NavTap: A Long Term Study with Excluded Blind Users
Tiago Guerreiro, Hugo Nicolau, Joaquim Jorge, Daniel Gonçalves · 2009 · Proceedings of the 11th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '09) · doi:10.1145/1639642.1639661
Summary
This paper presents a long-term evaluation of NavTap, a navigational text-entry method designed specifically for blind users who cannot effectively use standard mobile phone text input. Unlike traditional MultiTap — where users press a key multiple times to cycle through letters assigned to it, relying on visual feedback — NavTap divides the alphabet into five rows starting with different vowels and allows users to navigate using joystick-like directional keys with continuous audio feedback. Users hear each letter as they navigate to it and explicitly confirm their selection, meaning no action is irreversible and the cognitive load is dramatically reduced. The study went far beyond typical lab evaluations: eight blind users participated in a three-week iterative design phase, and five continued through 16 weeks of combined controlled weekly sessions and uncontrolled daily usage. The participants, aged 44 to 61, were recruited from a training center for blind people and represented a population often excluded from mobile technology research — older users with age-induced impairments, limited education, and some with cognitive difficulties. None could input text on their phones before the study. The researchers tracked performance through words per minute (WPM), keystrokes per character (KSPC), error rates, and real-world usage logs of SMS messages, calls, and contact management.
Key findings
Over the 16-week study, participants' typing speed roughly doubled, with WPM increasing from an average of 0.7 to 2.7 across the group. Three participants nearly reached the theoretical best-case KSPC for the 2-way navigation scenario, showing strong learning curves. Error rates remained consistently low (1-4% character deletion rate), confirming that NavTap's confirmatory input model prevented mistakes rather than requiring correction. Daily usage data was striking: participants collectively sent 1,825 text messages and received 1,200 — remarkable given that none could send SMS before the study. SMS usage exceeded voice calls for three of five participants, and over 20% preferred texting to calling. Users also managed 133 contact additions and 26 deletions. Subjective evaluations on 5-point Likert scales showed strong agreement that NavTap was easy to use (median 5), easy to learn (5), and made the phone accessible (5). The first 40 SMS messages had the biggest influence on performance improvement, suggesting rapid early learning. Even participants with cognitive difficulties and low education levels showed continuous improvement throughout the study.
Relevance
This study is a powerful demonstration of how thoughtful input design can transform digital inclusion for blind users who are typically excluded from mobile technology. The finding that over 82% of blind people are over 50 — often with age-related impairments affecting memory, tactile sensitivity, and cognition — challenges the common assumption that blind mobile users are young, tech-savvy individuals comfortable with screen readers. NavTap's success with this underserved population shows that reducing cognitive load and providing non-visual confirmation feedback can enable text communication for people previously locked out of it entirely. For accessibility practitioners, the longitudinal methodology is equally valuable: short lab studies would have missed the dramatic real-world impact on social participation and the steady performance improvement over months. The research underscores that accessible text entry is not merely a convenience but a gateway to social inclusion — participants' relationships with family and friends were noticeably improved through their newfound ability to send text messages.
Tags: mobile accessibility · blind users · text entry · assistive technology · longitudinal study · social inclusion · SMS · mobile devices