The effect of tactile feedback latency in touchscreen interaction

Touchscreens are becoming more and more popular, especially in mobile devices. There is also clear evidence of the benefits of tactile feedback in touchscreen interaction. However, the effect of the evident latency in interaction has been completely neglected in earlier investigations of touchscreen interaction. In this study we examined the effect of tactile feedback latencies on the usability of a touchscreen keypad. We used a realistic use case for number and character keypads; users entered three-number sequences and short sentences using the virtual buttons on the touch display. The experiments differed from each other in terms of the tactile feedback type (press-only or for press and release) and the keypad layout (number or QWERTY). The results were unexpected, but consistent in all three experiments: The performance did not drop significantly within the latency values used. However, the users evaluated the keypad with the shortest feedback latency more pleasant to use compared to others. We can conclude that latency makes the user experience worse, even though performance does not decrease significantly.