Memory is not exact. Like scientists who infer a dinosaur’s appearance from its remains, we infer our past from stored tidbits of information plus what we later imagined, expected, saw, and heard. We don’t just retrieve memories; we reweave them (Gilbert, 2006). Our memories are like Wikipedia pages, capable of continuous revision. When we “replay” a memory, we often replace the original with a slightly modified version (Hardt et al., 2010). (Memory researchers call this reconsolidation.) So, in a sense, said Joseph LeDoux (2009), “your memory is only as good as your last memory. The fewer times you use it, the more [unchanged] it is.” This means that, to some degree, all memory is false (Bernstein & Loftus, 2009).

Despite knowing all this, I [DM] recently rewrote my own past. It happened at an international conference, where memory researcher Elizabeth Loftus (2012) was demonstrating how memory works. Loftus showed us a handful of individual faces that we were later to identify, as if in a police lineup. Then she showed us some pairs of faces, one face we had seen earlier and one we had not, and asked us to identify the one we had seen. But one pair she had slipped in included two new faces, one of which was rather like a face we had seen earlier. Most of us understandably but wrongly identified this face as one we had previously seen. To climax the demonstration, when she showed us the originally seen face and the previously chosen wrong face, most of us picked the wrong face! As a result of our memory reconsolidation, we—an audience of psychologists who should have known better—had replaced the original memory with a false memory.

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Clinical researchers have experimented with memory reconsolidation. People recalled a traumatic or negative experience and then had the reconsolidation of that memory disrupted, with a drug or brief, painless electroconvulsive shock (Kroes et al., 2014; Lonergan, 2013). Someday it might become possible to erase your memory of a specific traumatic experience—by reactivating that memory and then disrupting its storage. Would you wish for this? If brutally assaulted, would you welcome having your memory of the attack and its associated fears deleted?

In more than 200 experiments involving more than 20,000 people, Loftus has shown how eyewitnesses reconstruct their memories when questioned after a crime or an accident. In one important study, two groups of people watched a film clip of a traffic accident and then answered questions about what they had seen (Loftus & Palmer, 1974). Those asked, “About how fast were the cars going when they smashed into each other?” gave higher speed estimates than those asked, “About how fast were the cars going when they hit each other?” A week later, when asked whether they recalled seeing any broken glass, people who had heard smashed in the leading (suggestive) version of the question were more than twice as likely to report seeing glass fragments (FIGURE 7.17). In fact, the film showed no broken glass.

In many follow-up experiments around the world, others have witnessed an event. Then they have received or not received misleading information about it. And then they have taken a memory test. The repeated result is a misinformation effect. Exposed to misleading information, we tend to misremember (Loftus et al., 1992). Coke cans become peanut cans. Breakfast cereal becomes eggs. A clean-shaven man morphs into a man with a mustache.

Just hearing a vivid retelling of an event may implant false memories. One experiment falsely suggested to some Dutch university students that, as children, they had become ill after eating spoiled egg salad (Geraerts et al., 2008). After absorbing that suggestion, they were less likely to eat egg salad sandwiches, both immediately and four months later.

Even repeatedly imagining fake actions and events can create false memories. Canadian university students were asked to recall two events from their past. One event actually happened; the other was a false event that involved committing a crime, such as assaulting someone with a weapon. Initially, none of the lawful students remembered breaking the law. But after repeated interviewing, 70 percent of students reported a detailed false memory of having committed the crime (Shaw & Porter, 2015).

Should we be surprised that digitally altered photos have produced the same result? In experiments, researchers have altered photos from a family album to show some family members taking a hot-air balloon ride. After viewing these photos (rather than photos showing just the balloon), children “remembered” the faked experience. And days later, they reported even richer details of their false memories (Strange et al., 2008; Wade et al., 2002).

In British and Canadian university surveys, nearly one-fourth of students have reported personal memories that they later realized were not accurate (Mazzoni et al., 2010). I [DM] empathize. For decades, my cherished earliest memory was of my parents getting off the bus and walking to our house, bringing my baby brother home from the hospital. When, in middle age, I shared that memory with my father, he assured me they did not bring their newborn home on the Seattle Transit System. The human mind, it seems, comes with built-in Photoshopping software.

What is the weakest part of a memory? Its source. Have you ever recognized someone but had no idea where you had met the person? Or dreamed about an event and later wondered whether it really happened? Or misrecalled how you learned about something (Henkel et al., 2000)? If so, you experienced source amnesia—you retained the memory of the event but not of its context. Source amnesia, along with the misinformation effect, is at the heart of many false memories. Authors and songwriters sometimes suffer from it. They think an idea came from their own creative imagination, when in fact they are unintentionally plagiarizing something they earlier read or heard.

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Psychologist Donald Thompson became part of his own research on memory distortion when police brought him in for questioning about a rape. Although he was a near-perfect match to the victim’s memory of the rapist, Thompson had an airtight alibi. Just before the rape occurred, he was being interviewed on live TV and could not possibly have made it to the crime scene. Then it came to light that the victim had been watching the interview—ironically about face recognition—and had experienced source amnesia. She had confused her memories of Thompson with those of the rapist (Schacter, 1996).

Source amnesia also helps explain déjà vu (French for “already seen”). Two-thirds of us have experienced this fleeting, eerie sense that “I’ve been in this exact situation before.” The key to déjà vu seems to be that we are familiar with a stimulus or one like it but can’t recall where we ran into it before (Cleary, 2008). Normally, we experience a feeling of familiarity (thanks to temporal lobe processing) before we consciously remember details (thanks to hippocampus and frontal lobe processing). Sometimes, though, we may have a feeling of familiarity without conscious recall. As our amazing brain tries to make sense of this source amnesia, we get an eerie feeling that we’re reliving some earlier part of our life.

We often are confident of our inaccurate memories. Because the misinformation effect and source amnesia happen outside our awareness, it is hard to separate false memories from real ones (Schooler et al., 1986). Perhaps you can recall describing a childhood experience to a friend and filling in memory gaps with reasonable guesses. We all do it. After more retellings, those guessed details—now absorbed into your memory—may feel as real as if you had actually observed them (Roediger et al., 1993). False memories, like fake diamonds, seem so real. False memories can be persistent. Imagine that we were to read aloud a list of words such as candy, sugar, honey, and taste. Later, we ask you to recognize those words in a larger list. If you are at all like the people in a famous experiment (Roediger & McDermott, 1995), you would err three out of four times—by falsely remembering a new but similar word, such as sweet. We more easily remember the gist—the general idea—than the words themselves.

Memory construction errors can help us understand why some people have been sent to prison for crimes they never committed. Of 337 people who were later proven not guilty by DNA testing, 71 percent had been convicted because of faulty eyewitness identification (Innocence Project, 2015; Smalarz & Wells, 2015). “Hypnotically refreshed” memories of crimes often contain similar errors. If a hypnotist asks leading questions (“Did you hear loud noises?”), witnesses may weave that false information into their memory of the event. Memory construction errors also seem to be at work in many “recovered” memories of childhood abuse. See Thinking Critically About: Can Memories of Childhood Sexual Abuse Be Repressed and Then Recovered?

If memories can be sincere, yet sincerely wrong, how can jurors decide cases in which children’s memories of sexual abuse are the only evidence?

Stephen Ceci (1993) thinks “it would be truly awful to ever lose sight of the enormity of child abuse.” Yet Ceci and Maggie Bruck’s (1993, 1995) studies have made them aware of how easily children’s memories can be molded. For example, they asked 3-year-olds to show on anatomically correct dolls where a pediatrician had touched them. Of the children who had not received genital examinations, 55 percent pointed to either genital or anal areas.

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In other experiments, the researchers studied the effect of suggestive interviewing techniques (Bruck & Ceci, 1999, 2004). In one study, children chose a card from a deck of possible happenings, and an adult then read the card to them. For example, “Think real hard, and tell me if this ever happened to you. Can you remember going to the hospital with a mousetrap on your finger?” In weekly interviews, the same adult repeatedly asked children to think about several real and fictitious events. After 10 weeks of this, a new adult asked the same questions. The stunning result: 58 percent of preschoolers produced false (often vivid) stories about one or more events they had never experienced (Ceci et al., 1994). Here’s one:

My brother Colin was trying to get Blowtorch [an action figure] from me, and I wouldn’t let him take it from me, so he pushed me into the wood pile where the mousetrap was. And then my finger got caught in it. And then we went to the hospital, and my mommy, daddy, and Colin drove me there, to the hospital in our van, because it was far away. And the doctor put a bandage on this finger.

Given such detailed stories, professional psychologists who specialize in interviewing children could not reliably separate the real memories from the false ones. Nor could the children themselves. The child quoted above, reminded that his parents had told him several times that the mousetrap event never happened—that he had imagined it—protested. “But it really did happen. I remember it!”

We shouldn’t forget that children can be accurate eyewitnesses. When a neutral person has asked nonleading questions soon after the event, using words the children could understand, children often accurately recalled what happened and who did it (Goodman & Quas, 2008; Pipe et al., 2004).