Two people witness the same incident. In the days that follow, they hear different descriptions of what happened - one in a conversation with a colleague, one from reading an account shared in a group message. When they are later asked to recall the incident, their accounts have diverged. Not because they saw different things, but because what they saw has been partially overwritten by what they subsequently encountered.

This is the misinformation effect.

What it is

The misinformation effect is a memory distortion where exposure to incorrect information after an event reduces the accuracy of later recall of that event. Exposure to misleading post-event information can reduce the accuracy of subsequent memory reports about the original event.

The effect is not about deliberate deception. It operates through ordinary memory processes - the way information encountered after an event gets encoded alongside the original memory, and can, under certain conditions, compete with or substitute for the original details during retrieval.

The mechanism

Memory is reconstructive, not reproductive. When you retrieve a memory, you do not play back a recording - you reassemble it from stored traces, filling in gaps with schema-consistent information and integrating material from multiple sources. Post-event information enters this reconstruction process as a source of material.

The effect operates through memory updating: post-event information is encoded and, when plausible and repeated, can compete with or overwrite the original memory trace during retrieval, especially when the original memory is weak or the misleading information is consistent with the general schema of what happened.

The more plausible the misinformation and the weaker the original trace, the more likely it is to be incorporated. Misinformation that closely matches the general shape of the original event - changing a detail rather than contradicting the whole account - is particularly likely to pass undetected into the reconstructed memory.

A decision autopsy

An employee witnesses a workplace incident. Their initial account is given promptly and is relatively detailed. Subsequent conversations in the team produce slightly different versions of events - different details, different emphasis. Some of these versions are inaccurate, but they are plausible.

When the employee is asked to give a formal account two weeks later, their report has shifted toward the version circulating in the team. They are not aware of this shift. The version they give now feels like a clearer memory than their original account - not because it is more accurate, but because it has been consolidated through repeated social exposure.

This is the misinformation effect in a professional setting: accurate initial recall, gradually contaminated by post-event information, producing a confident but partially inaccurate account.

Where it matters

Eyewitness testimony and legal contexts. The misinformation effect has particular significance in legal settings, where the accuracy of eyewitness accounts can affect significant outcomes. Post-event exposure to descriptions of events - through news, conversation, or repeated questioning - can alter what witnesses later report, even when they are genuinely trying to be accurate.

Investigations and incident reporting. In workplace investigations, the order and structure of interviews matters. Witnesses interviewed after others, or after exposure to group discussions about the incident, may report details that reflect the group's shared version rather than their own direct observation.

Everyday social contexts. The effect applies to any situation where a memory is formed and then a person encounters information about the same event through conversation, media, or social channels. Personal memories of shared events - arguments, trips, incidents, conversations - are susceptible to misinformation from subsequent accounts.

What it is not

The misinformation effect does not mean memories are completely fabricated. The effect typically alters specific details rather than creating wholly false memories. The core of the original event usually remains; what changes are peripheral details, specific descriptions, or ambiguous aspects that the misinformation fills in.

Intentional deception is not required. Subtle suggestions, plausible alternative descriptions heard in passing, or repeated social accounts are sufficient to produce the effect. The misinformation does not need to be planted deliberately to alter memory.

The effect is not only immediate. Misinformation encountered days or weeks after an event can still alter the memory of that event during subsequent recall. The effect is not confined to a narrow post-event window.

Sources