Acta Psychologica 58 (1985) 75-80

North-Holland

75

POST-DECISIONAL CONFIDENCE AND CONFLICT EXPERIENCED IN A CHOICE PROCESS

Dan ZAKAY * Tel-Aviv University, Israel

The present study investigated the relationships between time pressure, type of decision process, in terms of its being compensatory and non-compensatory, and post-decisional confidence. It was

hypothesized that time pressure would lead to more frequent use of non-compensatory strategies

and that post-decisional confidence would be higher after non-compensatory decisions than after

compensatory decisions. For each subject 36 choice situations were developed such that choice of

one alternative would suggest a compensatory decision process whereas choice of the other

alternative would suggest a non-compensatory process. Twenty student nurses made these choices

and rated their post-decisional confidence for each choice. Both hypotheses were supported

although time pressure was not found to influence level of confidence. An explanation based on

the amount of conflict accompanying each type of decision process was suggested.

Compensatory and non-compensatory decision processes underlie two categories of human decision-making models. Compensatory models (e.g., the EV model or Zeleny’s (1976) ADAM) are composition models in which the overall utility of an alternative is an additive combination of the utilities of its attributes, which contribute independently to its overall utility (Edwards and Tversky 1967). In non-compensatory mod- els (e.g., the lexicographic model or Tversky’s (1972) EBA) the utility of an alternative is composed of the utility of only some of its attributes. For example, according to the EBA model, alternative A can be chosen over B because A is superior to B in one attribute, despite the fact that B is superior to A in all other attributes. In reality people exhibit both compensatory and non-compensatory decision behavior (e.g., Einhorn 1970; Slavic and Lichtenstein 1971; Slavic 1975).

* The author wishes to thank Ms. Levia Paswil for assistance in the research.

Author’s address: D. Zakay, Dept. of Psychology, Tel-Aviv University, Ramat Aviv, 69978,

Israel.

OOOl-6918/85/$3.30 0 1985, Elsevier Science Publishers B.V. (North-Holland)

76 D. Zakay / Post -decisional confidence

The purpose of the present study is to test two aspects concerning the use of compensatory versus non-compensatory decision strategies. The first is the influence of time pressure on the selection of a decision strategy and the second is the influence of the strategy utilized on the feeling of confidence in the decision.

Ben Zur and Breznitz found that under high time pressure, a filtra- tion mechanism operated, that is, “information which was perceived by the individual as most important was processed first, and then process- ing was continued until time was up” (1981: 102). Einhorn (1970) noted that non-compensatory strategies may be cognitively simpler and re- quire the assessment of less information as compared to compensatory strategies. Hence, it is hypothesized here that increased time pressure will result in decreased employment of compensatory decision strate- gies.

Regarding the relationship between compensatory and non-com- pensatory decisions and confidence in the decision, it is hypothesized that confidence after non-compensatory decisions will be larger than confidence after compensatory decisions. The suggested reason for this is that the process of compensatory decision making involves the consideration of all attributes and, hence, some level of conflict must exist since at least one attribute of the chosen alternative is not desired by the decision maker. (Not considered here is the case in which one alternative dominates the other; in this case conflict will not exist and the results of compensatory and non-compensatory decision processes will be identical.) On the other hand, in a non-compensatory decision process, like the lexicographic model or Elimination By Aspects (Tver- sky 1972), the decision maker is left with a chosen alternative contain- ing only desired attributes, i.e., those that were considered until the process was stopped. Hence, the decision maker is not left with the bitter taste of conflict in his or her mouth.

In the present research, a decision process is called “compensatory” if the alternative chosen is superior to the other alternatives when considering the sum of the weighted utilities of all the attributes, but is inferior to the other alternatives when taking into account only the most important attribute. A “non-compensatory” decision, on the other hand, is one in which the alternative chosen is superior to the other alternatives only by virtue of its score on the most important attribute, and is inferior to the others when considering the weighted sum of the utilities of all the attributes.

D. Zakay / Post -decisional confidence

Method

Subjects

Twenty female student nurses in the second year of their studies volunteered to participate in the experiment.

Decision-making tasks and procedure

An expert professional nurse generated six typical decision problems, reflecting real-life decisions that nurses face in their work; for example, when two patients call for help simultaneously in the middle of the night, to whom to go first. Five expert nurses then assessed the most important attributes which should be considered in choosing between alternatives in each of these six decision problems. For example, in the situation of two patients calling simultaneously in the middle of the night, the attributes were age, way of calling, general condition according to doctor’s last check, and mental condition. The experts also decided on realistic profiles composed of those attributes which represented valid alternatives (i.e., profiles that represent typical patients’ characteris- tics and behavior that nurses actually meet in the course of their daily work at

hospitals). Each S was presented with each of the six simulated decision problems and asked to

assess the weights she felt appropriate for each attribute on a scale between 0 and 100. Each S also rated the levels within each attribute on a scale between 0 and 100, where 100 stood for the “ideal point” in that attribute in respect to the decision. Using the data derived from this first stage of the experiment, unique pairs of profiles were constructed for each individual nurse. That is, for each nurse a set of six binary decisions for each of the six decision problems (36 pairs in all) was constructed so that in every case it would be possible to ascertain whether the decision was based on a compensatory or a non-compensatory strategy. Hence, in each profile pair one altema- tive was superior to the other with respect to the attribute rated most important, but was inferior to the other with regard to the weighted sum of the utilities of all the attributes, where the rating of the level of each attribute was taken as its utility value.

The following is an example of a pair of profiles presented to one S in Hebrew, printed on a card (10 X 20 cm):

You are the only nurse on duty in the night. Two of the patients are calling simultaneously for help. To whom will you go first? The descriptions of the two patients are as follows: (1) Age: 55. General condition: Medium. Mental condition: Depressed. He is

ringing the bell. (2) Age: 25. General condition: Bad. Mental condition: Anxious. He is ringing the

bell.

The importance weights and values given by that S are presented in table 1. The choice of alternative 2 would suggest that this S relied on “General condition”

78 D. Zakay / Post - decrsional confidence

Table 1

Importance weights and values of one subject.

Attributes

Age Way of General Mental

calling condition condition

Importance weight 60 50 80 65

v1 a 85 40 60 60

vz a 40 40 85 50

a V, = value of the attribute in alternative i.

alone, while the choice of alternative 1 would suggest that all attributes were consid- ered. The possibility that age was the basis of choice is not plausible since age was ranked only third in importance.

The profile pairs were presented two days after the first stage of the experiment, in order to reduce memory effects. The Ss were randomly divided into two groups of ten. The first group made the 36 decisions without any time pressure, while the second group was allowed only 20 seconds for each decision (20 seconds having been found in a pilot study to constitute severe time pressure). The placement of the attributes within each alternative and the placement of alternatives (i.e., which one appeared on the card on top of the others) were counterbalanced within each S in order to eliminate any possible order effects. For each of the 36 pairs each S was asked to make a choice and then rate her degree of confidence on a scale between 0 and 100, where 0 stood for “no confidence at all in the correctness of the decision”, and 100 stood for “complete confidence in the correctness of the decision”. The experiment was conducted in the nurses’ school.

The choices of each S were classified according to compensatory and non-compensa- tory decisions, by the method explained previously. For each S the percentage of compensatory decisions was calculated. The mean percentage of compensatory deci- sions in the no-time-pressure group was 408, and in the time-pressure group 22%. The

Table 2

Mean confidence values.

With time pressure

No time pressure

Mean

Decision type

Compensatory

77.4

76.2

76.8

Non-compensatory

89.2

87.8

88.5

Mean

83.3

82.0

D. Zakay / Post -decisional confidence 19

difference is significant (t = 3.6, df = 18, p < 0.01, one-tailed). The confidence means

across Ss are presented in table 2. These confidence values were analyzed by an analysis of variance, with repeated

measures within decision type. Confidence was found to be significantly higher in

non-compensatory as compared to compensatory decisions (F (1, 19) = 5.85, p < 0.05). The main effect of time pressure and the interaction between time pressure and decision type were not found to be significant.

Discussion

The hypothesis regarding post-decisional confidence was supported; the level of confidence after non-compensatory decisions was higher than that after compensatory decisions. However, level of confidence was not influenced by time pressure. This might indicate that level of confidence is determined mainly by the type of decision strategy used which, in turn, affects the amount of conflict experienced in a choice process. This suggested dependency of post-decisional confidence on amount of experienced conflict is supported by the findings of Koriat et al. (1980) regarding reasons for overconfidence in the correctness of knowledge. They suggested that overconfidence was caused by “selec- tively focusing on evidence supporting the chosen answer and disre- garding evidence contradicting it” (1980: 107). The process of non-com- pensatory decision making may bias the feeling of confidence in a similar way since only attributes which support the feeling of confi- dence are included in the chosen alternative.

The hypothesis regarding the influence of time pressure was also supported; the utilization of compensatory strategy decreased under time pressure. This finding is consistent with Ben Zur and Breznitz’s (1981) evidence for a filtration mechanism used under time pressure. Post-experimental interviews held with the nurses indicated clearly that under time pressure they relied mainly on that information which they felt to be most important.

Fluctuations between compensatory and non-compensatory decision processes were found within each subject, without any obvious sys- tematic pattern. This might reflect inaccuracies in the capturing of the subjects’ utility models [l], changes in values on weights since elicita-

[l] Even simplified versions of utility theory usually require ratio-scale weights and utility scaling that is anchored at both ends (Edwards 1977).

80 D. Zakay / Posr - decisional con/idence

tion, use of decision processes different from the two assumed in the experiments, or temporary effects due to boredom or carelessness.

The findings that the level of confidence is higher after non-com- pensatory decisions than after compensatory ones has undesirable implications for real-life decisions since, as noted by Tversky (1972), from a rational point of view non-compensatory decisions might be inferior to compensatory decisions. The situation is, in a way, paradoxi- cal; how can we expect decision makers to decide more optimally if they feel more confident when they decide less optimally? The results of Koriat et al. (1980) show that by using appropriate methods, overconfi- dence biases about correctness of knowledge can be improved. This gives rise to the suggestion that training of decision makers should include some process by which confidence would be calibrated. Further research is needed in order to design such processes and test their effectiveness.

References

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