Editing Animal cognition (section)

==== Natural categories ====
Many animals readily classify objects by perceived differences in form or color.  For example, bees or pigeons quickly learn to choose any red object and reject any green object if red leads to reward and green does not.  Seemingly much more difficult is an animal's ability to categorize natural objects that vary a great deal in color and form even while belonging to the same group. In a classic study, [[Richard J. Herrnstein]] trained pigeons to respond to the presence or absence of human beings in photographs.<ref>{{cite journal | vauthors = Herrnstein RJ, Loveland DH | title = Complex Visual Concept in the Pigeon | journal = Science | volume = 146 | issue = 3643 | pages = 549–51 | date = October 1964 | pmid = 14190250 | doi = 10.1126/science.146.3643.549 | bibcode = 1964Sci...146..549H | s2cid = 11940233}}</ref>  The birds readily learned to peck photos that contained partial or full views of humans and to avoid pecking photos with no human, despite great differences in the form, size, and color of both the humans displayed and in the non-human pictures.  In follow-up studies, pigeons categorized other natural objects (e.g. trees) and after training they were able without reward to sort photos they had not seen before .<ref>{{cite journal | vauthors = Herrnstein RJ | year = 1979 | title = Acquisition, Generalization, and Discrimination Reversal of a Natural Concept | journal = Journal of Experimental Psychology: Animal Behavior Processes | volume = 5 | issue = 2| pages = 116–129 | doi=10.1037/0097-7403.5.2.116| pmid = 528881}}</ref><ref>{{cite journal | vauthors = Bhatt RS, Wasserman EA, Reynolds WF, Knauss KS | title = Conceptual behavior in pigeons: Categorization of both familiar and novel examples from four classes of natural and artificial stimuli. | journal = Journal of Experimental Psychology: Animal Behavior Processes | date = July 1988 | volume = 14 | issue = 3 | pages = 219–234 | doi = 10.1037/0097-7403.14.3.219}}</ref>  Similar work has been done with natural auditory categories, for example, bird songs.<ref>{{cite journal | vauthors = Tu HW, Smith EW, Dooling RJ | title = Acoustic and perceptual categories of vocal elements in the warble song of budgerigars (Melopsittacus undulatus) | journal = Journal of Comparative Psychology | volume = 125 | issue = 4 | pages = 420–30 | date = November 2011 | pmid = 22142040 | pmc = 4497543 | doi = 10.1037/a0024396}}</ref>  Honeybees (''[[Apis mellifera]]'') are able to form concepts of "up" and "down".<ref>{{cite journal | vauthors = Avarguès-Weber A, Dyer AG, Giurfa M | title = Conceptualization of above and below relationships by an insect | journal = Proceedings. Biological Sciences | volume = 278 | issue = 1707 | pages = 898–905 | date = March 2011 | pmid = 21068040 | pmc = 3049051 | doi = 10.1098/rspb.2010.1891}}</ref>