Research Methods in Psychology

•      Descriptive Methods

–  Naturalistic observation

–  Intensive individual case study

–  Surveys/questionnaires/interviews

–  Correlational studies

•      The Experimental Method

–   for determining cause-effect relationships


Naturalistic Observations by Jane Goodall

Observing Teens at the Mall

Observing Kids at Play


Using Various Research Methods
to Study a Behavior Problem

Attention Deficit/Hyperactivity Disorder (ADHD)

•      Diagnosed when a child shows

–  6 or more symptoms of inattention

–  also 6 or more symptoms of hyperactivity,

–  These symptoms are present at an early age & must have been present for at least 6 months.

Naturalistic Observation

•      Systematic, unobtrusive observations in classrooms      show that kids with ADHD:

•      can’t stay in their seats or sit still, don’t pay attention, don’t complete work, are impulsive, are rude to others, get into trouble more, & lose their temper more often.

•      This method makes use of real-life situations, but it is important to use well-trained, unbiased observers.

Survey Results:

•      5x more males than females

•      3-5% of USA schoolkids are taking Ritalin for ADHD

•      50-60% of ADHD kids show defiant behavior & higher risk of conduct problems as teens

•      30-60% continue to have symptoms as adults

•      40% have a parent with symptoms


•      Correlation: the degree to which one variable or set of data is related to another variable/set of data.

•      Correlation coefficient: number between  -1 and +1 showing the strength and direction of this relationship.

•      Correlations help us predict behavior but do not indicate the cause of the relationship.

•      Remember: Correlation does not prove causation.

Twin Studies
Look at Correlations

Is Hyperactivity Correlated in Twins?

•      Pairs of male fraternal twins show almost no correlation (+.05) in their level of motor activity

•      But pairs of male identical twins show a strong correlation (+.71) in their level of motor activity

•      Supports the hypothesis that genetics play a role in ADHD but does not prove a cause-effect relationship.

Pros/Cons of Other Methods

•      Survey: Easy to collect lots of data but may be biased if sample is poor or responses are not accurate

•      Case studies: Can provide in-depth data on an individual but we can’t assume it will apply to all others

•      Experiment: Most able to identify cause-effect relationships but sometimes results don’t generalize to real-life situations

Why are experiments different?

•      Compare the behavior of 2 or more groups of participants under very controlled conditions.

•      Groups are treated as similarly as possible EXCEPT for the critical variable(s) (the independent variable) that the researcher is interested in. The researcher intentionally manipulates or varies the independent variable to study its impact on behavior.

Random Assignment

•      To make the 2 groups as equal as possible, most often participants will be randomly assigned  to 1 group or the other. This assures that there are no systematic differences between the groups.

Why are experiments different?

•      If everything is kept constant except for the independent variable, then any differences in performance between groups should be caused by that independent variable.

•      In other words, the experiment tests whether the independent variable causes changes behavior.


•      Experimental group - the group of participants exposed to the independent variable that the researcher is really interested in

•      Control group - the group not exposed to the independent variable of interest but rather some substitute control condition.


•      Independent variable- what the researcher manipulates or varies; the thing that is different in the experimental group  versus the control group.

•      Dependent variable - the behavior that is observed, measured, tested; the actual data collected from both groups.

Random Assignment

•      Assigning participants to the groups in a study such that all subjects have an equal chance of being assigned to any group of condition.

•      Random assignment avoids any systematic differences between the groups as long as the size of your groups is sufficient

Operational Definition

•      A definition that describes the actions  or operations that will be made to measure, manipulate,  or control a variable in an experiment


•      Sometimes we need to use pre-existing groups in research (e.g. males vs females, alcoholics vs non-alcoholics). Since we can’t randomly assign participants to groups,  there may other differences between the groups  that impair our ability to draw conclusions.


•      A tentative statement or prediction about the relationship between 2 or more variables

•      Example:

–  Consumption of alcohol will impair short-term memory.

–  Relaxation training will reduce test anxiety and improve test performance.

Random or
Extraneous Variables

•      Any other variables besides the independent  variable that seem likely to influence  the dependent variable in a particular study

•      Every effort must be made to assure that the experimental and control groups do not differ with respect to these extraneous variables

Confounding of Variables

•      When it is difficult to separate the effects of an extraneous variable from those of the independent variable

•      Confounding of variables interferes with the ability to draw conclusions about the effects of the independent variable on the dependent variable

Avoiding bias

•      sampling bias

•      social-desirability bias in self-report data

•      experimenter bias

•      bias due to expectations (placebo effect)

Key features of the scientific process

•      always looking for alternative explanations

•      replication of findings