Loftus and Palmer (1974) – Eyewitness Testimony

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory.Journal of verbal learning and verbal behavior, 13(5), 585-589.

This is the classic cognitive psychology study which you will look at for your H167 AS OCR Psychology exam. You will also need this study for your OCR H567 A Level Psychology core studies exam.

Background

The theme of the cognitive psychology studies in the H167  exam is memory. This study by Loftus and Palmer (1974) focuses on an applied area of memory: eyewitness testimony. 

In order to best understand this study, it is highly recommended that you first read the following books written by Elizabeth Loftus:

 

 

What is eyewitness testimony?

 

Eyewitness testimony is a form of evidence used in the court systems. It relies on heavily on the memory of the eyewitness (person who saw an event) and until Elizabeth Loftus and colleagues started considering the reliability of memory, the court system assumed that the memory of eyewitnesses was highly accurate. We will see in this study and the further reading, how this might not be the case.

What theory is the research based on?

The research is based upon Barlett’s schema theory, which suggests that memories can be influenced by the previous knowledge of a person. For example, if I see something flying through the air, which is blue and quite small, but I can’t quite see what it is, and then someone asks me what I saw, I might reply it was a blue bird. In this example, I didn’t know exactly what I saw, but I used my previous knowledge to make a guess about what I saw. This is the idea what Loftus and Palmer’s research was based on: our previous knowledge knowledge influences our memory.

In the previous example about the blue bird, there was an interpretation of the information of the blue flying thing and it was recorded in memory as blue bird.

This example served to demonstrate some of the ways in which memory operates: by constructing and reconstructing information, based on what was observed and the previous information which we hold.

Aim of the Experiment

The aim of Loftus and Palmer’s (1974) study was to investigate the ways in which memory can be influenced by post-event information. 

Method and Design

Loftus and Palmer’s (1974) study consisted of two laboratory experiments. Both experiments used an independent measures design, with the participant’s only taking part in a single condition.

Experiment 1

Independent variable: verb used in the critical question: “About how fast were the cars going when they ‘verb’ into each other?”

There were five different verbs used, all of which had different levels of intensity.

  1. Smashed
  2. Collided
  3. Bumped
  4. Hit
  5. Contacted

Dependent Variable: the participants’ estimate of the speed of the cars when the they collided.

Experiment 2

Independent variable: verb used in the question: “How fast were the cars going when they ‘verb’ each other?”

There were three conditions:

  1. Hit
  2. Smashed
  3. Control group (this group was not questioned about the speed of the cars).

Dependent variable: Participants’ answer to the critical question: ‘Did you see any broken glass?’ (either: yes or no).

Sample and Sampling Method

Experiment 1

The sample in experiment 1 consisted of 45 undergraduate psychology students from the University of Washington.

Experiment 2 

The sample in experiment 2 consisted of 150 undergraduate psychology students from the University of Washington.

Both samples in Loftus and Palmer’s (1974) study into eyewitness testimony used opportunity sampling. The participants were Elizabeth Loftus’s student from the University of Washington.

Procedure

Experiment 1

All 45 participants were shown the same seven film clips of different traffic accidents which were originally made as part of a driver safety film.

After each clip participants were given a questionnaire which asked them firstly to describe the accident and then answer a series of questions about the accident.

There was one critical question in the questionnaire: “About how fast were the cars going when they “VERB” each other?”

One group was given this question while the other four groups were given the verbs “smashed’, ‘collided’, ‘contacted’ or ‘bumped’, instead of ‘hit’.

Experiment 2

All 150 participants were shown a one-minute video. During the video a four-second there was a 4-second multiple car crash.

They were then given a questionnaire which asked them to describe the accident and answer a set of questions about the incident.

There was a critical question about speed: – One group of 50 participants was asked, “About how fast were the cars going when they smashed into each other?” – Another group of 50 was asked, “About how fast were the cars going when they hit each other?” – The third group of 50 did not have a question about vehicular speed.

One week later, all participants, without seeing the film again, completed another questionnaire about the accident which contained the further critical question, “Did you see any broken glass – Yes/No?” There had been no broken glass in the original film.

Results

Experiment 1

The results in this experiment are the speed estimates of the participants after they had watched the video with the car crash and had been asked the critical question with one of the five verbs. The more inaccurate the participants’ estimate of the speed of the crash, the greater the memory distortion.

Here are the mean speed estimates for each of the five different verbs:

Smashed  40.5 mph

Collided 39.3 mph

Bumped 38.1 mph

Hit 34.0 mph

Contacted 31.8 mph

Loftus and Palmer (1974) suggest two possible reasons for these results. Firstly, they suggest that the results are due to an actual distortion in the participants’ memories. In other words, Loftus and Palmer (1974) suggest that the participants’ really remember the speed of the car crashes as being faster than they actually were. Secondly, Loftus and Palmer (1974) suggest that the results could in fact be due to a response bias, that is to say, the participant adjusted their estimate of the speed based upon the verb used and did not experience an actual distortion in their memory.

Experiment 2 

The results of experiment 2 are participants’ recollections of seeing broken glass in the video of the car crash. In the video, broken glass was not present. Therefore, any participant who recalled seeing broken glass may have had their memory distorted by the post-event information, that is, the verb used. If there were significantly more participants who recalled seeing broken glass in one condition compared with another, then we may determine that the results are due to the manipulation in the experiment or confounding variables.

Participants who saw broken glass: 

Smashed:  16

Hit: 7

Control: 6  

Participants who did not see broken glass:

Smashed: 34

Hit: 43

Control: 44 

These results are significant, which suggests that the experimenters manipulation did in fact cause the results.

Loftus and Palmer (1974) suggest there are two types of information which create memories. Information of an event and information after an event. They suggest these two sources of information work together to create the memory, which is what they suggest happened in their second experiment to lead some participants to believe that there was broken glass.

Conclusions

There are two kinds of information which contribute to the creation of memories: information gained during an event and information gained after the event. These two types of information may lead to a distortion of memories and even the creation of false ones. For example, seeing glass when there was in fact none.

Memory is not like a tape recorder. Human memory is susceptible to change and decay.

Small changes in information can cause distortions in memory.

Loftus and Palmer (1974) Evaluation

– Loftus and Palmer (1974) only consider two kinds of information which create memories: information about the event and information after the event. This may be an incomplete account of the information that goes in to creating memories, as they have not considered pre-event information, which may affect how individuals process the information of the event and the information after an event.

+ Laboratory study – the laboratory environment allows the researchers to control many aspects of the environment and experience of the participant, which reduces confounding variables and thus increases the internal validity of the study

– Ecological validity – the ecological validity in this study may be considered low because the study utilised laboratory experiments, which involved the participants watching videos of car crashes. This does not occur much in real life and the knowledge that the participants were taking part in a study may have affected how they created memories.

+ Application – Despite the low ecological validity in this study, we may find some ecological validity from the task which the participants were required to complete. They were asked, albeit with a questionnaire, about an event they had witnessed. This is very similar to how the police and court system addresses eyewitness testimony and thus this study has great applicablity for the criminal justice system, as it advises against the use of leading questions.

References

Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory.Journal of verbal learning and verbal behavior, 13(5), 585-589.

Further Reading

 

Eyewitness Testimony

The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse

Psych Yogi’s Top Ten Psychology Revision Tips for the A* Student

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Loftus and Palmer (1974) - Eyewitness Testimony
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Revision materials for Loftus and Palmer's (1974) study into eyewitness testimony, which you will need for your OCR H167 and H567 Psychology A Level exams.
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