Summary
- Experiment: Loftus and Palmer (1974) showed participants car crash videos and asked them to estimate speeds using different verbs like “hit” or “smashed.”
- Finding: When verbs like “smashed” were used instead of “hit,” people reported higher speeds and even remembered seeing broken glass that wasn’t there.
- Implication: The study revealed that memory is reconstructive, meaning it can be shaped and altered by the wording of questions.
- Application: This research highlighted the unreliability of eyewitness testimony and changed how police and courts handle questioning.
- Criticism: Critics argue the lab setting and use of video clips lack ecological validity, raising questions about how well the results apply to real-life events.
Psychologist Elizabeth Loftus has been particularly concerned with how subsequent information can affect an eyewitness’s account of an event.
Her main focus has been on the influence of (mis)leading information regarding both visual imagery and wording of questions concerning eyewitness testimony.
A leading question is a question that suggests what answer is desired or leads to the desired answer.
Loftus’ findings indicate that memory for an event that has been witnessed is highly flexible. If someone is exposed to new information during the interval between witnessing the event and recalling it, this new information may have marked effects on what they recall. The original memory can be modified, changed or supplemented.
The fact that eyewitness testimony can be unreliable and influenced by leading questions is illustrated by the classic psychology study by Loftus and Palmer (1974), Reconstruction of Automobile Destruction, described below.
Aim
To test their hypothesis that the language used in eyewitness testimony can alter memory.
Thus, they aimed to show that leading questions could distort eyewitness testimony accounts and so have a confabulating effect, as the account would become distorted by cues provided in the question.
To test this, Loftus and Palmer (1974) asked people to estimate the speed of motor vehicles using different forms of questions.
Estimating vehicle speed is something people are generally poor at, so they may be more open to suggestions.
Experiment One: 5 verbs in leading questions
Procedure
Forty-five American students from the University of Washington formed an opportunity sample.
This was a laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design).
Seven short films of traffic accidents, taken from driver’s education and police training videos, were shown to participants.
The clips lasted between 5 and 30 seconds, with some staged crashes filmed at real speeds of 20, 30, or 40 mph.
Each group saw the films in a different order to avoid order effects, and the whole session lasted about 90 minutes.
After each film, participants first gave a free account of what they saw, then answered the critical question.
“About how fast were the cars going when they (smashed / collided / bumped / hit / contacted) each other?”
Thus, the IV was the verb of the question, and the DV was the speed reported by the participants.
Findings
The estimated speed was strongly influenced by the verb used in the question.
The verb implied information about the speed, which systematically affected the participants’ memory of the accident.
“Smashed” produced the highest average estimate (about 40.8 mph), followed by “collided” (39.3 mph), “bumped” (38.1 mph), “hit” (34 mph), and “contacted” (31.8 mph).
In reality, the filmed crashes were staged at 20–40 mph, showing that participants greatly overestimated the speeds. Statistical analysis confirmed the effect of wording was significant.
Loftus and Palmer suggested this might be due either to response bias or to the verb actually altering the memory of the event, making it seem more severe.
Conclusion
The results show that the verb conveyed an impression of the speed the car was traveling and this altered the participants” perceptions.
This suggests that eyewitness testimony can be biased simply by the way questions are worded.
Loftus and Palmer proposed two explanations:
- Response-bias factors: The misleading information provided may have influenced the answer a person gave (a “response-bias”), but didn’t actually lead to a false memory of the event. For example, the different speed estimates occur because the critical word (e.g., “smash” or “hit”) influences or biases a person’s response.
- The memory representation is altered: The critical verb changes a person’s perception of the accident—some critical words would lead someone to perceive the accident as more serious. This perception is then stored in a person’s memory of the event.
To test this, Loftus and Palmer carried out a second experiment, designed to see whether leading questions simply bias responses or actually alter memory.
Experiment Two: The broken glass manipulation
In a second experiment, Loftus and Palmer tested whether leading questions simply bias responses or actually alter memory.
Procedure
150 students were shown a one-minute film which featured a car driving through the countryside followed by four seconds of a multiple traffic accident.
Afterward, the students were questioned about the film. The independent variable was the type of question asked.
- 50 participants were asked “how fast were the car going when they hit each other?”,
- 50 participants were asked, “How fast were the cars going when they smashed each other?”
- the remaining 50 participants were not asked a question about the car’s speed (i.e., the control group).
One week later, the dependent variable was measured – without seeing the film again, they answered ten questions, one of which was a critical one randomly placed in the list:
“Did you see any broken glass? Yes or no?”
There was no broken glass in the original film.
Findings
Participants were asked how fast the cars were going when they smashed were more likely to report seeing broken glass.
Conclusion
The results suggest that leading questions do more than just bias people’s answers in the moment — they can actually change how an event is remembered.
Loftus and Palmer argued that memory is reconstructive: it combines details from the original event with information introduced afterward.
Over time, these sources merge so that people cannot tell them apart, leaving a single memory that may include false details.
The addition of false details to a memory of an event is referred to as confabulation. This has important implications for the questions used in police interviews of eyewitnesses.
Strengths
High level of control
Perhaps the greatest strength of Loftus and Palmer’s experiment is the degree of control over confounding variables.
As the study was 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 affect the respondents’ answers and that only the verb condition was causing the participants to reevaluate their memories.
Practical Implications
The reconstructive memory hypothesis is extremely useful as a psychological explanation, for instance, in formulating guidelines for police questioning witnesses and suspects.
The conclusion that leading questions can affect memory has important implications for interviewing witnesses, both by police immediately or soon after an event and also by lawyers in court sometime later.
Interviewers should avoid leading questions and be careful to word questions in a way that does not suggest an answer to the person they are interviewing.
The study also had real-world implications; based on evidence such as Loftus’s, the Devlin Report (1976) recommended that trial judges instruct juries that it is not safe to convict on a single eyewitness testimony alone.
Replicable
A strength of the study is it’s easy to replicate (i.e. copy). This is because the method was a laboratory experiment which followed a standardized procedure.
Weaknesses
Low ecological validity
One limitation of the research is that it lacked mundane realism / ecological validity. Participants viewed video clips rather than being present at a real-life accident.
As the video clip does not have the same emotional impact as witnessing a real-life accident, the participants would be less likely to pay attention and less motivated to be accurate in their judgments.
Furthermore, watching a real crash provides much more context—the participants were cued to watch the video, whereas crashes in real life are largely unexpected.
In an experiment, you may expect to be asked questions about what you are watching, which may make you attend the film differently.
In real life, the answers you give may have consequences, which may put pressure on the witness.
Overall, we can probably conclude that this laboratory experiment had low ecological validity and thus may not tell us very much about how people’s memories are affected by leading questions in real life.
Conflicting research
A study conducted by Yuille and Cutshall (1986) conflicts with the findings of this study. They found that misleading information did not alter the memory of people who had witnessed a real armed robbery.
This implies that misleading information may have a greater influence in the lab rather and that Loftus and Palmer’s study may have lacked ecological validity.
He was especially interested in the characteristics of people whom he considered to have achieved their potential as individuals.
Biased Sample
A further problem with the study was the use of students as participants. Students are not representative of the general population in several ways.
Differences between students and the broader population, such as age, memory abilities, learning habits, driving experience, and susceptibility to demand characteristics, could make it difficult to generalize the findings.
Importantly, they may be less experienced drivers and, therefore, less confident in their ability to estimate speeds. This may have influenced them to be more swayed by the verb in the question.
Demand Characteristics
Participants know they are in a laboratory experiment, which will affect their behavior in several ways.
They will be looking for clues on how to behave (demand characteristics), and they will usually want to help the experimenters by giving them the results they think they want.
We cannot know that the leading questions had irretrievably altered the participants’ original memories.
Instead, participants could merely be following the researcher’s suggestions in both the original round of questions and the follow-up questions.
In effect, demand characteristics could be “carried forward” – as participants remembered being asked about the cars “smashing” into each other, they were prompted to say that they had seen broken glass in the follow-up study.
Independent Learning Tasks
- Draw a table showing the results of experiment one and draw a bar chart to show the results of experiment two.
- Read the original article of the study.
- Conduct your own study repeating one of the experiments by Loftus and Palmer.
- Use photographs (or video clips) of car accidents and write a set of questions, one of which will be the critical question.
- Test one group of participants using the “smashed” condition and the other group with the “hit” condition.
- Calculate the mean, median and mode speed estimates for both the “smashed” and “hit” conditions. Illustrate your results in either a table or graph.
Learning Check (1)
- Write an experimental hypothesis for experiment 1. Make sure it is clearly operationalized and include the independent and dependent variables.
- Why was it a good idea to ask 10 questions rather than just asking the critical question alone?
- Why was each group of participants shown the 7 video clips (of car accidents) in a different order?
- Outline the possible sampling technique that may have been used in this study.
- The participants knew they were taking part in a psychology experiment. How do you think this may have effected their behavior?
- Can you think of a way that this problem might of been overcome?
Learning Check (2)
- Write a null hypothesis for experiment 2. Make sure it is clearly operationalized and include the independent and dependent variables.
- What is a “control group”, and why is it necessary?
- What is an “experimental” group?
- Outline one difference between the responses given between the two experimental groups.
- Outline the quantitative measure used in this study.
References
Devlin Committee Report: Report of the Committee on Evidence of Identification in Criminal Cases, 1976 Cmnd 338 134/135, 42
Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of auto-mobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal behavior, 13, 585-589.
Yuille, J. C., & Cutshall, J. L. (1986). A case study of eyewitness memory of a crime. Journal of Applied Psychology, 71(2), 291.
