Decision Making in Groups: Group membership effects on post-decision processes

Per Eisele

Research output: ThesisDoctoral Thesis (compilation)


The present thesis examines differences in post-decision processes between members of groups and individual decision makers. The empirical studies employed a decision theoretical framework based on Differentiation and Consolidation (Diff Con) Theory. Diff Con theory proposes that decision makers strive to achieve sufficient differentiation in their evaluation of one alternative versus competing alternatives to be able to make a decision and that this process of differentiation continues during the post-decision period. This post-decision differentiation is also referred to as consolidation. In each of the four studies contained in the thesis, consolidation for group members was compared with that for individual decision makers. Study I involved two experiments. In Experiment 1 there were two group discussion conditions, being instructed to reach consensus before deciding and being instructed that a majority-vote would be sufficient to make a group decision. In Experiment 2, group decision making with face-to-face interaction was compared with that involving information exchange only. The results of both Experiment 1 and Experiment 2 indicated that, whereas individual decision makers consolidated their decisions, group members did not consolidate the decisions made by their groups. No differences in consolidation were found between the different group decision-making conditions.

In Study II, group members were classified on the basis of Bales´ SYMLOG instrument as being task-oriented or socially oriented in making their decisions. Whereas task-oriented group members were found to consolidate their decisions, socially oriented group members were not.

In Study III, consolidation in individual decision makers and in interactive decision makers (interacting in dyads or in triads an then making a persoanl decision) were compared. The decision makers were classified according to whether their preferred decision strategy as reported by them was a compensatory (considering all attributes) or a non-compensatory one (focusing only on the most important attributes). Only participants using a non-compensatory decision strategy were found to consolidate their decisions.

In Study IV, decision-making group members were found to consolidate the group decisions less than individual decision makers, and participants using a non-compensatory decision strategy to consolidate their decisions more than participants using a compensatory decision strategy, both results replicating earlier results. In addition, the disagreement information hypothesis, namely that disagreement (or decision-threatening) information increases post-decision consolidation, was tested. It was also argued that group members would be less susceptible to disagreement information than individual decision makers, due to their focusing on information shared by the group members, at the cost of the unshared information. Results indicated that disagreement information given to participants (both group members and individual decision-makers) after they have made a decision further enhance post-decision consolidation.
Original languageEnglish
Awarding Institution
  • Department of Psychology
  • [unknown], [unknown], Supervisor, External person
Award date1999 Sept 17
ISBN (Print)91-628-3658-7
Publication statusPublished - 1999

Bibliographical note

Defence details
Date: 1999-09-17
Time: 10:00
Place: Kulturens Auditorium
External reviewer(s)
Name: Verplanken, Bas
Title: Professor
Affiliation: [unknown]

Subject classification (UKÄ)

  • Psychology

Free keywords

  • group membership.
  • social interaction style
  • group decision-making
  • decision strategy
  • Decision
  • post-decision processes
  • Psychology


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