Although we do not often think twice about the accuracy of our memories, the past is quite often falsely remembered. Here’s how:

Does Mr. Monopoly wear a monocle? Like many others, you might think that the famous board game mascot does, but that is not the case.

A prevalent example of the Mandela effect, some suggest that people misremember Mr. Monopoly wearing a monocle because, in a parallel universe, he actually does. 

But what if it is merely a glitch in your memory, and not proof for the existence of an alternate universe?

Our memories are the source of everything we know about ourselves and the world, influencing our every step. However, although the human brain is powerful, it is also limited. We can make errors in encoding or registering memories into our minds and in recalling them.

These memory distortions constitute what psychologists call false memory. A caveat is that false memories can be as vivid and detailed as accurate memories despite not corresponding to reality, thus prompting high confidence in people, making them seem reliable.

A major factor that allows false memories to occur is that every memory is the reconstruction of a past reality. In this reconstruction process we often replace, exclude, or add details - like a monocle - to our recollection. And we do it subconsciously.

Drawing inferences

In making sense of the world, our minds continuously make inferences about our surroundings. This, despite being considered a crucial part of cognition, can be misleading.

A study revealed that when people were asked to wait in an office and later asked to recall which items they saw there, many respondents reported seeing books, along with other items that were indeed there.

Despite not seeing them, people were confident that books were present in the office because they fit the context, or their office schema, thus adding a detail to their recollection.

This is just a small example of many ways in which the mind can add, exclude, or change the details of an event to fit in with pre-existing information in the mind.

Misleading post-event information

Information that comes after the original event can influence its reconstruction in memory, leading to a blend of what actually happened and the post-event information.

This means misinformation that is picked up after the event can contaminate memories. Post-event information can come in many forms, like an overheard conversation or a detail that is noticed in the aftermath.

In extreme cases, misinformation can even replace the correct recollection of an event.

Suggestibility is also crucial in post-event recollection, such that memories can be altered or even implanted with suggestions.

In such cases, we subconsciously misattribute the source of information as our own minds instead of an external source.

Flashbulb memories

Among memories of personal events, or events one has personally experienced, flashbulb memories are memories of unusual, heavily charged events like the September 11 attacks.

They usually stand out among other memories, and are reported to be remembered in vivid detail despite the test of time.

A study found that people’s recollections of 9/11 declined in time, just like other memories, but people insisted that their memories' accuracy was impeccable.

Indeed, they had better recollections of their close surroundings and their own experience due to the event's emotional charge, but were still open to faulty recollections of factual information related to the event itself.

Individual differences

Some people are more likely to form false memories than others. Children have been found to be more prone to false memories due to increased creative imagination and naivety.

Older adults are also reportedly more prone to developing false memories than younger adults.

Suggestibility was also found to increase for people who exhibit greater dissociation or distraction, determined by examining their scores on the Dissociative Experiences Scale (DES).

Another study found that people who scored relatively low on intelligence scales and perceptual ability tests tended to be more prone to false information. 

Trauma

Last but not least, researchers found that people who have experienced trauma, as well as those who have suffered from depression and post-traumatic stress disorder (PTSD), are more susceptible to forming false memories.

The study also concluded that heightened experiences of negative events are relatively more likely to lead to increased false memory formation compared to neutral and positive events.