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Long before Safety and Distracted Driving we had the Yerkes–Dodson law!

The YerkesDodson law is an empirical relationship between arousal and performance, originally developed by psychologists Robert M. Yerkes and John DillinghamDodson in 1908. The law dictates that performance increases with physiological or mental arousal, but only up to a point.

So is this well know theory part of your investigation regarding an employees distracted driving or speeding!  In safety we compare it with The Inverted-U Model

Balancing Pressure and Performance

Yerkes and Dodson were Harvard physicians that were looking to understand the relationship between stress and learning. Their experiments looked at the effect of electric shocks on mice that were performing a task. If mice performed the task (entering a box through a white door) incorrectly they would receive a shock as corrective feedback. The experiment demonstrated that a small shock was insufficient to be a motivator for learning. Large shocks would prove too stressful or disorienting, again leading to poor results. It was the “medium” shocks that had the most positive effect on task performance.

Human performance at any task varies with arousal in a predictable parabolic curve. At low arousal, people are lethargic and perform badly. As arousal increases, performance also increases – but only to a point, after which increasing arousal actually decreases performance.

Without some motivating tension we have no reason to act. In this way, stress can be thought of as a good thing. We are built to be motivated by stress so this often happens.

Imagine if you were offered a huge sum for doing perfectly something you are good at. While normally you would perform the task well, the possible reward would weigh heavily on your mind, distracting you and increasing the likelihood that you would make a mistake. This happens to sports people when the pressure to win causes unforced errors.

The problem is that too much stress results can cause performance to decline again, sometimes sharply if cognitive or nervous breakdown is triggered. A downturn can also be caused by excessive attention to a task such that extra factors that are important get missed.

The behavior in the downturn has been called satisficing and is quite differently motivated from the earlier stages. Rather than gain satisfaction or reward from actions, the person who is is satisficing seeks any way of reducing their stress. This can lead to sub-optimal solutions being used, which accounts in part for the performance decline.

The Four Influencers

The shape of the Inverted-U curve in reality, the shape of the curve will depend on the situation, and the individual person.

There are four main “influencers” that can affect this. These are:

1.  Skill Level.

2.  Personality.

3.  Trait Anxiety.

4.  Task Complexity.

We’ll now look at each influencer in greater detail:

Skill Level

People’s levels of skill with a given task directly influence how well they perform, which is why you need to train your people intensively if you want them to cope in high pressure situations.

For instance, if they’re not practiced enough to do a task, they’ll feel under serious pressure, and they won’t perform well. What’s more, people are less able to think in a flexible, methodical way when they’re under pressure, which is why they need to be able to fall back on well-rehearsed responses.


A person’s personality also affects how well he or she performs.

For instance, some psychologists believe that people who are extroverts are likely to perform better in high-pressure situations. People with an introverted personality, on the other hand, may perform better with less pressure.

Trait Anxiety

Think of trait anxiety as the level of a person’s “self-talk.” People who are self-confident are more likely to perform better under pressure. This is because their self-talk is under control, which means that they can stay “in flow”, and they can concentrate fully on the situation at hand. By contrast, people who criticize or question themselves are likely to be distracted by their self-talk, which can cause them to lose focus in pressurized situations.

The more that people are able to lower their anxiety about a task (with practice, or with positive thinking , for example) the better they’ll perform.

Task Complexity

Task complexity describes the level of attention and effort that people have to put into a task in order to complete it successfully. People can perform simple activities under quite high levels of pressure, while complex activities are better performed in a calm, low-pressure environment.

THE BOTTOM LINE! So if the call is important pull over in safe location and take it, if that coffee or lunch is taste pull over and eat it in safe location. As noted above you may think your brain, body and skills can before the other tasks but even in 1908 it was noted YOU CANT!

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