AS Level Psychology: Cognitive Psychology: Loftus and Palmer (1974)

www.PsychologyStuff.com 7.1

IntroductionEyewitness testimony can be crucial in criminal trials, indeedguilt is often dependent on the evidence of bystanders. Thisreliance on eyewitness testimony is, however, predicated on theassumption that our memories are trustworthy. We assume thatwhen we see an event it is "recorded" in our brain and that inremembering the event we are simply "playing it back".Cognitive psychologists have, however, challenged thisassumption - as may (or may not) have been shown in the "gettingyou thinking" activity - highlighting a range of mental processeswhich may affect our memory and recall.

Before this study was conducted, many cognitive psychologistshad examined how recall of events could be distorted. Forinstance,

! Bird (1927) highlighted problems in the recall of numericalinformation such as time, speed and distance - particularlywhere the event being observed was complex.

! Gardner (1933) showed that there were huge variations inthe recall of car accidents between witnesses.

! This study was added to by the US Air Force, in a studywhich showed that - when shown a video of a moving carand asked to estimate speed - guesses varied from 10 to 50mph (the actual speed was 12 mph)

! Bartlett also argues that memory is reconstructive, in thatit can be re-evaluated and amended in the context of laterinformation.

Rationale and AimsLoftus and Palmer argue that - given the mismatch between thereliance on eyewitness testimony in courts and the actuallytrustworthiness of such evidence - it is important that we identifythe variables which may affect recall and memory. The aim ofthis study was to explore one such variable - namely howinformation provided after an event, in the form of leadingquestions, might affect people's memories. The study consists oftwo separate laboratory experiments

The First Experiment

ParticipantsThe participants in the study were 45 students from theUniversity of Washington.

Procedure Participants were shown seven videos of a car crashes, rangingfrom 4 to 30 seconds long. The videos were short excerpts offilms made for driver education courses (so the researchers wereaware of the speeds of the cars involved), and were shown in arandom order.

Following each video, participants were given a questionnaireasking them to first give an account of the film they had just seen.They were then asked to answer a number of questions based onwhat they had seen. Most of these were “filler questions” andwere not analysed by the researchers. There was, however, onecritical question which asked…

How fast were the cars going when they******* into each other

The participants were split into five groups, and for each the verb(indicated with *******) indicated a different level of drama.The five verbs were…

Smashed, Collided, Bumped, Hit, Contacted

Results

DiscussionLoftus and Palmer argue that memories are constructed based ontwo types of information: what we actually perceived ashappening at the time and information which is incorporated intoour memories afterwards.

The researchers argue that the latter of these categories can distortour memories. In the case of their experiment, the researchersargue that of one two possible things could be happening:

! Distortion: The verbal label attached to the event by thequestion could have led to the participant cognitivelyamend their memory - i.e. the prompt that the cars"smashed" may lead participants to re-evaluate theirmemories.

! Response-Bias: The participants may not have been sureabout the speed of the car to start for, and therefore mayadjust their answer to fit with the expectations of theresearcher (this is a form of demand characteristic).

Loftus and Palmer (1974): Reconstruction of Automobile Destruction

1. Imagine that you are an eyewitness to an armed robbery.Make a mind-map of the factors which might affect yourmemory and recall of the event. Split your answers intofactors at the time, and those after the event.

2. Evaluate the above sample (remember: the study is aboutmemory!)

Look at the above procedure…

3. What are the dependent and independent variables?

4. What is the experimental design?

5. Write a null and experimental hypothesis for the study.

6. Why do you think that the researchers showed the videos in arandom order for each group.

7. Comment on the ecological validity of the study.

Look at the results table below...

8. What conclusions can we draw?

9. Offer an explanation for these results.

10. It could be argued that the researchers ignored a potentiallyfascinating source of data. What is it and how could it havebeen interesting?

Results of the First ExperimentVerb Mean Speed Estimate

Smashed 40.8

Collided 39.3

Bumped 38.1

Hit 34.0

Contacted 31.8

Results significant at P < .005

AS Level Psychology: Cognitive Psychology: Loftus and Palmer (1974)

www.PsychologyStuff.com7.2

The Second ExperimentIn the first experiment, there is a degree of uncertainty overwhether prompts given by the researcher had led the participantsto alter their memories, or whether it had simply led them to givecertain answers. In the second experiment, the researchers aimedto show that information provided after an event is capable ofdistorting memories.

ParticipantsOnce again, the participants in this study were students at theuniversity of Washington. However, this time 150 participantswere used.

ProcedureParticipants were shown a short film of a multiple car crash -lasting one minute, although the actual action lasted only fourseconds. This time they were split into three different groups:

! The first group were asked "how fast were the cars goingwhen they smashed into each other?"

! The second group were asked "how fast were the cars goingwhen they hit each other?"

! The final group formed a control, and were not asked aquestion about the speed of the cars.

Participants were recalled one week later and asked another seriesof questions about the film. Once again, nine of these questionswere "filler" or "distraction" questions. The critical question was"did you see any broken glass?" (there was no glass in the actualfilm), and appeared randomly in the other questions

FindingsThe findings of the first part of this experiment supported thoseof the previous study, with participants overestimating the speedof the cars when asked how fast they had "smashed" into eachother.

More importantly, interesting results were found in relation to the"broken glass" question - these are summarised in the followinggraph.

DiscussionThe results of this experiment suggest that the labels attached tothe car-crash by the researcher affected the memories of theparticipants - altering their perception of events a week later. Theidea that the cars had "smashed" into each other had ledparticipants to incorporate the notion of broken glass into theirmemories (as "smashed" implies that glass was broken).

Consequently, Loftus and Palmer support the reconstructivememory hypothesis - arguing that information gathered at thetime of an event is modified by data gathered afterwards. Overtime, information from these two sources is integrated to thedegree that it is impossible to separate them - in effect we onlyhave one memory.

Evaluation

! Perhaps the greatest strength of Loftus and Palmer’s experimentis the degree of control over confounding variables. As the studywas lab-based, the researchers could ensure that a range of factors(age of participants, incident viewed, environment, etc).Consequently, they could ensure that these factors did not affectthe respondents answers - and that only the verb-condition wascausing the participants to re-evaluate their memories.

! As an psychological explanation, the reconstructive memoryhypothesis is extremely useful; for instance, in formulatingguidelines in for police questionning of witnesses and suspects.The study has also had real-world implications; based onevidence such as Loftus’, the Devlin Report (1976) recommendedtrial judges be required to instruct juries that it is not safe toconvict on a single eyewitness testimony alone.

" Perhaps the biggest problem in the study is its ecologicalvalidity. Viewing a video of a crash is different to experiencingone in “real life” - for instance, their is much less emotionalinvolvement, which will inevitably affect recall. Furthermore,when watching a real crash, there is much more context - and theparticipants had been cued to watch the video, whilst crashes inreal life a largely unexpected.

" The sample used in the study could also be criticised asparticipants were all students; on one level, this could introduceconfounding variables, as the students may be eager to pleasemore senior faculty members. More importantly, the memorycapacity of students may be systematically different to the generalpopulation - either because they are practised at memorisinginformation, or because they have too much “importantinformation” to remember to waste memory on the “trivial” dataprovided in the car-crash video.

" It should also be noted that some psychologists have criticisedLoftus and Palmer's conclusions. They argue that we have noway of knowing that the participants original memories had beenirretrievably altered by the leading questions. Instead, theysuggest that participants could merely be following thesuggestions of the researcher in both the original round ofquestions and the follow-up questions. In effect, demandcharacteristics could be “carried forward” - as participants haveremembered that they had been asked about the cars "smashing"into each other, they have been prompted to say that they haveseen broken glass in the follow up study.

11. Why did the researchers leave a week gap between the firstpart of this experiment and the second?

12. Why do you think the researchers used "filler" questions?

13. Why did the researchers show a one minute film when thereare only four seconds of "action"?

14. Why might the control group have been used in thisexperiment?

15. With reference to the aims of this experiment, whatconclusions can be drawn from these results?

16. What do these results tell us about the usefulness of controlgroups?

Results of the Second Experiment

05

1015

20253035404550

Smashed Hit Control

Verb Condition

Res

pons

es

YesNo

17. Evaluate the usefulness of Loftus & Palmers findings andconclusion, illustrating with examples.