Forgetting near-accidents: the roles of severity, culpability and experience in the poor recall of dangerous driving situations

Forgetting Near-Accidents: The Roles of Severity,Culpability and Experience in the Poor Recall

of Dangerous Driving Situations

PETER CHAPMAN* and GEOFFREY UNDERWOOD

University of Nottingham, UK

SUMMARY

It is often assumed that real-life events such as minor road accidents and near accidents will bewell remembered. However, surveys of self-reported accidents suggest that respondents appa-rently forget approximately one third of their road accidents each year. This paper explores thispossibility by looking at memory for the near-accidents in which drivers are involved. In a pilotstudy drivers carried microcassette recorders in their cars and reported near-accidents aftereach journey. These data con®rmed that the frequency of near-accidents is greatly under-estimated when subjects are simply asked to recall them. The main study then comparedreports and recalls of over 7000 car journeys from 80 subjects over the course of a year. Theseincluded more than 400 reports or recalls of near-accidents. The in¯uences of the driver'sexperience, the severity of the near-accident, and the driver's self-perceived degree of blamewere additionally explored. It is concluded that near-accidents are generally forgottenextremely rapidly, with an estimated 80% of incidents being no longer reported after a delay ofup to two weeks. Serious near-accidents and those where the driver admitted being to blame inthe incident were least likely to be forgotten. Copyright # 2000 John Wiley & Sons, Ltd.

In recent years memory researchers have increasingly looked at people's memories foreveryday experiences in real-world contexts. Such research provides extremelyvaluable information about the ways in which memory is used in everyday life andhighlights areas in which laboratory research may or may not generalize to appliedsettings. However, by concentrating on the contents of memories it is often possible toignore the huge quantity of information which is forgotten from such everydayexperiences. The study in this paper looks at types of experience which appear to beforgotten at surprisingly high rates in everyday life ± accidents and near-accidentsexperienced by drivers.

Recent memory research has explored people's normal memories for a variety ofpotentially arousing or traumatic events (e.g. Christianson, 1992a, b; Conway, 1997a;Winograd and Neisser, 1992), but memory for relatively common dangerous drivingevents has not so far been systematically explored. As well as being an area of theo-retical interest, memory for traumatic driving events is an issue of considerableapplied importance. Road safety researchers commonly use self reports of accidentsto assess an individual's accident liability and to evaluate factors that in¯uence

CCC 0888±4080/2000/010031±14 $17.50 Received 23 February 1998Copyright # 2000 John Wiley & Sons, Ltd. Revised 4 November 1998

Accepted 11 November 1998

APPLIED COGNITIVE PSYCHOLOGYAppl. Cognit. Psychol. 14: 31±44 (2000)

*Correspondence to: Peter Chapman, School of Psychology, University of Nottingham, University Park,Nottingham NG7 2RD, UK. E-mail: [email protected]

accident liability (e.g. Forsyth et al., 1995; Parker et al., 1995; West and Hall, 1997).Self-reports of potentially dangerous driving behaviours have also been frequentlyused to understand accident causation (e.g. Blockey and Hartley, 1995; Reason et al.,1990). Any known sources of error and particularly bias in such reports could thushave great practical signi®cance.

REMEMBERING DRIVING EVENTS

The suggestion that normal driving events may be rapidly forgotten is not con-troversial. It is frequently reported that drivers may be unable to recall the sections oftheir current journey even when the drive is still in progress (e.g. Reed, 1972). There isalso good evidence that individual journeys may be completely forgotten whensubsequent free recall is used to test memory. Smith and Wood (1977) report a studyin which employees were asked to recall the individual business journeys that they hadmade over the previous six or eight months. These recalls were then compared withthe expense claims submitted over the period. Assuming that such expense claimsaccurately re¯ect the journeys made by the employees this study demonstratedconsiderable forgetting even for these relatively rare journeys (an objective frequencyof approximately one journey per employee per month). Over six months 27.3% ofcar journeys appeared to be forgotten, rising to 34.8% over eight months.

It could be argued that a lack of explicit recall for portions of a journey might stemfrom a failure to encode information when performing highly automatized tasks.Such an explanation cannot be applied to whole business trips; here the problem mustbe one of storage or retrieval. One possibility is that numerous similar events becomestored as a single schema. As such a schema becomes more developed, the recall ofspeci®c schema-consistent events may become more di�cult. One interesting predic-tion from this framework would be that memory for individual driving events mightdepend on the expertise of the driver, with relatively inexperienced drivers being farmore likely to recall speci®c recent events than their more experienced counterparts.While these issues may be relevant in the recall of frequent mundane events, there isalso evidence that events as signi®cant and rare as road accidents are routinelyforgotten.

Loftus (1993) describes a study in which 14% of people involved in injury-provoking road accidents did not remember the event a year later. In cases where theinjuries were serious, it is possible that some forms of traumatic amnesia are involvedin the forgetting of accidents (Blanchard and Hickling, 1997; Mitchell, 1997).However, in general the evidence seems to suggest that the more serious an accident isthe more likely it is to be remembered. In a series of analyses Maycock and colleagueshave looked at the dating of self-reported accidents (Maycock and Lester, 1995;Maycock et al., 1991, 1996). In their studies they ®nd that when accidents are recalledover a three-year period more accidents are reported in recent parts of the period thanthose longer ago. Maycock and colleagues model these e�ects with an estimate thatapproximately 30% of accidents are forgotten each year. This forgetting rate declinesto 18% for accidents involving injuries ± a ®gure comparable to the 14% reported byLoftus (1993). It should be noted that e�ects observed in the dating of accidents maybe partly accounted for by forward telescoping ± the tendency to date rememberedevents as more recent than they in fact are (Thompson et al., 1988). Nonetheless there

32 P. Chapman and G. Underwood

Copyright # 2000 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 14: 31±44 (2000)

is reason to suspect that even severe accidents may be routinely forgotten by normaldrivers over periods as short as a year. It is possible that more minor accidents andnear-accidents are forgotten at much higher rates. The study reported in this paperexplores this possibility by looking at drivers' recalls of the minor accidents and near-accidents that occur in the course of normal driving.

REPORTING AND RECALLING NEAR-ACCIDENTS

A serious methodological problem for any study of accidents and particularly near-accidents is obtaining plausible estimates of the true incidence of such events. Oneapproach to this problem is to have subjects themselves report these events as soon aspossible after they have happened. Such an approach means that reports are given in asimilar way to the recalls generally required by road safety researchers and addition-ally allows subjective ratings of the incident to be collected at the same time. However,it must be remembered that such reports will themselves be subject to many of thesame biases that recalls might be, and where reports cannot be made until the end of along journey there may be a signi®cant memory component to even this task. In apilot study 29 subjects used a microcassette recorder to report near-accidents and avariety of other driving events for a two-week period. During this period they kept therecorder in their car and reported events at the end of each journey. Over the two-week period the 26 subjects that completed the study reported an average of 6.35 near-accidents (range from 0 to 29). This frequency of near-accidents is surprisingly high,particularly if it is assumed that some near-accidents may still not have been reportedbecause of bias or forgetting ± it corresponds to a near-accident being experienced onmore than one in four of the journeys undertaken. This relatively high incidence ofnear-accidents is particularly interesting when it is compared to the self-reports ofnear-accidents that are obtained using a questionnaire.

Chapman (1993) reported a series of studies exploring drivers' memories for anumber of di�erent driving and driving-related events. Many of the subjects in thesestudies addtionally ®lled in a questionnaire in which they were asked to estimate thenumber of near-misses that they had experienced in the last year. Here a near-miss wasdescribed simply as an occasion in which the subjects felt that they had almost beeninvolved in an accident. The mean number of near-misses reported by these 162subjects was 2.79 (range from 0 to 50). Although there are considerable di�erencesbetween the questionnaire study and the pilot study with microcassette recorders, notthe least of which is the change in de®nition from near-miss to near-accident, thecomparison between the two sources of data may still prove illuminating. From thequestionnaire study it would be naively estimated that drivers experience a mean of2.79 near-misses per annum. From the microcassette recorder pilot study it would beestimated that a broadly similar group of subjects in fact experience over 165 near-accidents per annum. If this di�erence were solely attributable to forgetting thiswould suggest that over 98% of near-accidents are forgotten over the course of a year.Of course, there were many other di�erences between these two sources of data as wellas the retention interval, nonetheless the results clearly suggest that a properlycontrolled study would ®nd evidence for very considerable underreporting of near-accidents from memory.

Forgetting Near-accidents 33


A simple study might involve having subjects report near-accidents on a micro-cassette recorder over some period and then subsequently giving them a memory testfor the near-accidents they had previously reported. This procedure would be similarto one that has been commonly used in research on autobiographical memories(e.g. Larsen, 1992; Wagenaar, 1986). While the results of such a study might provevaluable in assessing the relative memorability of di�erent events it seems inevitablethat such a design would substantially underestimate the true level of forgetting thatoccurs in everyday life. It has long been accepted that the act of recalling can con-siderably improve subsequent memory (e.g. Roediger et al., 1997). It has even beendemonstrated that e�ects of multiple testing for details of realistic events can be solarge that hypermnesia can be observed. In one experiment subjects who had beenrepeatedly tested were actually able to recall more details 48 hours later than theywere immediately after watching a traumatic ®lm (Scrivner and Safer, 1988).Repeated testing may also lead to a standardization of the contents of a memorywhether accurate or not (Conway, 1997b; Loftus, 1993; though see Neisser andHarsch, 1992, for evidence that this e�ect is not ubiquitous), and to an increase inpeople's con®dence in the accuracy of their memories (Robinson and Johnson, 1996).The solution adopted to this problem in the current study is to compare reports ofone set of events with recalls of a di�erent set of events which we nonethelessanticipate to be extremely similar in frequency and content. Although this makes itimpossible to test the accuracy of individual recalls, the methodology does provide asensitive test of the true level of recall in everyday life. It is also possible to test thehypotheses that severe near-accidents are more likely to be recalled than more minorones, and that more experienced drivers will generally have poorer recall than newlyquali®ed drivers. This second possibility is additionally explored by following thenewly quali®ed drivers over the ®rst year of their driving careers. We would anticipatethat as they gain substantial tra�c experience their recalls of individual near-accidents should decline.

METHOD

Subjects

The subjects were 80 drivers who were taking part in a separate study examining theirdriving skills. These subjects were in one of two groups, 30 experienced drivers(15 females and 15 males) and 50 newly quali®ed drivers (25 females and 25 males).Oversampling the newly quali®ed drivers relative to the experienced drivers com-pensated for the fact that this sample were less likely to complete the study in itsentirety. The experienced drivers ranged in age from 25 to 30, mean 27.0 years, hadbetween 5 and 10 years of driving experience, and reported driving an average of13,700 miles per year. These drivers were recruited by means of an advertisement in alocal newspaper. The newly quali®ed drivers ranged in age from 17 to 20, mean 17.5.They attended for the ®rst phase of testing between three and ten weeks after passingthe British practical driving test and gaining a full driving licence. Before passing thistest British drivers are not allowed to drive unaccompanied on public roads and willgenerally have very limited experience of hazardous driving situations. These driverswere recruited by means of a questionnaire and letter distributed to them by their



examiner on passing their driving test. Subjects were paid £15 for their participationin this study.

Design and procedure

There were three phases to this study. For the newly quali®ed drivers Phase A tookpart between three and ten weeks after they had passed the British practical drivingtest. Phase B was completed three to four months later and Phase C took place afurther three to four months after Phase B. At Phase C these drivers had betweenseven and ten months of driving experience since passing the practical test. Experi-enced drivers were recruited at the same time as the new quali®ed drivers and theirphases of testing were spaced in the same way, with testing of the two groupsproceeding simultaneously to avoid seasonal di�erences in driving habits betweengroups. At each time of testing subjects took part in two types of test, a recall task inwhich they recalled driving events from the last two weeks and a report task in whichthey reported similar driving events from the following two weeks.

Recall taskSubjects were given a hand-held microcassette recorder and instructed in how to useit. They then answered a series of questions about the driving they had done over theprevious two weeks. They recorded their responses with the microcassette recorder.They ®rst estimated the total number of journeys that they had made over the last twoweeks. It was speci®ed that only journeys where they were the driver should beincluded and that return journeys, such as driving to work and then coming backlater, should be counted as two separate journeys. Subjects then estimated the totalmileage that they had driven in the two-week period. Next, they were asked whetherthey could recall being involved in any accidents or near-accidents during the two-week period. Here an accident was de®ned as any occasion on which their car actuallytouched another vehicle, object or person, while near-accidents were de®ned asoccasions on which they had felt that such an accident could almost have occurred.For each incident that the subject was able to recall they ®rst described the event in asmuch detail as possible into the microcassette recorder. They then made two ratingsabout the incident, ®rstly a rating of how severe the near-accident was (on a ®ve-pointscale ranging from `Little danger of accident' to `Accident'), and second, a rating ofhow culpable they felt themselves to be in the incident (on a three-point scale ±`De®nitely not my fault', `Partly my fault', `Completely my fault').

Report taskSubjects now took the microcassette recorder and an instruction card away with themand were asked to keep these in their car for the next two weeks. Each time that theycompleted a journey in the car the subject recorded on the microcassette recorder thelength of their journey. They then reported any accidents or near-accidents that hadoccurred on the journey using the same procedure as in the recall phase, describingthe incidents and rating them for severity and culpability. It was stressed to subjectsthat they should only report events once their vehicle was safely parked and thatunder no circumstances were they to use the recorder while driving. After the twoweeks were up the subject posted the microcassette recorder back in a padded reply-paid envelope that was supplied.



RESULTS

Not all subjects completed all parts of the study. Some subjects proved unable orunwilling to take part in Phases B or C of testing. This was particularly the case fornewly quali®ed drivers, some of whom had left the region since passing their drivingtest to attend college elsewhere in the country. Other subjects have missing data owingto equipment failures, theft of the recorders from their vehicles, or other failures toreturn the microcassette recorders after two weeks. Of the microcassettes that werereturned some recordings were inaudible or obviously incomplete and these wereexcluded from the analysis; other subjects failed to reliably record all of the requestedinformation for all journeys (e.g. mileages), in these cases only the missing data typefor that subject was excluded from the analyses. Only 43 subjects (20 experienceddrivers, 23 newly quali®ed drivers) provided complete data for all three phases. Theindividual analyses below thus use a minimum of 43 subjects but more where addi-tional data were available for particular comparisons. Despite the above problems,using microcassette recorders to obtain reports of journeys and near-accidents provedviable and provided a wealth of data on the objective frequency of such events. Thetapes were transcribed and provided descriptions of 3592 individual journeysincluding 382 descriptions of near-accidents. The recall phases provided descriptionsof an additional 69 near-accidents from an estimated 4190 individual journeys.

Table 1 displays the total number of journeys recalled and reported for theexperienced and novice subjects at each of the three phases. These data, and those forthe other reporting tasks, are highly positively skewed, so to reduce skew and providehomogeneity of variance a cube root transformation was performed on all data beforeperforming analysis of variance. An overall analysis of variance, using only subjectswith complete data, demonstrated a signi®cant main e�ect of response condition,

Table 1. The mean number of journeys recalled and reported from two weeks of driving ateach of three phases. Results are given separately for newly quali®ed and experienced drivers.Maxima, minima, and the numbers of usable observations are also provided

Experienced drivers Novice driversReport Recall Report Recall

Phase AMean 25 31.9 14.9 21.72Maximum 54 140 59 52Minimum 5 8 3 2n 28 30 50 50

Phase BMean 23 39.76 17.84 28.45Maximum 49 140 62 150Minimum 7 14 4 3n 26 29 32 44

Phase CMean 20.17 38.96 14.97 25.82Maximum 49 300 52 150Minimum 2 3 0 0n 24 27 33 45



with more journeys tending to be recalled than were reported, F(1,42) � 18.85,p5 0.001. No other main e�ects or interactions were statistically signi®cant.

Table 2 gives the total mileage recalled and reported for the experienced and novicesubjects at each of the three phases. An overall analysis of variance demonstrated asigni®cant main e�ect of subject group, with experienced drivers travelling furtherthan the novices F(1,41) � 10.11, p5 0.01. There was also a signi®cant main e�ect ofphase, and an interaction between response condition and phase, F(2,82) � 3.70,p5 0.05. An analysis of simple main e�ects demonstrates that the two responseconditions di�er signi®cantly only at Phase C, where less mileage is reported thanrecalled, p5 0.05, and that the e�ect of phase is only signi®cant for reported mileage,p5 0.01, not for recalled mileage.

Table 3 shows the total number of near-accidents recalled and reported for theexperienced and newly quali®ed drivers at each of the three phases. An overallanalysis of variance demonstrated signi®cant main e�ects of response condition,F(1,44) � 74.50, p5 0.001, with far more near-accidents being reported thanrecalled, and phase, F(2,88) � 18.29, p5 0.001, with numbers of near-accidentsreducing over time. There were also interactions between subject group and responsecondition, F(1,44) � 9.40, p5 0.001, and response condition and phase,F(2,88) � 8.94, p5 0.001. Simple main e�ects analysis of the response conditionby phase interaction demonstrate that more near-accidents are reported than recalledat all phases, p5 0.001, but that the e�ect of phase is only signi®cant for reportednear-accidents, p5 0.001. The interaction of subject group and response condition isof particular interest since this relates to the possibility that newly quali®ed driversmay have better recall of near-accidents than older more experienced drivers. Analysisof simple main e�ects demonstrates that both groups report more near-accidents thanthey recall, p5 0.001, and that experienced drivers report more near-accidents thannewly quali®ed drivers, p5 0.05. Although, as predicted, newly quali®ed drivers

Table 2. The mean mileage recalled and reported from two weeks of driving at each of threephases


Phase AMean 357.6 350.7 159.17 145.1Maximum 989 1120 649 800Minimum 31 40 15 15n 28 30 49 50

Phase BMean 274.5 503.8 158.8 207.8Maximum 1063 2000 443 1000Minimum 55 30 28 18n 26 29 32 44

Phase CMean 286.4 319.1 129.4 240.2Maximum 1448 1000 451 1500Minimum 2.5 4 0 0n 24 27 33 45



actually recalled more near-accidents than the experienced drivers, this e�ect does notreach signi®cance.

The above analyses consider journeys, mileages, and near-accidents separately.These analyses are interesting from a theoretical point of view, but in applied settingsit would be more common to consider near-accidents once exposure was controlledfor in some manner. The commonest approach used is to calculate accidents per mile,but it has been suggested that this approach substantially underestimates the risks forthose completing many short journeys (Janke, 1991). For these analyses we have thuscalculated measures of both near-accidents per mile, and per journey. The pattern ofresults obtained is highly similar to that for raw numbers of near-accidents whichevermethod is used. There are still signi®cant main e�ects of response condition,F(1,41) � 72.82, and F(1,42) � 69.29, for near-accidents per mile and per journeyrespectively, both p5 0.001, and main e�ects of phase, F(2,82) � 10.94, andF(2,84) � 15.22, both p5 0.001. The interactions between group and responsecondition are again signi®cant, F(1,41) � 9.89, p5 0.01, and F(1,42) � 6.86,p5 0.05, but none of the simple main e�ects looking at group di�erences are nowsigni®cant. The response condition by phase interaction is signi®cant only for near-accidents per journey, F(2,82) � 2.94, p � 0.059, and F(2,84) � 4.55, p5 0.05, butin both cases simple main e�ects show e�ects of phase only for response condition,p5 0.001.

Figure 1 shows the distribution of severity ratings for recalled near-accidentscompared to reported ones. Because of the relatively small number of recalled near-accidents these distributions are plotted aggregating across both subject groups andphases of the study. If individual reports and recalls are treated as independent thesetwo distributions are found to be signi®cantly di�erent (w2 � 45.9, d.f. � 4,p5 0.001). Alternatively, mean ratings can be compared for just those 37 subjectswho described and rated at least one near-accident in both the recall and reportconditions. This analysis con®rms the pattern described above with recalled

Table 3. The mean number of near-accidents recalled and reported from two weeks ofdriving at each of three phases


Phase AMean 3.75 0.345 2.62 0.52Maximum 26 2 16 3Minimum 0 0 0 0n 28 29 50 50

Phase BMean 1.731 0.25 1.313 0.5Maximum 6 1 6 2Minimum 0 0 0 0n 26 24 32 30

Phase CMean 1.042 0.077 1.03 0.278Maximum 4 1 6 1Minimum 0 0 0 0n 24 26 33 36



near-accidents receiving signi®cantly higher severity ratings than reported ones,t(36) � 3.39, p5 0.01.

Figure 2 shows the distribution of culpability ratings for recalled near-accidentscompared to reported ones. Once again these distributions are plotted aggregatingacross both subject groups and phases of the study. If individual reports and recallsare treated as independent these two distributions are again found to be signi®cantlydi�erent (w2 � 17.5, d.f. � 2, p5 0.001). Alternatively, mean ratings can becompared for just those subjects who produced at least one near-accident in boththe recall and report conditions. This analysis also con®rms the pattern describedabove with recalled near-accidents receiving signi®cantly higher culpability ratingsthan reported ones, t(36) � 2.70, p5 0.05.

It is, of course, possible that the culpability and severity relationships with recall arein fact measuring the same thing. To see whether culpability and severity ratings were

Figure 1. Distribution of near-accidents in report and recall conditionsamong the ®ve severity categories

Figure 2. Distribution of near-accidents in report andrecall conditions among the three culpability categories



themselves generally related to one another correlations were calculated across thosesubjects describing and rating at least one near-accident in either the recall or reportcondition. To allow independence, only the ®rst near-accident produced by eachsubject was used in this analysis. The resulting correlations were negative, r(47)�ÿ0.36, p5 0.05, for recalls, though not signi®cantly for reports [r(67) � ÿ0.12],implying that, if anything, subjects rated themselves as less likely to be to blame forthe more severe near-accidents. The di�erence between these two correlations is notsigni®cant (z � 1.33, treating them as independent). The same pattern (negativecorrelations, though not signi®cantly di�erent from zero, or from each other) emergesif average ratings over all near-accidents are used for each subject rather than ratingsfor the ®rst near-accident only.

DISCUSSION

The data imply very high levels of forgetting for near-accidents, particularly for theless serious ones and those where the driver felt that they were not culpable in theincident. It was predicted from past research into actual accidents that more severenear-accidents would generally be better remembered. It should be noted that suchevents were also objectively less frequent and may have been more distinctive in anumber of other ways (cf. Schmidt, 1991). Although very few actual accidents werereported or recalled it is interesting to note that there was no particular evidence forforgetting of accidents ± ®ve were recalled in all compared to six from the reportconditions. Observing forgetting of actual accidents over two weeks would haveseemed highly unlikely ± such events would have sequela such as dents, garage repairs,and insurance claims which would be likely to be still ongoing at the time of recall.However, it is possible to regard these data as representing a continuum of forgettingwith regard to severity, with 95%, 91%, 55%, 50%, and 17% estimated forgettingrates for incidents of increasing severity ratings from `little danger of accident' to`accident'. Even though the increase in memorability with severity was predicted itshould be noted that there exist a number of studies showing impaired memory forarousing or stressful events (i.e. Loftus and Burns, 1982; Peters, 1988). The criticaldi�erence here appears to be that where moderate levels of arousal or stress impairmemory for events they do so in terms of the exact details that can be recalled from theevent, not in whether the event itself can be recalled at all. Where impairments fordetail information are found, such impairments may only be present for aspects of theevent that were not central to the plot or gist of the event (Burke et al., 1992;Christianson and Loftus, 1987; Heuer and Reisberg, 1990).

There were at least two possible a priori predictions about the culpability ratings.One would have been that in the recall phase subjects would selectively describeincidents in which they felt that they were not to blame. This might correspond to aself-presentational bias and would accord with the common ®nding that driversgenerally regard the quality of their own driving as being extremely good (Groegerand Grande, 1996; Svenson, 1981). The alternative prediction was that drivers wouldhave better memories for such incidents precisely because these are the ones that donot accord with subjects' schemas of themselves. Because of this such incidents maystand out in memory, and they may also be likely to be rehearsed as the subjectattempts to understand how to prevent such incidents in the future. The data provide



some support for both theoretical positions ± although the recall data are clearly inline with the second prediction, the report data may actually provide evidencesupporting the ®rst position. Figure 2 shows clearly that the overwhelming majorityof incidents are reported by the driver as being `de®nitely not my fault'. Although it ispossible that the subjects in this study were unusually unlikely to be to blame for near-accidents it seems more plausible that this re¯ects a general bias in the perception oftheir own driving. It is perhaps comforting that this bias is overturned in memory,suggesting that people may nonetheless be selectively learning from their mistakes.The ®nding that drivers are less likely to forget incidents where they were to blame isalso consistent with a large single case study of autobiographical memory (Wagenaar,1986, 1992, 1994) which demonstrated that the experimenter was especially unlikelyto forget unpleasant events for which he was responsible. This study thus goes someway to answering those critics of Wagenaar's study who suggested that the resultmight not generalize to other individuals (Baddeley, 1994; Neisser, 1994).

What this study demonstrates most clearly is that self-reports of near-accidentsfrom memory will dramatically underestimate the true frequency of such events.Recalls at the end of a two-week period resulted in only around 20% of the number ofnear-accidents that were estimated to have occurred in a similar period for whichreports were made at the end of each journey. The results con®rm our prediction thatnear-accidents will be forgotten at a very rapid rate. In the introduction we discussedstudies which suggested that injury-provoking accidents are forgotten at a rate ofaround 14±18% per annum while accidents in general might be forgotten at a rate of30% per annum. This study suggests that 80% of near-accidents may be forgottenover a period of just two weeks. Note that the forgetting e�ects observed with near-accidents are in exactly the opposite direction to the e�ect observed with the numberof journeys made, where more journeys were recalled than were reported. The reasonfor the over-recall of journeys is unclear ± it could result from a failure of subjects toreliably use the microcassette recorders for every single journey in the report phase, orit could be evidence for forward telescoping in the recall of journeys. The fact thatdi�erent strategies are being used for recalling and reporting journeys can also be seenfrom the types of responses made. In recall 50.9% of responses to the number ofjourneys made in two weeks were numbers divisible by 10. In contrast, the totaljourneys reported by subjects in the following two weeks was only divisible by 10 on7.6% of occasions. Clearly the recall of journeys contains a degree of estimation androunding which is not present in the report condition. While such e�ects areinteresting in their own right, they do not compromise the main ®ndings with respectto the poor recall of near-accidents. If such e�ects are present in the study they would,if anything, mean that the data give an underestimate of the true forgetting rate fornear-accidents.

From a more theoretical perspective it is interesting to consider the degree to whicha failure to report a near-accident in this paradigm can be taken as evidence forcomplete forgetting. It should be noted that although we refer to these incidents asbeing forgotten we make no claim that they are completely inaccessible to all forms ofmemory testing. We would certainly predict that if precise and varied recall cues wereprovided for individual events the level of recall would be increased substantially andthat the recognition of events which were not recalled would be far better than chance.Nonetheless, the forgetting that we report is both typical of people's everydayunderstanding of the concept of forgetting, and corresponds to a type of forgetting



which would result in systematic underestimates of near-accident frequency in anapplied context. However, to some degree the results obtained in this study will bedetermined by the subjects' interpretation of the phrase near-accident. Since there isno absolute de®nition available for this phrase it is possible that de®nition adopted bysubjects will be altered by the experimental context (cf. Schwarz, 1995; Wright et al.,1994, 1997), with subjects being more willing to consider an incident to be a near-accident soon after the event than when retrospecting over a two-week period.Although the questions asked of the subjects and the manner of recording wereidentical in the recall and report conditions, it is possible that a driver's concept ofnear-accident will change with context and over time. It is such a change which mayaccount for the reductions in the numbers of near-accidents reported over the threephases of the study. Note that this reduction is reliably observed, even when changesin mileage or number of journeys are taken into account, but that it appears only forreports, not for recalls.

The other prediction we had made was that newly quali®ed drivers might be lesslikely to forget near-accidents than more experienced drivers. The data are consistentwith this prediction ± interactions were found between subject group and responsecondition with older experienced drivers reporting more near-accidents, but newlyquali®ed drivers recalling more. However, the recall advantage for newly quali®eddrivers was not signi®cant and once exposure was taken into account, neither was thehigher reporting rate for more experienced drivers. This is not surprising, since wewould have anticipated that, if anything, the newly quali®ed drivers should have ahigher true accident liability than the experienced drivers. We cannot thereforeconclude that newly quali®ed drivers do have better memories for near-accidents thantheir more experienced counterparts, but this remains an interesting possibility. Toexplore the possibility further a study with matched exposure across groups andgenerally higher levels of recall would be necessary.

There are a number of important recommendations to be drawn from this researchfor those using self-reports of accidents and near-accidents in an applied context.First, when groups are to be compared in terms of accident liability it is vital thatidentical recall intervals are used for all groups. Although this study did not demon-strate unambiguous group di�erences in memory performance, the results were in thepredicted direction (newly quali®ed drivers showing better memory for near-accidentsthan experienced drivers) and researchers should certainly not assume that allpopulations will be equally good at such recall tasks. With respect to the types ofincident recalled it is clear that such recalls will certainly not provide a representativesample of the incidents actually experienced but will instead be biased towards severenear-accidents and those where the driver feels culpable.

ACKNOWLEDGEMENTS

This research was partially supported by a research grant from the Department of theEnvironment, Transport and the Regions (UK). Some of these data were presented atthe 2nd International Conference on Memory and the Transport Research Laborat-ory's 7th Research Seminar on Behavioural Research in Road Safety. The authorswish to thank Sharon Wright, Sara Batts, James Isaacs and Kate Lewis for theirassistance in data collection and coding, and Dan Wright, John Groeger and an



anonymous reviewer for their helpful comments on an earlier version of thismanuscript.

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Forgetting near-accidents: the roles of severity, culpability and experience in the poor recall of dangerous driving situations