How can we better understand how “risky” a particular person is when driving? Some people are very risky, whilst others are far more cautious and less likely to have an accident. We know that males are more risky than females and that there is increased risk of an accident if you are under 25 years old or over 75 years old, but other factors also contribute to how risky a person is.

One approach is to treat the tendency to take risks as a personality trait. This trait can then be measured through questionnaires such as the Traffic Locus of Control ScaleThese questionnaires can tell you a great deal about people and they do predict driving behaviour, but not as much as you might expect. One study found that personality traits could explain 39% of the variability in risky driving and only 20% for accident involvement[3].

It seems that these personality questionnaires can help us to understand driving risk, but only to some extent. Why is this? Obviously there are many other factors that contribute to risky driving and accidents: age, sex, alcohol consumption, etc. However, another issue is how accurately a person responds to a questionnaire.

Social desirability is a bias towards giving an answer on a question that is not necessarily an honest response, but a response that will be viewed more favourably by others. For example, when asked to rate how often you overtake a slow driver on the inside, you may report doing this less frequently than you really do to portray a more socially acceptable image of yourself. This might be even more exaggerated if the questionnaires are being completed for occupational reasons. You really wouldn’t want to tell your employer, or a potential employer, that you frequently undertake!

Is there any way to resolve this issue? It is obviously advantageous to know an individual’s level of risk taking, but does the subjective nature of a questionnaire reduce, at least to some extent, the validity of the data collected from them? If a more objective measure were available, one that could not be manipulated to “look better”, we might be able to make more accurate judgements of whether an individual is a risky driver.

Finger length might provide this more objective measure of risk taking when driving. Although it may sound bizarre, your finger length, more specifically the relative lengths of your ring finger and index finger, is determined by the amount of testosterone that you are exposed to whilst in the womb.

Take a look at your index finger (the second digit, 2D) and your ring finger (the fourth digit, 4D) on your dominant hand – the hand that you write with. In most men, the index finger is shorter than the ring finger, whereas in women, the index and ring fingers tend to be of similar lengths or the index finger is slightly longer than the ring finger. This relationship between the lengths of the index finger and ring finger is called the 2D:4D ratio.

If your index finger is shorter than your ring finger, you have a low 2D:4D and this means that you were exposed to high levels of testosterone prenatally. In contrast, if your ring finger is shorter than your index finger, you have a high 2D:4D and this indicates low levels of prenatal testosterone exposure.

Research has shown a strong relationship between personality and 2D:4D. One study found that people with lower, or more masculine, digit ratios scored higher on measures of sensation seeking[4]. The relationship between digit ratio and sensation seeking seems particularly relevant to driving risk as high sensation seekers are more likely to drive faster than 80 mph, drive after consuming alcohol and race other drivers[5].

A recent study looked directly at the possible relationship between 2D:4D and driving behaviours[6]. They found that people with low 2D:4D ratios, so those with higher levels of prenatal testosterone exposure, had more points on their licence. This seems to suggest that measurement of the 2D:4D ratio may provide a more objective indicator of how likely a person is to drive in a risky manner.

When assessing an individual to identify whether they drive in a risky manner it is important to get as much information as possible about their driving behaviours. Perhaps the measurement of digit ratio could contribute to this initial assessment and help to maximise the benefits of subsequent training.

Dr Victoria Bourne (BA Hons, DPhil)

Counsultant to Driving Risk Management

[1] Ozkan and Lajunen (2005)

[2] Reason et al. (1990)

[3] Iversen and Rundmo (2002)

[4] Austin et al. (2002)

[5] Arnett (1996)

[6] Schwerdtfeger et al (2010)

Road rage occasionally makes the news when drivers really lose their temper but there are earlier stages of this potentially dangerous condition that many of us witness, or are even subject to ourselves, on a day to day basis. Some of us are prone to a form of road rage because we take other peoples’ actions far too personally when we’re driving, so it may be helpful to have a look at why we do this.

So why do we take things so personally when we’re in our cars and why does it matter? Let’s tackle the second part of that question first. It matters because anything that takes our mind off the road can contribute to an on-road incident. When we allow ourselves to get angry with another road user, that person becomes the focus of our attention, which often clouds our ability to make good driving decisions and can increase the chance of being involved in collisions.
Take this typical scenario, which many of us might have witnessed first hand.
You’re on a motorway stuck in a traffic jam which extends well beyond an on-slip. A car drives down the slip road toward the traffic jam and you can almost see all the drivers in the vicinity saying “I’m not going to let him in…..I’m not going to give him an advantage.” Drivers can get quite belligerent about it, especially if they’ve been caught up in the jam for a while and tempers are wearing thin.
It’s as if those caught in the jam thought the joining driver had been following them for months, waiting for a chance to get one up on them and get further ahead in a traffic jam just to annoy them. The truth was of course much more mundane and far less threatening. Rather than being some strangely patient stalker, the other driver would have had little option but to drive the length of the slip road and join the traffic jam wherever he could. But many drivers don’t see it like that and gradually close the gap between their car and the one in front in a vain attempt to shut the newcomer out, which is of course when many typical motorway low speed rear end shunts occur.
So, back to the question of why we let other peoples’ actions affect us so badly. The first thing to note is that it isn’t the logical part of our brain that does the thinking when we are angry; it’s the more primitive areas. When someone cuts us up on a motorway we don’t think “Well that was rude” and carry on driving. Instead we react emotionally. Even if we don’t decide to hunt them down and remonstrate with them, there are a few seconds after the incident where our focus is not on the road in general or the traffic around us but on the person who cut us up.
There is even a sporting analogy to consider. How many times have you seen a football team score right after something unusual or distracting happens? The temptation is to allow our attention to become focussed on the wrong thing. Sports psychologists are only too aware of it. They know that when a team scores, the resulting euphoria causes their focus and attention to drop for just long enough to allow the opposition to score one back almost immediately.
The same is true on the road. If you allow your concentration to drop, so that you get caught out when others around you drive badly, you’re increasing the likelihood of being caught up in an incident for that short period. In short, you’re allowing your emotions to control your vehicle, rather than the logical part of your mind. You’re also allowing the other person affect how you drive. If you’re involved in an incident on the road, and then drive differently from the way you had originally intended, you’re effectively allowing that other driver to control your actions.
I would suggest that it’s far better to accept, from the moment you get behind the wheel, that you may come across others who won’t show you the courtesy you think you deserve. At that point it’s also crucial to accept that you can do nothing to influence their actions. Instead, it’s far better to drive as you had originally intended and be in total control of your actions; after all, that is the only way to win on the road. Remember that moments of anger and inattention pass relatively quickly if you don’t allow the feelings to take control. Also it’s vital to be aware that it’s those moments when you are most vulnerable to becoming involved in an incident.

Driving Risk Management Ltd