The diving reflex is modified by higher nervous stimulation within the central nervous system, and is thus closely related to those cognitive states also controlled by the central nervous system. The magnitude of the cardiovascular response to diving can be affected by conscious awareness, fear, and anticipation (Ross and Steptoe, 1980). The effects generated by a change in mental state gradually emerge over 60-second interval and have only been observed to impact the bradycardia mechanism, not vasoconstriction (McCulloch et al., 2010).

Arithmetic

In humans, mental arithmetic is often used as a method in which to mentally challenge the individual and alter conscious awareness. Mental arithmetic does reduce bradycardia and increase heart rates in both air and water; however, listening to prose has no effect upon the diver's heart rate(Ross and Steptoe, 1980). A similar mental effort make take place when hunting, and the subsequent decrease in bradycardia temporarily allows the diving organism an increased cardiac output to supply the brain with oxygen and increase concentration (Butler, 1982).

Fig. 1 from (Ross and Steptoe, 1980) with permission from the author. Heart rate responses in the mental arithmatic (MA). The four conditions are: dark circles with dotted lines for breath holding in air without MA, dark circles with sold lines for breath holding in air with MA, open circles with dotted lines for breath holding in water without MA, and opend circles with sold lines for breath holding in water with MA. Both in and out of the water, mental arithmatic increased the heart rate.

Fear

Fear is a second mental component that reduces bradycardia. During alarm dives of any duration, cardiovascular adjustments are immediate and intense. However, research is still being conducted on where this effect is due to the diving reflex response of bradycardia or simply to adrenaline (Butler, 1982).

Anticipation

Anticipation is the final mental component, and studies have found this component to have no effect upon the diving reflex. In experiments involving trained rats who by exposure now anticipate the experience, bradycardia remained unchanged in rats with and without diving training. This promotes the reflex nature of bradycardia within the diving response (Panneton et al., 2010; McCulloch et al., 2010).