What's happening to your brain that makes cell phones create all that havoc on the roadway?
Cognitive neuroscientists are using a variety of cutting edge technologies to understand brain functioning. One way to study the neural basis of attention is by attaching electrodes to the scalp (don't worry, it doesn't hurt). These electrodes pick up very small electrical signals generated by different parts of the brain (these electrical signals are called EEG - or electroencephalographic activity).
We measure EEG from volunteers as they drive in our simulator (show below). Our volunteers drove along a section of highway in stop-and-go traffic. For part of the time they drove without distraction (we refer to this as the single-task condition) and for the part of the time they drove while talking to a friend on a hands-free cell phone (we refer to this as the dual-task condition -- that is, they were driving and talking on a cell phone).
Traffic on the highway occasionally slowed and the brake lights on the car in front of our participant came on from time to time. Each time that the brake lights of the lead vehicle came on, we recorded a one second sample of the EEG from our volunteers. That is, our recordings of the EEG were synchronized with when the brake lights of the lead vehicle came on. (In the jargon of cognitive neuroscience, the EEG signals were time-locked to the onset of the brake lights).
When we average these samples of EEG, we obtain the brain activity associated with processing the brake lights. (In the jargon of cognitive neuroscience, the random noise in these EEG signals cancels out with the averaging process, leaving just the portion of the EEG that is time-locked with the processing of the brake lights by the volunteer - the averaged signal is called the Event-Related Brain Potential or ERP for short).
So what do these brain waves tell us about using a cell phone while driving?
The graph below shows the brain waves in the single-task condition (driving only) and the dual-task condition (driving and talking on a hands-free cell phone). The X-axis is time in milliseconds (thousandths of a second), with 0 indicating the time when the brake lights were illuminated. The Y-axis is the voltage of the EEG in microvolts (millionths of a volt).
Immediately evident in the graph is that the black line (single-task) and the red line (dual-task) are different. With these time-locked brain waves, a larger voltage means more in-depth processing. The activity in the brain associated with processing things like brake lights or other signals is cut in half when drivers talk on their cell phone!
So, this is a snapshot of your brain activity when you are on a cell phone. If you talk and drive, you are processing only half as much information as if you had not been distracted by your cell-phone.
Many accidents are caused by drivers failing to see traffic lights or other signals. Now you know why - cell-phones interfere with the neural processes associated with safely operating a motor vehicle.