Social Psychology
Lecture 11
Group Performance
Jane Clarbour
Room PS/B007 Email jc129@york.ac.uk
Eureka Task (Lorge et al, 1958)
Jealous husbands
• 3 married couples have to cross the
river but there is only 1 boat….
• Rules of the task:
– Only men can row the boat
– Wives can’t cross with another man unless
the husband is present
Lorge et al’s findings…
• Individuals
– only 3/21 solved problem
• Groups
– 3/5 solved problem
Why????
Overview
• Group processes
– Steiner’s typology of task
Additive tasks
Disjunctive tasks
• Brainstorming
• Processes involved in productivity
Objectives
• Give an account of Steiner’s typology of
tasks
• Specify the effects of group size on additive
tasks
• Specify the effects of group size on
disjunctive tasks
• Review evidence on the effectiveness of
‘brainstorming’ as a technique for maximising
group performance.
Theory of group performance
Theoretical framework (Steiner, 1972)
•
Performance is dependant upon 3
classes of variables:
1. Task demands
2. Resources
3. Process
Task demands
• The procedures necessary to
perform a task.
– Task demands as ‘building plans’
•
•
•
•
•
house being built
materials needed
tools to use
order of work
Management of total process
Resources
• Relevant possessions of people in
group
– knowledge
– abilities
– skills
– tools
Group Processes
• What the group does
– ‘Process’ refers to the actual steps taken when
confronted with a task
– The extent that the total sequence of behaviours
corresponds to the pattern demanded by the task
Formula:-
Actual productivity = potential productivity
(minus losses due to faulty processes)
Faulty Processes
What aspects of group behaviour result in
loss of production due to faulty
processes?
• Either poor supply of resources?
– (low potential productivity)
• Or processes fail to meet demands of
task?
• Or both!
Two forms of faulty processes
(Steiner, 1972)
Steiner identified 2 forms of faulty
process:
1. Coordination loss
– Lack of synchronisation
2. Motivation loss
– Lack of recognition
– Lack of benefit
Performance and group size
• “What is the effect of group size on the task
performance?”
– Are groups more productive than an individual?
– Are individuals more productive than a group?
– Are large groups more productive than small
groups?
• What are the task demands?
• How do the task demands relate to the available
resources?
Effect of group size on performance
• Task demands are initial determinants
of both potential and actual production.
– Differences in faulty processes may vary:
• Groups may be more productive than
individuals, or..
• Individuals may be more productive than a
group
– So, necessary to have some kind of typology of
task.
Task dimensions
Tasks can be distinguished along 3 main
dimensions:
1. Divisible vs. unitary tasks
2. Maximising vs. mimimizing tasks
3. Combinability of the tasks
Divisible vs. unitary tasks
Some tasks are readily divided into sub-tasks
– each of which may be performed by a
different individual
•
•
•
Building a house
Playing football
Creating a garden
– Other tasks make no sense if subdivided
•
•
Reading a page
Doing a maths sum
Maximising vs. minimizing tasks
•
Maximizing/optimizing
–
Maximizing: (quantity)
•
•
•
•
–
Optimizing: (quality)
•
•
•
•
Doing task as much as possible
Doing task as quickly as possible
Generating many ideas
Scoring the most runs
Accuracy of bookkeeping
Weather forecasting
Writing your essays!!!
Minimising
–
doing as little as possible
How combinable are the tasks for
group members?
•
Additive tasks
–
•
Group product = sum of the members
Conjunctive tasks
–
•
A task which everyone must perform
Disjunctive tasks
–
•
The group selects from individual member’s judgments, requires a
choice of answer among several possible alternatives
Discretionary tasks
–
Conditions sometimes may allow different members to contribute
more or less (varied weightings) by assigning:
•
•
•
Total weight to single member
Equal weight to everybody
Or granting each person a different weight
Individual products of group
members
• “What is the effect of group size on task
performance?”
– Meaningless question without a
satisfactory taxonomy of tasks (Steiner, 1972, 1976).
Additive tasks
Early experimental evidence
RINGLEMANN (1913)
A French agricultural engineer who conducted most of his research
in late 1880’s.
1, 2, 3, or 8 people pulling on rope
– Device measured the exact mount of forced exerted on the rope
•
•
•
•
63 kilo (1 person)
118 kilo (2 people)
160 kilo (3 people)
248 kilo (8 people)
Group efficiency
• Results showed an INVERSE relationship
between the number of people in the group
and individual performance
– As more people pulled, they used less effort!
– Found that a large group needed only half the
effort per person than a small group
• Attributed to co-ordination losses (pulling at different times)
• Additive tasks – group performance is better than individual’s
performance when on own, although relative efficiency per person
may decrease with increasing group size.
Conjunctive Tasks
• A task that every group member must
perform
– Performance of group dependant upon weakest
group member (i.e relay race, or group accent up the Tor)
– Performance depends on the relative abilities of
the individuals concerned
– With increasing group size performance would be
expected to decrease due to increased possibility
of weak group member.
Disjunctive Task
• A task that requires a choice amongst several
possible alternatives
– Potential productivity of group is determined by the most
competent member
• If one member of the group can perform the task, the
group can, possibly, still perform it
• With increasing group size, you expect better
performance
Conjunctive
more people =
lower performance
Disjunctive
more people =
better performance
Disjunctive task: early experimental evidence
TAYLOR & FAUST (1952)
Game of ’20 questions’ (disjunctive as have to make a choice
between several alternatives)
• Ss divided into categories
– Working alone (x 15)
– Working in pairs (x 15)
– Working in groups of 4 (x 15)
• Ss given 4 problems a day for 4 consecutive days and allowed
to ask 30 questions
– Experimenter can only reply:
• Yes / No / Partly / Sometimes / Not in the normal sense of the
word.
• DVs = no. of questions, failures, & time taken to solve problem
Results TAYLOR & FAUST (1952)
• Superiority of groups over individuals in terms of
– Fewer questions asked
– Fewer wrong answers given
– Less time taken per problem
• Groups superior to pairs:
– Fewer wrong answers given
• Individuals superior to groups and pairs:
– For ‘man-minutes’ (e.g. time x no of people in group) Individuals
were quicker than pairs, who were quicker than groups (in
terms of man-minutes to reach a solution, rather than actual time)
• So, cheaper to pay individuals by the hour than groups by the job
Early conclusions
(Taylor & Faust, (1952)
• Disjunctive tasks
– superior performance with groups (well
established finding)
• But this effect is inversely proportional to group
size
– Individuals are more effective (in terms of
man-minutes)
• Steiner suggests that superior performance of
groups is due to the greater resources which
they possess.
Brainstorming Osborn (1957)
• Special kind of group process
– This is creative
– Increased numbers of people disproportionately
increase number of ideas generated
• Rules of brainstorming
– Free the individual from self-criticism and criticism
of others
– The more ideas the better
– Can adapt others ideas
– Can combine ideas
– Should not be critical…
Empirical evidence (MULLEN et al. 1991)
Meta-analysis of 20 studies of
brainstorming
• Compared face-to-face groups operating
under brainstorming conditions against
‘nominal groups’
– Nominal groups were individuals who were
working alone but their ideas were subsequently
pooled.
– Productivity was measured in two different ways
• Quantity: the number of non-redundant ideas
• Quality: involved rating of the ideas
Results (MULLEN et al. 1991)
Meta-analysis of 20 studies of
brainstorming
– Individuals generated more ideas than face-toface groups
– Productivity LOSSES increase with the size of the
group
– Both individuals and groups work best without an
‘expert’ giving guidance
– Most ideas were generated when responses were
written down and not publicly shared
Why production losses in
brainstorming occur
• Free-loading (social loafing)
– Motivation loss
• Individual members expect that all ideas will be
pooled (group credit)
– Group allocation?
Effects of group allocation
(Diehl & Stroebe, 1987)
• Allocation of group affects productivity
– Design: 2 x 2
Group type
Credit type
Nominal
Brainstorming
Group credit
Individual credit
• Results:
– Only 8% of variance explained by credit given
– Most of the effect explained by group allocation
• Conclusion:
– BRAINSTORMING GROUPS LESS PRODUCTIVE
Summary
Task dependent performance
(Steiner)
• Additive & disjunctive tasks
– Performance increases with increased group size
– But relative efficiency declines
• Conjunctive tasks
– Performance decreases with increased groups
size in conjunctive tasks
Mullen et al. 1991
– don’t need to invoke any special group
process for brainstorming
– Group superiority over individuals can be
explained by interpreting brainstorming as
a conjunctive task
But all this depends upon equal status…
Group structure
• Structure of group is independent of the
people who occupy the various
positions
– Each person plays a ROLE within the
group
• Roles are determined by social norms, rules of
conduct
• Each role is evaluated differently by others
• Each role has differing status
– But how does status emerge?
Interaction process analysis
(IPA)
• Problem solving groups of unacquainted
persons
• Observational analysis of behavioural
categories (4 categories)
– Interpersonal style of leadership
• Positive socio-emotional behaviour
• Negative socio-emotional behaviour
– Task directed style of leadership
• Task behaviours
• Behaviours relating to exchanges of information
Expectation-states theory
• Emergence of group leaders
– Higher status roles exert more influence
over production than lower status roles
(Torrance, 1954)
• Assertive people are more influential than nonassertive people (Ofshe & Lee, 1981)
• Males are more influential than females, blacks,
and younger people (DeGilder & Wilke, 1994)
Matching of leaders with
resources
• By matching people with subtasks most
qualified to perform.
– Some resources give rise to higher
expectations of task completion than
others (but not always!)
– Hemphill (1961) suggests need to consider both the nature
of the task and the availability of a group member with the
required resources:
• Groups must feel that task success is possible
• Groups must attach value to task success
• The task must require co-ordination and communication
Supplementary reading for
group performance
• Wilke & Arjaan Wit (2001) Group
Performance (pp. 445 – 478)
In Hewstone, & Stroebe, ‘Introduction to Social
Psychology’ (3rd edn). Blackwell Press