We already know for some time that while we tend to multitask, our brain isn’t really capable of doing it. New research by Schweizer et al. shows again that talking on the phone, even if it is hands free, can be as dangerous. Most serious traffic accidents occur when drivers are making a left-hand turn at a busy intersection. When those drivers are also talking on a hands-free cell phone, “that could be the most dangerous thing they ever do on the road,” said Dr. Tom Schweizer

From the press release:

The researchers were able to show for the first time that making a left-hand turn requires a huge amount of brain activation and involves far more areas of the brain than driving on a straight road or other maneuvers.

When the drivers were also involved in a conversation, the part of the brain that controls vision significantly reduced its activity as the part that controls monitoring a conversation and attention was activated.

“Visually, a left-hand turn is quite demanding,” Dr. Schweizer said. “You have to look at oncoming traffic, pedestrians and lights, and coordinate all that. Add talking on a cell phone, and your visual area shuts down significantly, which obviously is key to performing the maneuver.”

The simulation had the drivers making six left turns with oncoming traffic, which required them to decide when to turn safely. It then distracted them, by making them answer a series of true-false audio questions, such as “Does a triangle have four sides?” The MRIs showed that blood moved from the visual cortex, which controls sight, to the prefrontal cortex, which controls decision-making.

“Brain activity shifted dramatically from the posterior, visual and spatial areas [of the brain] to the prefrontal cortex,” said Dr. Schweizer, a neuroscientist and director of the Neuroscience Research Program at the hospital’s Li Ka Shing Knowledge Institute.

“This study provides real-time neuroimaging evidence supporting previous behavioural observations suggesting that multitasking while driving may compromise vision and alertness. ‘Hands free’ not does mean ‘brains free.'”

Abstract of the research:

Introduction: Non-invasive measurements of brain activity have an important role to play in understanding driving ability. The current study aimed to identify the neural underpinnings of human driving behavior by visualizing the areas of the brain involved in driving under different levels of demand, such as driving while distracted or making left turns at busy intersections.

Materials and Methods: To capture brain activity during driving, we placed a driving simulator with a fully functional steering wheel and pedals in a 3.0 Tesla functional magnetic resonance imaging (fMRI) system. To identify the brain areas involved while performing different real-world driving maneuvers, participants completed tasks ranging from simple (right turns) to more complex (left turns at busy intersections). To assess the effects of driving while distracted, participants were asked to perform an auditory task while driving analogous to speaking on a hands-free device and driving.

Results: A widely distributed brain network was identified, especially when making left turns at busy intersections compared to more simple driving tasks. During distracted driving, brain activation shifted dramatically from the posterior, visual and spatial areas to the prefrontal cortex.

Conclusions: Our findings suggest that the distracted brain sacrificed areas in the posterior brain important for visual attention and alertness to recruit enough brain resources to perform a secondary, cognitive task. The present findings offer important new insights into the scientific understanding of the neuro-cognitive mechanisms of driving behavior and lay down an important foundation for future clinical research.