Scientists at the University of Sussex found telephone conversations while driving can cause the driver to visually imagine what they are talking about.
This uses a part of the brain normally used to watch the road, the study said.
It is illegal in the UK to ride a motorcycle or drive using hand-held phones or similar devices.
Drivers can get an automatic fixed penalty notice if caught using one. They will get three penalty points on their licence and a fine of 100 pounds, the BBC reported.
The study involved 20 male and 40 female volunteers who took part in video tests while sitting in a car seat behind a steering wheel.
One group of volunteers were allowed to "drive" undistracted while another two heard a male voice from a loudspeaker 3ft away.
Those who were distracted by the voice engaging them in conversation took just under a second longer to respond to events, such as a pedestrian stepping off the pavement, an oncoming car on the wrong side of the road or an unexpected vehicle parked at a junction.
Dr Graham Hole, senior lecturer in psychology at the University of Sussex, said the research laid bare the "popular misconception that using a mobile phone while driving is safe as long as the driver uses a hands-free phone".
"The problem is enforceability - it's very difficult for the police to tell if someone's using a hands-free phone," he said.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
