Studies into the dynamics of head and eye gaze behavior tend to hint that attention is linked to the types of movements of head and eye. A number of studies have shown that when presented with a stimulus in the field of view, the head tends to lag behind the eye during the gaze shift (Bartz,
1966; Goossens & Opstal,
1997). Others have found that early head motions, with respect to the saccade, are associated with target predictability, location, propensity to move the head, and timing (Freedman,
2008; Fuller,
1992; Khan, Blohm, McPeek, & Lefèvre,
2009; Morasso, Sandini, Tagliasco, & Zaccaria,
1977; Ron, Berthoz, & Gur,
1993; Zangemeister & Stark,
1982). These studies occurred in very controlled, arguably unnatural environments; more recent studies into “natural” tasks involving grasping, tapping, or sitting in a lecture (Doshi & Trivedi,
2009a; Herst, Epelboim, & Steinman,
2001; Mennie, Hayhoe, & Sullivan,
2007; Pelz, Hayhoe, & Loeber,
2001) have suggested that task-oriented gaze shifts may be associated with early head motions. These studies suggest the hypothesis that the interactive dynamics of head and eye movements may encode information about the type of attention shift, and thus the cognitive state, of the human subject.