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Testing the Accuracy of Eyewitness Testimony

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability Readily available
Cost Very Low (under $20)
Safety No issues

Abstract

Think back to the last time you went to the grocery store. How well can you describe the person who was ahead of you in the check-out line? How many details do you remember about the person? How accurate do you think your memory is? Here is a project to investigate the accuracy of people's observations during everyday life.

Objective

The purpose of this project is to determine whether eyewitness reports are reliable enough to be used as substantial evidence in criminal convictions, by examining whether gender, distance from subject, and delay in recollection time affect the accuracy of reporting.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

The idea for this project is from:

Cite This Page

MLA Style

Science Buddies Staff. "Testing the Accuracy of Eyewitness Testimony" Science Buddies. Science Buddies, 30 June 2014. Web. 19 Aug. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBeh_p014.shtml?from=Blog>

APA Style

Science Buddies Staff. (2014, June 30). Testing the Accuracy of Eyewitness Testimony. Retrieved August 19, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBeh_p014.shtml?from=Blog

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Last edit date: 2014-06-30

Introduction

Eyewitness accounts are continuously put into question in the court room. By studying how memory works and what factors influence what we remember, we can try to determine how credible eyewitness accounts are and if they are an accurate source of evidence in crimes.

Psychologists typically divide the process of remembering into three stages: encoding, storage, and retrieval. Encoding encompasses the initial perception of the event. Storage is making a lasting record of the perception. Retrieval is recalling the event in response to some cue or query. As you will see in your background research (and perhaps in your own experiment), the process of recall is not like replaying a video disc. Many factors can influence how events are recalled, including the time that has elapsed between storage and retrieval. See the Variations section for other possible avenues of exploration.

In this project, you will compare the accuracy of eyewitness accounts of an event when subjects are questioned immediately after the event vs. one day later. This project requires staging an event (it can be as simple as having a visitor interrupt a class to ask the teacher a question), and then conducting a written survey to measure how accurately your eyewitnesses recall the event (e.g., the appearance of the visitor, the sequence of the interaction with the teacher, etc.). You will have to prepare the survey, and analyze the results.

Refer to the Science Buddies resource, Designing a Question-Based Study, for guidance in designing your survey. The Science Buddies resource, How Many Survey Participants Do I Need?, will show you how to figure out how many respondents you need to recruit in order to achieve your desired level of confidence that your results are representative of the total population.

There are special considerations when designing an experiment involving human subjects (the eyewitnesses, in this project). ISEF-affiliated fairs often require an Informed Consent Form for every participant who is questioned. In all cases, the experimental design must be approved by a scientific review board prior to the commencement of experiments or surveys. Please refer to the ISEF rules for additional important requirements for studies involving human subjects: http://www.sciserv.org/isef/document/.

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts:

  • encoding,
  • storage,
  • retrieval,
  • forgetting curve,
  • false memory,
  • misinformation effect.

Questions

  • What are the differences between short-term memory, long-term memory, and working memory?
  • What are some of the possible effects that questioning can have on memory recall?

Bibliography

  • The Wikipedia article on human memory is a good place to start, and also has many suggestions for further reading:
    Wikipedia contributors, 2006. "Human Memory," Wikipedia, The Free Encylopedia [accessed July 27, 2006] http://en.wikipedia.org/w/index.php?title=Memory&oldid=66176857.
  • This article from the UCSD Department of Psychology is a good introduction and also offers a good selection of sources for further study:
    Flowe, H.D., 1996. "Eyewitness Identification: Cognitive Aspects," Department of Psychology, University of California, San Diego [accessed July 27, 2006] http://psy.ucsd.edu/~hflowe/eyepsych.htm.
  • Campbell, T.W., 2005. "Issues in Forensic Psychology: Eyewitness Recall," [accessed July 27, 2006] http://www.campsych.com/eyewitness.htm.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • sample group to serve as witnesses,
  • a person unfamiliar to the sample group to act out scenario,
  • surveys,
  • envelopes.
  • Optional: video camera and tripod to record the scenario.

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Experimental Procedure

Note: There are special considerations when designing an experiment involving human subjects. ISEF-affiliated fairs often require an Informed Consent Form for every participant who is questioned. You will also need to obtain advance permission from the teacher(s) whose classes are involved in this project. In all cases, the experimental design must be approved by the fair's scientific review committee (SRC) prior to the commencement of experiments or surveys. Please refer to the ISEF rules for additional important requirements for studies involving human subjects: http://www.sciserv.org/isef/document/.

Staging the Event

  1. Arrange to have a person (who is unfamiliar to the class) knock on the door, enter the class, interact with the teacher briefly, and then leave. You can think of your own scenarios, but some possible ideas are:
    1. flower delivery,
    2. asking a question,
    3. express package delivery.
  2. The survey should probe how accurately the students remember the event. Here are some ideas for questions to get you started (assuming a delivery person scenario):
    1. At what time did the delivery person enter the room?
    2. How long was the delivery person in the room?
    3. What did the delivery person bring?
    4. Did the delivery person leave anything behind?
    5. Did the delivery person take anything from the room?
    6. What did the delivery person say to the teacher?
    7. Please describe the delivery person, including as much of the following information as you can accurately remember: height, weight, skin color, hair color, eye color, clothing, distinguishing features.
    8. Note: the students should also fill out the time and date that the survey was completed, and the surveys should be anonymous.
  3. After the visitor leaves, give the students in the class sealed envelopes containing the survey. Half of the envelopes (and surveys) should be marked "complete now" and half should be marked "complete tomorrow."
  4. Have the students return the completed surveys to the teacher.

Analyzing the Results

  1. If you record the event, use your recording to double-check your own recall of the event before grading the surveys!
  2. For each component of the description, analyze the percentage of correct responses. Which components of the description were correctly observed most often? Which were correctly observed least often? Does the "average" response provide an accurate description of the subject?
  3. For numeric data, calculate the average, median, and standard deviation of the responses. A histogram showing the distribution of responses would be a good way to examine this data. How close is the average response to the actual number?
  4. For analyzing eyewitness accuracy of what was said, one idea would be to devise a rating scale for responses, perhaps something like this:
    1. 0 = no response
    2. 1 = inaccurate wording which changed the sense of what was said,
    3. 2 = accurately described sense of what was said, but not exact wording,
    4. 3 = accurately described wording
  5. The students who participate in the experiment might be interested to see the recording after they have completed their surveys. How many were surprised to find that they had made mistakes?

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Variations

  • Have test subjects view a scene from a film and then ask questions about recall of the scene. For example, you could select a scene depicting an automobile accident.
    • Test the effect of misleading questions on later recall. Separate your "witnesses" into two groups. For one group, ask a question about something that was not in the scene (e.g., a building or landmark not in the scene, or a character that was not present). Survey both groups about the accident scene at a later time (e.g., between 1–7 days later). Does the group exposed to the misleading question incorporate inaccurate information into their recall of the event? If so, how prevalent is the effect?
    • Test the effect of wording on immediate recall. Separate your "witnesses" into two groups. For one group, ask a question such as, "How fast were the cars moving when they smashed?" For the second group, change the wording to something like, "How fast were the cars moving when they collided?" Does the average speed reported by each group differ?
    • Test the effect of distractions during screening on recall. Separate your "witnesses" into two groups. Give each group identical instructions: they are going to watch a scene from a movie, and that they should try to remember every detail about the scene. For one group, the movie is shown uninterrupted. For the other group, have someone enter the room during the screening (e.g., to quietly bring a note to the teacher's desk and then leave the room). How do the two groups differ in the accuracy of their recall? Are they equally accurate for the portion of the scene before the distracting event occurred? During the distracting event? Following the distracting event?
  • Design an experiment to test the effect of longer delays on recall.
  • For another experiment related to forensic psychology, see the Science Buddies project Testing for Bias in a Photo Lineup.

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