Editing Animal cognition (section)

==== Time of day: circadian rhythms ====
{{main|Circadian rhythms}}
The behavior of most animals is synchronized with the earth's daily light-dark cycle.  Thus, many animals are active during the day, others are active at night, still others near dawn and dusk. Though one might think that these "circadian rhythms" are controlled simply by the presence or absence of light, nearly every animal that has been studied has been shown to have a "biological clock" that yields cycles of activity even when the animal is in constant illumination or darkness.<ref name="Shettleworth" /> Circadian rhythms are so automatic and fundamental to living things&nbsp;– they occur even in plants<ref>{{cite journal | vauthors = Webb AR |s2cid = 15688409 |year = 2003 |title = The physiology of circadian rhythms in plants |journal = New Phytologist |volume = 160 |pages = 281–303 |doi = 10.1046/j.1469-8137.2003.00895.x |issue = 2 |pmid = 33832173 |doi-access = free|bibcode = 2003NewPh.160..281W }}</ref> – that they are usually discussed separately from cognitive processes, and the reader is referred to the main article ([[Circadian rhythms]]) for further information.<ref>{{cite book | veditors = Call JE, Burghardt GM, Pepperberg IM, Snowdon CT, Zentall TE | title = APA handbook of comparative psychology: Perception, learning, and cognition | date = 2017 | volume = 2 | chapter = Chapter 23 : Timing in Animals | publisher = APA | location = Washington D.C.}}</ref>