Erasing Memories: Lies of Omission Can Spread Disinformation

Telling partial truths is the most effective way to lie: Simply leave out some critical information. How do these lies affect memory? Can they spread disinformation?

Lies of Omission

You can lie by telling the truth. We’ve all done this. We’ve told people some, but not all, of a story. Maybe you did this with your parents at some point. They asked where you were, who you were with, and what you did. You tell them true things. You tell them some of the places, some of the people, and some of the activities. But you may have left out something critical. Maybe you didn’t tell them the things you knew would upset them and get you in trouble. You implied that you were perfectly well-behaved last night. And your parents concluded everything was fine. An effective lie of omission.

Omissions, whether accidental ones or lies, can have interesting effects on memory. When we remember information and share that with others, we are unlikely to remember and report everything. Something will get left out. Sometimes that’s just the nature of remembering. And sometimes it is intentional—a lie to guide people to a particular perspective.

How Omissions Shape Memory

Omissions shape our memories in two ways. First, we remember what we rehearse. When we recall and share information, we become more likely to remember the same information later. Repetition increases memory. By telling a story, we create the version of the story that we keep telling.

But here’s the interesting part. We not only remember what we rehearse, but we also forget what gets left out (Anderson, Bjork, & Bjork, 1994). When you rehearse some information, you may be erasing the information you don’t rehearse. This is more than simply a lack of rehearsing. You’re less likely to remember the parts of a story left unrehearsed than parts of another story that wasn’t rehearsed at all. Rehearsal improves memory for the parts you practice. And it erases the parts of the story that are omitted. Of course, this makes it easier to keep your lie of omission consistent. You have strengthened the parts you tell and weakened the parts you chose not to share.

But this form of forgetting isn’t something that only happens in the mind of the person remembering. Forgetting by omitting also works in social groups too. If a set of people experience an event together, they may later remember and talk about it together. Imagine you are with a set of friends. One person is telling a story about something you’ve all done together. In telling the story, they emphasize some aspects. They also neglect other parts of the story. Those omitted pieces are likely to be forgotten later by the storyteller and by the audience (Cuc, Koppel, & Hirst, 2007).

This is how lying by omission changes memories. You strengthen the part you rehearse. You erase the parts you don’t rehearse. And your lies of omission have the same effects on your audience as you tell the story. If they experienced the event with you, hearing you tell the story will strengthen their memories for what you include—and they will also adopt information they may have forgotten and never noticed (Jalbert, Hyman, & Wulff, 2021) But they may also erase their memories for the omitted parts. Your omissions cause their forgetting.

How Lies of Omission Spread Disinformation

I’ve been thinking recently about how lying by omission can lead to the spread of disinformation. A news report, like someone sharing a memory, is always selective. The report may convey true information. But it invariably excludes other relevant true information. Later, people will remember the repeated information, but forget the parts that were left out of the stories.

Consider, for example, news stories about COVID vaccinations. Some news reports have focused on side effects and breakthrough infections in vaccinated people. These reports can provide true information. But they may omit critical sets of information—the very low rates of infection, hospitalization, and death in vaccinated people (or bury that at the end of the story people don’t read). These rates are incredibly low when compared to unvaccinated people. Honest news reports may focus on true negative news about the vaccines without including the true benefits. This can be misleading—even if not intended to be misleading. It may lead viewers to remember the risks and forget the benefits. Such stories may make people less likely to get the vaccine.

But let’s also consider a more nefarious example—one that is a direct lie by omission. Consider a new-entertainment person. Maybe they routinely discuss the risks of vaccines and have anti-vax people on their show. Maybe some of the anti-vax points are false. The news-entertainment person may lead their audience to rehearse the negative aspects. When asked if they have been vaccinated, they refuse to answer and change the topic. This is a lie by omission if they have been vaccinated. Failing to tell the complete truth leaves people with the impression that they aren’t vaccinated. Here is a link to a Vanity Fair article about such an example of lying by omission.

Memory Essential Reads

How to Change Your Outlook by Shaping Your Negative Memories

How to Hold On to Your Best Memories

My point is simple. We always are selective in what we remember and share with others. Sometimes we lie by using these omissions—intentionally omitting some information to leave people with an incorrect impression. These omissions can spread disinformation, like if that news-entertainer is vaccinated but doesn’t disclose when asked. If they spread negative information and encourage others to promote anti-vax views while not acknowledging that they and their family are vaccinated, then they are using omissions to lie to their audience. In a situation like this, their audience will remember the rehearsed anti-vax message. They will not learn the truth that even the person supporting anti-vax views has chosen to be vaccinated to protect themselves.