SocialInterac-onandPerformance
Session8
2016//June6th
GroupDecisions
RobertHepach
[email protected]
basedonthelectureseriesbyProf.RolandDeutsch
1
Outline
Date
Session Topic
4.April2016
1
IntroducCon
11.April2016
2
StereotypesandDiscriminaCon1
18.April2016
cancelled
25.April2016
3
StereotypesandDiscriminaCon2
2.May2016
4
Power
9.May2016
5
AnCsocialBehavior
16.May2016
Pentecost
23.May2016
6
Comparison&CompeCCon
30.May2016
7
ConflictandCooperaCon
6.June2016
8
GroupDecisions
13.June2016
9
Biases
20.June2016
10
AQtudesandConceptofSelf
27.June2016
11
CulturalPsychology
4.July2016
12
CommunicaCon(11.10am)
4.July2016
13
RecapandLectureSummary(13.00)
11.July2016
14
ExamPreparaCon
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Today’sSession
•
•
ProcessesandphenomenaofgroupcogniCon
FactorsinfluencingthequalityofgroupcogniCon
Fundamentalconcepts
• PromoCveeffectsofgroups:CollecCveintelligence
• ReducCveeffectsofgroupsandbiases
• conformity
• informaConrepeCCon
• informaContransfer
•
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Whydoweformgroups?
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FundamentalConcepts
Stasser&Dietz-Uhler(2001)
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FundamentalConcepts
•
IntellecCve:singlecorrectsoluCon,easypersuasion(e.g.,
mathassignment)
•
Judgemental:nosinglecorrectsoluCon,persuasion
difficult(e.g.,tastepreference)
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FundamentalConcepts
CategorizaConaccordingtotasktype
TypeofTask
Examples
Group
potenCal
addiCve
brainstorming,snow
shovelling
sumofindividual
members’performance
disjuncCve
mathemaCcalassignments,
problemsolving,reaching
adecision
bestsinglemember’s
performance
conjuncCve
mountainclimbing,
precisiontasks,keeping
secrets
worstsinglemember’s
performance
Schulz-Hardt&Brodbeck,2007;Steiner,1974
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7
CollecCveIntelligence
Copyright 1982 by the American Psychological Association, Inc.
0033-2909/82/9103-0517S00.75
Psychological Bulletin
1982, Vol. 91, No. 3, 517-539
Group Versus Individual Performance:
Are TV + 1 Heads Better Than One?
Gayle W. Hill
Michigan State University
Experimental comparisons of groups and individuals were analyzed on four dimensions: task, process, individual differences, and methodology. A standardized
terminology based on Lorge, Fox, Davitz, and Brenner was developed to preserve
operational definitions in the comparisons of (a) group versus individual, (b)
group versus the most competent individual in an aggregate, (c) group versus
pooled responses of an aggregate, and (d) group versus math models of performance. Research supported Steiner's theory of process loss but also suggested
evidence for process gain. To avoid confounding of group conditions and subject
variables, this review-focused on the results of random assignment of subjects
to conditions.
Belief in the adage that two heads are
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better than one can be seen in the acceptance
climate was dichotomized as individuals interacting versus individuals working sepa- 8
CollecCveIntelligence
Threemechanisms
• ReciprocalerrorcorrecCon
• CompetenceaddiCon
• SCmulaCon
CentralquesCon:
Isgroupperformancegreaterthanthesumofindividuals’
performance?
Thisdependsonthetypeoftaskandthedecisionrule.
Stasser&Dietz-Uhler(2001);Hill(1982)
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9
CollecCveIntelligence
Earlywork:FrancisGalton-VoxPopuli(Nature,1907):
• fieldstudyatlivestockfair
• visitorscouldesCmatetheweightofanoxandwin
money
• Galtonanalyzedof787esCmaCons
• parCcipantsincludedexperts
Result
• partlystrongdeviaCons
• medianesCmaCon:0.8%deviaConfromactualvalue
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CollecCveIntelligence
Galton(1907)
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CollecCveIntelligence
Galton(1907)
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CollecCveIntelligence
Galton(1907)
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CollecCveIntelligence
Galton(1907)
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CollecCveIntelligence
DemonstraConsofcollecCveintelligence:
•
•
•
•
•
Galton(1907):esCmaConofweights
Shaw(1932):simplebrainteasers
Fischer(1981):predicConofschoolgrades
Henry(1993):factualknowledge
Sniezek&Henry(1989):esCmaConofrisk
TeilsnachStasser&Dietz-Uhler(2001);Schultzeetal.(2012)
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CollecCveIntelligence
StudybySniezek&Henry(1989):
Aregroupjudgmentsmoreaccuratethanindividual
judgments?
• n=54MBA-students
• highrewardforaccuratejudgments
• firstindividualanswerthengroupdiscussionunCl
consensus
• parCcipantsreacheddecisionsingroupsof3
• IV:typeofjudgment->individualvs.group
• DM:esCmatedriskofdeathfor15typesofdeathrisksin
theUS
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CollecCveIntelligence
14
SNIEZEK
AND
HENRY
•I lndlvldual
I
10
Actual
100
1,000
Number
I0,000
of
100,000
Deaths
FIG. 2. Geometric means of individual and group judgments over the 15 causes of death.
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17
CollecCveIntelligence
14
SNIEZEK
AND
HENRY
Results:Groupdecisiononaverage23%more
accuratethanindividualdecisions,especiallywith
regardstorarecausesofdeath.
•I lndlvldual
I
10
Actual
100
1,000
Number
I0,000
of
100,000
Deaths
FIG. 2. Geometric means of individual and group judgments over the 15 causes of death.
Interpreta.on:Groupdiscussionfacilitatesprocess
ofreachingaccuratedecision.
ment between individuals and groups can be seen by comparing average
individual and average group estimates to the actual values (i.e., those
values given by public health statistics). Average individual and group
judgments are given in Fig. 2.4 They are expressed in terms of the geometric mean because the distributions were skewed. Accurate estimation
of frequency of death would result in data points falling on the diagonal
line. The geometric mean of the 18group judgments is more accurate, i.e.,
closer to the true value, than the geometric mean of the 54 individual
judgments for 12 of the 15 causes of death-all except lung cancer, homocide, and accidental falls. A Wilcoxon rank sum test on total Absolute
Percent Error (APE) over the 15 causes of death showed groups to be
significantly more accurate than individuals (W = 2.84, p < .003).
Standardized bias was computed for both the individual and group
4 Data from Lichtenstein et al. (1978) show systematic overestimation of low frequency
causes of death by individuals. The more common causes of death are not underestimated
as much in the present study; all estimates are larger. As noted by Fischhoff & MacGregor
(1982) and Lichtenstein et al. (1978), the magnitude of estimates is susceptible to response
format and anchoring effects. Unlike in the Lichtenstein et al. study, no standard stimulus
was used in the present study. And, rather than giving a rate per 100,000response, participants in the present study gave the total frequency in a population of 230,000,000. This
figure or even the estimate for the first cause, lung cancer, could have served as an anchor.
Or, perhaps increased attention to the higher frequency causes of death in recent years
improved the accuracy of available information or increased apparent size. It will always be
difficult to interpret the absolute magnitude of risk judgments; a better approach is to
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CollecCveIntelligence
Moderators:
Knowingsomethingaboutthepreferencesofother
parCcipantsworsenscollecCvedecisions(Mojzisch&SchulzHardt,2010)
DiversitypromotescollecCvedecisions(Hong&Page,2004)
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CollecCveDetriment
Underwhatcircumstancesdogroupsreachbaddecisions?
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CollecCveDetriment
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CollecCveDetriment
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GroupBiases-Conformity
Asch(1951)
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GroupBiases-Conformity
Asch(1951)
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GroupBiases-Conformity
Meta-analysisbyBond&Smith(1996):
• publishedstudiesusingAsch’sconformityparadigm
• 133studies
• 17countries
• publicaConsfrom1954–1994
•
averageeffectsize:r=0.43
“[...]conformitywassignificantlyhigher,(a)thelargerthesizeofthemajority,
(b)thegreatertheproporConoffemalerespondents,(c)whenthemajoritydid
notconsistofout-groupmembers,and(d)themoreambiguousthesCmulus.”
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25
Conformity-Origins
Child Development, November ⁄ December 2011, Volume 82, Number 6, Pages 1759–1767
Conformity to Peer Pressure in Preschool Children
Daniel B. M. Haun
Michael Tomasello
Max Planck Institute for Evolutionary Anthropology;
Max Planck Institute for Psycholinguistics;
and University of Portsmouth
Max Planck Institute for
Evolutionary Anthropology
Both adults and adolescents often conform their behavior and opinions to peer groups, even when they themselves know better. The current study investigated this phenomenon in 24 groups of 4 children between 4;2
and 4;9 years of age. Children often made their judgments conform to those of 3 peers, who had made obviously erroneous but unanimous public judgments right before them. A follow-up study with 18 groups of 4
children between 4;0 and 4;6 years of age revealed that children did not change their ‘‘real’’ judgment of the
situation, but only their public expression of it. Preschool children are subject to peer pressure, indicating sensitivity to peers as a primary social reference group already during the preschool years.
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a row facing the Experimenter (E). E showed the
children warm-up picture books with six sets of
animals. During this warm-up period E established
the three left-hand animals on each double page as
a family picture (large = daddy, middle = mommy,
small = baby). The right side of the same double
page pictured a replication of one of the three
animals. E explained that one of the three family
members had run over to the right-hand side. The
children were asked to identify this individual picture as daddy, mommy, or baby. Children were
probed individually to ensure understanding. Then
children were asked to identify the single individ-
lamp was switched on. The lamp was meant to
ensure that children do not speak between trials.
Then children were sent back in their booths.
Speak trials: Each group completed 18 speak trials. On any trial, children were asked individually
in succession to say out loud the family member,
which had moved to the opposite page. The target
child always responded last. On 12 of these trials
the minority book deviated from the majority books
(conflict trials). On the other 6 trials (Trials 1, 2, 3,
8, 13, and 18) all four books were identical (no conflict trials). This trial order replicates exactly Asch’s
original design (Asch, 1956).
Conformity-Origins
Figure 1. (A) Experimental setup from a birds-eye perspective. Light bulbs identify the location of the lamps. (B) Example of a stimulus
from the relative size judgment task.
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Conformity-Origins
en received six
ren were again
silently point to
orresponding in
e opposite page.
ast.
n had been told
, in a surprised
ntally mixed up
if anyone had
her book. Then
see that one of
hers and apoloprocedure, we
e consequences
or reputation.
Figure 2. Mean percent correct (±SE) for all four conditions of
videotaped all
Experiment 1 for majority and minority children.
(pointing and
n situ notes. The
Most importantly, minority children performed
check, probing
significantly better in the speak–no conflict than in
on the task at
the speak–conflict condition (speak–no conflict:
HPSTS//2016//June6th//Session08//GroupDecisions
ion. We further
28
ad moved to the
of 30 trials. On
ldren might have
ty children comone in which all
hich the minority
ers. On these six
asked to speak.
re introduced in
hild feel excluded
ked to point. The
s responses were
response: point ⁄
books different).
his split resulted
nflict, 6 speak ⁄ no
. Trial order was
hat the first three
and one of the
group to point.
gnificantly differr of the majority
wo majority opin-
ative to the speaking trials when there was a conflict with the majority opinion, t(17) = 3.16, Cohen’s
d = 1.5). In conflict trials minority children
Conformity-Origins
Figure 3. Mean percent correct (±SE) for all four conditions of
Experiment 2 for majority and minority children.
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GroupPolarizaCon
Moscovici&Zavalloni(1969):
•
•
•
•
HowdogroupdiscussionsinfluencegroupaQtudes?
AssessedparCcipants’opinionofpoliCcaltopics.
Rated11-12statementsonascalefrom-3to+3
Procedure:individualraCng->groupdiscussionunCl
agreement->individualraCng
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GroupPolarizaCon
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GroupPolarizaCon
Result:Moreextremejudgementsfollowinggroup
discussions(bothposiCveandnegaCve).
Interpreta.on:Groupdiscussionsandgroupdecisions
resultinpolarizaCon.
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GroupPolarizaCon
Phenomenondemonstratedinseveralareas:
• prejudice(Myers&Bishop,1970,1971)
• workplacesaCsfacCon(Mason&Griffin,2002)
• readinesstoassumerisks(Levine,Higgins&Choi,2000)
• jurydecisions(Kalven&Ziesel,1966)
• assessmentcenters(Palmer&Loveland,2008)
->indifferentcountries
->acrossdifferentages
Smith&Mackie(2007);Hogg&Vaughan(2008);Baron&Kerr(2003)
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GroupPolarizaCon
Moderators:
•
incasesof50-50decisions(pro&cons)->depolarizaCon
(Burnstein&Vinokur,1977)
•
subsCtuCnggroupmembers(Mackieetal.,1992;Mackie&
Cooper,1984)
•
saliencyofgroupmembership(Spearsetal.,1990)
Baron&Kerr(2003)
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ConformityPressure
PotenCalconsequencesoncollecCveintelligence(Lorenzet
al.,2011):
Opinion-agreement(moCvetoconform)reducesdiversity
andunderminesacoremechanismofcollecCve
intelligence.
MoCvestoconform:
• suspicionthatothersarebewerinformed
• knowledgeof“wisdomofthecrowd”
• conformitypressure
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ConformityPressure
PotenCalconsequencesoncollecCveintelligence(Lorenzet
al.,2011):
•
•
•
•
•
n=144,12sessionswith12parCcipantseach
subjectsworkedon6esCmaContasks(geography,criminalstaCsCcs)
foreachtaskparCcipantsprovided5judgements(inprivate)
IV:informaConconcerningothergroupmembers’judgementsayerevery
round:none,averagejudgmentofgroup,oralljudgmentsofallgroup
members
financialincenCvesforgoodjudgments
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ConformityPressure
C
D
E
1. Result:Socialinfluencereducesdiversity;thejudgmenterrorremainsunchanged.
Social influence effect: Social influence diminishes group diver
Confidenceinjudgmentincreaseswithsocialinfluence.
out diminishing the collective error. (A) Typical examples of experimental
for
all three information conditions, displaying the five individual respon
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Lorenzetal.,(2011)
GroupBiases
InformaConRepeCCon:
TheconsequencesofrepeatedprocessingofinformaCon
duringgroupdecisions:
•
increasedandfacilitatedprocessing(Bornstein&D‘AgosCno,
1994)
•
•
greaterlikability(Zajonc,1968)
greatersubjecCvevalidity(Reber&Schwarz,1999)
Fosteretal.,(2012);Unkelbachetal.(2007)
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GroupBiases
StudybyForsteretal.(2012):RepeCConorValidaConthrough
mulCplesources?
•
•
•
•
•
Subjectsareaskedtoprovideeyewitnessreportsfrom
videosequences.
IV1:other‘witnesses’areaccurateorfalse
IV2:nr.ofrepeCConsoffalsestatements(1or3)
IV3:nr.ofpeoplewhoproducedfalsestatements(1or3)
DM:accuracyofmemoryrecall
Fosteretal.,(2012)
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39
GroupBiases
322
J.L. Foster et al. / Acta Psychologica 139 (2012) 320–326
Fig. 1. Illustration of Experiment 1 methods. In Phase 1, people watched a video of a mock crime containing eight critical items that were digitally manipulated between two versions. In Phase 2, people read three eyewitness reports attributed to either one eyewitness or three different eyewitnesses. Some people read three reports with misleading details
(the gray reports) while others read one report with misleading details and two control reports (the white reports) with no misleading details. In Phase 3, subjects took a surprise,
two-alternative forced choice recognition test about what they remembered from the video and were asked to rate their confidence in their answer.
van.” The misleading versions (the gray reports in Fig. 1) described four of
the eight critical items inaccurately—the van, for instance, was described
as a “blue AJ's Electricians van” when people had actually seen a blue
RJ's Electricians van. The remaining four critical items were described
only generically. In short, misleading reports misled people on four critical
items (e.g. blue AJ's Electricians van; Time magazine), while the
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remaining four critical items—and all eight critical items in the control
about details from the movie. We instructed them that the questions
were about their memory for the video. For the eight critical items,
they chose between the correct and misled option; the remaining
Fosteretal.,(2012)
12 items served as fillers. People circled their responses and
rated
their confidence on a five-point scale (1 = Not at all Confident,
5 = Very Confident). Afterwards, they were debriefed.
40
GroupBiases
J.L. Foster et al. / Acta Psychologica 139 (2012) 320–326
uracy of misled and control claims by repetition and number of sources in Experiment 1. Error bars represent a 95% confi
burglar's electrical company, Emily will be
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idan
had told her only once. Interestingly, if
Fosteretal.,(2012)
references to control claims should have no effe
remember misled claims.
41
GroupBiases
J.L. Foster et al. / Acta Psychologica 139 (2012) 320–326
323
n accuracy of misled and control claims by repetition and number of sources in Experiment 1. Error bars represent a 95% confidence interval.
the burglar's electrical company, Emily will be
if Aidan had told her only once. Interestingly, if
epeated, it would make little difference if Aidan
Ben, and Cheryl each had made the same claim
Emily hears it three times and is similarly misled.
references to control claims should have no effect on how well people
remember misled claims.
Of course, it is one thing if repeating misinformation three times
makes people less accurate about what they saw. Years of research
on the misinformation effect has shown that people make these errors because of an inability to differentiate the sources of what they
originally saw and what they later heard (Johnson et al., 1993;
Lindsay, 2008)—repeating misinformation may simply add more opportunities for people to make these types of errors. In other words,
trying to distinguish between four sources—the original event and
misleading information presented three times—may be more difficult
than trying to distinguish between two sources—the original event
and misleading information presented only once.
But it would be another thing if repeating that information changed people's beliefs about what happened when they never saw the
crime unfold in the first place. On the face of it, judging what happened when you didn't see the crime would appear to be qualitatively
different than remembering what happened when you did see the
crime. Indeed, the source confusion thought to drive the misinformation effect should play little role in altering people's beliefs about
what really happened because they did not see the crime; by definition, there is no original source with which to confuse the eyewitness
reports. But a different kind of source monitoring error might lead
people to put more stock into a single eyewitness who repeats his
claims than if he were to make the same claim only once. In one
study, when one group of people read a New Jersey homeowner's repeated opinions about preserving open spaces, they thought his
views more representative of the wider population of homeowners
than another group who read his opinion only once (Weaver et al.,
2007). The idea is that repeating claims makes them seem more familiar, more available, and more true (Kelley & Lindsay, 1993;
Unkelbach, 2007). If a similar mechanism applies to people's confidence in eyewitness claims, we should see that the repeated claims
of one eyewitness are more credible to people who never saw the
crime than if that eyewitness simply states them once. We addressed
this issue in Experiment 2.
Result:RepeaCnginformaConreducesaccuracyindependentofnumberof
witnesses.
ore confident about their responses to misled items
66) than control items (M = 3.55, SD = 0.66), a
mented in the misinformation effect literature
al., 2006). But their confidence did not depend on
es misinformation was repeated or the number of
ther words, a 2 (source) × 2 (repetition) × 2 (item
ealed a main effect of item type, F(1,60) = 6.74,
here were no other effects (all Fs b 1.35).
Interpreta.on:FluencycreatesfeelingoffamiliarityresulCngin‘trust’in
accuracy
nations and criticisms
lanation for our results is that people paid little atr one or three eyewitnesses repeated the stateesults might reflect the fact that they attended to
ms, but not to who reported those claims. To adsis, we examined the data from people who read
ims in only one report (n = 32). When reports
three eyewitnesses, people were similarly accurate
ms appearing in the third (M = 0.66, SD = 0.19) and
D = 0.23) reports t(14) = 0.60, p = .56 , d = 0.16.
ports were attributed to one eyewitness, people
ess misled for misleading claims appearing in the
SD = 0.19) rather than the first (M = 0.53,
t(14) = 1.99, p = .07, d = 0.99 1. This finding fits
when a single eyewitness made all three reports,
for the first time in the third report seemed less
finding also suggests that people noticed whether
ere made by one or three eyewitnesses, yet notichese claims did not affect people's accuracy.
suggest that because people read about control
, repetition improved memory for those items. In
ng “blue van” three times cued people who saw a
Unkelbachetal.(2007)foundthe‘repeCConeffect’tobedifficulttocontrolto
influencedecisions
3. Experiment 2
HPSTS//2016//June6th//Session08//GroupDecisions
Fosteretal.,(2012)
42
GroupBiases-DivisionofInformaCon
•
•
•
•
IngroupcogniConnotallmemberssharethesame
informaCon.
sharedinformaCon:accessibletoallmembers
non-sharedinformaCon:accessibleonlytoindividuals
‘hiddenprofiles’:non-sharedinformaConhas
contradictoryimplicaConsthansharedinformaCon
Howdoesthisaffectdecisions?
Stasser&Titus(1985)
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43
GroupBiases-DivisionofInformaCon
CoremechanismsinfavorofsharedinformaCon(Wiwenbaum
etal.,2004;Kerr&Tindale,2004):
•
•
•
higherrecallprobabilityofsharedinformaCon
posiCveevaluaConofsharedinformaCon
greatersubjecCvevalidityofsharedinformaCon
Stasser&Titus(1985)
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DominanceofSharedInformaCon
Meta-analysisLuetal.(2012)
• 65studies,101effectsizes,3189groups,11317subjects
• selecConcriteria:
• WhichinformaConwasdiscussed?
• HowcanhiddeninformaConaffectdecisions?
• idenCfymoderatorvariables
•
•
•
DominanceofsharedinformaConincreaseswith
• groupsize
• amountofinformaCon
• amountofuniqueinformaCon
ThisistrueforintellecCveandjudgmentaltasks.
Qualityofdecisiondecreaseswith
• groupsize
• amountofinformaCon
Luetal.,(2012)
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DominanceofSharedInformaCon
Factorsthatreduce„sharedbias“:
• longerdiscussions(Larsonetal.,1994)
• non-sharedinformaConwithsingleindividual(Stasser&
Stewart,1998)
•
•
•
•
informaConprovidedinwriwenform(Sawyer,1997)
discussioninwriwenform(Voigtländeretal.,2009)
leadershipwithfocusonexploraCon(Larsonetal.,1996)
rankingofalternaCves(Hollingshead,1996)
Kerr&Tindale(2004)
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