Editing Finger (section)

====Fingertip wrinkling in water====
Although a common phenomenon, the underlying functions and mechanism of fingertip wrinkling following immersion in water are relatively unexplored. Originally it was assumed that the wrinkles were simply the result of the skin swelling in water,<ref>{{Cite book |last=Herlihy |first=Barbara |url=https://books.google.com/books?id=yD8rEAAAQBAJ&dq=Aside+from+the+genitals,+the+fingertips+possess+the+highest+concentration+of+touch+receptors+and+thermoreceptors+among+all+areas+of+the+human+skin&pg=PA239 |title=The Human Body in Health and Illness - E-Book: The Human Body in Health and Illness - E-Book |date=2021-04-25 |publisher=Elsevier Health Sciences |isbn=978-0-323-81123-1 |language=en}}</ref> but it is now understood that the furrows are caused by the [[Vasoconstriction|blood vessels constricting]] due to signalling by the [[sympathetic nervous system]] in response to water exposure.<ref name=Changizi>{{Cite journal | last1 = Changizi | first1 = M. | last2 = Weber | first2 = R. | last3 = Kotecha | first3 = R. | last4 = Palazzo | first4 = J. | title = Are Wet-Induced Wrinkled Fingers Primate Rain Treads? | doi = 10.1159/000328223 | journal = Brain, Behavior and Evolution | volume = 77 | issue = 4 | pages = 286–90 | year = 2011 | pmid =  21701145| doi-access = free }}</ref><ref name=Haseleu>{{cite journal|doi=10.1371/journal.pone.0084949|title=Water-Induced Finger Wrinkles Do Not Affect Touch Acuity or Dexterity in Handling Wet Objects|year=2014|editor1-last=Goldreich|editor1-first=Daniel|last1=Haseleu|first1=Julia|last2=Omerbašić|first2=Damir|last3=Frenzel|first3=Henning|last4=Gross|first4=Manfred|last5=Lewin|first5=Gary R.|journal=PLOS ONE|volume=9|issue=1|pages=e84949|pmid=24416318|pmc=3885627|bibcode=2014PLoSO...984949H|doi-access=free}}</ref> One hypothesis for why this occurs, the "rain tread" hypothesis, posits that the wrinkles may help the fingers grip things when wet, possibly being an adaption from a time when humans dealt with rain and dew in forested primate habitats.<ref name=Changizi/> A 2013 study supporting this hypothesis found that the wrinkled fingertips provided better handling of wet objects but gave no advantage for handling dry objects.<ref name=Kareklas>{{cite journal|doi=10.1098/rsbl.2012.0999|title=Water-induced finger wrinkles improve handling of wet objects|year=2013|last1=Kareklas|first1=K.|last2=Nettle|first2=D.|last3=Smulders|first3=T. V.|journal=Biology Letters|volume=9|issue=2|pages=20120999|pmid=23302867|pmc=3639753}}</ref> However, a 2014 study attempting to reproduce these results was unable to demonstrate any improvement of handling wet objects with wrinkled fingertips.<ref name=Haseleu/>