In the context of [[human–computer interaction]], a '''modality''' is the classification of a single independent channel of [[input/output]] between a computer and a human. Such channels may differ based on sensory nature (e.g., visual vs. auditory),<ref name="HCI Overview2">{{cite journal|last1 = Karray|first1 = Fakhreddine|last2 = Alemzadeh|first2 = Milad|last3 = Saleh|first3 = Jamil Abou|last4 = Arab|first4 = Mo Nours|title = Human-Computer Interaction: Overview on State of the Art|journal = International Journal on Smart Sensing and Intelligent Systems|date = March 2008|volume = 1|issue = 1| pages=137–159 | doi=10.21307/ijssis-2017-283 |url = http://www.s2is.org/issues/v1/n1/papers/paper9.pdf|accessdate = April 21, 2015|archive-url = https://web.archive.org/web/20150430205510/http://s2is.org/Issues/v1/n1/papers/paper9.pdf|archive-date = April 30, 2015|url-status = dead}}</ref> or other significant differences in processing (e.g., text vs. image).<ref>{{cite arXiv | eprint=2301.13823 | author1=Jing Yu Koh | last2=Salakhutdinov | first2=Ruslan | last3=Fried | first3=Daniel | title=Grounding Language Models to Images for Multimodal Inputs and Outputs | date=2023 | class=cs.CL }}</ref>
A system is designated unimodal if it has only one modality implemented, and [[multimodal interaction|multimodal]] if it has more than one.<ref name="HCI Overview2" /> When multiple modalities are available for some tasks or aspects of a task, the system is said to have overlapping modalities. If multiple modalities are available for a task, the system is said to have redundant modalities. Multiple modalities can be used in combination to provide complementary methods that may be redundant but convey information more effectively.<ref>{{Cite book|title = Interactive Systems. Design, Specification, and Verification|last1 = Palanque|first1 = Philippe|publisher = Springer Science & Business Media|year = 2001|isbn = 9783540416630|pages = [https://archive.org/details/springer_10.1007-3-540-44675-3/page/n50 43]|last2 = Paterno|first2 = Fabio|url = https://archive.org/details/springer_10.1007-3-540-44675-3}}</ref> Modalities can be generally defined in two forms: computer-human and human-computer modalities.
==Computer–HumanComputer–human modalities==
Computers utilize a wide range of technologies to communicate and send information to humans:
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** [[Equilibrioception]] (balance)
Any human sense can be used as a computer to human modality. However, the modalities of [[visual perception|seeing]] and [[hearing (sense)|hearing]] are the most commonly employed since they are capable of transmitting information at a higher speed than other modalities, 250 to 300<ref name=Ziefle98>{{cite journal|last1=Ziefle|first1=M|title=Effects of display resolution on visual performance.|journal=Human Factors|date=December 1998|volume=40|issue=4|pages=554–68|pmid=9974229|doi=10.1518/001872098779649355}}</ref> and 150 to 160<ref>Williams, J. R. (1998). Guidelines for the use of multimedia in instruction, Proceedings of the Human Factors and Ergonomics Society 42nd Annual Meeting, 1447–1451</ref> [[words per minute]], respectively. Though not commonly implemented as computer-human modality, tactition can achieve an average of 125 wpm<ref>{{cite web|title=Braille|url=http://www.acb.org/node/67|website=ACB|publisher=American Council of the Blind|accessdate=21 April 2015}}</ref> through the use of a [[refreshable Braille display]]. Other more common forms of tactition are smartphone and game controller vibrations.
