Loftus and Palmer Car Crash Experiment

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.

Verb	Mean Speed Estimate (mph)
Smashed (or “smashed into”)	40.5 – 40.8
Collided	39.3
Bumped	38.1
Hit	34.0
Contacted	31.8

“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.

Conclusion

These results illustrate how the emotional intensity of the verb directly influenced the participants’ estimations of the vehicles’ speed, with more intense verbs like “smashed” yielding significantly higher speed estimates than less intense verbs like “contacted”.

This suggests that eyewitness testimony can be biased simply by the way questions are worded.

Loftus and Palmer proposed two explanations:

1. 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.
2. 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.

The researchers found that the emotional intensity of the verb used in the initial questioning significantly influenced the probability that participants would falsely report seeing broken glass.

The results were as follows:

In the “smashed” condition, 32% of the participants (16 out of 50) incorrectly reported seeing broken glass.

In the “hit” condition, only 14% of the participants (7 out of 50) reported seeing broken glass.

In the control condition (who had not been asked about the speed), only 12% reported seeing broken glass.

Conclusion

The findings of Experiment 2 were critical for understanding how human memory operates.

Loftus and Palmer had to differentiate between two potential explanations for why the leading verb influenced speed estimates: a simple response bias (where a participant is unsure and uses the verb as a cue to guess) versus a genuine change in the memory representation.

Because the study demonstrated that a high-intensity verb could cause participants to vividly recall details that never actually occurred, the researchers concluded that the response bias explanation should be rejected in favor of genuine memory change.

The results strongly support the memory-as-reconstruction explanation, which posits that memory is not a passive recording of an event, but an active process.

Specifically, memory for a complex event is formed from two integrated sources: information encoded during the original perception of the event, and external post-event information provided afterward. Over time, these two sources blend together, making individuals unable to tell them apart.

Furthermore, these findings are highly consistent with schema theory. The intensely evocative verb “smashed” likely activated a specific cognitive schema for severe car accidents, which typically carry the expectation of shattered glass.

As a result, the witnesses’ fragile memories were systematically distorted, and they reconstructed the scene to include the broken glass that fit their activated schema, proving that even minor wording changes in a single question can permanently alter a person’s recollection of an event.

Confabulation

In cognitive psychology, confabulation is the process by which a person unintentionally introduces untrue elements into their recall of a past event, often to fill in missing information or “gaps” in their memory.

Confabulation is not a deliberate lie or an attempt to deceive; rather, it is a natural characteristic of how human memory reconstructs the past.

While the term is sometimes used to describe severe memory disorders (such as Korsakoff’s syndrome, where amnesic patients routinely guess to fill in memory blanks), in the context of Elizabeth Loftus and John Palmer’s research, it refers to the everyday memory errors made by eyewitnesses.

Confabulation is the exact mechanism that explains the results of their second experiment. Participants who were asked how fast the cars were going when they “smashed” into each other were significantly more likely to falsely report seeing broken glass a week later, even though no glass was present in the film.

Psychologists differentiate between two related memory errors that occurred here:

• Distortion: Changing actual information to fit an existing mental framework (schema).
• Confabulation: Completely filling in missing information (gaps) through the use of a schema.

Because human memory is not a passive video recording, it relies on an active process of reconstruction. If a witness misses details because they were distracted or frightened, the brain naturally infers what must have happened based on their existing schemas (mental expectations) of similar events.

When Loftus and Palmer used the emotionally intense leading verb “smashed,” it activated the participants’ schema for a severe car accident.

Because severe accidents typically involve shattered glass, the participants’ brains confabulated the broken glass to fill the gaps in their visual memory, successfully making the memory feel complete and logical.

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

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.

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.

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.

Conflicting research

Real-world eyewitness testimony exhibits remarkable resistance to misleading post-event information over extended periods.

This finding directly refutes laboratory-based claims regarding the fragility of human memory.

When individuals experience high-stress, naturalistic events, their cognitive retention behaves differently. Because artificial laboratory settings lack emotional weight, they fail to capture authentic psychological phenomena.

Yuille and Cutshall (1986)

• Aim: To assess the accuracy of eyewitness accounts over time when subjected to misleading post-event information within a naturalistic setting.

• Procedure: Thirteen witnesses to a real-life armed robbery in Vancouver were interviewed four to five months after the incident. These research interviews were subsequently compared against original police reports. Two misleading questions regarding non-existent details, including a broken headlight, were deliberately embedded into the interview protocol.

• Findings: Misleading questions had virtually no distorting effect on the participants’ recall accuracy. High levels of detail were correctly retained by all 13 witnesses. Furthermore, participants who experienced the highest stress levels demonstrated the greatest accuracy.

• Conclusions: Reconstructive memory errors may be artifacts (artificial products of a specific experimental environment) rather than true reflections of cognition. Real-world trauma can trigger flashbulb memories, which are vivid, highly detailed, and permanent recollections of emotionally shocking events. Consequently, original memory traces remain stable despite external pressure.

Conflicting Results and Implications:

• Immunity to Misleading Information: In direct contradiction to Loftus and Palmer’s findings, the use of misleading questions had virtually no effect on the witnesses’ recall.
• High Accuracy over Time: Despite the passage of several months and the intentional presentation of false post-event information, the witnesses accurately recalled a massive amount of detail, and their recollections very closely matched their original police reports.
• Emotion Enhances Memory: Loftus and Palmer’s laboratory studies often lacked the severe emotional weight of a real crime. Yuille and Cutshall found that the witnesses who were most deeply distressed by the violent incident were actually the most accurate.
• Theoretical Challenge: These findings suggest that reconstructive memory—where misleading information seamlessly distorts the original memory—might be an artifact found primarily in the artificial conditions of laboratory experiments. In highly naturalistic settings involving strong emotional reactions, an entirely separate memory mechanism known as flashbulb memory may be activated, deeply imprinting the event and overriding the reconstructive memory distortions seen in Loftus and Palmer’s work.

McCloskey and Zaragoza (1985)

In their second experiment, Loftus and Palmer concluded that misleading questions cause a genuine memory change, meaning the original memory is overwritten, altered, or destroyed.

McCloskey and Zaragoza (1985) directly conflicted with this conclusion, proposing instead that Loftus and Palmer’s results were merely a product of response bias.

• Aim: To determine whether misleading post-event information permanently alters original memory traces or simply induces a response bias.

• Procedure: Participants were shown a slide sequence of a maintenance man stealing money and a calculator from an office. In one slide, a specific tool, a hammer, was clearly displayed. Later, a text narrative containing misleading information was read by the participants. This text falsely stated that the tool was a wrench. Finally, a modified forced-choice recognition test was administered to the subjects. Crucially, participants were asked to choose between the original hammer and a completely new tool, a screwdriver.

• Findings: The correct item was selected by 66% of the misled participants. Similarly, the correct item was chosen by 69% of the control group. No significant performance difference was found between these two experimental groups.

• Conclusions: Misleading post-event narratives do not alter or erase the original visual memory trace. If the original memory had been destroyed, participants would have guessed randomly. Instead, high retention rates demonstrate that original memories remain intact and fully accessible. Errors in previous studies reflect response bias rather than genuine memory impairment.

Conflicting Results and Implications:

• Original Memories Remain Intact: When the misleading information (wrench) was not an option on the test, participants who had been exposed to the misleading narrative performed just as well (66% correct) as the control group who received no misleading narrative at all (69% correct).
• Theoretical Challenge: McCloskey and Zaragoza argued that if the original visual memory of the hammer had truly been overwritten or destroyed by the verbal narrative (as Loftus theorized), participants would have been forced to guess randomly between the hammer and the screwdriver. Because participants still successfully chose the hammer when the wrench was removed as an option, the researchers concluded that the misleading information did not alter or distort the original memory trace.
• Response Bias over Memory Impairment: They concluded that the errors seen in Loftus’s original studies occurred because some participants had simply forgotten the original detail and used the narrative to fill in the gaps, or they merely guessed the misleading option because they thought it was what the experimenter wanted. This indicates that eyewitnesses are susceptible to response bias, but their actual memories are not fundamentally erased or impaired by post-event information.

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.

McCloskey, M., & Zaragoza, M. (1985). Misleading postevent information and memory for recent events: Misinformation effect or memory impairment? Journal of Experimental Psychology: General, 114(1), 1–16.

Yuille, J. C., & Cutshall, J. L. (1986). A case study of eyewitness memory of a crime. Journal of Applied Psychology, 71(2), 291.