Lab Experimentation
Prof. Xiao-Ping Chen
University of Washington
Lab Experiment:
the tradeoff
Advantages
Testing causal effects

Allow for rigorous control to
rule out alternative
explanations

Isolate the phenomenon, focus
on key variables, and eliminate/
neutralize the influence of
irrelevant extraneous variables

Conducive to examine
mediating processes

Precision of measurement

Study behavior itself instead of
self-reports of behavior
2
Lab experiment: the
tradeoff
Disadvantages

Reactivity of the participant

Limitations posed by ethics




Human subjects committee
Consent from participants
Artificiality of environment
Seldom suited to studying
long-term effects
3
Should I do a lab
experiment?

Depends on your research
objective



Parameter estimation research
Hypothesis testing research
Whether causal effect is of the
primary interest
4
Cover story and
experimental context
1.
Experimental realism is the
key, mundane realism is a plus
2.
Provide a believable context
for introducing manipulations,
experimental tasks, and
dependent measures and must
be credible throughout the
experiment
3.
Hide research hypotheses
from the subjects (i.e., guard
demand characteristics)
4.
Try to reduce the reactivity of
the participant (e.g., evaluation
5
apprehension)
Experimental
manipulation
1. Construct validity is the key
2. Investigate previous
research to see how they did
it and then use your
creativity
3. Use multiple operations/
methods if possible
6
Team Cooperation
Prisoner’s dilemma
Your Partner’s
Choice
C
D
$7
Your
C
Choice
$7
$10
$2
$2
D
$10
$4
$4
8
Social Dilemma
Mean Contribution of Other Members
Your Contribution 0
1
2
3
… 10
0
1
2
3
…
10
10
9.33
8.67
8.0
…
3.33
11.67
11.0
10.33
9.67
…
5.0
13.33
12.67
12.0
11.33
…
6.67
15.0 … 26.67
14.33 … 26.0
13.67 … 25.33
13.0 … 24.67
…
… …
8.33 … 20.0
Your Payoff = (10 – C) + 2* [(n-1) MC + C] / n
9
Pillutla and Chen (1999): Social
norms and cooperation in social
dilemmas: The effects of context
and feedback
Experimental Implicit
Condition
Norm
Economic
Non-Econ.
Perceived
Norm
Comp.
Coop.or
comp.
Coop.
Coop. or
comp.
10
Pillutla and Chen
(1999)
实验条件
1 （不合作反馈)
2 （合作反馈）
3 （无反馈）
4 （合作反馈）
5 （不合作反馈）
6 （无反馈）
第一阶段
第二阶段
经济情景
32.35%
29.68
27.54
社会情景
29.56
49.39
36.52
社会情景
43.04
39.61
32.08
经济情景
51.67
11.69
39.58
11
Chen, Bussmann, & Bachrach (2007):
Reciprocity in ultimatums: the effects of
fairness perceptions, negative emotions,
and partner closeness

Multi-operations of
reciprocity:



Acceptance/ rejection decision
Reciprocating amount
Intention for a long-term
relationship
12
Chen, Bussmann, & Bachrach (2007):
Reciprocity in ultimatums: the effects of
fairness perceptions, negative emotions,
and partner closeness


Experimental design:
2 x 3 factorial

Proposed amount:


Partner relationship:


35%, 50%, or 65%
stranger or friend
Measures:



Fairness perception
Negative emotion
Partner closeness
13
Chen, Bussmann, & Bachrach (2007):
Reciprocity in ultimatums: the effects of
fairness perceptions, negative emotions,
and partner closeness
Hypothesized structural model with
parameter estimates
FP1 FP2 FP3
FI1
β53=.29
(.17)
Fairness
Perceptions
Initial
Offer – DV1
γ32=-.25
(.14)
Initial
Offer – DV2
β54=-.35*
(.14)
β43=-.75*
(.15)
γ41=.98*
(.41)
Negative
Emotions
β64=.29
(1.31)
γ42=.12
(.16)
NE1
NE2
NE3
NE4
NE5
FI3
Willingness
for future
relationship
β63=2.99
(1.59)
γ31=-2.70*
(.22)
FI2
Counter
Offer
NE6
Unstandardized coefficients are provided with standard error in parentheses.
* p < .05
Bold arrows indicate a significant relationship at p = .05
14
Chen, Bussmann, & Bachrach (2007):
Reciprocity in ultimatums: the effects of
fairness perceptions, negative emotions,
and partner closeness

Post-hoc structural model
with parameter estimates
FP1 FP2 FP3
FI1
β53=.29
(.17)
Fairness
Perceptions
Initial
Offer1
β54=-.35*
(.14)
β43=-.76*
(.15)
Negative
Emotions
γ41=.91*
(.39)
NE1
NE2
NE3
NE4
β64=.29
(1.30)
NE5
FI3
Willingness
for future
relationship
β63=3.03
(1.61)
γ31=-2.55*
(.22)
FI2
Counter
Offer
NE6
Unstandardized coefficients are provided with standard error in parentheses.
* p < .05
Bold arrows indicate a significant relationship at p = .05
1 Initial offer represented by first dummy variable (30% vs. 50% & 70%)
15
Conclusion


Experiments can be used to
rigorously test causal effects
of variables; and to test
mediating or moderating
effects
Experiments are a lot of fun!
16