Moreover, different states of arousal have different relationships to performance, and can occur separately or at the same time. Attentive alertness, as a form of arousal, increases performance as arousal increases. On the other hand tension and attendant autonomic arousal, or anxiety, always decreases performance (see tomorrow's post for more). Interestingly enough, separate them both and the Yerkes-Dodson curve disappears, but combine them and out it pops. For example, a person who is highly and pleasurably aroused while climbing a mountain or creating art doesn't suffer in performance as his arousal increases, but actually gains in performance. On the other hand, a person who is frustrated while performing a task progressively loses his ability to perform well as anxiety increases. Nonetheless, as demand increases and decreases, these two very different types of arousal can occur simultaneously, and produce a performance curve very similar to the Yerkes-Dodson model.
As an aroused state, attentive alertness scales with the novelty or surprise of moment to moment behavior. As a function of the release of the neurochemical dopamine, touch and go events that entail continuous positive surprises (e.g. rock climbing, gambling, creative behavior) positively correlate with aroused alertness, which not only feels good but helps you think better. Thus the bigger the positive surprise, the more alert you become, and the better your performance becomes. If however, surprises start to trend from good to bad, alertness decreases as we become progressively more depressed, but tension and associated autonomic arousal (i.e. anxiety) increases. That is, as news moves from good to bad, arousal doesn't increase, it just changes to an entirely new form! The problem though is that positive surprises always come at the risk that things will take a decided turn for the worse, as the rock climber get stuck in a snow storm and the creative artist hits a writers block. Thus, the cost of higher good feelings is the chance you take that a turn of fortune will turn those good feelings bad. Generally, as demand increases risk increases, and at first we can handle it and be pleasantly surprised by and are motivated by the continuous moment to moment surprise of our success. But as demand ratchets up we are more likely to experience failure, and another type of arousal, that of anxiety. Hence as demand goes up, so does performance and arousal until performance reaches a crest and arousal begins to change not in amplitude but begins changing in kind. So the Yerkes Dodson bell curve survives, it is rather the idea that arousal does not change in kind across the level of performance that falls away.
The lesson we learn from all this is that the highest motivation or performance stands at the cusp of failure, as we are rarely motivated by the sure and thus boring thing. Unfortunately, what psychologists take from the Yerkes-Dodson curve is the wrong lesson entirely, that arousal is a monolithic and indivisible thing that does not categorically change as demand increases. In other words, the lesson that no pain equals no gain is wrong. Rather, if you have pain you will likely have no gain. For folks that are a bit wary of the school of hard knocks, this is perhaps a lesson one can get a bit excited about.