Reliability of Reliability of one cognitive one cognitive

processprocessEyewitness TestimonyEyewitness Testimony

Elizabeth LoftusElizabeth Loftus

AIM

This aim of this study was to investigate the effect of leading questions on eyewitness accounts and also the effect that leading questions might have on later memory for what happened.

Is eye witness testimony reliable?

Method

2 Lab experiments

Design: Both between subjects 5 groups in experiment 1, 3 groups in experiment 2

Experiment 1 Hypothesis

There will be differences in speed estimates of a car crash dependant on the verb used in the critical question

What would the null hypothesis be?

Experiment 1: How the data was collected

Sample: 45 University students. Mainly young and white. Both sexes.

Situation: Several short clips of traffic accidents from a safety film were shown on a television

Task: Participants were put into 5 different groups depending on which verb they would get in the critical question. They then watched the clips.

After each clip the participants were given a questionnaire asking them to describe what they had seen and then answer the critical question “estimate how fast the cars were going when [hit, smashed, bumped, collided, contacted] each other”

Experimenter recordings: Recorded the estimate of speed in MPH

Critical Question

The five conditions (verbs) were

CONTACTED HIT BUMPED COLLIDED SMASHED

What do you think their findings were?

Experiment 1: Findings

The experiment found that there was a difference between the speed estimates of the 5 groups.

The ‘smashed verb’ created the highest speed estimate in mph which was approximately 40mph

The ‘contacted verb’ created the lowest speed estimate which was approximately 30mph

Experiment 1: Conclusion

The findings suggest that eye witnesses recall of events can be influenced by wording of a question.

The influence can be due to response bias at the time of the question or actual altering of memory permanently. A second experiment is required to answer this question

Look carefully at the scene I’m going to show you.

Did you see any broken glass on the ground at crash scene?

Experiment 2 Hypothesis Participants will more likely falsely recall

broken glass one week after watching footage of a car crash if the verb used in the question is stronger.

Experiment 2: How the data was collected

Participants 150 university students mainly young and white of both genders. Split into 3 groups; group one gets hit verb, group 2 gets smashed verb, group 3 gets no question (control group)

situation: shown 1 minute clip of car accident on television

Task: After the footage the 2 verb groups of participants were asked to describe what they had seen and answer the critical question used in experiment 1. The control group was asked nothing. A week later the participants came back and answered the question ‘did you see any broken glass?’

Experimenter recordings: Recorded speed estimates and whether the participant said yes or no to the question ‘did you see broken glass?’.

Experiment 2 Results

There was a difference between recall of broken glass between the 3 conditions

The ‘smashed verb’ caused the greatest recall of broken glass (approximately 20%)

There was little difference between the control group and the ‘hit verb’ recall (over 90%)

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Experiment 2: Conclusion

The semantics of the question becomes integrated with the memory of the event, thus changing the memory and causing a false memory to be constructed.

What happens after we have witnessed an event can alter our memory of the event.

Evaluation of studies:Limitations of the study All Loftus & Palmer’s participants

were students. Their memories may have been different to other groups of people, because they have to learn lots of things for their studies. This means they may be a biased group.

Limitations of the study Loftus & Palmer’s studies are not true

to life because they are conducted in a lab setting. So for instance, watching video clips of car accidents would lack the emotional impact of seeing an accident for real, and this could affect accuracy of memory. We know that emotion affects memory. This means the findings can’t confidently be

generalised to real life.

Limitations of the study Loftus & Palmer’s findings can’t

confidently be generalised to the whole population, partly because their study lacked ecological validity so it isn’t true to life, and partly because they used a biased sample.

Limitations of the study

Loftus & Palmer’s findings can’t confidently be generalised to the whole population, partly because their study lacked ecological validity so it isn’t true to life, and partly because they used a biased sample.

Strengths of the study In a lab experiment, extraneous variables

are controlled. This means the procedure is replicable, and it means that cause and effect can be linked.

The video clips and the length of time they were seen were controlled so that all participants had the same extraneous variables – only the wording of the critical question varied between participants.

Strengths of the study

The method used is true to life, so the findings can be generalised beyond the research setting to everyday life.

(It is possible that the participants could witness a car crash.)

Strengths of the study

The findings can confidently be generalised to more people than just the participants.

Application toeveryday life

Can be used to explain behaviour that wasn’t previously understood

The findings and conclusion can be used to somehow improve the quality of life in the future.

Loftus & Palmer’s findings can be used to help police develop improved interview techniques that avoid using leading questions, therefore increasing the accuracy of witnesses’ testimonies.Loftus & Palmer’s findings

have helped us understand why it is that eye witnesses often make mistakes when giving evidence.

Improving Loftus & Palmer’s methodAs you will have seen, Loftus & Palmer’s experiments can be criticised in a variety of ways.

1.Your job is to design an improved method for investigating the effect of leading questions on eyewitness testimony. You need to write your suggested method on a piece of A3 paper. The points you must include are:•The method (lab experiment, field experiment, or case study)•The design (independent measures or repeated measures)•The sampling method (opportunity, systematic, volunteer, or random)•The IV•The DV•Possible extraneous variables, and how you will control them•A bullet-pointed, step-by-step procedure

2.Swap your A3 sheet with another group. Evaluate each other’s methods. Use as many evaluative points as you like, but they must be applied to the method, not general.

3.When it’s your turn, your group must describe the other group’s method to the whole class, and explain your evaluation of it. You need to rate their suggested method on a scale of 1 to 5, where 1 = very poor method (lots of errors or bias, possibly unethical) and 5 = excellent method (well controlled and ethical).