How Your Brain’s Speed Limit Works
We’ve all experienced it. We’re sharing a story, and we can’t think of a name. We picture the person and maybe think of their initials. But the name? It takes a while for it to come.
This can happen at any age, but it does occur more frequently as we get older due to slower retrieval speed.
“Processing speed is one of the main things that decline as people get older,” said Hayley B. Kristinsson, PsyD, a neuropsychologist at the University of California, Irvine Medical School. “It’s typically due to changes in the white matter in the brain, but it’s mild and gradual. It’s not something that happens suddenly or is really pronounced.”
We also tend to worry about it because it’s so noticeable and emotionally charged. We may feel embarrassed or angry that we can’t remember something so seemingly simple.
“It’s a frustrating difficulty for all of us, so you notice it every single time it happens,” Dr. Kristinsson said.
Measuring Brain Speed
Information that flows through your brain includes speaking, making decisions while driving, or multi-tasking, such as watching TV while knitting. Brain speed is measured in “bits,” which is a very small chunk of information.
Scientists say the average “speed limit” for processing information in the human brain is 10 bits per second, although some researchers believe that the speed could be higher.
“Processing speed is one of the main things that decline as people get older. It’s a frustrating difficulty for all of us, so you notice it every single time it happens.”
Your processing speed changes throughout life. As children grow and learn new things, their processing speed increases. It usually stays steady in early to mid-adulthood and then starts to slow down, with most people noticing it between midlife and their later 60s or 70s. But brain health shouldn’t be measured just by brain speed, according to experts.
“Faster isn’t always better,” said Laura Lacritz, PhD, a neuropsychologist at the University of Texas Southwestern Medical Center. “Faster can result in people being more impulsive. They may do things without thinking them through or having all the information. So, slowing down to process and get the information they need is not always a bad thing.”
It can also take longer for an older person to learn a new task or memorize something, but experts say that a healthy older adult who has enough time to learn the skill or complete the task does just as well as a younger person—and maybe even better given their level of experience and knowledge.
Of course, the task at hand plays a role in how important speedy decisions might be. Navigating a tricky intersection while driving takes more effort because you have to make many sudden decisions. As people notice their reaction speed dropping, they may start driving more cautiously at slower speeds. They may leave more space between cars, cut down on driving distances, and even avoid driving at night to accommodate these slower reaction times.
These adjustments appear to pay off. Statistics show that fewer drivers in their 60s and 70s die in motor vehicle crashes than their younger counterparts.
Slower brain speed isn’t just limited to aging. Anyone of any age can experience temporary slower thought processes. “[It can be caused by] sleep deprivation, stress or anxiety, depression, pain, certain medications or drugs, alcohol, or fatigue, as well as hormonal changes and certain illnesses, Dr. Lacritz. “There are lots of things that can temporarily affect processing speed.”
Speed and Multi-tasking
If you’re in the habit of doing more than one thing at a time, slower processing time affects that, too. When you’re multi-tasking, you’re really not doing two or more things at once, although it seems that way. Instead, you’re switching between tasks very quickly, Dr. Lacritz explained.
The two tasks are actually being done separately, but your brain allows you to switch so quickly between the two that you have the impression you’re doing both at the same time. As processing speed drops, it takes longer for you to make the switches. So, if you’re trying to cook while talking on the phone or checking messages, mentally going back and forth might not feel as seamless as it once did.
Aging’s Brain Benefits
We can’t forget that although our brains might slow down as we age, we also have a mental library stocked with shelves of information that we’ve accumulated over the decades. For example, we have larger vocabularies and know more about many topics with greater depth than younger adults who haven’t experienced as much life as we have.
“One of the greatest things that you gain with aging is experience and knowledge, and those things can continue to grow across the lifespan,” Dr. Lacritz said. “These become very important for things like making decisions.”
Dr. Kristinsson added that this life experience also often helps older adults handle emotion better in everyday life, react less strongly to minor stressors, and recover from negative feelings more quickly.
“In general in society, we put a big emphasis on speed,” she said. “[But] there aren’t a lot of things that really require super-fast processing.”
When to Be Concerned
Slower processing speed in normal aging can affect retrieval, resulting in occasional lapses and “tip-of-the-tongue” moments. So, when should you start to worry?
“A neurodegenerative disorder such as Alzheimer’s disease tends to impact storage of new information,” Dr. Kristinsson said. “So, it is more concerning when someone doesn’t realize that anything was lost, or if the information never comes back, particularly when this becomes a pattern.”
She suggested that if others notice these things before you do, or if the lapses are following a pattern or impacting your daily life—such as missing appointments or mixing up medications—it would be a good idea to see a doctor for an evaluation.
