February 04, 2005
Dyslexics React To Road Events More Slowly When Driving?

Hermundur Sigmundsson of the Norwegian University of Science and Technology, Trondheim Norway, found that in simulated driving conditions dyslexics took longer to react to flashing signs.

The six dyslexic drivers took on average 0.13 seconds longer to react during the rural drive than the non-dyslexic controls and were 0.19 seconds slower in the city, where the simulated environment was more complex. In both tests the controls took around 0.6 seconds to respond, so the dyslexic drivers were experiencing a delay of 20 to 30 per cent (Brain and Cognition, DOI: 10.1016/j.bandc.2004.11.007).

The article says this level of delay is worse than what happens as a result of moderate drinking.

Some people see this result as offensive to dyslexics.

Dr John Rack, of the Dyslexia Institute, said: "It's a small study and it's an overgeneralisation and oversimplification of what dyslexia is.

"It could really be quite offensive, I feel, to the many, many dyslexic people who are actually quite talented and skilled in those areas."

Perhaps some will be offended. But is it true? If this result is true is it true for all dyslexics? Are there dyslexics who can react very rapidly to sudden changes on roads? Also, does the average person who gets into a car accident have slower reaction times than the average person who does not get into a car accident?

In the future wouldn't it make sense to use objective tests of speed of responses to simulated road events to measure how well or poorly each prospective driver will do on the road? Even if dyslexics have slower reaction times on average surely there are non-dyslexics who naturally have reaction times that are worse than the average.

Also, picture devices in cars of marginal drivers or alcoholics that would test their reaction times and accuracies every time a bad driver wanted to start the car and go somewhere. Anyone unable to reaction in a timely manner could be denied the ability to make the engine start.

The more that different categories of people are compared the more differences will be found between those categories. This is inevitably going to lead to calls for rules changes that take into account the knowledge of these differences.

A study on brain development shows another example of differences in how the different brains react to road situations. Full development of a brain area involved in the tendency toward behavioral inhibition in the face of risks does not occur until age 25.

A National Institutes of Health study suggests that the region of the brain that inhibits risky behavior is not fully formed until age 25, a finding with implications for a host of policies, including the nation's driving laws.

"We'd thought the highest levels of physical and brain maturity were reached by age 18, maybe earlier -- so this threw us," said Jay Giedd, a pediatric psychiatrist leading the study, which released its first results in April. That makes adolescence "a dangerous time, when it should be the best."

Suppose it becomes possible to measure brains to show that some people never fully develop the part of their brain that causes them to inhibit risky behavior. Should those adults be kept off the road just because they are too prone to risks when behind the wheel? Or if some people develop tendencies to risk-aversion earlier should they be granted drivers licenses earlier than the majority of the population?

The problem with judging people only by what they do is that for many actions waiting for people to do undesired things (like cause a car accident) causes too much damage. We are going to gain greater abilities to predict what people might do. How to reconcile the coming greater abilities to predict human behavior with the legal ideal to treat all equally before the law?

Share |      Randall Parker, 2005 February 04 02:16 AM  Biological Mind

David Nishimura said at February 4, 2005 9:28 AM:

I would think it fairly trivial to come up with a battery of tests that could be strongly indicative of driver risk. Not only reaction time, but appropriate reaction (think of those older drivers who end up plowing into crowds after mistaking the accelerator for the brake pedal and then persisting in pressing harder); skill testing, as in coping with sliding around in ice and snow, could also be done easily in a simulation. Then, though it might be less straightforward, one could test for aggression and impatience.

As I'd expect the insurance companies would readily embrace such testing, the only problem I can see is political: but that may be insurmountable. Think of how long it has taken to stiffen testing requirements for very old drivers, and how much remains to be done there.

ziel said at February 4, 2005 9:42 PM:

The whole "reaction-time" thing is one big red-herring. Engineers like it because it's easy to test, but not relevant in the real world. Accidents happen due to a confluence of events beyond drivers' control; or because of mistakes in judgement (driving too fast, turning at the wrong time, distraction); inebriated drivers falling asleep at the wheel; old people's minds checking out momentarily (wrong pedal). Think about all the accidents you've known about or been involved in. How many were due to slow reaction times? If reaction time were a relevant factor in accidents, then young people would be the safest drivers around, not the worst.

Bob Badour said at February 6, 2005 9:35 AM:


I think instead of all the potential accidents I avoided due to my fast reactions and excellent depth perception.

Certainly, a number of factors affect collision outcomes. Ignorance and recklessness account for a lot of accidents including every accident involving an intoxicated driver. Inattentiveness or aggression account for many more accidents. I suspect in the past a lot more accidents were caused by misinterpretation of visual cues than today, because those same engineers spent a lot of effort making visual cues less ambiguous for drivers.

Different people will have accidents for different reasons. Unless intoxicated, young males are unlikely to have accidents related primarily to reaction times and depth perception. Eighty year old grandmothers are unlikely to have accidents due to their aggressiveness and road rage.

When my grandmother's car collided with a child who ran in front of her, I suspect reaction time contributed to the accident. (No serious injury, thankfully.)

I reject your premise that only sleep causes drunks to have accidents. My father is an alcoholic, and many times when I was a child I observed him driving drunk. While still fully conscious albeit drunk, he would drive in the oncoming traffic lane, unintentionally drift from lane to lane, blow through stop signs and red lights he failed to notice as well as stop a car length past the stop line because he applied the brakes too late. Certainly, his drinking affected his reaction time and this led to several accidents.

ziel said at February 6, 2005 10:52 PM:

Bob, I grant that I overstated my case a bit. Seriously inebriated drivers are serious hazards at any stage in their travels. But is your grandmother's reaction time any worse than a driver engaged in a conversation with a passenger? I think reaction time is a poor proxy measure for driving safety. Young men have terrific reaction times but poor judgement, and are the most dangerous drivers on the road. I don't think we can start pre-determining drivers' safety by reaction times. A test on a road course shouldn't be assumed to predict results on real road conditions.

Bob Badour said at February 7, 2005 4:06 PM:

What makes you think my grandmother wasn't engaged in a conversation with a passenger?

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