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LINKAGES Memory and Perception in the Courtroom
225 Constructing Memories FIGURE 6 .8 The Effect of Schemas on Recall Figure shown to participants In a classic experiment, people were shown figures like these, along with labels designed to activate certain schemas (Carmichael, Hogan, & Walter, 1932). For example, when showing the top figure, the experimenter said either “This resembles eyeglasses” or “This resembles a dumbbell.” When the participants were later asked to draw these figures from memory, their drawings tended to resemble the items mentioned by the experimenter. In other words, their memory had been altered by the schema-activating labels. LINKAGES How accurate is eyewitness testimony? (a link to Sensation and Perception) Group 2 Group 1 T Label given Figure drawn by participants Label given Eyeglasses Dumbbell Hourglass Table Seven Four Gun Broom Figure drawn by participants LINKAGES here are few situations in which accurate retrieval of memories is more Memory and Perception in important—and constructive memory is more dangerous—than when an eyewitness the Courtroom testifies in court about a crime. Let’s consider the accuracy of eyewitness memory and how it can be distorted. To a jury, the most compelling evidence a lawyer can provide is that of an eyewitness, but eyewitnesses often make mistakes (Loftus & Ketcham, 1991; Wells, Olson, & Charman, 2002). In 1984, for example, North Carolina college student Jennifer Thompson confidently identified Ronald Cotton as the man who had raped her at knifepoint. Mainly on the basis of Thompson’s testimony, Cotton was convicted of rape and sentenced to life in prison. He was released eleven years later, when DNA evidence revealed that he was innocent (and identified another man as the rapist). The eyewitness/victim’s certainty had convinced a jury, but her memory had been faulty (O’Neill, 2000). Like the rest of us, eyewitnesses can remember only what they perceive, and they can perceive only what they attend to (Backman & Nilsson, 1991). The witnesses’ task is to report as accurately as possible what they saw or heard. But no matter how hard they try to be accurate, there are limits to how valid their reports can be (Kassin, Rigby, & Castillo, 1991). For example, hearing new information about a crime, including in the form of a lawyer’s question, can alter a witness’s memory (Belli & Loftus, 1996). Experiments show that when witnesses are asked “How fast were the cars going when they smashed into each other?” they are likely to recall a higher speed than when asked “How fast were the cars going when they hit each other?” (Loftus & Palmer, 1974; see Figure 6.9). There is also evidence that an object mentioned during questioning about an incident is often mistakenly remembered as having been there during the incident (Roediger et al., 2001). So if a lawyer says that a screwdriver was lying on the ground (when it was not), witnesses may recall with great certainty having seen it (Ryan & Geiselman, 1991). This misinformation effect can occur in several ways (Loftus & Hoffman, 1989). In some cases, hearing new information can make it harder to retrieve the original memory (Tversky & Tuchin, 1989). In others, the new information may be integrated into the old memory, making it impossible to distinguish from what was originally seen (Loftus, 1992). In still others, an eyewitness report might be influenced by the person’s assumption that if a lawyer or police officer says an object was there, or that something happened, it must be true. 226 FIGURE 6 .9 The Impact of Questions on Eyewitness Memory After seeing a filmed traffic accident, people were asked, “About how fast were the cars going when they (smashed into, hit, or contacted) each other?” As shown here, the witnesses’ responses were influenced by the verb used in the question. “Smashed” was associated with the highest average speed estimates. A week later, people who heard the “smashed” question remembered the accident as being more violent than did people in the other two groups (Loftus & Palmer, 1974). Chapter 6 Question About how fast were the cars going when they each other? Original information Verb Estimated mph smashed into 40.8 hit 34.0 contacted 30.8 External information Memory The “memory” About how fast were the cars going when they SMASHED INTO each other? Jurors’ belief in a witness’s testimony often depends as much (or even more) on how the witness presents evidence as on the content or relevance of that evidence (Leippe, Manion, & Romanczyk, 1992). For example, many jurors are particularly impressed by witnesses who give lots of details about what they saw. Extremely detailed testimony from prosecution witnesses is especially likely to lead to guilty verdicts, even when the details reported are irrelevant (Bell & Loftus, 1989). Apparently, when a witness reports details, such as the exact time of the crime or the color of the criminal’s shoes, jurors assume that the witness had paid especially close attention or has a particularly good memory. This assumption seems reasonable, but there are limits on how much people can pay attention to, particularly when they are emotionally aroused and the crime happens quickly. Witnesses whose attention was drawn to details such as shoe color might not have had time to accurately perceive the criminal’s facial features (Backman & Nilsson, 1991). So the fact that an eyewitness reports many details doesn’t guarantee that all of them were remembered correctly. Jurors also tend to believe witnesses who are confident about their testimony (Leippe et al., 1992). Unfortunately, research shows that witnesses’ confidence is frequently much higher than the accuracy of their reports (Shaw, 1996; Wells et al., 2002). In some cases, repeated exposure to misinformation and the repeated recall of that misinformation can lead witnesses to feel certain about their testimony even when—as in the Jennifer Thompson case—it may not be correct (Lamb, 1998; Mitchell & Zaragoza, 1996; Roediger, Jacoby, & McDermott, 1996). The weaknesses inherent in eyewitness memory can be amplified by the use of police lineups and certain other criminal identification procedures (Haw & Fisher, 2004; Wells & Olson, 2003). In one study, for example, participants watched a videotaped crime and then tried to identify the criminal from a set of photographs (Wells & Bradfield, 1999). None of the photos showed the person who had committed the crime, but some participants nevertheless identified one of them as the criminal they saw on tape. When these mistaken participants were led to believe that they had correctly identified the criminal, they became even more confident in the accuracy of their false identification (Semmler, Brewer, & Wells, 2004; Wells, Olson, & Charman, 2003). These incorrect, but confident, witnesses became more likely than other participants to claim that it had been easy for them to identify the criminal from the photos because they had had a good view of him and had paid careful attention to him. Since 1973, at least 123 people, including Ronald Cotton, have been released from U.S. prisons after DNA tests or other evidence revealed that they had been falsely convicted—mostly on the basis of faulty eyewitness testimony (Death Penalty Information Center, 2006; Scheck, Neufeld, & Dwyer, 2000; Wells et al., 2000). DNA evidence