Scientists have assumed for a long time that actively paying attention to things is a “gateway” to working memory — the memory that helps people remember small information to do cognitive tasks. Think remembering someone’s home address while processing the directions.

But new research shows that this is not always the case. Sometimes, the brain can actively inhibit certain things from entering people’s memory, even if they’ve paid full attention.

The study, published last week in Science Advances, noted that previous research ignored the exact relationship between attention and memory; it overlooked how information that is redundant in the long term is processed. The subconscious brain knows that information, such as one-time passwords, will soon be “outdated.” The brain then does little to retain this information, no matter how much one may try to memorize those digits.

“Working memory,” the researchers note, is a “severely capacity-limited system that would overload if it stored outdated (although attended) information.” In the new study, they found that the brain does have a blocking mechanism of sorts to prevent this overload.

Over a series of six experiments, scientists showed participants different shapes, colors, and other features of a particular object. They tested how well the participants remember each feature depending on what they were specifically asked to remember.

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Participants were asked to note and record the attended but “outdated” information (such as the shape of the object); the irrelevant information was the one they weren’t asked to report at all (such as the color). The results showed that people were able to recall the irrelevant information more often than the attended but outdated information. That is, the brain deliberately ignored some of the things it paid attention to.

“In other words, we found a counterintuitive phenomenon in which paying more attention to a piece of information weakened working memory rather than strengthened it,” the paper states.

Researchers concluded that our brain actively inhibits outdated information in our working memory.

While this may seem counterintuitive, there’s a reason why it happens. “We believe this active discarding/inhibition of outdated information serves as an adaptive function of our brain,” scientists noted, in order to constantly update working memory efficiently. In other words, it is a functioning necessity to overlook outdated information in order for people to remember more important things.

One theory as to why the brain sometimes filters out attended but outdated information more than irrelevant information, however, is that there may be a “lower activation” of a stimulus. In the present research, when told to ignore a particular feature, the color of the object, meant the brain spent less time actively inhibiting it than information which is attended to.

The applications of the findings are varied. Researchers believe that these new insights into the link between attention and working memory can help in treatments for PTSD. Moreover, the idea that working memory is selective in the information it retains holds relevance for eyewitness testimonies also — it impacts what the brain thinks would be important later.

With attention being one of the most integral cognitive functions that shape our memories and the information we retain, understanding it better helps us understand how we perceive and interact with the world at large.