how reliable is eyewitness testimony n.
Skip this Video
Loading SlideShow in 5 Seconds..
How reliable is eyewitness testimony? PowerPoint Presentation
Download Presentation
How reliable is eyewitness testimony?

Loading in 2 Seconds...

play fullscreen
1 / 136
Download Presentation

How reliable is eyewitness testimony? - PowerPoint PPT Presentation

Download Presentation

How reliable is eyewitness testimony?

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. How reliable is eyewitness testimony? Concept - Leading questions can cause false or distorted recall…

  2. How reliable is eyewitness testimony? - Describe the issue • An important issue because of the number of cases where people are found guilty of crimes with no other evidence except for eyewitness testimonies. • An eyewitness is a witness to a crime, who must give their account of the event, and possibly identify the criminal from an identity parade or appear in court. • This can lead to a conviction, so if the eyewitness testimony is wrong, someone has been wrongly convicted of a crime they did not commit.

  3. How reliable is eyewitness testimony? • Elizabeth Loftus is a leading expert in the area and has done a lot of research into the reliability of eyewitness testimonies. • She has identified many useful factors. • For example, eyewitnesses can be swayed by identity parades (this is likely to be because they want to help so feel they must answer, or might assume that the criminal has to be in the line-up). • They will be looking to find the nearest match to the person they saw, not the actual person: this can lead to wrongful convictions.

  4. Wrongful Convictions • Cornelius Dupree • Convicted of rape and robbery • Exactly one week after the attackDupree & Anthony Massingill were stopped by police as they walked along a street near the site of the incident. • Police claimed they stopped them because they fit the general description of two other black men who were suspected in a separate sexual assault case. • Both men were searched and although Dupree was unarmed, Massingill had a handgun roughly similar to the one described in the recent attack.

  5. Wrongful Convictions • Both Dupree and Massingill were taken into custody and their photos were submitted for an identification lineup. • Although the male victim did not identify them in the photo array, the female victim picked both Dupree and Massingill when presented with the same photos. • Later in the investigation, police showed the photos to two women who worked at the store where the perpetrators tried to sell the fur coat, and both women did not identify either Massingill or Dupree. 

  6. Wrongful Convictions • On July 30, 2010, the lab issued a report on the evidence which conclusively excluded both Dupree and Massingill as possible sources of the DNA found on the victim’s pubic hair samples.

  7. Wrongful Convictions • Jean Charles de Menezes • Brazilian man shot dead by the London Metropolitan police at Stockwell tube station on the London Underground after he was misidentified as one of the fugitives involved in the previous day's failed bombing attempts. These events took place two weeks after the London bombings of 7 July 2005, in which 52 people were killed. • Later police and media accounts contradicted each other, specifically regarding Menezes's manner and clothing as he entered the station, and whether there had been any police warnings before they fired.

  8. Wrongful Convictions • Jean Charles de Menezes • Brazilian man shot dead by the London Metropolitan police at Stockwell tube station on the London Underground after he was misidentified as one of the fugitives involved in the previous day's failed bombing attempts. These events took place two weeks after the London bombings of 7 July 2005, in which 52 people were killed. • Later police and media accounts contradicted each other, specifically regarding Menezes's manner and clothing as he entered the station, and whether there had been any police warnings before they fired. • He was misidentified and eyewitness testimony of shootings were incoherent

  9. The issue with EWT • Witnessing a crime, etc will be emotional. If you saw a shooting would you think about yours or others life's? • An eyewitness testimony will not be exact like a video recording. • So how reliable is it? • Witnesses can be swayed in line ups as they assume the perpetrator is there. • Loftus and Ketcham (1991) found that innocent individuals were wrongly convicted 45% of the time by eyewitness testimonies from the police cases they studied

  10. Application • Loftus and Palmer (1974) Study • Aim: To test their hypothesis that the language used in eyewitness testimony can alter memory. • 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

  11. Procedure – Experiment 1: • Forty-five American students/ opportunity sample. • Laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design). • 7 films of traffic accidents, ranging in duration from 5 to 30 seconds, were presented in a random order to each group. • After watching the film participants were asked to describe what had happened as if they were eyewitnesses.  • They were then asked specific questions, including the question “About how fast were the cars going when they (smashed / collided / bumped / hit / contacted) each other?” • Thus, the IV was the wording of the question and the DV was the speed reported by the participants

  12. Results

  13. Procedure – Experiment 2: • 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. • Afterwards the students were questioned about the film. • The independent variable was the type of question asked. • It was manipulated by asking 50 students 'how fast were the car going when they hit each other?', another 50 'how fast were the car going when they smashed each other?', and the remaining 50 participants were not asked a question at all (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 on the original film.

  14. Results

  15. EWT can be affected! • Juries tend to pay close attention to eyewitness testimony and generally find it a reliable source of information.  • However, research into this area has found that eyewitness testimony can be affected by many psychological factors: • Anxiety / Stress
 • Reconstructive Memory
 • Weapon Focus

  16. However, a study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory. • They showed that witnesses of a real life incident (a gun shooting outside a gun shop in Canada) had remarkable accurate memories of a stressful event involving weapons. • A thief stole guns and money, but was shot six times and died.

  17. The police interviewed witnesses, and thirteen of them were re-interviewed five months later.  • Recall was found to be accurate, even after a long time, and two misleading questions inserted by the research team had no effect on recall accuracy. • One weakness of this study was that the witnesses who experienced the highest levels of stress where actually closer to the event, and this may have helped with the accuracy of their memory recall. • The Yuille and Cutshall study illustrates two important points: • 1. There are cases of real-life recall where memory for an anxious / stressful event is accurate, even some months later. • 2. Misleading questions need not have the same effect as has been found in laboratory studies (e.g. Loftus & Palmer).

  18. The participants were all students; they may not be representative of the population as a whole– Generalisability • The findings show that memory is easily distorted, which has implications for eyewitness testimony in police statements and courts. The evidence shows that leading questions can bias the eyewitnesses’ answers. - Application

  19. Order effects controlled by random sequence of presentation of films to each group. Demand characteristics: student participants may work out the aim of the research– confounding variables • Low ecological validity as it was conducted in a laboratory. There would be differences between seeing a car accident on film and seeing it in real life (e.g., other distractions, high emotional involvement)– Low ecological validity

  20. This study was very well controlled. For example, in experiment 2, one group of participants were not asked the critical ‘broken glass’ question. Good control over variables is possible as it was conducted in a laboratory; doing this study outside would lack control over all variables (but increase ecological validity)– Controls • What about the methodology?

  21. Cognitive practical: • Big Brain • Context Cue

  22. Cue-dependent theory of forgetting: Tulving 1975 • This theory of forgetting applies to long-term memory, not the short-term store. • It states that forgetting occurs when the right cues are not available for memory retrieval. • Tulvingput forward this theory in 1975, stating that memory is dependent on the right cues being available, and forgetting occurs when they are absent.

  23. Tulving’s theory states that there are two events necessary for recall: 1) a memory trace (information is laid down and retained in a store as a result of the original perception of an event) 2) a retrieval cue (information present in the individual’s cognitive environment at the time of retrieval that matches the environment at the time of recall)

  24. For Tulving, forgetting is about the memory trace being intact, but memory failing because the cognitive environment has changed. • There is no appropriate cue to activate the trace. • The most noticeable experience of this cue-dependent forgetting is the Tip of the Tongue Phenomenon (Brown and McNeill, 1966). • This refers to knowing a memory exists but being temporarily unable to recall it.

  25. Cues have been differentiated into: • context-dependent cues – the situation or context (Godden and Baddeley, 1975) • state-dependent cues – the person’s state or mood

  26. Evaluaiton • The theory is supported by much anecdotal evidence (personal experiences – most people have experienced the “Tip of the Tongue Phenomenon” where you cannot quite recall what you know exists). • There is also a great deal of experimental evidence (provided by studies) which support the theory. • A further strength is that the theory has practical applications, which are related to cognition and improving memory and ability to recall information. • Also, the theory can be tested, unlike theories such as trace-decay theory. • Experiments can test the importance of cues as they are tangible and measurable, unlike memory traces.

  27. Evaluaiton • However, one major weakness is that the tasks from all studies supporting the theory are artificial: most often learning words lists. • Also, it is only an explanation for forgetting from long-term memory, it does not include anything about the short-term store. • The theory may not be a complete explanation either, as it cannot explain why emotionally-charged memories can be really vivid – even without a cue (such as posttraumatic stress disorder or PTSD). • It is also hard to prove whether a memory has been revived from the cue or from the memory trace simply being activated, therefore it makes the theory hard to refute.

  28. Applying this to the cognitive practical: Procedure • 20 participants were asked to arrive at a classroom. • At this point they were all given the right to withdraw. • They were randomly allocated to cued and non cued groups by drawing names from a hat. • Both groups were briefed about the aims and the procedure (given the right to withdraw, assured confidentiality and anonymity).

  29. Both groups were seated in the classroom and shown a list of 20 words one at a time via powerpoint. • Each word was shown for 3 seconds. • Non-cued group asked to go to the library and the cued group asked to remain seated. • After 5 minutes the groups were given a blank piece of paper and a pen top recall all the words they could remember in 5 minutes. • Both groups were debriefed, told the aims again and thanked. They were given the right to withdraw a final time and told the results of the experiments would be made available.

  30. Variable and hypothesis • This experiment is investigating a cause and effect relationship between context and recall • IV – environment • DV – ability to recall • Hypothesis – participants will recall fewer words when they recall in an environment that is different from the learning environment, than when learning and recall take place in the same environment. • So here the direction has been clearly stated so this is a one-tailed/ directional hypothesis.

  31. Why have we used a one-tailed hypothesis? • This experiment is based upon an established psychological theory. • If it was not what then we would use a…? • The null hypothesis (required for every experiment)states that any difference is likely due to chance: There will be no difference in recall of a word list recalled in the same of different environment and any difference found is due to chance.

  32. Controls • What variables must we consider? • Participants asked to refrain from talking to each other throughout the study • Mobile phones switched off • Participants seated away from each other so not to copy • Used a booked room which was quiet and posters put up on door explain there was an experiment going on • All times the same

  33. Selecting participants • Cue-dependent is a common way of forgetting so no specific selection is required. • 20 students, opportunity sampling from around the school/college

  34. Design • Independent measures design used. • Why choose this over repeat measures?

  35. Results • Consider the results on page 65 – 66 of big brain.

  36. Jan 2011 – 5 marks • As part of the course requirements for cognitive psychology you will have conducted a practical using an experiment. • Evaluate your experiment. You may wish to look at: • your sample • how you controlled variables • your research design decisions • any ethical issues

  37. Evaluative points: • Because the sample was opportunity we could have deliberately picked people we knew had the desired characteristics • We all used the same standardised instructions which increases the reliability of our study • It was carried out in a quiet classroom, which is a natural setting for the participant so increasing ecological validity • Some participants may have told others about the study so they may have tried to give us the results they thought we wanted • All participants were 16 to 18 so we cannot generalise the results to older people • As it was an experiment so we don't know if the participant’s behaviour was natural or a result of demand characteristics

  38. Level 3 – 5 marks • A thorough answer, giving very good strengths and/or weaknesses, comprehensively communicated. • The candidate has referred to their own study in some way at least once. • Given time constraints and limited number of marks, full marks must be given when the answer is reasonably detailed even if not all the information is present.

  39. Jan 2009 • Explain why it might be preferable to use a research method that produces qualitative rather than quantitative data(4) - If candidate explains why quantitative methods are better than qualitative methods then zero marks.Candidate can gain credit for applying question to their own study (but does not have to). • Qualitative methods conducted in more natural circumstances tend to produce more ecologically valid data as they are real life situations/eq; (2 marks) - Quantitative data produces narrow, unrealistic information which only focuses on small fragments of behaviour/eq; - Qualitative methods produces more rich detailed type of information/eq; - Qualitative methods enables the researcher to delve into the reasons behind their quantitative findings/eq; - Qualitative data can be broken down to quantitative data but not vice versa/eq; Look for other reasonable marking points.

  40. May 2009 • A field experiment was carried out to see if environmental cues can aid recall. A student ice hockey team learned a list of 20 unrelated words in an ice rink. Half the group were then taken to a library (control group) whilst the other half (experimental group) stayed in the ice rink. Both groups then had to recall as many of the 20 words as possible. • The results are shown in the table below: • Which design is being used in this study?

  41. Independent measures design

  42. Explain why this design is appropriate for this study. (2)

  43. Explain why this design is appropriate for this study. • 2 marks for a complete answer, 1 mark for a partial answer.If more than one advantage given mark all and credit the best. • There is no practice/fatigue effect/eq; 1 markAs the participants either went to the library or the ice rink/eq; 1 mark • No order effects/eq; 1 markNo order effects as different participants are used in each condition/eq; 2 marks • Need two groups to compare the results/eq; 1 markA comparison group is required to see if the change in environment had an effect on recall/eq; 2 marks -Look for other reasonable ways of expressing this answer

  44. Which measure of central tendency is being used in the table below?

  45. Which measure of central tendency is being used in the table below? The Mean

  46. Would this study have high or low validity? Explain your answer.

  47. Would this study have high or low validity? Explain your answer. (2) • 2 marks for a complete answer, 1 mark for a partial answer. A suitable example would serve as elaboration. MAX 1 mark if no reference made to the actual study. • High validity as it was in a natural setting for the hockey team (ice rink)/eq; 1 markEven the students in the library were in their natural setting as well as those in the ice rink which would be high validity/eq; 1 mark • Low validity as learning a wordlist is an artificial task which is not carried out in everyday life/eq; 1 markLow (construct) validity as a task such as learning a list of words may not be testing how memory normally works/eq; 1 mark • Look for other reasonable ways of expressing this answer

  48. The researchers would have followed ethical guidelines. With reference to this study, explain two ethical guidelines they would have to consider .

  49. The researchers would have followed ethical guidelines. With reference to this study, explain two ethical guidelines they would have to consider . • 1 mark for each guideline (ID mark) + 1 for each explanation • NB: 1 mark for ID, second mark in each case must relate the study to the ethical guideline to gain credit • There are many guidelines that could be chosen. If more than two are given mark all and credit the best. • Right to withdraw; ID markThe ice hockey team/players had to know that they could pull out from the memory experiment at any time and withdraw the data they had recalled/eq; • Debriefing; ID markThe ice hockey team should be told all about the purpose of the experiment on cue dependent memory so they know what they have participated in/eq; • Informed consent; ID markThe ice hockey team/student team must give their permission to take part in the memory experiment after they are told what is involved/eq; • Confidentiality; ID markThe results and personal details of the ice hockey team/‘group’ should not in any way be made public to anyone without their permission/eq;

  50. Outline one weakness of field experiments in general. (2) • 2 marks for a complete answer, 1 mark for a partial answer. • If more than one weakness mark all and credit the best • E.g. Lack of full control over variables/eq; 1 mark • Difficult to replicate due to lack of full control over extraneous variables /eq; 2 marks • E.g.Couldbe lack of informed consent/eq; 1 mark • Informed consent is difficult to obtain as informing the participants they are being studied would disrupt natural behaviour/eq; 2 marks • E.g.Maybe more expensive and time consuming/eq; 1 mark • The researcher may require additional skills in arranging and setting up a field experiment compared to the skills required for a lab experiment/eq; 2 marks