Acta Psychologica 66 (1987) 221-224 North-Holland

221

IMAGE THEORY AND DOMINANCE SEARCH THEORY: HOW IS DECISION MAKING ACTUALLY DONE?

A comment on ‘Image Theory: principles, goals, and plans in decision making’ by Beach and Mitchell

Henry MONTGOMERY * University of Giiteborg Giiteborg Sweden

How is decision making actually done? To answer this question Beach and Mitchell (1987) apparently assume that it is necessary to make a fresh start. Forget theories of rational decision making! Forget the conventional models! In my own research I have developed a theory - Dominance Search Theory (Montgomery 1983, 1987) - with similar aims to those of Image Theory. Both theories are descriptive and they concern how decisions are framed and how they are made given a certain framing of a decision problem. Below, I will compare the two theories and discuss how they relate to conventional thinking about decision making as well as to empirical data.

The most striking discrepancy between Beach and Mitchell’s Image Theory and conventional thinking about decisions concerns how a decision problem is framed. In conventional models decision makers choose between alternative acts. In Beach and Mitchell’s Image Theory decision makers do not choose primarily between acts. Rather, ‘deci- sions consist of (1) adopting or rejecting potential candidates to be new principles, goals, or plans, and (2) determining whether progress toward goals is being made’. Principles, goals or plans are assumed to be represented as ‘images’ (according to Miller et al.‘s (1960) terminology).

It appears that according to Image Theory a decision process may be decomposed into a number of local decisions, i.e., decisions about goals, principles, or plans and decisions about whether progress is made or not. Of course, such local ‘decisions’ actually are made. But

* Author’s address: H. Montgomery, P.O. Box 14158, S-40020 Giiteborg, Sweden.

OOOl-6918/87/$3.50 0 1987, Elsevier Science Publishers B.V. (North-Holland)

222 H. Montgomtvy / Image Theory and decision making: a comment

these local ‘decisions’ are not equivalent to what I would call real decisions. As I see it, and this is in line with conventional thinking, real decisions concern acts and only acts. The local ‘decisions’ described in Image Theory are operations made in order to facilitate a real decision, i.e., a decision about acts.

In a recent account of Dominance Search Theory (Montgomery 1987) the link between decision and action is highlighted. Decision making is seen as preparation for action. When making decisions people attempt to find arguments which make it possible to stick to a certain line of action whatever happens (within limits given by the decision problem). If the chosen alternative can be seen as dominating other alternatives the decision maker will have access to arguments which may serve such a function. Because of this, decision makers search for a cognitive representation in which a promising alternative can be seen as dominant. Put differently, the goal of the decision process is to build up a stable enough intention to act in a certain way. If the decision maker succeeds in doing so with respect to a given alternative the decision is made.

Sometimes, people decide for lines of action which follow relatively general principles, e.g., to live a free life or to be a good person. But also in these cases people choose to act in a certain way. It is important to note that such a decision is not equivalent with adopting a principle. A person may think that a principle (or goal or plan) is worth pursuing, and in this sense adopt the principle, but he or she may still refrain from acting in line with the principle. The mental process which leads to a commitment for acting in line with a principle (or ‘image’) is the core of a decision-making process as I see it. It appears that Image Theory does not deal with this interesting process - at least not explicitly. It may be asked, however, whether there are processes described by Image Theory which in fact serve the function of building up a commitment for action. I will return to this issue after having discussed how decisions are made according to Image Theory.

Image Theory describes two decision-making principles. Normally decisions are based on the compatibility between candidates and con- stituents of the decision maker’s images. A candidate is adopted if the number of violations of the relevant image constituents is below a certain critical value (the rejection threshold). Otherwise it is rejected. If more than one candidate survives the compatibility test, then the choice between the survivors is made in terms of their profitability,

H. Montgomery / Image Theory and decision making: a comment 223

which is assumed to be conceptually similar to expected utility and hence corresponds to a compensatory decision rule.

This general picture of how a decision process may develop largely seems to be consonant with empirical data. However, I would like to hear arguments why the rejection/adoption threshold corresponds to a certain number of violations. How is this number determined? And why not instead assume that an alternative may be rejected if it is deemed unsatisfactory on just one (important) attribute as is the case in the so-called conjunctive decision rule?

The idea that choices between candidates which survive the compati- bility test follow a compensatory decision rule gets some support in a computer-based process-tracing study carried out by Dahlstrand and Montgomery (1984). However, the data in this study indicate that non-compensatory rules focussing on positive aspects may also be used for predicting final choices. Probably, compensatory thinking is used in varying degrees across situations and individuals for choices between candidates that have survived a compatibility test.

Dominance Search Theory asserts that if a decision maker finds that a promising alternative violates dominance he or she will attempt to restructure his or her representation of the alternatives in such a way that the promising alternatives may be seen as dominant. In a similar way Image Theory asserts that decision makers attempt to ‘rectify things’ when in so-called progress decisions it is found that no progress is made toward adopted goals. Perhaps it may be said that these restructuring operations aim at building up a stable enough intention to act in line with a given plan. Hence, Image Theory may not be at odds with Dominance Search Theory with respect to the link between decision and action. However, as I see it, the nature of that link is blurred in Image Theory by the over-inclusive use of the term ‘decision’ in the theory.

The more I penetrate Image Theory the closer it comes to Domi- nance Search Theory. It appears that the two theories have similar ideas about how a decision process develops across time. In both theories it is possible to identify four phases of a decision process, viz. (1) rejection of non-acceptable or uninteresting alternatives, (2) identi- fication of a candidate for the final choice, (3) tests whether such a candidate could be chosen definitely, and (4) restructuring operations when these tests give a negative result. However, in Image Theory the process basically is controlled by the compatibility of plans with

224 H. Montgomery / Image Theory and decision making: a comment

adopted principles or goals, while in Dominance Search Theory the process is controlled by violations of dominance and of possibilities of constructing dominance structures (which, however, involve principles and goals). Moreover, Dominance Search Theory emphasizes the link between decision and action more clearly than Image Theory does. It would be interesting to highlight in further research, and in further discussions, how great these discrepancies between the two theories actually are.

References

Beach, L.R. and T.R. Mitchell, 1987. Image Theory: principles, goals, and plans in decision

making. Acta Psychologica 66, 201-220.

Dahlstrand U. and H. Montgomery, 1984. Information search and evaluative processes in decision

making: a computer based process tracing study. Acta Psychologica 56, 113-123.

Miller, G.A., E. Galanter and K.H. Pribram, 1960. Plans and the structure of behavior. New

York: Holt, Rinehart, and Winston.

Montgomery, H., 1983. ‘Decision rules and the search for a dominance structure: towards a

process model of decision making’. In: P.C. Humphreys, 0. Svenson and A. Vari (eds.),

Analysing and aiding decision processes. Amsterdam/Budapest: North-Holland and

Akaddmiai Kiadb. Montgomery, H., 1987. ‘From cognition to action: the search for dominance in decision making’.

In: H. Montgomery and 0. Svenson (eds.), Process and structure in decision making. (In

preparation.)