The Star (Nairobi)

26 November 2012

Kenya: What Is Your Reaction Time?

Pure sodium is a silver-white soft metal that can be cut with a knife. You will almost never come across the pure metal because on its own it is unstable.

Put a small piece of sodium in a beaker of water and it will react violently, skipping and hopping about as if it has been burnt. Which in fact is what is happening.

Sodium reacts with water to produce sodium hydroxide and hydrogen gas. The reaction is exothermic, which means heat is produced. The hydrogen gas ignites and so the effect of adding pure sodium to water is a spectacular event of this thing zigzagging about climaxing in flames leaving behind nothing.

Sodium melts at 98 degrees Celsius. Yet the element sodium is essential to human life. We need it as sodium chloride - common table salt. We use it as sodium bicarbonate in cooking and in making soap and detergent.

Sodium is so ubiquitous yet why it decides to be so shy is a mystery. Its' super fast reaction time to water means that the metal has to be stored under an inert liquid such as kerosene or mineral oil.

The reaction of sodium to water is a function of the chemical properties of the metal and is therefore consistent and predictable. Human beings as we all know are anything but consistent and predictable unless well trained.

Super world record beating athletes are predictable. In the Olympics the average reaction time for sprinters off the blocks from the time the start gun is fired is 166 milliseconds for men and 189 milliseconds for women. (The difference is attributed to the way measurement is done with women generating less force of the block leading to delay in recording take off time).

That is after years of training. Try any exercise to test your reaction time and you will find it in the region of 200 milliseconds. To get it any faster will require some training.

Why is this important? There are activities that the difference between safety and serious injury or even death is your reaction time. The most obvious and commonplace is driving a car. Many of us pride ourselves that we are good drivers, believing in the myth that it is always the 'other driver' that is poor, forgetting that we are all part of the same system and therefore if the other fellow is mediocre we are likely to be closer to the average than we think.

Because of our poor road etiquette, avoidable danger is never far away. Reaction time depends on a number of factors. The first is the time taken to appreciate danger.

In experiments done college age individuals take on average 160 milliseconds to detect an auditory stimulus and 190 milliseconds to detect visual stimulus.

This mental processing time is like that of the athletes. But remember they are conditioned to expect it. Many of us sit in sealed off cars, windows up and music on.

Most of us using public transport are in noisy badly maintained vehicles. We are all stressed with life. When is the next strike? Where will I find money? Who should I date? Am I really this fat?

Either way our ears are assaulted with various sounds both internal and external. Danger signals via an auditory stimulus requires a very loud bang and it is often too late.

A visual stimulus is relatively slower and usually works better if you are looking out for something. This is one reason why policemen when they stop you quarrel loudly.

They glance at you and realize that you have this dazed, goofy look that most Kenyan drivers have. After appreciating that there is danger you must recognise it.

How serious is it? This requires some processing in the brain and depends on the stimulus, our physical and mental state, previous experience we have and the environment; for example if we were expecting a one-foot speed bump to be there. Our mental processing time is therefore slow because even without setting foot into a vehicle the cognitive load of the typical driver is high.

Once we have appreciated that there is a danger, we have to respond to it, usually through some physical movement. Other than the state of the vehicle we are driving, a response is better if we are physically fit.

Formula One drivers need a lot of exercise to be able to maintain physical form through an hour and a half of high spend driving. Should matatu and bus drivers be required to jog every day and attend gym?

It is not just about eyesight checks, the foot has to be able to move off the accelerator and get on to the breaks. But no matter how quick the reaction time, for the vehicle to stop it has to obey the laws of physics. About 50 per cent of stopping distance is attributed to driver reaction time and the other 50 per cent to the vehicle.

So how do we reduce the sodium elements on our roads? We need predictability - predicable enforcement of road rules and management of traffic. And we need drivers who are fit to drive.

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