Table 1 Subjective scale measures and Cronbach’s alpha values.

Predictability (α = 0.73)(1) The robot consistently moved in a way that I expected.
(2) The robot’s motion was not surprising.
(3) The robot responded to my motion inputs in a predictable way.
Fluency (α = 0.64)(1) The robot and I worked fluently together as a team.
(2) The robot contributed to the fluency of the interaction.
Trust (α = 0.64)(1) I trusted the robot to do the right thing at the right time.
(2) The robot was trustworthy.
Goal perception (α = 0.76)(1) The robot perceives accurately what my goals are.
(2) The robot does not understand what I am trying to accomplish.
(3) The robot and I are working toward mutually agreed upon goals.
Usefulness (α = 0.75)(1) It helps me be more effective.
(2) It is useful.
(3) It makes the things I want to accomplish easier to get done.
Robot intelligence (α = 0.74)(1) The robot was intelligent.
(2) The robot was able to independently make decisions throughout the task.
(3) The robot had an understanding of the task.
(4) The robot had an understanding of my goal during the task.
Satisfaction (α = 0.86)(1) I am satisfied with it.
(2) I would recommend it to a friend.
(3) It is fun to use.
(4) It works the way I wanted it to work.
(5) It is wonderful.
Ease of use (α = 0.87)(1) It is easy to use.
(2) It is simple to use.
(3) It is user friendly.
(4) It is flexible.
(5) It is effortless.
(6) I can use it without written instructions.
(7) I do not notice any inconsistencies as I use it.
(8) Both occasional and regular users would like it.
(9) I can recover from mistakes quickly and easily.
(10) I can use it successfully every time.