A person’s level of arousal can be described as a function of alertness, situational awareness, vigilance, level of distraction, stress and direction of attention. The levels of arousal can be connected to the Yerkes-Dodson Stress Curve, which shows that at low levels of arousal, our performance level is also low. At the other end of the scale, when arousal is too high, perhaps due to overload, then once again we start to make more errors, find it harder to be decisive and take longer to react. Somewhere in between the two extremes, a point of optimum-arousal, which is appropriate and effective for the situation, will exist allowing for optimum performance. The levels of arousal can be described as under-arousal, optimum-arousal, and over-arousal, with under-arousal manifest by unconsciousness, and over-arousal manifest by a range of symptoms such as panic, aggression, and irrational behaviour. Two specific examples of under-arousal are habituation and lacuna of indecision. Some stressor(s) are required to rouse us from a low level of arousal into the optimum zone, and when we are in this zone, our mental capacity, situational awareness, alertness, attention, vigilance, decision-making, and actions are all heightened in sensitivity and execution. The five levels of arousal are not explicitly stated, but can be inferred as low arousal, moderately low arousal, optimum arousal, moderately high arousal, and high arousal.