Effects of MPI and Gender 1 Running Head: EFFECTS OF MPI AND GENDER Effects of Misleading Postevent Information and Gender on Eyewitness Memory Brittany Hale and Heather Hays San Jose State University
Effects of MPI and Gender 2 Abstract It is important to research the effect that MPI and gender have on eyewitness memory in order to make sure that innocent people are not incarcerated. Research has shown that misleading postevent information (MPI) has a significant affect on eyewitness memory. The research on gender is mixed between results that males have a more accurate memory and results that females have a more accurate memory. A total of 57 participants (27 males, 30 females) viewed two separate short video clips of a crime being committed, each with a length under 2 min long. After each clip, participants were either provided with an MPI summary or no MPI summary. All participants completed a detailed questionnaire pertaining to the details of each video clip. The experiment resulted in a significant effect of MPI on eyewitness memory. Gender produced a mixed result with males performing better on one video and females performing better on the other video. The results obtained in the current study reflected the outcome predicted by previous research. Further research should examine the reason for the mixed results on the impact of gender.
Effects of MPI and Gender 3 Effects of Misleading Postevent Information and Gender on Eyewitness Memory Today, in America, eyewitness testimony is used as reliable evidence in many criminal cases. It is often assumed that if a person witnesses a crime committed, they will be able to accurately remember and relay the events that took place. Each year thousands of people are called upon to serve their civic duty as a juror. Often the only compelling evidence these jurors are provided with are testimonies based on eyewitness memory. Eyewitness memory, however, is not perfect and can be affected by many factors. It can deteriorate over time, and it also can grow, being reconstructed as new information is presented (Loftus, E., 2005). With the rise of DNA evidence technology, much focus has been on exonerating those falsely convicted of a crime. By 2007, over 200 convictions had been overturned by DNA evidence, and the previously convicted exonerated. Eyewitness misidentifications played a role in77% of these overturned convictions (www.innocenceproject.org). There are many psychologists whose main focus is examining the actual reliability of eyewitness memory and consequentially the testimony given. In order for our justice system to work properly, extensive research on the accuracy of eyewitness memory and the factors that may affect it is necessary. A better understanding of how eyewitness memory works and may be affected will lead to a more efficient procedure of gathering eyewitness information and using that information as credible evidence in trial. Many people s freedoms and lives are at stake. Episodic memory is a type of explicit or conscious long-term memory. Episodic memory refers to specific events and their context of time and place. The episodic memory is responsible for remembering personal experiences that have taken place at any time in the individual s past (Tulving, 2002). It can include what was seen on a billboard a few minutes ago as well as a childhood memory from years prior. Eyewitness memory is a type of episodic
Effects of MPI and Gender 4 memory, describing the specific events viewed by a person. Eyewitness memory is often discussed in the context of the criminal justice system. Often witnesses will be asked to recall certain events that they viewed pertaining to a crime. The accuracy of these memories can affect the testimony given and ultimately the course of the investigation. Effects of Misleading Postevent Information and Gender Misleading Postevent Information Exposure to misleading postevent information (MPI) has been known to affect eyewitness memory (Eakin, Schreiber, & Sergent-Marshall, 2003). MPI is post-event information a witness receives that is contradictory to the actual event witnessed. This can occur through interactions with other witnesses who may remember events differently or through leading questions posed by authority figures (Roper & Shewan, 2002). Eyewitnesses tend to remember the misleading information presented to them instead of the actual event that they witnessed. This is the misinformation effect (Tomes & Katz, 1997). Empirical evidence from several articles displays the effect of misinformation on the memory of an eyewitness. Several participants in a recent study watched a video depicting an alleged crime being committed. Some participants received MPI from a confederate falsely depicting the crime as a car theft, while others, in a control group, did not. When asked the nature of the crime, 0% of participants reported a stolen car as the crime immediately after the video. After receiving MPI from the confederate 43% of the participants reported a stolen car as the crime and 8% of the control group, who did not receive MPI, reported a stolen car as the crime. These reflect the enormous effect MPI can have on eyewitness memory (Mudd & Govern, 2004).
Effects of MPI and Gender 5 Gender Gender is another factor that may affect eyewitness memory. Currently, there is much research being conducted on the effects of gender on eyewitness memory, however the results yielded are conflicting. Some studies have shown that females are able to recall details of a witnessed event more accurately than males, whereas other studies have shown that males are superior in the recall of events (Loftus, Levidow, & Duensing,1992; Cunningham & Bringmann, 1986). Existing studies on gender and eyewitness memory appear to be split evenly between which gender performs better when asked to accurately recall an event. There seems to be a difference in the types of information males and females focus on and remember (Maitland, Herlitz, Nyberg, Lars, & Nilsson, 2004). Females generally will remember fine details better than males, whereas males will generally remember more logical and spatial details better (Loftus et al., 1992). Misleading Postevent Information and Gender Individually, the two factors play a large role in affecting the memory of an eyewitness; however there is a significant lack of information regarding the interaction between the two. Some available research suggests that females tend to respond more accurately than males to questions concerning the witnessed event, whereas other research suggests that females may be more susceptible to MPI than males (Lipton, 1977; Tomes & Katz, 1997). Research has shown that both MPI and gender can have an affect on an eyewitness recollection of an event, however very little research exists on the affect that the interaction of both factors may have on eyewitness memory. While most studies have focused on either one factor or the other, this study will attempt to bridge the gap and concentrate on the interaction between the two and sets to provide insight as to how accurate eyewitness memories actually can
Effects of MPI and Gender 6 be, depending on the gender of the person involved and the validity of the information they have been exposed to after the fact. Method Participants The participants consisted of 57 consenting adults living in the San Francisco Bay Area. Participants were from a convenience sample of 27 males and 30 females, between the ages of 18 and 54. A set time and location were provided by the experimenters. Materials The materials consisted of two video clips, basic addition and subtraction worksheets to act as a clearing task, two detailed questionnaires pertaining to the details of each video clip viewed by the participants, and a written summary of the details of each video clips containing MPI, and a background questionnaire. One video clip was taken from an episode of the TV series NCIS and the other from the motion picture The Usual Suspects. Video Clip #1, from the NCIS episode entitled Family Secret, was 1 minute and 15 seconds in length (Binder & Whitmore, 2007). Video Clip #2, from the movie The Usual Suspects,was 1 minute and 40 seconds in length (Singer & McDonnell, 1995). The detailed questionnaires for the video clips were multicomponent recall tests. The Video Clip #1 questionnaire (Appendix B) contained eleven questions. The Video Clip #2 questionnaire (Appendix D) contained twelve questions. Each recall test was comprised of both multiple-choice and open-ended response questions. Participants were also asked to complete a brief free write summary of the video clips. This combination of question types was developed in an attempt to avoid concerns regarding forced choice answers. The provided summaries of both video clips contained MPI, false statements
Effects of MPI and Gender 7 contradicting the actual details of the events witnessed. The background questionnaire (Appendix A) consisted of twelve questions intended to gather general information about the participants. Procedure The researchers conducted the study in two set locations at two specific times. Participants were told before hand where and when the experiments would be conducted. Both locations were similar in size and set up and both times were in the evening. The participants received consent forms and were informed that their participation was optional and that they may leave at any time. Groups were divided according to two conditions, with one location acting as the MPI condition and one location acting as the non-mpi condition. The MPI group, containing 27 participants viewed Video Clip #1 on a projection screen located at the front of the room. After the clip ended, participants completed a basic addition worksheet to act as a clearing task. Researchers provided the participants with a copy of the Video Clip #1 summary (Appendix C), which included MPI. Researchers read the summary aloud as participants read along. Participants then completed the Video Clip #1 questionnaire (Appendix B). Participants then viewed Video Clip #2. Then they completed a basic subtraction worksheet to act as a clearing task. A copy of the Video Clip #2 MPI summary (Appendix E) was provided and read aloud. Participants then completed the Video Clip #2 questionnaire (Appendix D). The non-mpi group, containing 30 participants viewed Video Clip #1 on a projection screen located at the front of the room. After the clip ended participants completed the basic addition worksheet. These participants were not provided with any form of MPI. Participants then completed the Video Clip #1 questionnaire (Appendix B). Participants viewed Video Clip #2. Then they completed a basic subtraction worksheet. Participants then completed the Video
Effects of MPI and Gender 8 Clip #2 questionnaire (Appendix D). Afterwards all participants completed the background questionnaire (Appendix A) and were debriefed. Design and Analysis. The experiment was designed using a 2x2 ANOVA model. The genders of male and female were measured between subjects. The MPI and non- MPI groups were also measured between subjects. The researchers counted the number of correct responses in each group. The number of correct responses was the dependent variable. The dependent variables for all groups were compared to measure the effects of the factors on eyewitness memory. Results Effects of Gender There was not a significant difference between the results of males and females, F(1,57)<1. This result was not expected. Effects of Misleading Postevent Information On Video Clip 1, the participants who did not receive a MPI summary were able to remember more (M=82.09, SD=1.07) than the participants who received a MPI summary (M=40.36, SD=1.93). On Video Clip 2, the participants who did not receive a MPI summary were also able to remember more (M=85.83, SD=1.24) that the participants who received and MPI summary (M=52.57, SD=1.36). The combined scores showed that, overall, the participants who did not receive a MPI summary did better (M=84.04, SD=2.01) than the participants who did receive an MPI summary (M=46.87, SD=2.39). The effect was statistically significant, F(1,57)=207, p<.0001. This result was expected.
Effects of MPI and Gender 9 Interactions of Gender and Misleading Postevent Information In Video Clip #1, the interaction of gender and MPI was nearly significant, F(1,57)=3.3, p<0.075. Female participants who received an MPI summary did better (M=45.45, SD=1.31) than male participants who received an MPI summary (M=34.09, SD=2.38). There was not a significant difference between males and females who did not receive an MPI summary, F(1,57)=1.7, p<0.19. In Video Clip 2, the interaction of gender and MPI was significant, F(1,57)=4.45, p<0.04. Male participants who received an MPI summary did better (M=58.33, SD=1.04) than female participants who received an MPI summary (M=48.33, SD=1.37). There was not a significant difference between males and females who did not receive an MPI summary, F(1,57)=2.27, p<0.138. In the sum of the answers for the two video clips, the interaction of gender and MPI was not significant, F(1,57)<1. The difference between the males and females in the MPI group was the same as in the non-mpi group. The highest average was for males and females who did not receive MPI (M=84.04, SD=2.01). The lowest average was for males and females who received MPI (M=46.87, SD=2.39). Discussion The current study examined the effect that Misleading Postevent Information (MPI) and gender have on eyewitness memory, a sub process of long-term memory. Many previous studies have demonstrated that MPI has a drastic impact on eyewitness memory, whereas other studies have provided mixed data on the impact that gender has on eyewitness memory. There is little available research on the combined effects MPI and gender have on eyewitness memory. In the current study, participants viewed two short video clips and answered corresponding
Effects of MPI and Gender 10 questionnaires after either receiving or not receiving MPI. In addition to both multiple choice and open ended questions, all questionnaires also required the participants to complete a short free write, summarizing the detailed of the videos. Both males and females were included in both the MPI and non-mpi conditions, thus investigating the effects of both factors on eyewitness memory. The accuracy of responses for both conditions were scored and compared. The results of this experiment support our hypothesis that MPI does, in fact, affect the participants ability to accurately recall details of events witnessed. These results are also consistent with previous research. The present study measured the effect of MPI on the accuracy of the memory of an eyewitness. The present study supported the hypothesis that MPI changes an eyewitness memory. Not only did participants answer the questions wrong, they chose answers that they were told were correct through the MPI summary. This result provides evidence that eyewitnesses can have their memory altered by MPI, causing their testimony to be less accurate and the relay of false information. The results of this experiment do not support our hypothesis that gender affects the participants eyewitness memory. These results are consistent with previous research, showing that both males and females have the same results in recalling details of a witnessed event (Loftus, Levidow, & Duensing, 1992; Cunningham & Bringmann). These results can be due to an equal number of spatial and detail questions. The summary that each participant completed for the videos demonstrated a difference between the content of male and female memory. Males tend to remember more spatial details, whereas females tend to remember more specific details. These summaries also suggested that males tend to more accurately recall visual details, whereas females tend to recall more audio details. The questionnaires produced averages that were equal between males and females, showing that both genders were able to remember the same number
Effects of MPI and Gender 11 of details on the questionnaire; however the content of the memories were different in that males remember more of what was seen and females remember more of what was heard. The results of this experiment provide conflicting evidence that supports that both males and females are more susceptible to MPI than the other. In video clip #1, males proved to be more influenced by the MPI summary than females were, which is consistent with prior research (Lipton, 1977). In video clip #2, females proved to be more influenced by the MPI summary than males were, which is also consistent with prior research (Tomes & Katz, 1997). These contradictory results could be attributed to the difference in the content of the two video clips. In video clip #1, two paramedics were riding in their ambulance when a fire broke out on the back bumper. This clip was relatively non-violent compared to video clip #2, in which five masked gunman assault and rob a police car. Males may have found the violence and weapons depicted in video clip #2 more interesting, causing them to pay closer attention and remember details more vividly. This more vivid memory may have in turn made them less likely to believe the MPI. Further research on this topic should be focused on the content of the media used, as there is a difference in the types of information each gender tends to remember. The results of the current study suggest that that males and females each have more accurate memories for different styles of videos. Future research should specifically center around which styles males remember more accurately and which styles females remember more accurately. These may help determine which types of crimes each gender can remember more correctly. The content that should be considered are: variations in violent content and amount of verbal and visual content. Even with the substantial advances made in the area of DNA science, eyewitness testimony remains one of the most common forms of evidence used in trial. While lawyers and
Effects of MPI and Gender 12 jurors alike would love to have DNA evidence to work with, this is not always the case. Often only circumstantial evidence exists and comes in the form of an eyewitness s account of the crime. It is incredibly important to gain a better understanding of how eyewitness memory works and what types of testimony retrieval work best for the individual concerned. It is also tremendously important to research and monitor possible factors such as MPI; which might affect the eyewitness s memory. The justice system in the United States has flaws, however with further research these flaws can be diminished, increasing the chances that only the guilty are incarcerated.
Effects of MPI and Gender 13 References Binder, S. (Writer), & Whitmore, J. (Director). (2007). Family secret [Television series episode]. In D. Bellisario (Producer), NCIS. New York: CBS Broadcasting, Inc. Cunningham, J. L., & Bringmann, M. W., (1986). A re-examinationof William Stern s classic eyewitness research. Perceptual and Motor Skills, 63, 565-566. Eakin, D. K., Schreiber, T. A., & Sergent-Marshall, S. (2003). Misinformation effects in eyewitness memory: The presence and absence of memory impairment as a function of warning and misinformation accessibility. Journal of Experimental Psychology, 29(5), 813-825. Exonerations. (2007, October).Retrieved September 04, 2009, from www.innocenceproject.org Loftus, E. (2005). Planting misinformation in the human mind: A 30-year investigation of the malleability of memory. Learning and Memory, 12, 361-366. Loftus, E., Levidow, B., & Duensing, S. (1992). Who remembers best? Individual differences in memory for events that occurred in a science museum. Applied Cognitive Psychology, 6, 93-107. Maitland, S. B., Herlitz, A., Nyberg, L., Lars, B., & Nilsson, L. G. (2004). Selective sex differences in declarative memory. Memory & Cognition, 32, 1160-1169 Mudd, K. & Govern, J. M. (2004). Conformity to misinformation and time delay negatively affect eyewitness confidence and accuracy. North American Journal of Psychology, 6(2), 227-238. Roper, R. & Shewan, D. (2002). Compliance and eyewitness testimony: Do eyewitnesses comply with misleading expert pressure during investigative interviewing? Legal and Criminological Psychology, 7, 155-163.
Effects of MPI and Gender 14 Singer, B. & McDonnell, M. (Producers). (1995). The usual suspects [Motion picture]. United States: Polygram Filmed Entertainment. Tulving, E. (2002). Episodic memory: From mind to brain. Annual Review of Psychology, 53, 1-25. Tomes, J. L. & Katz, A. N. (1997). Habitual susceptibility to misinformation and individual differences in eyewitness memory. Applied Cognitive Psychology, 11, 233-251.
Effects of MPI and Gender 15 Appendix A: Background Questionnaire 1. Current Age (in years): 2. Gender (circle one): a. Female b. Male 3. Major: 4. Class and time period in which this questionnaire is being answered: 5. GPA (Cumulative): 6. Occupation (current job): 7. Ethnicity: Please circle one answer for each of the following questions 8. Do you wear corrective eyewear (i.e., glasses, contacts, etc.)? a. Yes b. No 9. If yes, were you wearing corrective eyewear when you witnessed these videos? a. Yes b. No
Effects of MPI and Gender 16 10. Are you color blind? a. Yes b. No 11. Have you seen Video Clip #1(with ambulance) before? a. Yes b. No 12. Have you seen Video Clip #2 (with police car) before? a. Yes b. No
Effects of MPI and Gender 17 Appendix B: Video Clip #1 Questionnaire Please answer according to the details from the video. 1. Please write all details that you can remember from the video clip. 2. What was the color of the Morgue sign? a. Black b. Blue c. Green d. Brown 3. What was the name of the hospital? 4. What was the color of the ambulance star of life? a. Red and white b. yellow and blue c. black and green d. blue and white 5. How many oxygen tanks were in the back of the ambulance? a. 1 b. 2 c. 3 d. 4 6. Where was the ambulance from? a. Rockville b. Fairfax c. Oakton d. Bethesda 7. What branch of the military did the dead man belong to? a. Marines b. Army c. Navy d. Air force 8. What was the occupation of the two men in the video?
Effects of MPI and Gender 18 9. What was the ethnicity/race of the man asking for advice? a. Caucasian b. African-American c. Asian-American d. Hispanic 10. What color jumpsuit are the men wearing? a. Purple b. Grey c. Blue d. Black 11. What defining facial feature does the African-American man have? 12. What part of the ambulance lights on fire first? a. Back door b. Bumper c. Gurney d. Oxygen tank(s)
Effects of MPI and Gender 19 Appendix C: Video Clip #1 Summary You have just witnessed a video depicting two EMTs picking up a dead naval officer from the Morgue. They were discussing advice on talking to women. After placing him in the ambulance the African-American man with the mustache went back into the morgue to get the release form. When he returned to the ambulance he started the engine and began to drive away. As they drove away they began to smell gas, they looked back and saw that the 3 oxygen tanks were on fire. They jumped out of the ambulance and ran as it blew up behind them.
Effects of MPI and Gender 20 Appendix D: Video Clip #2 Questionnaire Please answer according to the details from the video. 1. Please write all details that you can remember from the video clip. 2. What numeral did the identification number on the police car begin with? a. 2 b. 6 c. 3 d. 4 3. How many people were inside the car being attacked? a. 2 b. 4 c. 3 d. 1 4. How many people inside the car being attacked worked in law enforcement? a. 1 b. 3 c. 2 d. None 5. What was the make of the vans the assailants used in their attack? a. Chevrolet b. Dodge c. Ford d. Volkswagen 6. How many cars did the assailants use in their attack? a. 2 b. 4 c. 3 d. 1 7. What color was the car that made physical contact with the car under attack? a. Black b. White c. Grey d. Blue 8. How many assailants were there?
Effects of MPI and Gender 21 a. 7 b. 5 c. 3 d. 4 9. What color clothes were the assailants wearing? a. Blue b. Grey c. Black d. White 10. What color stockings did the assailants use to disguise their faces? a. All beige b. All black c. Beige & black d. Beige & white 11. How many items were stolen? a. 1 b. 2 c. 3 d. 4 12. How many shots were fired? 13. How many victims were shot?
Effects of MPI and Gender 22 Appendix E: Video Clip #2 Summary In the video clip that you just viewed, a crime was committed. Police car # 4623 was traveling south down a city street when it came under attack. Four assailants all dressed in blue and wearing beige stockings to disguise their faces ambushed the police car with one driver and one passenger. The assailants ran their black Dodge van into the victims car. Once the assailants had the victims trapped, they robbed them and opened fire. The assailants stole a white envelope and a black wallet from the victims. Three shots were fired and one of the victims was hit. The assailants sped off and got away before authorities were notified.
Effects of MPI and Gender 23 Table 1 Mean (and standard deviation) Percentage Correct Answers as a Function of Gender and Presence or Absence of MPI (N = 57) Gender MPI Non-MPI Male Video Clip 1 34.09 (2.38) 83.00 (0.92) Video Clip 2 58.33 (1.04) 85.00 (1.27) Total 46.74 (3.08) 84.04 (1.95) Female Video Clip 1 45.45 (1.31) 81.18 (1.22) Video Clip 2 48.33 (1.37) 86.67 (1.24) Total 46.96 (1.78) 84.04 (2.13)
Effects of MPI and Gender 24 Figure 1 Mean Percentage Correct Answers as a Function of Gender and Presence or Absence of MPI (N = 57)