Group Judgment and Decision Making

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Group Judgment and Decision Making
Judgment and Decision Making in Information
Systems

• Yuval Shahar M.D., Ph.D.

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Group Decision Making

• Essentially, an extension of individual decision
  making with all faults and biases
• Unique features Social influence, mutual
  discussion, a group decision-making procedure
• Process and mode of decision making (e.g.,
  interactive discussion, majority vote) are
  crucial
• Advantages Potential brainstorming, multiple
  types of expertise and points of view,
  facilitation of problem solving and creativity
• Disadvantages Social loafing, conformity,
  polarization of previous opinions, groupthink
  phenomenon might lead to unreasonable decisions

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Are N1 Heads Better than One?

• Groups are often better in solving problems,
  especially involving unfamiliar domains
• Example The NASA moon landing survival
  experiment (ranking of 15 items by degree of
  importance) The group error is much smaller than
  the average of the personal errors
• Review studies show that improvement occurs in
  several different areas
• Quantitative judgment (up to 23 to 32 accuracy
  increase)
• Brain teasers and logic problems (better then
  average)
• General knowledge questions (better than average
  member)
• Creativity and problem solving (groups can pool
  resources)
• However, it is not clear that the group
  interaction is useful
• The best individual usually outperforms the group
  as a whole in all types of judgments Hastie,
  1986 and their accuracy is even reduced!
• brainstorming is more effective when ideas are
  generated independently and later combined, than
  when conducted in a group session Hill, 1982
  (might include a social loafing element as well)

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ConformityAsch, 1951, 1955, 1956

• Is the test line equal in length to A, B, or C?
• Small (3 of 4) majorities are sufficient to
  elicit substantial conformity with a wrong result
• Any opposition can have a major effect even a
  single dissenting individual can nullify the
  effect!

Test line
A
B
C
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Asch Results The Pressure to Conform
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GroupthinkJanice, 1982

• A deterioration of mental efficiency, reality
  testing and moral judgment that results from
  in-group pressures
• Famous examples Bay of Pigs invasion Challenger
  space shuttle launch Israel before the October
  1973 war etc.
• Occurs when groups are cohesive and insulated
  from the outside, while inside pressures for
  group loyalty and conformity lead to muddled
  thinking

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Groupthink Symptoms Janice 1982

• Illusion of invulnerability leads to unjustified
  optimism and risk taking
• Collective efforts to discount warnings
• Unquestioned belief in groups morality
• Stereotyped views of adversaries (too evil to
  negotiate with, too stupid to be a threat)
• Pressure directing at any dissenting group member
• A shared illusion of unanimity
• Self censorship of deviations from group
  consensus
• Self-appointed mind guards protect group from
  information that might challenge the complacency

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Group PolarizationMoskovici Zavaloni, 1969

• The risky shift phenomenon Stoner, 1961
  Individuals tend to take more risks after a group
  discussion
• Can be also a cautious shift, and in any
  judgment
• Possible explanations
• The extreme majority alternative gets more
  discussion time
• Responsibility is shared among individual members
• Extreme individuals become more extreme when they
  discover that their opinion is not as extreme as
  viewed
• The extreme alternative is valued higher due to
  group effect
• Groups are risk-neutral while members are
  risk-averse

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Social Loafing

• People do not work as hard in groups as they work
  alone (e.g., rope tugging, even when blindfolded)
• Responsibility for the final outcome is diffused
  among members of the group
• Multiple examples from reality and research
• Reporting a crime viewed by many people in New
  York
• Assisting a child lost on the highway in Italy
• Assisting a stranger pick up coins in an elevator
• Intervening as a bystander to report a fire, or
  to assist a stranger who cries for help in a
  nearby room
• Presence of others reduces likelihood of
  intervention

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Group Discussion Modes

• Multiple facilitation techniques are potentially
  applicable
• Collective averaging without interaction
• Consensus Face to face discussion until
  agreement
• Dialectic members discuss biasing factors
• Dictator Discussion leads to selection of
  representative (best) member
• Delphi Judgments provided ahead of time and
  consensus is established iteratively in several
  rounds
• The Collective method was the worst, but the
  Dictator method was up to three times more
  accurate in an experiment involving sales
  prediction Davis, 1973

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Group Decision Making Rules

• How does a group reach a decision?
• Multiple potential methods exist, such as a
  simple majority, total agreement, etc.
• A crucial difference exists between
• choosing among two alternative
• Choosing among three or more alternatives
• The difference is in the ability
• to reach non-paradoxical results, such as an
  undesirable effect of irrelevant options
• To avoid potential manipulation by one of the
  decision makers

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The Condorcet 1785 Paradox

• 1/3 of the group prefers xyz
• 1/3 of the group prefers yzx
• 1/3 of the group prefers zxy
• Thus
• an absolute 2/3 majority prefers x to y
• an absolute 2/3 majority prefers y to z
• But an absolute 2/3 majority prefers z to x
• Inconsistent with a transitivity assumption (!!)

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The Borda Scoring Rule

• Each group member ranks all K alternatives,
  giving the best K points and he worst 1 point
• Points are summed to determine the decision
• However, the assumption of independence from
  irrelevant alternatives (IIA) is violated
• For example, removing 3 inferior alternatives
  from a list of 5 alternatives can change the
  preference order for the two main alternatives!

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Example of Borda IIA Violation

• Assume 5 individuals and 5 alternatives
  a,b,c,x,y
• xyabc Note xy
• yacbx Note yx
• cxyab Note xy
• xybca Note xy
• ybaxc Note yx
• Thus, score(y) 21 score(x) 17 yx by group
• But removing a,b,c leads to
• score(x) 8 score(y) 7 xy by group!

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The Importance of the Comparison Order

• Assume 3 individuals and 3 alternatives x,y,z
• xyz
• yzx
• zxy (or xzy)
• If we first compare x to z, z wins and then y
  wins if we first compare x to y, x wins and then
  z win
• The comparison order (e.g., as determined by a
  committee head in a parliament) is crucial!
• The third individual can change the eventual
  winner by manipulating their preferences so that
  x wins when compared to z and then wins over y!

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The Arrow 1951, 1963 Impossibility Theorem

• It is impossible to find a group decision rule
  for choosing the preferred alternative out of
  three or more alternatives, without potentially
  leading to a paradoxical result (i.e., more than
  one chosen alternative)
• Shows that at least one of four given
  assumptions, such as independence of irrelevant
  alternatives, cannot be maintained
• Later results show that every reasonable election
  method for one candidate out of three or more can
  be manipulated by voting against ones own
  preferences

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SummaryGroup Decision Making

• Advantages
• Multiple views and types of expertise
• Social facilitation due to directed open
  discussion
• Brainstorming might lead to creative solutions
• Disadvantages
• Often fails to equal the best individual solution
• Conformity bias (e.g., the Asch (1951-1956) 3
  lines experiments)
• Groupthink (overconfidence, ignorance of facts)
• Polarization effect (e.g., risky shift
  phenomenon)
• Social loafing (pool, elevator experiments)
• In general No optimal decision rule exists for
  more than 2 options
• Much depends on how the discussion is managed
  (e.g., order of speaking use of a discussion
  facilitator a consensus, dictator or a Delphi
  methodology)