Editing Touchscreen (section)

===Touchscreen enable===
For touchscreens to be effective input devices, users must be able to accurately select targets and avoid accidental selection of adjacent targets. The design of touchscreen interfaces should reflect technical capabilities of the system, [[Human factors and ergonomics|ergonomics]], [[cognitive psychology]] and [[human physiology]].

Guidelines for touchscreen designs were first developed in the 2000s, based on early research and actual use of older systems, typically using infrared grids—which were highly dependent on the size of the user's fingers. These guidelines are less relevant for the bulk of modern touch devices which use capacitive or resistive touch technology.<ref>{{cite journal|title=ANSI/HFES 100-2007 Human Factors Engineering of Computer Workstations|journal=Human Factors & Ergonomics Society|year=2007|location=Santa Monica, CA}}</ref><ref>{{cite journal|title=Ergonomic Requirements for Office Work with Visual Display Terminals (VDTs)–Part 9: Requirements for Non-keyboard Input Devices|journal=International Organization for Standardization|year=2000|location=Geneva, Switzerland}}</ref>

From the mid-2000s, makers of [[operating systems]] for [[smartphones]] have promulgated standards, but these vary between manufacturers, and allow for significant variation in size based on technology changes, so are unsuitable from a [[Human factors and ergonomics|human factors]] perspective.<ref>{{cite web|url=https://developer.apple.com/library/ios/documentation/userexperience/conceptual/mobilehig/LayoutandAppearance.html|title=iOS Human Interface Guidelines|publisher=Apple|access-date=2014-08-24|url-status=live|archive-url=https://web.archive.org/web/20140826113309/https://developer.apple.com/library/ios/documentation/userexperience/conceptual/mobilehig/LayoutandAppearance.html|archive-date=2014-08-26}}</ref><ref>{{cite web|url=http://developer.android.com/design/style/metrics-grids.html|title=Metrics and Grids|access-date=2014-08-24|url-status=live|archive-url=https://web.archive.org/web/20140716165521/https://developer.android.com/design/style/metrics-grids.html|archive-date=2014-07-16}}</ref><ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/windows/apps/hh465415.aspx|title=Touch interactions for Windows|publisher=Microsoft|access-date=2014-08-24|url-status=dead|archive-url=https://web.archive.org/web/20140826120338/http://msdn.microsoft.com/en-US/library/windows/apps/hh465415.aspx|archive-date=2014-08-26}}</ref>

Much more important is the accuracy humans have in selecting targets with their finger or a pen stylus. The accuracy of user selection varies by position on the screen: users are most accurate at the center, less so at the left and right edges, and least accurate at the top edge and especially the bottom edge. The [[Circular error probable|R95]] accuracy (required radius for 95% target accuracy) varies from {{convert|7|mm|abbr=on}} in the center to {{convert|12|mm|abbr=on}} in the lower corners.<ref>{{cite web|last=Hoober|first=Steven|url=http://www.uxmatters.com/mt/archives/2013/03/common-misconceptions-about-touch.php|title=Common Misconceptions About Touch|publisher=UXmatters|date=2013-02-18|access-date=2014-08-24|url-status=live|archive-url=https://web.archive.org/web/20140826114743/http://www.uxmatters.com/mt/archives/2013/03/common-misconceptions-about-touch.php|archive-date=2014-08-26}}</ref><ref>{{cite web|last=Hoober|first=Steven|url=http://www.uxmatters.com/mt/archives/2013/11/design-for-fingers-and-thumbs-instead-of-touch.php|title=Design for Fingers and Thumbs Instead of Touch|publisher=UXmatters|date=2013-11-11|access-date=2014-08-24|url-status=live|archive-url=https://web.archive.org/web/20140826160836/http://www.uxmatters.com/mt/archives/2013/11/design-for-fingers-and-thumbs-instead-of-touch.php|archive-date=2014-08-26}}</ref><ref>{{cite journal|last1=Hoober|first1=Steven|last2=Shank|first2=Patti|last3=Boll|first3=Susanne|title=Making mLearning Usable: How We Use Mobile Devices|year=2014|location=Santa Rosa, CA}}</ref><ref>{{cite journal|last1=Henze|first1=Niels|last2=Rukzio|first2=Enrico|last3=Boll|first3=Susanne|title=100,000,000 Taps: Analysis and Improvement of Touch Performance in the Large|journal=Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services|year=2011|location=New York}}</ref><ref>{{cite journal|last=Parhi|first=Pekka|title=Target Size Study for One-Handed Thumb Use on Small Touchscreen Devices|journal=Proceedings of MobileHCI 2006|year=2006|location=New York}}</ref> Users are subconsciously aware of this, and take more time to select targets which are smaller or at the edges or corners of the touchscreen.<ref>{{cite book|last1=Lee|first1=Seungyons|last2=Zhai|first2=Shumin|title=Proceedings of the SIGCHI Conference on Human Factors in Computing Systems |chapter=The performance of touch screen soft buttons |year=2009|page=309|location=New York|doi=10.1145/1518701.1518750|isbn=9781605582467|s2cid=2468830}}</ref>

This user inaccuracy is a result of [[parallax]], visual acuity and the speed of the feedback loop between the eyes and fingers. The precision of the human finger alone is much, much higher than this, so when assistive technologies are provided—such as on-screen magnifiers—users can move their finger (once in contact with the screen) with precision as small as 0.1&nbsp;mm (0.004&nbsp;in).<ref>{{cite book|last=Bérard|first=François|title=Proceedings of the 2012 ACM international conference on Interactive tabletops and surfaces |chapter=Measuring the linear and rotational user precision in touch pointing |year=2012|page=183|location=New York|doi=10.1145/2396636.2396664|isbn=9781450312097|s2cid=15765730}}</ref>{{dubious|date=December 2017}}