Section 6: The Experiment:
Hunting for Causes
PSYCHOLOGY CHAPTER 1
Experiment-
allows the researcher to
control or manipulate the situation
being studied
Allows the experimenter to draw
conclusions about cause & effect
Must
adhere to ethical guidelines
In college, a review committee must
approve all proposed studies
Participants must volunteer & know
enough about the study to make an
intelligent decision (informed consent)
Must protect the participants from
physical or mental discomfort or harm
Also applies to animals
EXPERIMENTAL VARIABLES
Independent Variable:
A variable that an
experimenter
manipulates
Dependent Variable:
A variable than an
experimenter predicts
will be affected by
manipulations of the
independent variable
Every
experiment has at least one IV &
one DV
Ideally everything in the experimental
situation except the IV is held constant
(same for all participants)
Ensures that whatever happens is due
to the researchers manipulations &
nothing else
EXPERIMENTAL & CONTROL CONDITIONS
Experiments
usually require both an
experimental & control condition
Experimental Condition: A condition in
which subjects are exposed to
manipulations of the IV
Control Condition: A comparison
condition in which subjects are not
exposed to the same treatment as in the
experimental condition
Without
a control condition you can’t
be sure that the behavior you are
interested in would not have occurred
anyway without manipulation
EXPERIMENTAL DESIGN
Hypothesis:
Nicotine in
cigarettes impairs
driving.
All conditions kept the
same for both groups
except nicotine.
Control condition is
given placebo
(inactive) cigarettes
Number of collisions is
measured
1-8
Use
random assignment to balance
individual characteristics
A procedure for assigning people to
experimental and control groups in
which individuals have the same
probability as an other of being
assigned to either group
May
use placebos
An inactive substance
or fake treatment
used as a control in
an experiment or
given by a practitioner
to a patient.
Critical when testing
new drugs
EXPERIMENTER EFFECTS
Because
expectations can influence the
results of a study, participants should
not know if they are in the experiment or
control groups
Single blind study
Researchers
also bring expectations &
may cause unintended changes in
subjects’ behavior due to cues
inadvertently given by the experimenter
Facial expressions, posture, tone of
voice, or some other clue
One
solution to this problem is to do a
double blind study
Experiment where neither subjects
nor people running the study know
which subjects are in the control
group and which are in the
experimental group until after results
are tallied
Standard in drug research
ADVANTAGES & LIMITATIONS OF EXPERIMENTS
Experiments
allow conclusions about
cause-effect relationships.
Participants in experiments are not
always representative of larger
population.
Much psychology research is carried
out using college students as
participants.
Researcher
determines which
questions are asked & which
behaviors are recorded & the
participants try to do what they are
told
May act different than normal
Dilemma-
the more control they exercise
over the situation, the more unlike real
life it may be
Do more field research
Descriptive or experimental
research conducted in a natural
setting outside the laboratory
0
