The Effects of Perceptual Grouping on Text Entry Performance
http://www.surl.org/usabilitynews/61/perceptual_grouping.asp

Hamblin, Christopher J., Michael Bohan and Alex Chaparro
Usability News
2004

Abstract:

One of the primary challenges confronting designers of mobile computing devices is the issue of efficient text entry. One potential solution is to group multiple letters onto single keys, similar to the T9 keyboard currently used on telephones. Two experiments examined the effects of perceptual grouping on soft keyboard transcription rates. Results from Experiment 1 showed significantly slower transcription rates for QWERTY keyboards with grouped keys. Results from Experiment 2 showed various levels of perceptual interference due to the different Gestalt grouping effects. These results indicate that perceptual grouping can negatively affect text entry performance, and placing multiple letters onto single keys reduces the speed at which users can transcribe words.