  With respect to machine operation tasks, the experiences from different skill
level operators, especially novices, can provide worthy understanding about the
manner in which they perceive the operational environment and formulate
knowledge to deal with various operation situations. In this study, we describe
the operator's behaviors by utilizing the relations among their head, hand, and
operation location (hotspot) during the operation. A total of 40 experiences
associated with a sewing machine operation task performed by amateur operators
was recorded via a head-mounted RGB-D camera. We examined important features of
operational behaviors in different skill level operators and confirmed their
correlation to the difficulties of the operation steps. The result shows that
the pure-gazing behavior is significantly reduced when the operator's skill
improved. Moreover, the hand-approaching duration and the frequency of
attention movement before operation are strongly correlated to the operational
difficulty in such machine operating environments.
