I sometimes forget where I put my glasses, so I look for them and eventually find them on my head. Most people have had such experiences. And the few who haven’t could probably be made to believe that they have. Dr. Steven Novella has said of our recollections, “You have a distorted and constructed memory of a distorted and constructed perception, both of which are subservient to whatever narrative your brain is operating under.”

That is one reason why 70 percent of participants in a study conducted by Dr. Julia Shaw confessed to a crime that never occurred. Some even offered details of this non-event. Shaw swayed the subjects by mixing facts with misinformation over three hours of friendly conversation. So confessing to crimes never committed can involve more than plea-bargaining. Suspects under duress and torture are even more vulnerable.

I have countless memories of playing Wiffle Ball growing up, but wonder now how accurate they are. The sport was my favorite outlet for suspended adolescence and I played into my 30s, recording some of the latter days on film. Even two days later, my memories of things said and plays made clashed with what I was watching on tape. False memories such as this can be a distortion of something that happened, a combination of past events, or something invented.

Some are called “source memory errors,” in which the event is remembered, but the particulars confused. For instance, I may remember being picked off first base by Jerry, when it was really his brother Steve who nailed me. Or I may confuse this with a scene from the Bad News Bears.

In extreme cases, there is source amnesia. A woman, in good faith, wrongly accused psychologist Donald Thompson of raping her. The doctor was cleared because at the time of the assault, he had been on live television. It was eventually deduced that the victim had been watching the show when she was assaulted, and blocked most of it out, but associated the doctor with the attack.

I have about a dozen memories of the place I lived at ages 2 and 3: Getting candy from my uncle, a bicycle-built-for-two, and most gloriously, winning Pin the Tail on the Donkey at my third birthday party. Memories this distant are rare because the left inferior prefrontal lobe, required for long-term memory, is underdeveloped in toddlers. Furthermore, memories this ancient are usually fragmented.

Fragmented memories don’t end with adolescence. Author Martin Conway documented the case of a woman who became upset when encountering bricks or paths. It turned out she had been raped as a child on a brick path. Returning to the scene of the crime upset her, though she failed to recall the attack. False and fragmented memories are especially worrisome when they are used by prosecutors and therapists. An unscrupulous individual can encourage a patient or witness to dig deeper for memories that aren’t there, or use an incident to suggest something further happened.

False memories are sometimes the result of one anticipating that something will happen, then remembering it as if it did. I was a basketball manager in high school, stuck watching the boring JV game at the recreation center. The game was running long, and I really wanted to leave to catch the start of the varsity game. While I watched from a distance, another manager asked the JV coach if we could leave. I figured the coach would want us to go, since keeping the varsity statistics took precedence. He nodded his head yes, and off I flew. He later asked why I had left, I told him this story, and he insisted he had shaken his head no. Indeed, he had. I wanted so bad and anticipated so much that he would affirm the request, that’s what I ‘saw.’ This anticipation can be even more influential if leading questions are used, if misinformation comes from a trusted source, or if social and peer pressures are in play. UFO abductions began being perpetrated by gray aliens after the creatures appeared in a 1975 television program.

The McMartin preschool case unraveled when children began reporting that their tormenters were flying or that they included Chuck Norris. But in cases where the supposed memory is realistic, the injustice goes unnoticed.

Another key point is that memories are much more likely to be recovered after contact with a familiar object, place, or aroma, rather than in a therapist’s office or police interrogation room. And if a smell or sight rekindles a memory, it will flow naturally, whereas a detective or therapist may help the person fill in details that are imagined, or encourage them to omit others. Children are especially vulnerable to suggestion and leading questions. When children say they have no memory of something, it is unethical to prod them further.

I was in third hour English class when I heard about the first Space Shuttle disaster. My neighbor on his riding lawnmower told me about the Ronald Reagan assassination attempt. That’s how I remember these things, anyway. Cognitive psychologist Ulric Neisser had persons write down where they were when a momentous event occurred, then asked them the same question years later. Memory had a spotty performance in Neisser’s research, with some subjects even denying they had written the entry.

Phrasing can be crucial. When asked how tall a person was, test subjects estimated a whopping 10 inches more than those who were asked how short the person was. In another study conducted by psychologists Elizabeth Loftus and John Palmer, subjects were shown videos of a car crash that occurred at either 20, 30, or 40 miles per hour. Subjects were then asked to estimate the speed. They guessed the speed not based on the rate of travel, but on which verb described the incident. If the word was “contact,” most respondents said 20 mph. It the verb was “collided,” 30 mph was the most frequent answer, while “smashed” yielded mostly answers of 40 mph.

At least the car was traveling. But later in the experiment, researchers asked the participants if they had seen any broken glass, when there wasn’t any. Again, depending on the verb used, respondents were more likely to report seeing broken glass, a completely invented memory. Likewise, when subjects were asked if they had seen “a stop sign,” they usually said no. But there was a sharp increase when subjects were asked if they had seen “the stop sign,” insinuating there was one. These instances show the vulnerability of someone whose memory is being challenged, especially by someone in a position of authority. And don’t you forget it.