As slide shows go, it wasn't even in the same league as your aunt's vacation snapshots, but the audience was paying close attention: there was going to be a quiz. In one sequence a student sitting in a packed lecture hall topples onto the floor. In others, a hand retrieves oranges that have rolled all over a supermarket, and a woman picks up groceries scattered across a floor. Between 15 minutes and 48 hours later, the Boston University undergrads--volunteers in this psychology experiment--scrutinize more photos and, for each one, decide whether they ever saw it before. Yup, saw the student carelessly leaning back in his chair. Yeah, also saw the guy stupidly take an orange from the bottom of the pile. Uh-huh, saw the grocery bag rip. In all, 68 percent of the time the students remembered seeing the "cause" picture (a ripping bag) whose effect (spilled groceries) had been part of the show.
There was only one problem. The slides did not include a single such cause photo. "When people saw the effect photo but not the cause photo, they 'filled in the blank' by saying they had seen the cause with their own two eyes," says psychologist Mark Reinitz of the University of Puget Sound. Writing in the July issue of the Journal of Experimental Psychology, he and Sharon Hannigan of Bard College conclude that the mind's drive to infer causes can fool people into "remembering" something they never saw. In other words, says Reinitz, "memories can be illusions."
When it comes to memory problems, forgetting is only the tip of the iceberg. The failures and failings of memory run much deeper than an inability to recall your neighbor's name, the capital of Illinois or the location of your keys. Much recent memory research has focused on why we forget, shedding light on tragedies like Alzheimer's as well as puzzles like why we often know the first letter of a name or word we're trying to remember, but not the rest of it. But unlike absent-mindedness and other "sins of omission," as psychologist Daniel Schacter of Harvard University calls them in his new book, "The Seven Sins of Memory," memory's "sins of commission" shape--and often distort--our view of reality and relationships. Some of the sins:
Blocking. Somewhere between remembering and forgetting lies blocking. You know that the word for an oration at a funeral begins with a vowel, maybe even a "u"... but it just won't spring into consciousness. You know the name of the longtime neighbor who's approaching as you talk to the new people next door, but as the seconds tick down until you'll have to make the introduction, the best you can come up with is that his name begins with an "R." Proper names are blocked more than any other words, memory researchers find, and more in old people than young. The problem with names is that they are (in Western cultures, at least) completely arbitrary: that guy looks no more like a Richard than he does a Paul. Also, the sound of a word is encoded in the brain in a different place from its meaning. If the links from concept (the context in which you know a person) to visual representation (aha, that face belongs to my neighbor!) to the word itself (Paulie Walnuts) are weak, then we can't get to the word even though we may remember everything about it. You may tickle neurons here, but the reverberations never reach those deeper in the circuit.
Sometimes we get to the first sound in the word but no further: the phonemes of words are apparently encoded separately, too, and coming up with that "eu-" sound doesn't guarantee that you'll move on to "-lo." Words we use infrequently are especially subject to this tip-of-the-tongue phenomenon. If you need to remember which medicine to take for a common ailment, you'll probably come up easily with "aspirin" for a headache or "antacid" for a stomach upset. But you might well struggle before remembering what's needed to treat a sudden allergic reaction: "antihistamine."
Misattribution. The El Al cargo flight had smashed into an apartment building outside Amsterdam, killing 39 residents and all four crew members in a fiery explosion. Ten months after the 1992 disaster, Dutch psychologists quizzed colleagues about how well they remembered television footage of the crash. Most remembered it so well that they could describe whether the fuselage was aflame before it hit, where the plane fell after impact and other details. But there was no such footage: people attributed to video what they had inferred from newspapers, discussions with friends and other sources.
In misattribution, people unconsciously transfer a memory from one mental category to another--from imagination to reality, from this time and place to that one, from hearsay to personal experience. The brain has made what psychologists call a "binding error," incorrectly linking the content of a memory with its context. The fault may lie in the hippocampus, a seahorse-shaped structure deep in the brain's temporal lobe, whose job includes binding together all facets of a memory. When the hippocampus is damaged, patients are more prone to binding errors. So next time you believe that you experienced something you only imagined, or that you mentioned your impending business trip to your wife when in fact you told only your secretary, blame a hiccup in your hippocampus.
Suggestibility. In this memory error, people confuse personal recollection with outside sources of information. Suggestibility is therefore a form of misattribution, but an especially pernicious one. "Leading questions or even encouraging feedback can result in 'memories' of events that never happened," says Schacter. In one recent case, Korean War veteran Edward Daly became convinced that he participated in the horrific massacre of civilians at No Gun Ri. Military records show he was nowhere near the site at the time, suggesting that he had confused hearing rumors of the massacre with witnessing it. (Some reporters, though, believe he was outright lying.) But that wasn't the end of it. As Daly talked to vets who were present at the massacre, "reminding" them of his deeds that day, several became convinced, as one told The New York Times, that "Daly was there. I know that. I know that."
Suggestibility can lead to false eyewitness IDs because even seemingly innocuous feedback can distort recall. In one study, psychologist Gary Wells of Iowa State University and colleagues showed volunteers a security video of a man entering a Target store. Moments later, Wells told them, the man murdered a guard. He then showed them photos and asked them to identify the gunman (who actually appeared in none of the snapshots). Good, you identified the actual suspect, the scientists told some of the volunteers. Those who received this encouragement later told Wells they were more confident in their recall and had had a better view of the man on the video than those who did not get a verbal pat on the back for their "correct" ID. Certainty and your assurance that you got a good look at the suspect are the kinds of details a jury uses when weighing eyewitness testimony. Positive feedback seems to cement memory and even erase any original uncertainty.
Persistence. Memories that refuse to fade tend to involve regret, trauma and other potent negative emotions. All emotions strengthen a memory, but negative ones seem to write on the brain in indelible ink, Schacter finds. That's especially true if the memory reinforces your self-image: if you think of yourself as a screw-up, you'll have a hard time erasing the memory of the time you spilled wine all over your boss. Blame your amygdala. When you experience a threatening event like the approach of a menacing stranger, the level of activity in this clutch of brain neurons predicts how well you will remember the experience. Stress hormones seem to strengthen the neuronal circuit that embodies a traumatic memory.
Bias. It is a cliche that couples in love recall their courtship as a time of bliss, while unhappy pairs recall that "I never really loved him [or her]." But the cliche is true. "We rewrite our memories of the past to fit our present views and needs," says Schacter. That may be an outgrowth of forgetting: we can't recall how we felt in the past, so we assume it must be how we feel today. But often bias arises when more powerful mental systems bully poor little memory. The left brain, driven to keep thoughts of yesterday and today from conflicting, reconciles past and present as boldly as the Ministry of Truth in Orwell's "1984."
Linda Levine of UC, Irvine, showed exactly this when she interviewed supporters of Ross Perot right after he unexpectedly dropped out of the 1992 presidential race that July. How did they feel about his decision? she asked. Soon after Perot re-entered in October, Levine revisited the same supporters, asking again how they had felt about the July drop-out. Those who'd never wavered in their support remembered feeling less sad about Perot's quitting than they had claimed in July: their happiness over his return had overwritten their unhappy memory. Disgruntled supporters who had initially switched to another candidate but had gone back to Perot recalled feeling less anger in October than they reported in July. Their relief over his return to the race trumped their ire at feeling abandoned.
Stereotyping can also bias memory. Researchers at Yale University led by Mahzarin Banaji asked students which names on a list they recalled as those of criminals recently in the news. The students were twice as likely to "remember" the stereotypically black names ("Tyrone Washington") as they were the stereotypically white ones ("Adam McCarthy"). None of the names had been in the news as criminal suspects or anything else, the scientists reported in 1999. When memory conflicts with what you're convinced is true, it often comes out on the losing end. And that can make forgetting where you put your keys seem trivial indeed.