Looking down towards the ground or below the central face activates brainstem neurons associated with calm and sleepiness.

“We have clusters of neurons in our brain stem. And those clusters of neurons control our eyelid muscles and they control our eye movements up and down and to the sides. Now the neurons that control those muscles have a very interesting feature which is that when we are looking down toward the ground or anywhere below basically the the central region of our face. The neurons that control that eye movement are intimately related to areas of the brain stem that release certain types of neurom modulators and neurotransmitters and they activate areas of the brain that are associated with calm and indeed even with sleepiness.”