Abnormal Psychology

156 CHAPTER 5

Experiments
Research studies in which investigators
intentionally manipulate one variable at a
time, and measure the consequences of such
manipulation on one or more other variables.

Independent variable
A variable that a researcher manipulates.

Dependent variable
A variable that is measured and that may
change its values as a result of manipulating
the independent variable.

Types of Scientifi c Research

Any individual researcher does not need to go through the entire sequence to be doing

science. For instance, you went from having an observation to identifying a question—

about relationship breakups and depression—to stating a full-fl edged theory: Chil-

dren who felt helpless in response to a loss grow up to be especially susceptible

to becoming depressed after a relationship fails. However, your observation could

have led you down many other research paths, depending on the specifi c question

you developed. For instance, your question might have focused not on loss during

childhood, but on the degree to which the adult was not totally surprised by the

breakup of the relationship.

Psychologists employ different research methods when they pose and attempt

to answer various questions; such methods include experiments, quasi-experiments,

correlational research, case studies, and meta-analysis. As we review the various re-

search methods, we will point out not only their strengths, but also their weaknesses.

You might be tempted to conclude that the weaknesses are so severe that you can

never understand anything with certainty from psychological research. Resist that

temptation! Although each method has limitations, different methods have different

limitations. Thus, if different methods produce the same answer to a question, we

can be confi dent that the limitations of any one method are not responsible for the re-

sults. This method of converging evidence, where the same answer is produced using

different techniques, has produced a wealth of knowledge about psychopathology.

Conducting Research with Experiments

Ideally, researchers prefer to employ experiments, which are research studies in

which investigators intentionally manipulate one variable at a time, and measure

the consequences of such manipulation on one or more other variables.

Independent Variables and Dependent Variables

You probably noticed that the defi nition of an experiment mentioned two kinds

of variables: those that are manipulated and those that then are measured. In an

experiment, researchers manipulate one variable at a time in order to observe possible

changes in another variable. The variable that a researcher manipulates is called

theindependent variable (so named because it is free to change—it is independent).

The variable that may change as a result is called the dependent variable (because

its value depends on the independent variable). When the independent variable is

changed, the accompanying changes in the dependent variable are the effect.

Figure 5.1

5.1 • Steps of the Scientifi c Method

g

51•St f th S i tifi M th d

Identify the

question

Why do some

people get

depressed after

a relationship

ends, rather

than bounce

back?

Collect Initial Observations

Make observa-

tions, which may

include specific

measurements,

such as

responses to a

questionnaire

rating mood

and functioning

(such data can

be replicated).

Develop a Hypothesis

Individuals

who suffered a

major loss

during

childhood

(such as the

death of a

parent) are

more likely to

get depressed

after a

relationship

ends during

adulthood.

Collect Data to Test the Hypothesis

Participants are

people who

have just had a

relationship

breakup; they

complete a

questionnaire

about their

losses in

childhood and a

questionnaire

about their

current mood

and

functioning.

Develop a Theory

Loss during

childhood leads

to a sense of

helplessness,

which in turn

predisposes

people to

become

depressed in

adulthood after

a relationship

breaks up, when

they again feel

helpless.

Test the Theory

Test people who

did or did not have

an uncontrollable

loss during

childhood by

giving them

increasingly

difficult puzzles;

as a measure of

helplessness,

assess how easily

participants give

up trying to solve

the puzzles.