Brain Buys (7 page)

On July 29, 1984, Jennifer Thompson, a 22-year-old college student, was raped in her home in the town of Burlington, North Carolina. During the ordeal she made a conscious effort to memorize the face of the man who was raping her; she vowed that if she survived she’d ensure her assailant was caught. Later that same day, she picked out a man named Ronald Cotton from a selection of six photographs. Understandably, immediately after the photo lineup, she sought some feedback from the detective: “Did I do OK?” she asked. He responded, “You did great, Ms. Thompson.” Eleven days later, after picking out Ronald from a physical lineup, she again wondered how she did; the detective told her “We thought that might be the guy. It’s the same person you picked from the photos.” At trial, based almost exclusively on Jennifer’s eyewitness testimony, Ronald was sentenced to life in prison.

In prison Ronald crossed paths with another African American man who by some accounts resembled Ronald in appearance. The man, Bobby Poole, was from the same area and had also been convicted of rape. Ronald heard that Bobby boasted about raping Jennifer. A few years later Ronald’s case was retried. Based on Jennifer’s testimony, as well as that of an additional victim who had been raped the same night, Ronald was again sentenced to life in prison, despite testimony by another prisoner stating that Bobby had confessed to raping Jennifer. Thanks to Ronald’s persistence, a zealous attorney, and emerging DNA fingerprinting technology, genetic tests were eventually performed. DNA from the second victim matched Bobby Poole’s, and when confronted with the new evidence, he confessed to raping Jennifer, providing information about the case that only the rapist could have known. After an 11-year forced separation from his sick mother and the few loved ones who stood by his side during his ordeal, Ronald was finally released. Jennifer was sickened by the consequences of her mistake, and genuinely bewildered as to how her memory could have betrayed her. Eventually she sought forgiveness from Ronald Cotton. The two slowly became good friends and have campaigned together for reforms in witness interview procedures and the use of eyewitness testimony in trials.
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CORRUPTED MEMORIES

As we have seen the associative architecture of human memory makes us prone to certain mistakes, such as falsely remembering a word that was closely related to the actual words on a list. Other types of memory bugs, however, such as the one responsible for Ronald Cotton’s 11-year incarceration are different, in both their causes and consequences. Causes, because they are not solely a product of the associative nature of human memory; and consequences because they can result in tragic life-altering errors.

Digital memory, whether in the form of a hard drive or a DVD, relies on distinct mechanisms for the storage and retrieval of information—the writing and reading operations are fundamentally different processes. On a hard drive there are separate read and write elements: the first can measure the polarity of a tiny dot of ferromagnetic material, whereas the second can alter the polarity of the magnetic granules. Similarly a DVD player can only retrieve the memory burned into a DVD. The read operation is performed by a laser beam directed onto the surface of the DVD; if the light is reflected back, a “1” has been stored; if not, a “0.” There is no danger whatsoever that retrieving information from a DVD will alter its content; for that, a DVD burner, which has a more powerful laser, is required. In the brain, on the other hand, the read and write operations are not independent; the act of retrieving a memory can alter its content. When Jennifer Thompson was looking at the picture of her potential assailant, she was not simply retrieving an established memory, but melding new and old ones. In particular, the positive feedback from the detective immediately after she picked a suspect likely contributed to the “updating” of her memory. By the time she got to trial, months after the rape, the memory of the rapist was the well-lit and clear image of the man in the photos and lineup, rather than the dark fragmented image from the night of the rape. Jennifer Thompson’s memory betrayed her because it overwrote Bobby Poole’s image with Ronald Cotton’s (Poole’s picture was not in the first lineup).

Most of us have had the experience of not recognizing someone we have met, or the converse experience of incorrectly believing we’ve seen someone somewhere before. So it seems surprising that the American judicial system has traditionally relied heavily on the accuracy of memories of victims and witnesses. Memory errors that can derail the judicial process are not limited to mistaken identities, but also include incorrect recall of factual information and erroneous judgments about how long an event lasted or when it took place. Take the trial of Andrea Yates, the Texas woman who drowned her five children in a bathtub in 2001. In this case it was the testimony of a psychiatrist that proved incorrect. In court, Andrea Yates stated that voices in her head told her that her children would be tormented in hell forever; but, if she killed them, Satan would be destroyed. Hallucinations featuring Satan fit with the family’s devotion to Scripture, a fact reflected in the name of the five victims: Mary, Luke, Paul, John, and Noah. During her trial a psychiatrist for the prosecution testified that an episode of the TV program
Law & Order
may have been pertinent to the case, stating “there was a show of a woman with postpartum depression who drowned her children in the bathtub and was found insane, and it was aired shortly before the crime occurred,” implying that the murders may have been premeditated. This testimony may have contributed to the jurors’ rejection of Andrea’s insanity defense, and the sentence of life in prison. It later came to light that the episode the psychiatrist was thinking of was aired after the crime, and differed in some of the details. Trials often take place years after the crime; remembering an episode of a TV program is one thing, correctly remembering the “time stamp” of the memory is a different process all together. You may recall events related to the O.J. Simpson trial, but did it occur before or after the Atlanta Olympic Games?
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Every computer file is stored along with the date it was created; there is no such time stamping with our memories. It is easy to see how even the most honest witness can generate false recollections that could ultimately prove critical to determining the course of someone else’s life. In the case of Andrea Yates, a retrial was granted on the basis of the erroneous testimony, and the new jury judged her to be insane at the time of the homicides.
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The psychologist Elizabeth Loftus, now at the University of California in Irvine, has devoted her career to exposing the brain’s propensity to make errors of the type committed in the testimony of Jennifer Thompson and the trial of Andrea Yates. Studying such false memories in the real world is, of course, often impossible because it is difficult to verify what witnesses or victims actually experienced. Indeed, when courts rely on eyewitness testimony it is precisely because of the lack of incontrovertible evidence. To overcome this limitation Loftus and her colleagues developed experiments aimed at simulating some aspects of real-world eyewitness testimony. In a classic study Loftus and colleagues showed 200 students a sequence of 30 slides depicting an automobile accident involving a car at an intersection.
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All subjects saw the same images with one important difference: half saw a stop sign and half saw a yield sign at the intersection where the accident occurred. Immediately after the presentation subjects were asked several questions such as the color of the car. Among these questions one was key to the experiment because it was actually used to plant a false memory: for half the subjects in each of the two groups the question was, “Did another car pass the red car while it was stopped at the
stop
sign?” while the other half in each group was asked, “Did another car pass the red car while it was stopped at the
yield
sign?” In other words, half of the subjects were asked a question with misleading information about the sign; the misinformation was fairly subtle because it was not relevant to the question being asked. Twenty minutes after this questionnaire subjects were given a recognition test: pairs of slides were presented and the subjects had to indicate which picture of each pair they had seen before—the crucial pair being when they had to choose between slides with either a stop or yield sign. When the key question had contained consistent information, 75 percent of subjects correctly reported the image they had seen. But when the key question had contained misinformation, only 41 percent correctly chose the slide they actually saw during the initial presentation. Not only did a misleading question dramatically impair memory reliability, but it actually made performance worse than chance: an erroneous question about reality trumped reality.

In another study students watched movies in which teachers were interacting with children. They had been told the movies were about educational methods. Toward the end of the movie, the subjects witnessed a male thief removing money from the wallet of one of the female teachers. There were two groups in the study: the experimental group, in which the subjects also saw a male teacher reading to a group of students shortly before the theft of the female teacher’s wallet, and the control group, in which subjects saw the book being read by the female teacher who was robbed. After the movie, the subjects were told the true objective of the study, and were asked to pick out the thief in a photo lineup composed of foils (random people) as well as the innocent male teacher; the thief, however, was not in the lineup of seven people. The participants in the study had three options: identify who they believed was the thief, state that the thief was not in the lineup, or say that they were unsure if the thief was in the lineup. In the control group (no male teacher) 64 percent correctly stated that the thief was not in the lineup.
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In the experimental group 34 percent stated, correctly, that the thief was not in the lineup, but 60 percent picked the innocent male teacher as the thief. If this had been the scenario of a real police case, the innocent bystander would have been accused of the crime in 60 percent of the cases.

Magicians can also tap into this misinformation bug to re-create reality in the minds of their audience. After handing you a deck of cards and asking you to cut it, a magician may perform a trick that involves multiple steps before magically revealing the card you had chosen earlier. After the finale, the magician may verbally recount the sequence of events for effect, casually reminding you that you initially “shuffled” the deck of cards—when it comes to card tricks there is a world of difference between shuffling and cutting a deck of cards. By doing this the magician effectively injects misinformation and decreases the likelihood that you will remember this critical event, thus amplifying the mystery.

Although magicians and psychologists have long known about how memory can be overwritten by interference or misinformation, the judicial system has been slow to acknowledge this. Efforts are being made, however, to improve the procedures for questioning witnesses. It is now recommended that during an interview police should rely on open-ended questions such as “Please describe the scene of the accident,” as opposed to “Was there an SUV at the scene of the accident?” because the mention of an SUV contaminates the remembered scene of the crime. Also, it is better to show suspects one by one rather than in a lineup which encourages the witness to pick someone even when unsure. Still, the fact remains that human memory was simply not designed by evolution to rapidly and accurately store details such as whether the speeding car was a hatchback or coupe, whether the thief had brown or green eyes, or whether the police took one or two minutes to arrive at the scene.

WRITE AND REWRITE

Our memories are continually being edited—features are added, deleted, merged, and updated over time. In part this is because, as mentioned earlier, for human memory the act of storing information is not distinct from retrieving information—the writing and reading operations interfere with each other. We have seen how the storage of memory relies on the strengthening (or weakening) of synapses. Learning a conceptual association between two concepts that you are familiar with requires that their nodes become connected. If a child has a node in her brain representing grapes and a node representing raisins, the process of learning that raisins are grapes relies on the “grape” and “raisin” nodes becoming directly or indirectly connected through strengthening of existing synapses or the formation of new ones.
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As discussed in the previous chapter, because both concepts were activated in close temporal proximity the synapses become strengthened—as dictated by Hebb’s rule. That’s the storage process, but the retrieval process is very similar. If someone asks, “What is a raisin?” the answer would depend on activation of the raisin node triggering activity in the grape node, which uses the same synapse. In both storage and retrieval, not only are the same synapses used, but both sets of neurons are reactivated (Figure 2.1).