NIH study suggests human brains work like online search engines to remember certain words better than others

The National Institute of Health released a study detailing why some words are far easier to remember than others.

“We found that some words are much more memorable than others. Our results support the idea that our memories are wired into neural networks and that our brains search for these memories, just the way search engines track down information on the internet,” said Weizhen (Zane) Xie, Ph.D., a cognitive psychologist and post-doctoral fellow at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), who led the study published in Nature Human Behaviour. “We hope that these results can be used as a road map to evaluate the health of a person’s memory and brain.”

A memory test taken by 30 epilepsy patients was re-analyzed and it was during this observation when Dr. Xie and his colleagues noticed these words, according to an NIH study news release.

“Our goal is to find and eliminate the source of these harmful and debilitating seizures,” said Kareem Zaghloul, M.D., Ph.D., a neurosurgeon and senior investigator at NINDS. “The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers we have been able to uncover some of the blueprints behind our memories.”

Patients were shown pairs of words that had no real relationship with one another, such as “hand” and “apple,” from a list of 300 common nouns. Seconds later, they were shown one of the words again, for example “hand,” and asked to remember its pair, which in this case was “apple.”

The test results revealed that patients successfully recalled some words more often than others, regardless of the way the words were paired. Of the 300 words used, the top five were on average about seven times more likely to be successfully recalled than the bottom five, according to the study.

For many years scientists have thought that successful recall of a paired word meant that a person’s brain made a strong connection between the two words during learning and that a similar process may explain why some experiences are more memorable than others, according to the news release.

However, once doctors saw similar results after 2,623 healthy volunteers took an online version of the word pair test, their outlooks changed.

“We saw that some things – in this case, words – may be inherently easier for our brains to recall than others,” said Dr. Zaghloul. “These results also provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside of the study.”

“Our exciting finding is that there are some images of people or places that are inherently memorable for all people, even though we have each seen different things in our lives,” said Wilma Bainbridge, Ph.D., an assistant professor in the department of psychology at the University of Chicago. “And if image memorability is so powerful, this means we can know in advance what people are likely to remember or forget.”

Electrical recordings of the brain's language center, showed that the patients' brains replayed the neural signatures behind those words earlier than the less memorable ones. The researchers saw this trend when they looked at both averages of all results and individual trials, which strongly suggested that the more memorable words are easier for the brain to find, according to the news release. 

Results suggested that the more memorable words were more often linked to the meanings of other words used in the English language. This meant that when researchers plugged these similarities into a computer model, it correctly guessed which words were memorable from patients and healthy volunteer tests. This supported previous studies which suggested that the brain may revisit these highly connected memories, like the way animals forage for food or a computer searches the internet, the news released concluded.

“You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences,” said Dr. Xie. “Our results also suggest that the structure of the English language is stored in everyone’s brains and we hope that, one day, it is used to overcome the variability doctors face when trying to evaluate the health of a person’s memory and brain.”

NIH is currently exploring ways to incorporate their results and computer model into the development of memory tests for Alzheimer’s disease and other forms of dementia.