Toolbox or adjustable spanner? A critical comparison of two metaphors for adaptive decision making.

For multiattribute decision tasks, different metaphors exist that describe the process of decision making and its adaptation to diverse problems and situations. Multiple strategy models (MSMs) assume that decision makers choose adaptively from a set of different strategies (toolbox metaphor), whereas evidence accumulation models (EAMs) hold that a uniform mechanism is employed but is adapted to the environmental change (adjustable spanner metaphor). Despite recent claims that the frameworks are hard to disentangle empirically, both metaphors make distinct predictions concerning the information acquisition behavior, namely, that search is terminated according to the selected strategy (MSMs) or that information is acquired until an evidence threshold is passed (EAMs). In 3 experiments, we contrasted these predictions by providing participants with different degrees of evidence in a half-open/half-closed information board. For the majority of participants, we find that their stopping behavior is well captured by the notion of an evidence threshold that is either undercut or passed by the given evidence.