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Social Psychology Lecture 11. Group Performance Jane Clarbour Room PS/B007 Email [email protected] 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

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Social psychology lecture 11 l.jpg

Social PsychologyLecture 11

Group Performance

Jane Clarbour

Room PS/B007 Email [email protected]

Eureka task lorge et al 1958 l.jpg
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

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Lorge et al’s findings…

  • Individuals

    • only 3/21 solved problem

  • Groups

    • 3/5 solved problem


Overview l.jpg

  • Group processes

    • Steiner’s typology of task

  • Brainstorming

  • Processes involved in productivity

Additive tasks

Disjunctive tasks

Objectives l.jpg

  • 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.

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Theory of group performanceTheoretical framework(Steiner, 1972)

  • Performance is dependant upon 3 classes of variables:

    • Task demands

    • Resources

    • Process

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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

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  • Relevant possessions of people in group

    • knowledge

    • abilities

    • skills

    • tools

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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


      Actual productivity = potential productivity

      (minus losses due to faulty processes)

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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!

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Two forms of faulty processes (Steiner, 1972)

Steiner identified 2 forms of faulty process:

  • Coordination loss

    • Lack of synchronisation

  • Motivation loss

    • Lack of recognition

    • Lack of benefit

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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?

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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.

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Task dimensions

Tasks can be distinguished along 3 main dimensions:

  • Divisible vs. unitary tasks

  • Maximising vs. mimimizing tasks

  • Combinability of the tasks

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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

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Maximising vs. minimizing tasks

  • Maximizing/optimizing

    • Maximizing: (quantity)

      • Doing task as much as possible

      • Doing task as quickly as possible

      • Generating many ideas

      • Scoring the most runs

    • Optimizing: (quality)

      • Accuracy of bookkeeping

      • Weather forecasting

      • Writing your essays!!!

  • Minimising

    • doing as little as possible

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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

  • Discretionarytasks

    • 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

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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).

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Additive tasks

Earlyexperimental evidence


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)

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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.

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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.

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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 Disjunctive

        more people = more people =

        lower performancebetter performance

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Disjunctive task: early experimental evidence


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

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ResultsTAYLOR & 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

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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.

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BrainstormingOsborn (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…

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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

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Results(MULLEN et al. 1991)

Meta-analysis of 20 studies of brainstorming

  • Individuals generated more ideas than face-to-face 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

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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?

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Effects of group allocation(Diehl & Stroebe, 1987)

  • Allocation of group affects productivity

    • Design: 2 x 2

  • Results:

    • Only 8% of variance explained by credit given

    • Most of the effect explained by group allocation

  • Conclusion:


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SummaryTask 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

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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…

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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?

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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

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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 non-assertive people (Ofshe & Lee, 1981)

      • Males are more influential than females, blacks, and younger people (DeGilder & Wilke, 1994)

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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

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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