Why do some sentences stay in your head much longer than others?

A short sentence can fade fast. Another can hang around for minutes, or years. New research from MIT suggests the difference is not style or spelling. It is meaning.

In a study of 500 people and 2,500 sentences, cognitive scientists found that sentences with distinctive meanings are easier to remember. They stand apart from what you have seen before. That separation gives your memory a clearer handle later.

“Every cloud has a blue lining!” is odd and vivid. “You still had to prove yourself.” feels familiar. A few minutes later, the first line is more likely to return.

“One might have thought that when you remember sentences, maybe it’s all about the visual features of the sentence, but we found that that was not the case. A big contribution of this paper is pinning down that it is the meaning-related space that makes sentences memorable,” says Greta Tuckute PhD ’25, now a research fellow at Harvard University’s Kempner Institute.

Tuckute and MIT graduate student Thomas Clark are lead authors. MIT graduate student Bryan Medina is also an author. Evelina Fedorenko is the senior author. She is an MIT associate professor of brain and cognitive sciences. She is also a member of MIT’s McGovern Institute for Brain Research.

Researchers have long asked why certain things stick. Past work showed that people often remember the same images. In a 2011 study, Aude Oliva and colleagues found strong patterns. Photos with people were most memorable. Natural landscapes were least memorable.

That earlier work sparked another question. Do words also vary in memorability? A recent study from the same research team suggests they do. Words with a single, specific meaning can be easier to recognize later. Words with many meanings or many synonyms are harder.

Now the researchers have taken the same idea to sentences. A sentence can be simple and still feel unique. Another can share meaning with many others you have heard.

To test that, the team built a sentence set of 2,500 items. Each sentence had exactly six words. The lines came from public databases. They included text from novels, news articles, movie dialogue, and other sources.

"Each participant saw about 1,000 sentences. Some sentences repeated later. When a line returned, the person pressed a button if they remembered it," Tuckute shared with The Brighter Side of News.

"We found that the pattern was clear. Some sentences were recognized quickly and accurately. Others produced slower responses and more uncertainty," she continued.

Among the most memorable lines were “Homer Simpson is hungry, very hungry,” and “These mosquitoes are — well, guinea pigs.” The study text includes that second sentence with an em dash. In plain writing, it reads better with a pause. The researchers kept the original wording in their examples.

The deeper result was not about humor or pop culture. It was about meaning.

The team compared several ways to predict memorability. One model used the memorability of each word in a sentence. That approach did a decent job. Still, it did not match the power of a model built to measure meaning.

For meaning, the researchers used a large language model called Sentence BERT. It can represent each sentence as a vector. That vector captures semantic similarity, meaning how close one sentence is to another in “meaning space.”

This let the team compute a distinctness score. A sentence scored as distinctive if it sat far from other sentences. A sentence scored as less distinctive if it clustered among many similar ones.

The results showed that semantic distinctness lined up strongly with human memory. Sentences with unusual meanings were more memorable. This held even when word-level memorability was taken into account.

The key idea is that your mind does not store every sentence as a perfect copy. It stores an impression. The impression can blur, and it can collide with other impressions.

The study supports a view called the noisy representation hypothesis. Under this idea, memories are not crisp files. They are noisy representations that lose detail.

“The representation is gradually going to accumulate some noise. As a result, when you see an image or a sentence for a second time, your accuracy at judging whether you’ve seen it before will be affected, and it’ll be less than 100 percent in most cases,” Clark says.

Meaning makes the difference because of crowding. If many sentences share meaning, they overlap in memory space.

“When you encode sentences that have a similar meaning, there’s feature overlap in that space. Therefore, a particular sentence you’ve encoded is not linked to a unique set of features, but rather to a whole bunch of features that may overlap with other sentences,” Fedorenko says.

That overlap can make recognition shaky. You may feel a sentence is familiar, but you cannot place it. A distinctive meaning reduces that confusion.

“Your memory may still be noisy, but your ability to make judgments based on the representations is less affected by that noise because the representation is so distinctive to begin with,” Clark says.

This finding may match your lived experience. You can remember a strange headline with ease. You may forget ten ordinary updates. Your mind seems to tag the unusual. The study suggests the tag is not just emotion or style. It is semantic distance.

The researchers give a blunt example of distinctiveness. A question like “Does olive oil work for tanning?” carries a meaning you likely have not stored often. That novelty makes it less crowded. It becomes easier to pick out later.

The study also hints at how your brain keeps learning without wiping old memories. If memories pack into meaning space, you can still store new material. Some will collide. Some will stand alone.

The team plans to test other sentence features next. They want to study whether vivid, descriptive language adds memorability. They also want to explore how the language system interacts with hippocampal memory structures during encoding and retrieval.

This work could reshape how you design learning and communication. If meaning distinctness drives memory, educators may craft examples that differ sharply in idea, not just wording. Writers may aim for lines that express a clear, uncommon point.

Health campaigns and safety messages might become stickier by choosing meanings that avoid familiar, crowded phrasing.

Researchers may also use semantic distinctness to predict what people will remember from long texts, improving studies of attention, misinformation, and learning.

Research findings are available online in the Journal of Memory and Language.

Like these kind of feel good stories? Get The Brighter Side of News' newsletter.