Action dynamics reveal parallel competition in decision making.

When deciding between two alternatives, such as whether to order the pasta or the chicken, or whether to pursue a career in academia or industry, a person may feel torn—as if the options literally pull him or her in two directions. This metaphor may have some surprising literal truth. If asked, for example, whether ‘‘murder is sometimes justified,’’ individuals may be inclined to both agree and disagree with the statement. Here, we document, for the first time, the pull toward contrasting responses during evaluative thinking, reporting the results of a study examining the trajectory of participants’ reaching movements toward different response options. Our results suggest that a decision process is not necessarily completed in the brain’s cognitive subsystems before it is shared with other subsystems, as has been traditionally assumed. Rather, simultaneous ‘‘pull’’ from multiple response alternatives seems to influence the execution of movement itself. This finding suggests that a dynamic approach to mental processing—an approach that has already provided descriptions of perception, attention, and categorization (e.g., Abrams & Balota, 1991; Gold & Shadlen, 2000; Gratton, Coles, Sirevaag, Eriksen, & Donchin, 1988; Hovland & Sears, 1938; McClelland & Rogers, 2003; Spivey, 2007; Tipper, Howard, & Houghton, 1999)—may shed new light on high-level cognition (Roe, Busemeyer, & Townsend, 2001; Townsend & Busemeyer, 1989).