  We present a controlled, quantitative study with 12 participants comparing
interaction with a haptically enhanced mixing board against interaction with a
mouse in an abstract task that is motivated by several practical parameter
space exploration settings.
  The study participants received 24 sets of one to eight integer values
between 0 and 127, which they had to match by making adjustments with physical
or graphical sliders. Based on recorded slider motion path data, we developed
an analysis algorithm that identifies and measures different types of activity
intervals, including error time moving irrelevant sliders and end time in
breaks after completing each trial item. Our results showed a significant
increase in speed of the mixing board interaction accompanied by reduced
perceived cognitive load when compared with the traditional mouse-based GUI
interaction. The gains in speed are largely due to the improved times required
for the hand to reach for the first slider (acquisition time) and also when
moving between different ones, while the actual time spent manipulating
relevant sliders is very similar for either input device. These results agree
strongly with qualitative predictions from Fitts' Law that the larger targets
afforded by the mixer handles contributed to its faster performance. For
further investigation, we computed a measure of motion simultaneity based on
velocity correlation, which allowed to identify types of items for which
increased simultaneous adjustments occur.
  For continuous parameter space exploration our findings suggest that mixing
boards are a good option to provide detailed multi-value control. The strengths
of this input method particularly show in settings where screen space is
precious and undisrupted visual focus is crucial.
