Three Roads to Commitment: A Trimodal Theory of Decision Making

Three Roads to Commitment: A Trimodal Theory of Decision Making 50
Control. Aids should help users adapt to constraints of time and stakes. This includes reducing risks by
increasing the robustness of courses of action (Forestalling), reducing the cost of delaying irreversible commitment
(Buying time), and acting immediately on the current best solution when benefits of further risk reduction are
outweighed by the costs of delay (the Suppress tactic).
Transitions. Displays for different modes should support seamless transitions to other modes when appropriate.
For example, displays for creating options and goals (matching) should relate transparently to displays for
comparing options in terms of goals (when choice is appropriate), and both should relate transparently to displays
for vetting courses of action before implementation and for monitoring goal achievement during implementation
(reassessment).
Uncertainty. Aids should focus on the appropriate intersection of decision mode and action uncertainty. Issues
relevant to the decision mode should be highlighted as discussed under Focus, e.g., obstacles in determining rule fit
in matching, option efficiency in choice, and course of action reliability in reassessment. Variations in levels of
action uncertainty across problems and users should be accommodated, e.g., pattern recognition tactics should be
reserved for the lowest levels of action uncertainty; weak methods and lengthy reasoning processes should be
reserved for the highest levels of action uncertainty; strategies for adaptive deliberation should be supported for
moderately difficult problems in familiar domains. Displays should seamlessly track uncertainty levels as they
change in response to uncertainty handling tactics; for example, affording users the opportunity to evaluate and
modify peripheral assumptions in cases of low action uncertainty, or more central ones if overall implausibility
increases.
The standard story, which identifies decision making with choice, encourages people to make retrospective
sense of their actions to themselves and others as deliberate and optimal (March, 1979) – and conversely, to fault
others’ decisions for not achieving the same perfection. This story is an ideal congealed into a cultural myth. It has
also proven to be a trap for designers, who are still capable of being surprised by the low level of user acceptance
even for well-engineered decision support, when it focuses exclusively on deliberative comparison of options.
Trimodal Decision Making insists on the normative validity of three paths to commitment, describes different levels
of affordance for those paths, and prescribes principles of decision aiding. It fleshes out and corrects the standard
story and other overly narrow approaches to decision making, and, we hope, will be a useful source of implications
and challenges for cognitive engineering practice and research in the future.
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