Brain Patterns Reveal Why Elderly Drivers Are Prone to Mistaking the Gas Pedal for the Brake Pedal

Summary: Older people have longer reaction times, slower decision times, and greater activation in brain areas involved in inhibition and task switching. The findings may shed light on why many older drivers mistake the accelerator for the brake pedal.

Source: Nagoya University

Scanning the brains of elderly people and college students while performing braking and acceleration simulations, researchers in Japan have found that older participants have longer reaction times, slower decision times, and greater brain activation in the parts of the brain involved with inhibition and switching tasks.

These findings suggest insights into the causes of accidents involving elderly drivers who mistake the brake for the accelerator. 

As reported in the media, accidents have increased in which older drivers mistakenly step on the accelerator instead of the brake.

Concerned that cognitive decline may be a leading cause of such incidents, the National Police Agency of Japan, a country with one of the oldest populations in the world, requires adults over 75 years of age to take periodic cognitive tests.

However, few studies have investigated executive functions and brain activity among older adults in terms of foot responses during braking and accelerating.  

To address this gap, a group led by Professor Nobuyuki Kawai of the Graduate School of Informatics at Nagoya University in Japan scanned the brains of elderly people and students while performing pedal-pressing simulations.

The researchers were particularly interested in the left dorsolateral prefrontal cortex, the part of the brain associated with inhibition and switching responses.  

To simulate the response of a person’s feet and hands when driving a car, they created a new task in the laboratory called the bimanual and bipedal response selection and response-position compatibility task. During this task, a signal directed participants to press the left or right button with their left or right foot, or their left or right hand.

Sometimes participants pressed the pedal in front of them, whereas at other times they had to press it diagonally. This was done to  allow the researchers to assess how the participants responded in situations where the cognitive load was higher.

Administering this task to both university students and elderly participants, the researchers then monitored blood flow in their brains.

The results were published in Behavioural Brain Research. 

They found that older participants had longer reaction times, slower decision times, and greater brain activation than younger people. Furthermore, pressing the diagonal pedal required longer reaction times and greater brain activation than pressing directly ahead in the left dorsolateral prefrontal cortex.

Interestingly, this was only found when people were asked to use their feet but not their hands. In short, older people had to do more active thinking than younger people when deciding which ‘pedal’ to press with their feet. 

“This indicates that the cognitive load is higher when pushing the pedal diagonally with the foot, such as when pressing the brake,” explains Professor Kawai.

This shows a foot on a break pedal
Study found the left dorsolateral prefrontal cortex (yellow) showed greater activation when pressing a pedal diagonally with a foot, compared to pressing the pedal straight. Credit: Dr. Nobuyuki Kawai, Reiko Matsushita

“When you push a diagonal pedal with your foot, you are using the frontal lobe more than when you push the pedal straight in front. In particular, the left dorsolateral frontal lobe, which is important for response switching, is more active when the foot is pressed at an angle than when the pedal is pressed straight.

“In these tasks, older adults have higher neural activity throughout the frontal lobe than college students.” 

This study’s findings suggest that to compensate for the decline in cognitive functions, greater brain activation may be necessary in elderly people. Older people may struggle in situations with a high cognitive load, such as parking a vehicle in a narrow space.

“This study suggests that the performance of older adults is vulnerable in these situations,”  Professor Kawai explains.

“Elderly drivers should not be overconfident that their driving is fine. Even elderly people who are normally able to drive without any problems, when a cognitive load is applied, such as when switching from one parking space to another or when talking to a passenger, things may be different and there is a chance of pressing the wrong pedal. We believe that it is important to educate elderly drivers about this fact.”   

Funding: This work was supported by JSPS KAKENHI. 

About this neuroscience research news

Author: Matthew Coslett
Source: Nagoya University
Contact: Matthew Coslett – Nagoya University
Image: The image is credited to Dr. Nobuyuki Kawai, Reiko Matsushita

Original Research: Open access.
Do older adults mistake the accelerator for the brake pedal?: Older adults employ greater prefrontal cortical activity during a bipedal/bimanual response-position selection task” by Nobuyuki Kawai et al. Behavioral Brain Research


Do older adults mistake the accelerator for the brake pedal?: Older adults employ greater prefrontal cortical activity during a bipedal/bimanual response-position selection task

Successful aging depends upon maintaining executive functions, which enable flexible response coordination. Although flexible responses are required for both hands and feet, as in driving, few studies have examined executive functions and brain activity in older adults, in terms of foot responses.

In this study, younger (mean age = 20.8) and older participants (mean age = 68.7) performed a newly developed bimanual/bipedal response-position selection compatibility task while we measured their brain activity using functional near-infrared spectroscopy.

Participants had to press either a left or right button using either their left or right foot (or hand), as directed by a two-dimensional cue signal. They executed either a straight or diagonal press response that mimicked stepping on the accelerator or brake pedal in a car. Foot responses produced more errors, longer reaction times, and greater brain activation than hand responses.

Greater brain activation in the left dorsolateral prefrontal cortex (BA 46) was observed in incongruent (i.e., diagonal) than in congruent (straight) trials for foot responses, but not for hand responses, suggesting that participants had difficulty executing a diagonal foot response (as braking in a car), but not a diagonal hand response.

Older participants exhibited greater brain activation across the PFC than younger participants, indicating that older adults activate additional brain circuits to compensate for declining executive functions.

We discuss potential relationships between declining executive functions of older adults and the frequent automobile accidents (i.e., missteps) in which they are involved.

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