition, the experimenter left the second-ranked toy on the table but said he did not want the child to play with it during his absence. If the child did play with the toy, he would get angry and would not allow the child to play with any of the toys.

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The child was then left alone and observed for 10 min. None of the children in the threat condition played with the forbidden toy (and of course, children in the no threat condition were not given the opportunity to play with the toy). When the experimenter returned, he obtained a second set of preference rankings for the five toys. This was the measure of interest, because the experimenter wanted to find out whether the forbidden toy would be found (a) less attractive or (b) more attractive by the children in the threat condition than by the children in the no threat condition. Procedure. In the first session, subjects were given booklets containing the descriptions of the experiments and study instructions. Subjects were informed that the descriptions were of experiments that had been carried out by different researchers in psychology. Their task was to read through each description and to write down any thoughts that occurred to them about the outcomes of the experiment, and any thoughts, ideas, or feelings they had about the methods or procedures used. In particular, subjects were to think of possible reasons why and how the experiment might turn out one way or the other, and to note for each idea whether it supported outcome a, outcome b, or both. Subjects were advised that they could draw on any knowledge they had of psychology, their intuitions about human nature, personal experience in situations similar to those involved in the experiments, and their knowledge of other people’s experiences in such situations, when thinking about how each experiment might turn out. Subjects were advised to spend about 10 min on each experiment. As a rationale for the first session, subjects rated how clearly they had understood the purposes and procedures of each experiment. In the second session approximately 2 weeks later, subjects were represented with the experiments and assigned to one of the four judgment conditions. In the outcome-review condition (N = 22), subjects were told how each experiment had turned out, and their task was to estimate the likelihood of the experimental outcomes as if they had been asked before they knew how the experiments turned out. To help them recapture their foresight perspective, their original record of their thoughts and ideas was supplied and they were urged to review this record carefully. Subjects in the outcome-no review condition (N = 20) were given the same instructions except that their original record was not supplied. Instead, these subjects were urged to try to recall the thoughts and ideas they had originally produced in order to remember how they would have judged the likelihoods of the experimental outcomes before they knew how each experiment turned out.

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Subjects in the two no outcome conditions were not told the outcomes of the experiments. They were asked to estimate the likelihood of the experimental outcomes. In the no outcome-review condition (N = 19), subjects were supplied with their original record of thoughts and ideas which they were asked to read through carefully before making their judgments. In the no outcome-no review condition (N = 20), subjects were not supplied with original records but were urged to try to recall their original thoughts and ideas before making their judgments. In all conditions, subjects rated the relative likelihood of outcome a vs outcome b on a loo-mm scale, where 100/O = “definitely outcome a,” 50/50 = “50/50,” and O/100 = “definitely outcome b.” Results and Discussion

Table 1 shows the mean likelihood ratings of the experimental outcomes as a function of outcome knowledge, review/no review, and case study. There was a significant main effect of outcome vs no outcome knowledge (F(1,77) = 32.81, p < .OOOl)such that subjects who were told how the experiments turned out judged the reported outcome as more likely (M = 59.0) than did subjects not told the outcomes of the experiments (M = 47.8). Thus, with the present case study materials, the typical hindsight or knew-it-all-along effect is replicated. Although the review/no review variable did not reach significance as a main effect (F(1,77) = 2.28, p < .20), it was significant in interaction with the outcome knowledge variable (F(1,77) = 3.88, p < .06). Whereas there was a strong hindsight effect (outcome vs no outcome) with no review (F( 1,77) = 29.63, p < .OOOl),hindsight bias was much less for the review condition-although still significant (F(1,77) = 7.06, p < .Ol). As can be seen from Table 1, for the no review condition, outcome knowledge increased likelihood estimates significantly in all four case studies, whereas, for the TABLE 1 MEAN LIKELIHOOD RATINGS OF EXPERIMENTAL OUTCOMES AS A FUNCTION OF OUTCOME KNOWLEDGE, REVIEW OF NOTES, AND CASE STUDY Outcome knowledge

No outcome knowledge

Case study

Review

No review

Review

No review

Forbidden Toy Observer Effects Emergency Helping Discredited Eyewitness

59.4, 51.0, 56.1, 56.5,

67.1, 58.5, 65.8, 59.4,

54.7&b 41.6, 50.8, 45.9,

48.3, 44&z,, 52.3, 44.2,

Note. Within rows, those means not sharing the same subscript are significantly at the .05 level by Newman-Keuls test.

different

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review condition, outcome knowledge increased likelihood estimates significantly in only two of the case studies. Comparing the review and no review conditions under outcome knowledge, it can be seen that hindsight likelihood estimates were significantly reduced by the review-ofnotes manipulation in three case studies (Forbidden Toy, Observer Effects, and Emergency Helping). The case study variable was not significant overall either as a main effect or in interaction with the other variables (Fs < 2.08). These results provide evidence that reconstructing one’s foresight state by reviewing one’s contemporary cognitions is effective in reducing, if not eliminating, hindsight bias. Analysis of the comprehension ratings given in the first session showed no differences between the outcome/no outcome and review/no review conditions. The case studies were rated equally comprehensible with the exception of the Discredited Eyewitness study, which was rated least comprehensible. This may account for the fact that this study showed least effect of reviewing notes on reducing hindsight bias. Subjects’ comprehension of the studies and their likelihood ratings were examined by correlating rated comprehension with extremity of likelihood ratings across subjects. Subjects who have difficulty understanding the purposes and procedures of the studies would be more likely to give neutral likelihood ratings, particularly in the absence of outcome knowledge, reflecting their greater uncertainty about how either outcome could occur. This was indeed the case since the correlations were significantly positive for the no outcome conditions (review r = .S4: no review r = .38). Correlations were also carried out between likelihood ratings and differences in the number of reasons generated in support of each outcome. Koriat, Lichtenstein, and Fischhoff (1980) have shown that the more evidence generated in favor of a given outcome over its alternative, the greater the judged likelihood of that outcome. If subjects base their hindsight judgments on the extent to which they can recall their original foresight thoughts, then the correlation between relative number of reasons generated in support of the reported outcome and judged likelihood of that outcome should be greater in the review condition than in the no review condition. The relevant correlations (pooled over subjects and case studies) were found to be larger in the review conditions (outcomereview r = 32; no outcome-review r = .41) than in the no review conditions (outcome-no review r = .14; no outcome-no review r = .08), thus providing some confirmation of the value of the notes in reviving the original foresight state of knowledge. Or, put the other way around, relying on one’s memory for previously generated evidence is likely to lead to an unreliable evaluation of one’s foresight state of mind.

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EXPERIMENT

2

Although the Experiment 1 results show that the hindsight effect can be reduced by reinstating the original foresight cognitions, it is possible that the act of generating these cognitions in foresight is sufficient to establish a memory trace of the foresight state of knowledge, which is accessible in hindsight without the re-presentation of the original cognitions. That is, there may be an encoding advantage in generating foresight cognitions independent of any retrieval benefit in reviewing such cognitions. The production or recording of one’s thoughts before the event may result in a more elaborate and durable trace of one’s state of knowledge or uncertainty, such that this foresight state is more easily accessed in hindsight-in the same way as episodic memory for facts is improved by encoding operations that produce elaboration of stimulus events (Anderson & Reder, 1979; Bradshaw & Anderson, 1982). Experiment 2 investigated this possibility by comparing hindsight judgments of subjects who had previously generated and recorded their foresight cognitions with subjects who had not. Method Design and subjects. As in Experiment 1, subjects were tested in two sessions. In the first session, subjects read descriptions of the four psychology experiments. Subjects in the notes conditions were required to record their thoughts and reasons for possible outcomes to the experiments, while subjects in the no notes conditions simply read through the descriptions. In the second session, subjects were re-presented with the experimental studies and judged the likelihood of the outcomes, half the subjects having been given outcome feedback, and the other half not. Subjects came from the same subject population as in Experiment 1. They were 32 male and 40 female undergraduates aged between 18 and 27 recruited for a study of people’s perceptions of psychological research. Data from one subject were discarded because of prior familiarity with one of the experimental studies. Materials and procedure. The stimulus materials were the same as those used in Experiment 1. In the first session, subjects were given booklets containing the descriptions of the four experiments and study instructions. The task in the notes condition was the same as the firstsession task of Experiment 1, i.e., reading through each description and writing down any thoughts that came to mind about the experiment, particularly noting possible reasons how and why each experiment might turn out one way or the other. Subjects were advised to spend about 10 min on each experiment. At the completion of the note-writing task, sub-

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jects gave their comprehension ratings as in Experiment 1. Subjects in the no notes condition were asked to read through each experimental description carefully, after which they gave their comprehension ratings. The second session approximately 2 weeks later was similar to that of Experiment 1, with the exception that subjects were not re-presented with their notes. Subjects in the outcome knowledge conditions were told how each experiment had turned out and were asked to estimate how they would have judged the likelihood of the experimental outcomes if they had been asked before they knew the reported outcomes. Subjects in the no outcome-knowledge conditions were not told how the experiments turned out and were asked to judge the likelihoods of the possible outcomes. In the outcome-notes condition (N = 18), subjects were urged to remember the thoughts and ideas they had produced in the first session in order to recapture their foresight state. In the outcome-no notes condition (N = 18), subjects were urged to remember any thoughts and ideas they had while reading the descriptions in the first session in order to recapture their foresight state. In the no outcome-notes condition (N = IS), subjects were urged to remember the thoughts and ideas they had originally produced in the first session before making their judgments. In the no outcome-no notes condition (N = IQ, subjects were urged to remember any thoughts and ideas they had while reading the descriptions in the first session before making their judgments. Likelihood judgments were made in the same way as Experiment 1. Results and Discussion Likelihood ratings of the experimental outcomes are shown in Table 2 as a function of first-session note writing, outcome knowledge, and case study. The hindsight effect was again found-the likelihood of the reported outcome was significantly higher (F(1,68) = 37.16, p < .OOOl)in the outcome knowledge conditions (M = 63.3) than in the no outcome knowledge conditions (M = 49.4). However, there was neither a significant main effect of notes/no notes nor a significant interaction with outcome knowledge (Fs < 1). The note vs no note difference was not significant in either the outcome knowledge or the no outcome knowledge conditions (Fs < 1). As can be seen in Table 2, although the Emergency Helping and Observer Effects studies showed a smaller hindsight effect in the notes condition than in the no notes condition, the reverse was the case for the Forbidden Toy and Discredited Eyewitness studies. The case study variable reached significance as a main effect (F(3,204) = 3.46, p < .05) but not in interaction with the other variables. Outcomes for the Forbidden Toy and Emergency Helping studies were judged overall more likely than the outcomes of the Observer Effects and Discredited Eyewitness studies.

60

MARTIN F. DAVIES TABLE 2 MEANLIKELIHOODRATINGSOFEXPERIMENTALOUTCOMESASAFUNCTIONOF OUTCOMEKNOWLEDGE,NOTEWRITING,ANDCASESTUDY Outcome knowledge

No outcome knowledge

Case study

Notes

No notes

Notes

Forbidden Toy Observer Effects Emergency Helping Discredited Eyewitness

73.3,

67.8, 60.6, 72.2, 58.2,

53.9, 46.b 49.1, 45.5,

53&,,

61.0, 59.8,

No notes 52.3, 43.7, 55.7,,b

49.0,

Note. Within rows, those means not sharing the same subscript are significantly different at the .05 level by Newman-Keuls test.

The above findings do not seem to provide any support for the idea that hindsight bias can be reduced solely by increasing foresight encoding elaboration. There is a possibility that any memorial advantage of the encoding-elaboration manipulation was offset by certain other consequences of the note-writing task. One of these consequences might have been to make the scenarios clearer and more comprehensible, such that, on learning the outcomes of the scenarios, subjects in the note-writing condition updated their memories more rapidly and completely. Any hindsight bias reduction due to foresight encoding elaboration may then have been canceled by an increase in hindsight bias due to the greater comprehensibility of the scenarios, making the outcomes appear more obvious and predictable. However, little support for such a differential clarity mechanism was found in the comprehension ratings. In fact, comprehension was, if anything, slightly lower in the notes conditions than in the no notes conditions (F = 1.62). It might be argued that, although subjects in the no notes conditions were not required to engage in elaborative processing during foresight, they may nonetheless have done so, despite the absence of any explicit requirement to do so. Such an argument is difficult to refute because there is no direct yet nonreactive way of tapping subjects’ thoughts in the present paradigm. Certainly, subjects in the no notes conditions spent less time on their task (an average of 11.6 min) than did subjects in the note-writing conditions (an average of 34.2 min), which provides some indicator of differences in the amount of elaboration engaged in. In addition, evidence from studies of the role of explanation in social perceptions and beliefs (Anderson, Lepper, & Ross, 1980; Pyszczynski & Greenberg, 1981; Wong & Weiner, 1981) suggests that people only engage in cognitive activity necessary to generate reasons or explanations when the stimulus events are important, unusual, or personally involvingwhich does not seem to be the case with the present stimulus materials.

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The conclusion to Experiment 2 would appear to be that foresightful encoding elaboration is ineffective in reducing hindsight bias, despite the known effectiveness of elaborative encoding in improving episodic memory for facts (cf. Craik & Tulving, 1975). However, even for episodic fact memory, there are constraints on the effectiveness of encoding elaboration (Jacoby & Craik, 1979; Stein, Morris & Bransford, 1978). If the retrieval environment does not reinstate key elements of the encoding context, then elaborative encoding will have little effect-as is demonstrated by the encoding specificity principle (Tulving & Thomson, 1973) and state-dependent retrieval (Eich, 1980). In the present context, the elaborative encoding manipulation did not serve to establish a memory trace of the foresight state of uncertainty that was sufficiently discriminable from the new, updated trace to allow subjects to see how events could have turned out differently. Rather, encoding elaborations of the foresight state would seem to be effective in reviving a foresight perspective only when they are re-presented at hindsight (as in the Review condition of Experiment 1). EXPERIMENT

3

From a practical point of view, it would not appear to be as valuable to rely on foresight strategies as to rely on hindsight strategies in order to counteract hindsight bias. Frequently, we only appreciate the importance of an event after it has taken place, and it may even seem in foresight that there is no event or eventuality to be foreseen. Any foresight strategieseven though effective in principle-would be ineffective in practice because they would be unlikely or impossible to be implemented. It is important therefore to consider the extent to which postoutcome manipulations are effective alone in reducing hindsight bias. Using scientific experiments as case studies, Slavic and Fischhoff (1977) found that hindsight bias can be significantly reduced by requiring subjects in hindsight to explain not only the reported outcome but the outcomes that did not occur. According to Slavic and Fischhoff, the effect of outcome knowledge is to concentrate subjects’ attention on the reported outcome at the expense of the nonreported outcomes. When asked to consider future replications of the scientific studies, hindsightful judges may be so intent on explaining the reported outcome that they can no longer see how the studies could turn out otherwise. In terms of the “availability” heuristic (Tversky & Kahneman, 1973), the reported outcome remains more available than nonreported outcomes because of the ease with which it can be generated or imagined from the event scenario. Forcing subjects to consider the alternative outcomes by explaining or imagining their occurrence redresses this imbalance and makes the reported outcome seem relatively less obvious in hindsight.

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This “availability-of-reasons” mechanism may account for the effectiveness of the review-of-notes manipulation of Experiment 1 in reducing hindsight bias, in contrast to the process model adopted in Experiment 1, where it was assumed that the initial certainty of the reported outcome is adjusted downward by retrieving memories of the original foresight state. Reviewing one’s foresight thoughts and reasons might serve to reduce hindsight bias simply by increasing the amount of attention devoted to the outcome and explanations for the outcome that did not occur, thus increasing the availability of the nonreported outcome without necessarily reviving the original foresight beliefs about it. On this view, the amount of hindsight reduction obtained by reviewing foresight cognitions would be equivalent to the amount of hindsight reduction obtained by hindsight generation of reasons. However, assuming that subjects can access their original foresight knowledge, the foresight-review manipulation might produce greater reduction in hindsight bias because, in addition to increasing the availability of reasons for the nonreported outcome, it has the memorial advantage over the hindsight-generation manipulation of providing more direct cues to the original foresight state-feelings of certainty, doubt, or confidence, for example. Experiment 3 set out to compare the relative effectiveness of foresightreview and hindsight-generation manipulations in reducing hindsight bias. Method Design and subjects. As in Experiment 2, subjects were tested in two sessions, with half recording their thoughts and reasons for the possible experimental outcomes and the other half simply reading through the experimental descriptions. In the second session, those subjects who had written down their thoughts in the first session were re-presented with their notes, while those subjects who had not written down their thoughts in the first session were required to write reasons for each experimental outcome. Half the subjects were given outcome knowledge, the other half were not, resulting in a 2 (Review/Generate) x 2 (Outcome/No outcome knowledge) design. Subjects were 35 male and 53 female undergraduates aged between 18 and 28 from the same subject population and recruited in the same way as in Experiments 1 and 2. Materials and procedure. The stimulus materials were the same as in Experiments 1 and 2. The first-session tasks and instructions were the same as those given in Experiment 2 with half the subjects assigned to the note-writing task and the other half assigned to the read-only task. In the second session 2 weeks later, subjects in the outcome knowledge conditions were told which outcome had occurred for each experiment.

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In the outcome knowledge-review condition (N = 22) and no outcome knowledge-review condition (N = 22), subjects were re-presented with their notes from the first session and were urged to review these notes before making their judgments of the likelihood of the experimental outcomes. In the outcome knowledge-generate (N = 22) and no outcome knowledge-generate (N = 22) conditions, subjects were required to give reasons how and why each outcome could have occurred before making their judgments of the likelihood of the experimental outcomes. The likelihood judgments were made in the same way as in Experiments 1 and 2. Results and Discussion Mean likelihood ratings of the experimental outcomes are shown in Table 3 as a function of outcome knowledge, review/generate, and case studies. Hindsight bias was again found; likelihood estimates under outcome knowledge were significantly higher than likelihood estimates under no outcome knowledge for both the review condition (F( 1,84) = 9.20, p < .Ol) and the generate conditions (F(1,84) = 4.52, p < .05). However, the magnitude of the hindsight effect exhibited in the review and generate conditions was significantly less than that shown in the standard (no review) hindsight conditions of Experiments 1 and 2 (F(1,156) = 7.88, p < .Ol). After reviewing notes written in foresight, subjects given outcome knowledge judged the reported outcomes as more likely (M = 57.9) than subjects given no outcome knowledge (M = 49.1). Similarly, after generating reasons in hindsight, subjects in receipt of outcome knowledge judged the reported outcomes as more likely (M = 54.8) than subjects given no outcome knowledge (M = 48.6). As can be seen from Table 3, the hindsight effect in the review condition is significant for the Forbidden Toy and Observer Effects studies but not for the Emergency Helping or Discredited Eyewitness studies. For the generate condition, the hindsight effect was significant for the Observer Effects TABLE 3 MEANLIKELIHOODRATINGSOFEXPERIMENTALOUTCOMESASAFUNCTIONOF OUTCOME KNOWLEDGE, REVIEW/GENERATE, AND CASE STUDY Outcome knowledge

No outcome knowledge

Case study

Review

Generate

Review

Generate

Forbidden Toy Observer Effects Emergency Helping Discredited Eyewitness

63.5, 58.2, 55.7, 54.3,

52.8, 63.5, 53.8, 49.1,

49.7, 45.3, 53.3” 48.1,

55.2, 51.1, 48.5, 39.7,

Note. Within rows, those means not sharing the same subscript are significantly at the .05 level by Newman-Keuls test.

different

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and Discredited Eyewitness studies but not for the Forbidden Toy or Emergency Helping studies. With respect to the main purposes of the experiment, the review/generate x outcome/no outcome interaction was not significant (F = 0.41), and, although hindsight judgments in the review condition (M = 57.9) were slightly higher than in the generate condition (M = 54.Q this difference was not significant (F = 1.16). Case study was not significant either as a main effect (F = 1.72) or in interaction with the other variables (Fs < 1.20). These findings suggest that reviewing one’s foresight cognitions is not more effective, if anything slightly less effective, in reducing hindsight bias then generating reasons for the outcomes in hindsight. This is so despite the fact that subjects who generated reasons in hindsight produced significantly fewer (p < .Ol) reasons in support of the nonreported outcome than in support of the reported outcome, whereas subjects in the outcome-review condition-who had generated their reasons before receiving outcome knowledge-did not show such a bias in favor of the reported outcome. Therefore, even though subjects in the outcome-review condition were exposed to a less biased set of cognitions/reasons than subjects in the outcome-generate condition, this does not appear to have been reflected in their likelihood judgments. However, although the production of foresight cognitions and reasons may not have been biased toward the reported outcome, subjects in the outcome-review conditions may have reviewed them in a biased manner. Knowing which outcome occurred may have led subjects in the outcome-review condition to concentrate more on the reasons supporting the reported outcome than on the reasons supporting the nonreported outcome. Unlike subjects in the outcome-generate condition who were required to devote at least some attention to the outcome that did not occur (in order to explain it), outcome-review subjects were free to ignore the nonreported outcome. For this reason, active generation of reasons in hindsight may constitute a more powerful means of making the nonreported outcome appear more likely or available (Tversky & Kahneman, 1973) compared with reviewing foresight cognitions. GENERAL

DISCUSSION

The above conclusion suggests that efforts to reduce hindsight bias should concentrate on postevent or postoutcome manipulations. From a practical standpoint, it would often not be feasible to institute foresight, preoutcome strategies because the importance of an event may not be clear in foresight, or it may not even be clear that an event is going to occur (cf. Fischer, 1970). However, before dismissing foresight strategies it is worth noting that few previous studies of hindsight bias have examined foresight manipulations and strategies.

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Encoding-elaboration manipulations are only one of a number of possible foresight strategies. Following Fischhoff (1977) it may be that instructional manipulations-such as exhorting people to work harder or warning them about hindsight effects-although ineffective in hindsight, may be more useful in foresight. And, compared with the laborious and time-consuming nature of the encoding-elaboration tasks involved in the present experiments, simple exhortations to oneself would be easier to implement. In fact, a generally applicable precept-such as “Know or beware thy state of uncertainty!“might be more valuable than specific foresight strategies, although evidence from other areas of judgment and decision making (cf. Fischhoff, 1982b; Nisbett, Krantz, Jepson, & Fong, 1982) suggests otherwise. The particular encoding-elaboration manipulation employed in the present experiments was fairly nonspecific and nondirective (in keeping with the exploratory nature of the studies)-involving subjects’ thoughts, feelings, reasons, and whatever else could be thought upwhich contrasts with the typical manipulations used in episodic fact memory such as embedding words in sentence frames. More directive encoding strategies might prove more effective for retrieving foresight states of knowledge. In addition, diffuse and heterogeneous elaborations are not easy to remember because of their lack of organization and structure. Even with episodic fact memory, it is no use engaging in elaborative encoding if the elaborations themselves cannot be retrieved. Organizational mnemonics might therefore prove useful in foresight encoding strategies, just as they do in episodic memory for facts (Bellezza, 1981). particularly useful where the details of events, actions, and interpretations are not well-known before the fact. Unlike the present paradigm, where the details of the scenarios were known in foresight (and were the same as those available in hindsight), real-world events may not be known in any great detail in foresight. Decision makers may frequently ignore or misunderstand particular facts. Actions and events which can now appear to explain the outcome-but which were overlooked before the event-may be given prominence; protagonists may interpret their actions so as to appear reasonable “in the light of developments.” In such cases, after-the-fact explanations of how alternative outcomes could have occurred would be based on information and evidence different from that on which before-the-fact explanations could have been constructed. Foresightful organizational strategies for one’s thoughts and reasoning might then lead to more accurate recall of the details of events and actions-particularly the sequence and timing of events. And yet, unlike the recall of lists of unrelated words in episodic memory experiments, real-world events might be said to already have a built-in structure in the form of a theme, scenario, script, or narrative of cause-effect se-

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quences. [If real-world sequences of events do not already possess an inherent “story-mnemonic,” we have a tendency to spontaneously impose such a structure on them (Abelson, 1981).] Thus, in many instances of hindsight bias, one of the most powerful mnemonic devices-the story mnemonic or script-already operates in foresight to organize one’s memory for events. Despite such misgivings about the effectiveness of foresight encoding manipulations, it would seem worthwhile investigating foresight strategies for those social, political, or personal events whose occurrence and importance is known in advance-such as elections, examinations, space launches, and so on. With respect to such events, it might be argued that had the judges in the present experiments been experts in the fields of concern, then their susceptibility to hindsight bias might have been less and the effectiveness of the foresight manipulations greater. High involvement and expertise might lead the foresightful judge to produce more detailed and more organized records of their foresight state of knowledge (cf. Voss, Vesonder, & Spilich, 1980) that would then serve as more powerful retrieval cues in hindsight. However, there may be grounds for doubting that expertise would reduce hindsight bias. Arkes, Wortmann, Saville, and Harkness (1981) found that medical experts operating in their own field of expertise showed sizable hindsight bias in their clinical judgments. Although direct comparisons of experts and novices have yet to be made in the hindsight domain, it is possible that expertise would increase hindsight bias because the greater knowledge base of the expert provides greater scope for the biasing of cognitive activity in hindsight, such as favoring evidence, reasons, and explanations which support the reported outcome. Finally, with respect to issues concerning the mechanisms underlying hindsight bias, the present studies did not provide any direct evidence that reviewing foresight cognitions improves people’s memory of their foresight state. Strictly speaking, in order to assess the accuracy of subjects’ memory, a repeated-measures design is required to compare foresight and hindsight judgments. Given the failure of the encoding-elaboration manipulation of Experiment 2 and the equivalence of foresightreview and hindsight-generation of reasons in Experiment 3, the most parsimonious account of the present findings should be that the foresight-review manipulation allows judges to construct their hindsight judgments so that they look more like foresight judgments, rather than enabling judges to recover or retrieve their original foresight memory. Indeed, the present results cannot rule out the possibility that receipt of outcome knowledge did in fact erase the original foresight memories and that the hindsight judgments were generated without the aid of old foresight memories. Further investigation of those factors that have been

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