Social Psychology
Group Dynamics
• In a given situation, you may behave
quite differently when you're in a
The Bystander Effect
• When there is an emergency, the
more bystanders there are, the less
likely it is that any of them will
actually help.
• People are less likely to provide
needed help when they are in groups
than when they are alone.
Factors that Lead
to the Bystander Effect
Homeless Man in NYC: What Happened? • Hesitation leads to inaction
• Diffusion of responsibility ("someone else will help") • Situational Ambiguity
• Perceived cost to ourselves
• Similarity of victims to ourselves
• Internal attributions of the cause of need (he “deserved what he got”)
Other factors
• Unfamiliar environments
• Mood
Bystander Studies
Study 1: The smoke filledroom
• 75% of the subject in the room alone reported the smoke within 2 minutes.
• 13% of the subjects waiting with others reported the
smoke this quickly.
• 10% of the subjects waiting with the confederates
reported the smoke even after 6 minutes.
Bystander Studies
Study 2: The fallen female experimenter
• Twice as many subjects got up to help when they were alone than if they were waiting with others.
• Those who did not respond reported
that they were uncertain that it was an emergency.
Bystander Studies
Study 3: The man who collapses on the subway
• The victim with
the cane received help 95% of the time and usually within 5 seconds • The “drunk”
received help 50% of the time after an average of 1½ minutes.
Bystander Effect
Study 4: College student who has a seizure
• All the subjects who thought they were waiting alone left the room to help within about 52 seconds.
• 85% of the subjects who thought they were in a three person group left to
help in an average time of 93 seconds. • 62% of the subjects who thought they
Wrap-up
• Heroes: those who defy the
bystander effect
Brainstorming Session
• “How to be a good college
roommate”
• In groups assigned, you have TWO
MINUTES to brainstorm as many
ideas as possible.
Increasing Group Size, Increasing
Group Output
Number of Ideas Generated
67 72 48 34 25 0 10 20 30 40 50 60 70 80
1 2 4 8 12
Number of Group Members
…But Decreasing Individual
Input
Ideas Per Group Member
25 6 8 12 17 0 5 10 15 20 25 30
1 2 4 8 12
Group Productivity
• How productive are you in class when you work in a group? Why?
• Social loafing: reduction in effort by individuals when they work in groups as
compared to when they work by themselves • Why does productivity decrease in groups?
– Diffusion of responsibility
Group Productivity
• Combating Social Loafing:
• Identifiability: People are motivated when they believe that their work is identifiable and separable from the work of others.
– Divide tasks – Assign roles
Group Decision Making
• Think about a time
when you were part of
a group that made a
poor
decision.
– What happened? – How did it happen?
Advice?
• My wife is a very talented writer. So, far her writing has been limited to her blog about life and cancer. Recently, she has come up with an idea to write a book. If it is written and
accepted, it could really make a difference in someone’s life and perhaps propel her into a literary career. However, if it doesn’t work
out, she will have potentially spent thousands of hours, hundreds of days, many months
Advice?
• Imagine that you are advising her. Please select the
LOWEST probability that you would consider acceptable for Tara to attempt to write her book.
• “Tara should try and write this book if the chances are at least:”
Group Decisions: Polarization
•Who leans towards more
cautious decisions: individuals
or groups?
– Common sense says groups!
(Compromises and balance of
interests)
– James Stoner (1961) found that
Group Decisions: Polarization
• When group discussion
strengthens a group's dominant
point of view and produces a shift
in the more extreme position
• Why does this happen?
– Group discussion exposes members
to persuasive arguments
– When a person's views are shared by
others, they tend to express even
The Psychology of Groups
• Alex Rodriguez
Group Decisions: Groupthink
• When group members emphasize
agreement
and "thinking alike.”
Symptoms include:
– Illusions of invulnerability
– Belief in the group's inherent morality – Rationalizing away serious problems: – Stereotyping the opposition
– Illusions of unanimity – Pressuring dissenters
Group Decisions: Groupthink
•What causes it?
– Group cohesiveness
– Group Isolation
– Directive and dominant leader
– Stress
Wrap-up
“We cannot live for ourselves alone. Our lives are connected by a thousand invisible threads.”
Herman Melville
• We just studied a few of these threads in social psychology…
• How can we use what we learned to bring out the
