ASSUMPTIONS OF A SCIENCE OF PSYCHOLOGY

• Realism– The world exists independent of observer

• Causality– Events (mental states and behavior) are

caused by prior and current conditions

• Regularity– Cause-effect relationships are stable over time

(even if collective relations are unique

• Discoverability– Those stable relationships (laws) can be

learned through careful observation

GOALS OF A SCIENCE OF PSYCHOLOGY

• Discover stable relationships among conditions

• Develop theories that:– Explain (sets of) relationships– Generate hypotheses about new relationships

• Theories vary in level and completeness of explanation

– Parsimony and Occam’s Razor– The “transparency-sufficiency” trade-off– She who predicts the most data with the fewest

“parameters” wins

RELATIONS AMONG VARIABLES

• Range of possible “functional relations”– Coffee and reaction time– Meditation and memory– Anxiety and test performance

positive

negative

linear +accell -accell complex curvilinear (nonmonotonic)

(mis)INTERPRETING RELATIONS

Problem: Construct Validity• The link between theoretical and

“operational” variables

Solution: Operational definitions• Anxiety: scores on questionnaires• Memory: number of items recalled• Attention: instructions to stress Task A• Intelligence: ?

(mis)INTERPRETING RELATIONS

Problem: correlation = causation• A > B, B > A, or C > A & B

Solution: Experimental method!• Take charge and manipulate one

circumstance– The Independent Variable(s)

• Measure its effect on behavior– The Dependent Variable(s)

CONTROLLING MISCELLANEOUS FACTORS

Problem: Confounding Variables• Other factors that “covary” with your

Independent Variable

Solution: Control!• Keep those other variables constant• If you can identify them ahead of time..

CONTROLLING MISCELLANEOUS FACTORS

Problems with Control Variables• Low external validity and generalization• Hard to keep all relevant factors constant

Solution: Randomization!• Randomly assign participants / materials to

conditions if possible• Constrain it if necessary• The larger the sample, the better