Mastery of language could predict longevity

However, intelligence isn't a simple characteristic. There are many traits that contribute to it that can be tested -- from memory to mathematical logic. In a 2024 Clinical Psychological Science study, Paolo Ghisletta of the University of Geneva linked longevity specifically to one of those traits: verbal fluency, the measure of one's vocabulary and ability to use it.

Ghisletta's research used samples from the Berlin Aging Study, which started collecting data shortly before the Berlin Wall came down in 1989 (Baltes & Mayer, 1999). It tracked 516 people aged 70 to 105 from enrollment to their death, over as long as 18 years in some cases. The study measured factors like dental health, stress levels, and economic well-being, as well as cognition. This makes it a "rich and rare data set," said Ghisletta in an interview.

For the current study, researchers sampled nine different cognitive tests to understand if different aspects of intelligence might be more closely linked to longevity than others.

The tests measured four cognitive abilities: verbal fluency, perceptual speed, verbal knowledge, and episodic memory. Perceptual speed is a measure of one's ability to compare, scan, or perform pattern-assessing tasks with visual cues quickly. Verbal knowledge is a measure of one's vocabulary. Episodic memory is a measure of one's ability to recall and remember personal experiences.

Each of these categories was measured with several tests. One of the tests, for instance, measured verbal fluency by requiring participants to name as many animals as they could within 90 seconds.

Compiling data on the different cognitive skills, Ghisletta and his team incorporated information about how the participants' performance changed and estimated their risk of dying over time. They then developed a model that related the observed changes to risk of death. This required input from researchers across multiple universities with expertise in a type of data analysis called joint multivariate longitudinal survival model.

"Today, it's gotten much easier to do this kind of research because there are more data available. There are more people who are willing to collaborate. There are better tools," Ghisletta said.

Applying these novel tools, the researchers discovered that verbal fluency alone seemed to be significantly linked to longevity, though the explanation behind this connection is not clear. One popular theory, Ghisletta explained, is that the physical body is inextricably linked to mental, emotional, and cognitive processes. "All of these domains are just declining together, whether it's cognition, personality, emotions, or biological, medical decline in general," he said.

Following that theory, verbal fluency would be a good measure of well-being, Ghisletta explained, because it's a complex process that relies on multiple cognitive abilities. This might include long-term memory, vocabulary, efficiency, and visual memory. So, when you're testing your verbal fluency, "you are doing something very interesting," he said.

This research answers questions that Ghisletta has had since his time as a postdoctoral researcher in the 1990s. But it only became possible to perform analyses of this sort recently. He said this paper underscores the importance of collaboration between labs and makes him hopeful for more fruitful papers to come.

"It's a good time to be doing research. I'm really happy to work with young PhD students and have them play around with these different data sets and variables and the theoretical questions that we want to answer," Ghisletta said. "Although we are building up knowledge, every day, there's still so much here to discover."