A common defense in murder cases is "focal retrograde amnesia": the defendant claims to have simply forgotten what occurred around the time of the crime (perhaps due having consumed too much alcohol or other drugs). In fact, "amnesia" is claimed in as many as 45 percent of murders. Psychologists know that this sort of amnesia is actually quite rare, so it's very likely that most, if not all of these defendants are faking amnesia.
We can confirm that many of these cases are faked: when defendants are given multiple-choice questions about the crime, they get the answers wrong too often. Think about it this way: if you are given a ten-item true/false test and you know none of the answers, you should get five of the answers right just by guessing. But if you actually know the answers and are just pretending not to know, you might get every single answer wrong. Unfortunately, this sort of test can't tell us who's faking and who's not, because some honest respondents might legitimately have an especially "bad" performance, purely based on chance. On a large scale, we know there's a lot of cheating going on, but there's no way to reliably pick out the cheaters.
But in testing for faking amnesia, a secondary phenomenon seemed to be appearing. Several studies found that people who were asked to pretend to have amnesia were later unable to recall as much as people who told the truth from the start.
The studies worked like this: Volunteers were told a story -- or actually acted out a story -- where they were the primary character: "you" robbed someone, or beat a man to death with a pool cue, or killed a girl in a car accident. Then half these participants were told to pretend not to remember the key details of the crime in an effort to avoid punishment, while the other half was told to remember as many as possible of the details. They were tested on their memory (or their false reconstruction) immediately after the story, and then returned to the laboratory a week later, and this time everyone was asked to try to recall the details of the crime accurately. The volunteers who told the truth the first time around did better on the second test. Does this mean that faking amnesia impairs your memory later on? Not necessarily.
There were a couple problems with these studies. First, it could be that the memory difference was due to the fact that the truth-tellers had "practiced" giving the correct responses, not the faking of amnesia. Indeed, one study included a third group, which was not tested immediately after the "crime." This untested group performed just as badly the fake amnesics one week later. Second, these scenarios weren't very realistic for the college students acting them out. It could be that the students remembered (or forgot) details because of the unusual nature of the stories they were listening to or acting out.
So a team led by Xue Sun designed a study to address these problems. They divided their student volunteers into three groups: fake amnesics, truth-tellers, and untested. Students heard one of two stories while they read along with a script. Here's an excerpt from one of the stories, describing a party where the student has been drinking and meets a dog named Ollie:
When you walk into the kitchen, you find it empty except for Ollie, who is curled up and sleeping in a little ball on his blue shag rug in the corner. Hearing you, he wakes up and leaps toward you, trying to play. You pick him up and he licks your face. When you put him down, he keeps jumping up trying to reach the counter. You realize he's trying to get at the pile of chicken bones that have been left on an aluminum platter next to the sink. Thinking, "dogs like bones, " you pick the biggest one an give it to him, saying, "Here you go, Ollie. You'd better not tell Sam I gave this to you!" ....
[later] You turn around and realize that Ollie is choking... You realize that it could be that he's choking on the bone you just fed him, which is now nowhere in sight.
Eventually the dog dies, and the students (in the fake amnesic and truth-telling groups) were asked to imagine confronting the owner the next day and explaining what happened. They wrote out a description of the key events and also answer a multiple-choice test. Then, a week later, everyone returned to write out the story again and retake the test. This time, everyone was instructed to try to answer accurately. Here are the results:
While the truth-tellers did respond more accurately than the fake amnesics, the fake amnesics didn't do any worse than the students who weren't tested at all. The results were the same for a second story, which involved giving nuts to a person with allergies, resulting in their death. Sun's team says the difference between the fake amnesics and the truth-tellers is probably completely due to the fact that the truth-tellers had a chance to practice the accurate story.
In other words, pretending to have amnesia doesn't hurt your memory, but rehearsing the correct answers improves it. There's still a separate question about how all this applies to the real world. A criminal probably does rehearse his or her alibi. How does this rehearsal affect memory for the actual crime? It's hard to say, and also difficult to envision a study that would address this question. Perhaps our readers have some ideas.
Sun, X., Punjabi, P., Greenberg, L., & Seamon, J. (2009). Does feigning amnesia impair subsequent recall? Memory & Cognition, 37 (1), 81-89 DOI: 10.3758/mc.37.1.81
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Okay, this is a bit elaborate, but I think it does the trick.
Have volunteers go to a private area to read the "killing Ollie" script. Make it appear that they were given a sealed, numbered, and randomized script, and that they are not to tell anyone what was in the script they received.
After they've read the script, tell them to re-seal it and give it back to the experimenter (who should make note of the script number).
Put the volunteers in 1 of 3 groups:
GROUP 1 (the deceiving group):
Lead them into a room with a volunteer who is playing the "interrogator" (actually an experimentor) and fake "lie-detector". Tell them
1) the interrogator has been trained on an experimental voice-analysis lie detector, and is rewarded $10 for correctly assessing whether you are guilty or amnesiatic
2) knows that the dog choked on a chicken bone
3) knows that you were in the kitchen shortly beforehand
4) does NOT know if you read a GUILTY script, with clear details of the kitchen and of giving the bone, or an AMNESIATIC script with vague recollections of the kitchen and no recollection of giving Ollie the bone (in fact, try to sell as much as possible the notion that *nobody* knows which script they got, and that there was an 50/50 chance that they actually got the AMNESIA script)
Explain that if you convince the interrogator that you read the AMNESIATIC script, you win $10.
Have the interrogator read a list of 10 questions, paying close attention to the "lie-detector", and ultimately choosing to find the person "innocent" (reward the $10).
GROUP 2 (the honest group): Lead the volunteer into a room with the interrogator, and instruct them to "confess" as many details as possible. Ask them 10 questions about the crime, and indicate that each right answer rewards them $1.
At the end, reward them $10.
GROUP 3 (the control group): Pay them $10 and say, see you next week.
Oops - I hit submit before finishing the experiment with the obvious: re-convene all vonlunteers the next week to ascertain how much they recalled.
Excellent post, and it brings up what I think are the incredibly interesting and important way(s) that our memory is (or becomes) distorted, in the very act of using (or not using) it.
I do have a quibble: focal retrograde amnesia is actually not at all common as a defense in criminal cases. I am a forensic psychologist and a former prosecuting attorney, and I have never seen the defense actually used in trial. Criminal defendants often believe (maybe from popular culture, and TV, and certainly also based on jailhouse lore and "wisdom") that it's helpful to them if they claim not to remember anything that happened during the time period of the alleged criminal conduct. In fact, failure to remember would in no way provide a real defense, unless it was comorbid with some legitimate mental disorder that rendered the defendant unable to understand the "nature, quality, or wrongfulness" of his/her behavior (usually a severe psychosis).
From what I have observed, I can also say that it seems clear that criminal defendants routinely manipulate their own memories about their behavior, in the ordinary course of finding and asserting a run-of-the-mill type of defense (e.g., self-defense) to the charges they are facing. By the time it's all over, I think that many of them have entirely convinced themselves of the accuracy of their own preferred view of the events, as opposed to what they undoubtedly knew, early on, that they "really" had done.
Is it really true that "this sort of amnesia is actually quite rare"? Is there actually any evidence demonstrating its rarity? I do not doubt that criminals may often lie about having amnesia when they do not, but that is not evidence that it rarely happens. I have certainly experienced this sort of amnesia on at least one occasion, under conditions that were very ordinary.
As a young man I did occasionally drink to excess (although I was by no means a heavy drinker in comparison to many of my peers). A few days after one of these drinking bouts, two attractive young women came up to me and greeted me familiarly by name. I had no memory of ever having met or even seen either of them before. It turned out that I had met and had a conversation with them when I was drunk, but neither at that time nor since have I been able to recall anything at all about our first meeting.
Given that I only learned I had forgotten meeting them purely through the coincidence of running into them again a few days later (and of having apparently having made quite a good impression on them, even when I must have been very drunk), it seems more than likely that I also forgot things that happened on other occasions when I was comparably drunk, but I never learned about it because no other witnesses happened to tell me about it in such a clear and memorable way. (It was memorable because the women in question were so attractive and so friendly. I really wished I could have remembered getting to know them!) Furthermore, many of my peers would get at least as drunk as I did more often than I did, and, of course, it is very common for young men (and even some women and some not-so-young men) in many cultures all over the world to drink to excess quite often. I suspect that, in fact, these sorts of memory "blackouts" are very common, but even those who have them may rarely be aware of the fact, and even when they are, they are rarely likely to tell a doctor or anyone else likely to gather data on the matter. After all, the "cure" is obvious enough.
I just cited this post in my blog and then noted you're on the Research Blogging site as well. An interesting post and study.
I think the flaw is much earlier on, though. The situation itself didnât happen to anyone, so everyone was essentially making something up, or authenticating the experience for themselves. The test would seem to work better if people were given an experience, maybe put in a situation in which they were to take some action and then asked by people who hadn't witnessed it what had taken place. The subjects could then be instructed to tell the truth or make something up.
It think what Delany Dean, JD, PhD had to say here is closer to it, though: There's much more evidence of people convincing themselves of their own version of events rather than that they don't remember them.
I'd be more interested in understanding the cognitive principles behind why we care if someone remembers the crime they committed or not.
Delaney Dean: The 45 percent figure comes from the journal article itself, which cites the Handbook of Memory Disorders. The range cited is 25-45 percent.
I'm not sure the defendants are actually claiming "focal retrograde amnesia" in these cases. They're just saying they were drinking or on drugs and don't remember what happened during key periods that coincide with when the crime was committed.
Thanks, Dave. I think the confusion may lie in the distinction between *claiming a memory failure* and *using memory failure as a defense to criminal charges*. It's quite true that many criminal defendants claim memory failures (and some falsely make the claim in hopes that it will help their defense). However, it is not the case that such a claim will normally result in a legal defense to the charges.
Nils: Good question. Traditionally, the law itself does not "care" whether the defendant remembers what he (allegedly) did, or not. Failure to remember does not create a defense that legally can be argued.
However, defense lawyers do care, partly because a genuine failure to remember (a) hinders the lawyer in figuring out what "really" might have happened, and thus how to evaluate the accuracy and strength of the government's evidence, and how to build a decent defense; and (b) genuine failure to remember could conceivably indicate some sort of neurological problem that the lawyer will need to investigate, establish, or rule out, in order (again) to have done his/her job in figuring out what the proper defense might be.
While faking amnesia wouldn't serve as a defense, "pleading the 5th" and not divulging details or confessing to a crime is difficult in practice. Police, prosecutors, and, occasionally, media are pressuring for some sort of a story. Faking amnesia, or over-playing a weak memory is a convenient excuse and doesn't require confabulation.
Interestingly, it seems only a confabulation would simultaneously decrease memory performance and increase metacognitive confidence, as in the trend Delany Dean cites.
Does this mean that if you pretend to be a zombie, you"ll turn into one?
Accessing (not "rehearsing" or "practicing"; why this odd terminology?) particular memories refreshes them and enhances the "depth" of their imprint (deeper imprints last longer, with more detail). Frequency of access is one of the ways the brain retains "important" materials while letting unimportant ones fade; intensity of experience and/or focus is another.
I agree with these findings. I have found the best way to lie convincingly is to "rewrite history". View the memory you WANT to remember in your mind over and over and picture an argument with a disbeliever where you are arguing your cause.
For that matter, this can work for emergency-response training, which is why fire drills at school or even safety instruction demonstrations on airplanes do actually help a little. It's worked for me on a couple of minor first-aid emergencies. It's like your brain thinks it has "experience" with the situation and responds in what it has "experienced" is a successful manner.