Editing Animal cognition (section)

===Cognitive bias===
{{main|Cognitive bias}}
[[File:Glass-of-water.jpg|thumb|150px|Is the glass half empty or half full?]]
A '''cognitive bias''' refers to a systematic pattern of deviation from norm or rationality in judgment, whereby inferences about other individuals or situations may be drawn in an illogical fashion.

Cognitive bias is sometimes illustrated by using answers to the question "[[Is the glass half empty or half full?]]". Choosing "half empty" is supposed to indicate pessimism whereas choosing "half full" indicates optimism. To test this in animals, an individual is trained to anticipate that stimulus A, e.g. a 100&nbsp;Hz tone, precedes a positive event, e.g. highly desired food is delivered when a lever is pressed by the animal.  The same individual is trained to anticipate that stimulus B, e.g. a 900&nbsp;Hz tone, precedes a negative event, e.g. bland food is delivered when the animal presses a lever. The animal is then tested by being given an intermediate stimulus C, e.g. a 500&nbsp;Hz tone, and observing whether the animal presses the lever associated with the positive or negative reward. This has been suggested to indicate whether the animal is in a positive or negative mood.<ref>{{cite journal | vauthors = Harding EJ, Paul ES, Mendl M | title = Animal behaviour: cognitive bias and affective state | journal = Nature | volume = 427 | issue = 6972 | pages = 312 | date = January 2004 | pmid = 14737158 | doi = 10.1038/427312a | bibcode = 2004Natur.427..312H | s2cid = 4411418 | doi-access = free}}</ref>

In a study that used this approach, rats that were playfully tickled responded differently than rats that were simply handled. The rats that had been tickled were more optimistic than the handled rats.<ref>{{cite journal | vauthors = Rygula R, Pluta H, Popik P | title = Laughing rats are optimistic | journal = PLOS ONE | volume = 7 | issue = 12 | pages = e51959 | year = 2012 | pmid = 23300582 | pmc = 3530570 | doi = 10.1371/journal.pone.0051959 | bibcode = 2012PLoSO...751959R | doi-access = free}}</ref> The authors suggested that they had demonstrated "...for the first time a link between the directly measured positive affective state and decision making under uncertainty in an animal model".

There is some evidence for cognitive bias in a number of species, including rats, dogs, rhesus macaques, sheep, chicks, starlings and honeybees.<ref>{{cite book| vauthors = Haselton MG, Nettle D, Andrews PW | chapter = The evolution of cognitive bias |year=2005| location = Hoboken, NJ, US | publisher = John Wiley & Sons Inc.| veditors = Buss DM | title = The Handbook of Evolutionary Psychology |pages=724–746}}</ref>