ABSTRACT
Day and night, darkness and light: due to the Earth’s daily rotation around the sun, these are the most pervasive recurring environmental stimuli to which virtually all living organisms are exposed. Mammals-humans included-have adapted to this phenomenon by organizing their behavior into periods of rest or sleep and activity, depending on the time of day or night. Some animals are more active at night-usually those with enhanced olfactory and auditory senses-whereas most are more active during the day, utilizing vision as their primary sense [1].
