Speaking slowly is a better indicator of congnitive decline than forgetting words!

In everyday life, many of us experience letology without even realizing it. What is it about? Well, it's simply because of the difficulty in finding the right word, which tends to get worse with age. Although this difficulty may indicate changes in the brain consistent with the early ("preclinical") stages of Alzheimer's disease, a recent study from the University of Toronto, Canada, suggests that it is primarily speech speed that serves as an indicator of brain health in older adults.

To reach that conclusion, the researchers asked 125 healthy adults, ranging in age from 18 to 90, to describe a scene in detail. The recordings of these descriptions were then analyzed using artificial intelligence (AI) software that extracted features such as speech speed, the duration of pauses between words, and the variety of words used.

The Challenge of Finding the Right Word

Participants also completed a series of standard tests that measured concentration, speed of thought, and the ability to plan and carry out tasks. The age-related decline of these "executive" abilities was closely linked to the rhythm of a person's everyday speech, suggesting a broader decline than mere difficulty finding the right word

A novel aspect of this study was the use of an "image-word interference task," a task designed to separate the two steps of naming an object: finding the right word and sending the command to the mouth to say it aloud.

During this task, participants were shown images of everyday objects (such as a broom) while playing an audio clip of a word related in meaning (such as mop) or similar sounding (such as at).

Interestingly, the researchers found that the natural speed of speech in older adults was related to their speed in naming pictures. This highlights that the cognitive and linguistic changes that occur with age could be due to a general slowdown in processing, rather than a specific problem of retrieving words in memory.

A conversation is more complex

Although the results of this study are interesting, word search in response to image-based cues may not reflect the complexity of vocabulary in an unconstrained everyday conversation.

Verbal fluency tasks, which require participants to generate as many words as possible from a given category (e.g., animals or fruits), or to start with a specific letter within a time limit, can also be used to better analyze the "tip of the tongue" phenomenon.

It's important given that while verbal fluency doesn't decrease significantly with normal aging (as demonstrated in a 2022 study), poor performance on these tasks can alert you to neurodegenerative diseases like Alzheimer's.

A verbal fluency test involves several brain regions related to language, memory, and executive functioning, so it can help to understand which regions of the brain are affected by cognitive decline.

If the authors of the University of Toronto study had also delved into participants' subjective sensations when struggling to retrieve words, they could help create more powerful tools to quantify and detect early cognitive decline.

Detect cognitive changes as early as possible

Nonetheless, this study has opened exciting doors for future research, showing that it's not just what we say, but also how quickly we say it, that can reveal cognitive changes.

Leveraging natural language processing technologies (a type of AI), which use computational techniques to analyze and understand human language data, this work advances previous studies that observed subtle changes in the spoken and written language of public figures such as Ronald Reagan and Iris Murdoch in the years leading up to their dementia diagnosis.

While those reports were based on a retrospective look after dementia diagnosis, the new study offers a more systematic, data-driven, future-oriented approach.

Rapid advances in knowledge of natural language processing will automatically detect changes in language, such as slowing down in speech speed, which could help identify at-risk individuals before more severe symptoms appear.