The researchers chose spiders as a topic of conversation to see if more emotionally charged discussions impaired driving ability more than mundane ones.
"We needed to find a conversation topic which we could use for all of our participants, but for half of whom it would have greater emotional relevance and evoke anxiety," wrote lead researcher Gemma Briggs at The Open University in the United Kingdom.
Most of us don't need scientists to tell us that distracted drivers, especially those talking on cellphones, can make for menaces on the road. Even so, plenty of studies back up this observation.
The theoretical reason is simple: The additional task of carrying on a conversation increases the driver's cognitive workload — their mental effort — and their performance on one or both tasks can deteriorate. This is why hands-free phones don't make talking while driving safe, the researchers say.
Briggs and colleagues were curious whether or not certain types of cellphone conversations put more demands on drivers and therefore impaired their performance more.
On the road
Half of the 26 study participants the team recruited were terrified of spiders. These participants were asked to drive at 50 miles per hour (80 kilometers per hour) in driving simulators set in beginner mode. They did this once undistracted and once while talking about spiders on a cellphone. The researchers monitored their eye movements to see how the drivers were scanning the road, and looked for changes in heart rates, since heart rate has been shown to increase proportionally with increasing mental demand.
Driving performance dropped for both groups once they engaged in the conversation, but, while talking about spiders, the arachnophobes made more errors overall — such as failure to signal, getting into collisions — and had much more trouble staying at 50 mph as instructed.
Changes in the arachnophobes' heart rates revealed they were more affected by the conversations and were experiencing a higher cognitive workload. The arachnophobes' eye movements revealed they were scanning a narrowed area within their fields of vision, a phenomenon known as visual tunneling. As a result, the phobic drivers failed to take in a wide range of visual cues, instead tending to focus on one highly concentrated and compacted area immediately ahead of them, Briggs explained.
"As drivers cannot predict the type of conversation they may become involved in whilst driving, any type of phone conversation should be avoided if possible," Briggs wrote.
Their work appeared online March 21 in the journal Transportation Research Part F: Traffic Psychology and Behaviour.