2.2 Eye Movement Analysis
A growing number of researchers use video-based eye
tracking to study eye movements in natural environments.
This has led to important advances in our understanding of
how the brain processes tasks, and of the role that the visual
system plays in this [15]. Eye movement analysis has a long
history as a tool to investigate visual behavior. In an early
study, Hacisalihzade et al. used Markov processes to model
visual fixations of observers recognizing an object [16]. They
transformed fixation sequences into character strings and
used the string edit distance to quantify the similarity of eye
movements. Elhelw et al. used discrete time Markov chains
on sequences of temporal fixations to identify salient image
features that affect the perception of visual realism [17].
They found that fixation clusters were able to uncover the
features that most attract an observer’s attention. DempereMarco
et al. presented a method for training novices in
assessing tomography images [18]. They modeled the
assessment behavior of domain experts based on the
dynamics of their saccadic eye movements. Salvucci and
Anderson evaluated means for automated analysis of eye
movements [19]. They described three methods based on
sequence-matching and hidden Markov models that interpreted
eye movements as accurately as human experts but
in significantly less time.
All of these studies aimed to model visual behavior
during specific tasks using a small number of well-known
eye movement characteristics. They explored the link
between the task and eye movements, but did not recognize
the task or activity using this information