  Gaze input has been a promising substitute for mouse input for point and
select interactions. Individuals with severe motor and speech disabilities
primarily rely on gaze input for communication. Gaze input also serves as a
hands-free input modality in the scenarios of situationally-induced impairments
and disabilities (SIIDs). Hence, the performance of gaze input has often been
compared to mouse input through standardized performance evaluation procedure
like the Fitts' Law. With the proliferation of touch-enabled devices such as
smartphones, tablet PCs, or any computing device with a touch surface, it is
also important to compare the performance of gaze input to touch input.
  In this study, we conducted ISO 9241-9 Fitts' Law evaluation to compare the
performance of multimodal gaze and foot-based input to touch input in a
standard desktop environment, while using mouse input as the baseline. From a
study involving 12 participants, we found that the gaze input has the lowest
throughput (2.55 bits/s), and the highest movement time (1.04 s) of the three
inputs. In addition, though touch input involves maximum physical movements, it
achieved the highest throughput (6.67 bits/s), the least movement time (0.5 s),
and was the most preferred input. While there are similarities in how quickly
pointing can be moved from source to target location when using both gaze and
touch inputs, target selection consumes maximum time with gaze input. Hence,
with a throughput that is over 160% higher than gaze, touch proves to be a
superior input modality.
