This paper presents the results of a within-subject longitudinal evaluation on Inscript keyboard, which is the national standard layout for Indian scripts. We studied the practical upper bound speed and accuracy as well as the effect of practice. Through longitudinal transcription task of 400 repeated attempts, we observed typing speeds for highly experienced users consistently peak close to 120 cpm i.e. 2.5 times that of fastest speeds reported in literature. Our analysis compared the lower bound times for Tap, Tap+LongPress and Shift+Tap, the three text input mechanisms in this keyboard. Among the two alternative methods, our findings established Tap+LongPress method to be faster than Shift+Tap method and almost equally accurate. Also, we derived a model which explains the influence of corrected errors and number of practice attempts on the typing speed.

As part of an ongoing standardization effort, we were asked to evaluate Marathi text input mechanisms on smartphones. We undertook a between-subject longitudinal evaluation of four existing keyboards with 153 novice users who participated for 31 sessions each, spread over 3--4 weeks. In this paper, we present the empirical results of the performance of these keyboards and discuss them with respect to their designs. We found that keyboards with logical layouts performed marginally better than keyboards with partially frequency-based layouts. Results also showed that users performed poorly on keyboards that have word prediction features in comparison with keyboards that don't have prediction features while typing Marathi. We speculate that this difference in performance is related to a "cognitive toll" that the users pay to use word prediction. We identify several directions for future research.

Lack of an easy and efficient text input mechanism in Indic scripts has been a barrier to large-scale adoption of ICTs in India. We present findings from a usability evaluation of three keyboard designs for Indic scripts for touch screen phones. The design of one of the keyboards is based on the frequency of characters, while the designs of the other two are based on the logical structure of the script. We evaluated the keyboards with participants with low-level of education through a first-time usability test and a longitudinal usability test. One of the logically structured keyboards started out with significantly higher success rate, typing speed, and lesser errors than the other two. The longitudinal test involving text input of 500 words did not conclusively prove that either design was better. Our study establishes benchmarks for text input speeds, errors and ratings for the initial learning phase for text input in Marathi among less educated users.