psychology relies on empirical methods

theories are general propositions about causal relationships amongst constructs

hypotheses are conceptual statements that require operationalization

science is a process of “conjecture and refutation”

Hypothesis: Southern white males are more prone to aggression than are Northern white males. (conjecture)

We’ll look at different strategies to examine hypotheses. (refutation)

putting theories to the test

What evidence supports (and, more importantly, disconfirms) our theories?

assesses the amount or average level of a given variable in a population› e.g., public opinion surveys

not a true test of an hypothesis› What is the white male homicide rate in

the South?

What is the white male homicide rate in the South?

Region

Homicide Rates (White Male Offender Rate)

New England 2.62 Middle Atlantic 1.90 Midwest 2.92 Pacific 4.62 Mountain 4.67 Southwest 5.13 South 8.23

adapted from Nisbett (1993)

critical issues› random sampling› basis of comparison

informative, but not a hypothesis test› What else could account for the findings?

investigates whether changes in one variable are related to changes in another variable› What is the relationship between being

from the South and aggressive behavior?

correlation coefficients› range from +1.00 to -1.00› positive correlation: increase/decrease

in the same direction

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7

correlation coefficients› range from +1.00 to -1.00› negative correlation: increase/decrease

in opposite directions

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7

correlation coefficients› range from +1.00 to -1.00› strength of the relationship: closeness to

+1.00/-1.00, not by the valence (+/-)

› Which indicates a stronger correlation: -.74 or +.21?

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7

What is the relationship between being from the South and aggressive behavior?› Nisbett (1993)

homicide rate and “southernness”: rs = .37 & .52

› in the social sciences (Cohen, 1992) r = .50 (strong) r = .30 (moderate) r = .10 (small)

strengths of this approach› can be a random sample› actual behavior› has good generalizability (i.e., external

validity)› potential for numerous variables

weakness of this approach› cannot infer a cause-effect relationship

factors for inferring causality› association -- yes› temporal priority -- no› rule out a spurious relationship -- no

temporal priority

southernness

homicide rates

time

temporal priority

southernness

homicide rates

homicide rates

southernness

or

time

time

temporal priority

direction of causality problem

southernness

homicide rates

homicide rates

southernness

or

time

time

rule out a spurious relationship

southernness

homicide rates

another variable

spurious

rule out a spurious relationship

southernness

homicide rates

poverty

rs = .38 & .42

(Nisbett, 1993)

rule out a spurious relationship

3rd variable problem

southernness

homicide rates

another variable

spurious

strengths› potential for numerous variables› good generalizability

weaknesses› cannot make causal conclusions

direction of causality 3rd variable problem

direction of causality problem› Does “southernness” lead to more

aggression or does a propensity for aggression lead to more “southernness”?

› solution: we cause (i.e., manipulate) one of the variables insult one group on Southerners, but not

another

direction of causality problem› if we control who is insulted, then

measure aggressiveness, we know the direction of causality

› but, we still have the 3rd variable problem SES poor social skills

random assignment to condition› if SES or social skills have an effect on

aggression, it should be equal for both groups

› We can address the problems of correlational research by doing experiments.

characteristics› manipulation of a variable

solves the direction of causality problem

› randomly assign to conditions solves the 3rd variable problem

language of experiments› independent variable› dependent variable› operational variable› random assignment

testing theory› Does the independent variable cause

changes in the dependent variable?

southernness

aggressioncause

the Southern culture of honor hypothesis› Cohen et al. (1996)› 2 (Southern/Northern) X 2 (insult/no

insult)› “chicken”, cortisol, testosterone

0

20

40

60

80

100

120

Northern

Southern

Insult No Insult

Dis

tan

ce a

t w

hic

h p

art

icip

an

ts

gave

way

to c

on

fed

era

te (

inch

es)

0

20

40

60

80

100

120

Northern

Southern

Insult No Insult

Dis

tan

ce a

t w

hic

h p

art

icip

an

ts

gave

way

to c

on

fed

era

te (

inch

es)

0

10

20

30

40

50

60

70

80

Northern

Southern

Insult No Insult

Perc

en

tag

e C

han

ge i

n C

ort

isol

Leve

l

0

10

20

30

40

50

60

70

80

Northern

Southern

Insult No Insult

Perc

en

tag

e C

han

ge i

n C

ort

isol

Leve

l

0

2

4

6

8

10

12

Northern

Southern

Insult No Insult

Perc

en

tag

e C

han

ge i

n

Test

ost

ero

ne L

eve

l

0

2

4

6

8

10

12

Northern

Southern

Insult No Insult

Perc

en

tag

e C

han

ge i

n

Test

ost

ero

ne L

eve

l

strengths› allows for causal conclusions to be made --

best test of theory

weaknesses› not all questions are amenable to

experiments› concerns about generalizability

expectancy effects demand characteristics of the situation social desirability concerns ethical dilemmas

refutation: process of testing theories descriptive research is informative,

but limited in theory testing correlational research is more

informative, but does not allow for causal explanations

experiments are the best test of theories

social cognition› how we think about the social world