CONDUCTING RESEARCH IN SOCIAL PSYCHOLOGY EXPERIMENTAL METHOD

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Social Psychology (PSY403)

Lesson 08

CONDUCTING RESEARCH IN SOCIAL PSYCHOLOGY

EXPERIMENTAL METHOD

Aims:

To make students understand how to conduct social psychology research using diverse scientific

methodologies.

Objectives:

Describe experimental research method

Describe basic experimental design

Understand differences between field and laboratory research methods

Understand experimental research designs

Understand complex laboratory designs

Experimental methods

Experimental methods are research designs to examine cause-effect relationships.

The variable that is manipulated is called the independent variable, while the variable whose changes

are considered to be the effect of the manipulated changes in the independent variable is called the

dependent variable (e.g., varying lighting conditions and performance of students)

Experimental and control groups are two main groups used in experimental methods

Basic Experimental Design

Figure 1 illustrates a basic experimental design using random sampling procedure

Figure 1

Unfortunately, we are seldom able to obtain

such a sample. We must, therefore, often rely

Basic Experimental Design (simple,

on using subjects who are readily available -a

syst.)

convenience sample - and then split them into

two groups using a technique called "random

assignment."

Random

Figure 2 illustrates a basic experimental design

Sampling

Random

Population

using cluster sampling technique, as mentioned

Sample

above.

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Figure 2

Basic Experim ental D esign (cluster

sam ple)

Convenience

Sample

Random Assignment

Experimental

Control Group

Group

Figure 3 illustrates the use of control and experimental groups and the manipulation of independent

variable

B a s ic E xp e rim e n ta l D e s ig n

Present

Independent V ariable

Experim ental

C ontrol G roup

G roup

M easure

D ependent V ariable

C o mpare

G roups

B a s ic E x p e r im e n t a l D e s ig n

Figure 4 tests the hypothesis that the use

of highlighters in text can increase

C onvenien ce

learning. First of all subjects will be given

S am p le :

U ndergraduate

several pages to read. After they have

S tuden ts

done so, they will be dismissed and asked

R a n d om A ssign m e n t

to return to the experimental lab the next

day.

H igh ligh te rs fa c ilita te m e m o ry of facts read f ro m te x tb oo ks"

E x p e r im e n ta l

C o n tr o l G r o u p

G roup

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Figure 5: Each subject is given five pages from an Introductory Psychology text and told to read

the pages carefully because they will be tested on the material next day. The subjects are dismissed after

they finish reading and asked to return the next day. The quiz next day will determine whether availability

of highlighters helped greater learning or not. Highlighters will only be available to the experimental

group.

Basic Experimental Design

Experimental Method:

Description

Present Independent Variable

Because correlational studies

Availability of Highlighter

cannot definitively tell us why variables

are related to one another, social

Highlighter Available

psychologists

use

experimental

No Highlighter

methods to examine cause-effect

relationships. In an experiment, the

Experimental Group

Control Group

scientist manipulates one variable by

Measure

exposing research participants to it at

Dependent Variable: Number of

contrasting levels (for example, high,

correctly recalled facts on quiz

medium, low, no exposure), and then

observes what effect this manipulation

has on the other variable that has not

Compare Groups

been manipulated. The variable that is

manipulated is called the independent variable, and it is the one the experimenter is testing as the possible

cause of any changes that might occur in the other variable. The variable whose changes are considered to

be the effect of the manipulated changes in the independent variable is called the dependent variable. The

dependent variable is the response measure of an experiment that is dependent on the participant's response

to the experimenter's manipulation of the setting (the independent variable)

A number of experimental studies have explored whether watching violent entertainment programs

leads to increased aggressiveness in children. For example, Jacques-Philippe Leyens and his colleagues

(1975) conducted an experiment in a Belgian private institution for secondary-school boys. The

independent variable in this study was exposure to violent films. In two cottages at the school, boys were

shown a violent film every night for one week (for example, Bonnie and Clyde, The Dirty Dozen). The

boys in two other cottages were shown the same number of nonviolent films during the same period of time

(for example, Lily, Daddy's Fiancée.

Significant differences were found between the two groups of boys, with the treatment group

exhibiting higher levels of aggression both toward other boys and toward inanimate objects. Based on these

findings, the social psychologists concluded that exposure to violent films had indeed caused increased

aggressiveness.

FIELD EXPERIMENTS

The study just described is a special type of experiment called a field experiment, which is similar

to the more common laboratory experiment, except that it is run in a natural setting, and participants often

do not realize they are being studied. This greater realism increases the study's external validity, which is

the extent to which its findings can be generalized to people beyond those in the study itself.

Unfortunately, one drawback to field experiments is that researchers have less control over what is

happening to each participant during the study because they are in a setting where many variables are

uncontrollable. These problems of control decrease the study's internal validity, which is the extent to

which cause-and-effect conclusions can validly be made (Cook & Shadish, 1994).

LABORATORY EXPERIMENTS

By far, most social psychology experiments are conducted in laboratories. As an illustration,

consider the following experiment investigating the effects that two independent variables, television

violence and anger; have on boys' aggressive behavior. In this study, Donald Hartmann (1969) randomly

assigned teenage boys to different levels of the two independent variables. At the beginning of the

experiment, the boys, anger was manipulated by either having a confederate of the experimenter--who

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was posing as a fellow participant--insult him or treat him in a neutral fashion. Following the anger

manipulation, the boys were assigned to one of three film conditions lasting two minutes. The first minute

of each film showed two boys shooting baskets on a basketball court. For the remaining minute, the boys in

the control group film merely played basketball, while in the two treatment-group films one of the boys

began beating the other following an argument

After viewing the film, each boy participated in a seemingly unrelated learning study. As the

"teacher" in the study, the participant was instructed to administer an electrical shock to a "learner"

whenever the learner made a mistake on the learning task. The learner was the confederate who had either

insulted the participant or treated him neutrally. The intensity of the shock chosen by the boys was the

dependent variable. In reality, no shocks were ever delivered, but the boys were not aware of this until the

end of the experiment. As predicted, boys exposed to a violent film and boys previously angered tried to

deliver stronger shocks to the learner than did boys in the control conditions. Further, boys who had been

both angered and exposed to a violent film chose the strongest shock levels of the six groups of boys. Thus,

the combination of being exposed to a violent film while angry caused the greatest amount of aggression.

The experiment of Hartman is an example of complex experiments, which is illustrated in the

following complex Lab designs.

Complex Lab designs

Figures 6 and 7 show a complex design with 2 independent variables and 2 experimental and one

control group.

Figure 6

L a b o r a t o r y E x p e r im e n t s D o n a ld

H a r tm a n n 's s tu d y ( 1 9 6 9 )

C on ven ience

Sam p le:

U ndergradu ate

Studen ts

R a n d o m A s sig n m e n t

C o m bination of a nger a nd violent m ovie v iew ing pro m otes aggression

E x p e rim en ta l

C o n tr o l G r o u p

G ro up s 1 & 2

Figure 7 shows the manipulation of independent variables

Complex Experimental Design: Interaction

Present Independent Variable

Induced anger + violent movie

1. Anger induced

1.Neutral treatment

2. Violent movie

2.Neutral movie

Control Group

2 Experimental Groups

Measure

Intensity of shocks delivered to

confederate

Compare Groups

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The main advantage of a lab experiment like Hartmann's is that variables can be well controlled,

thus increasing internal validity. An important component of this control is that participants can be

randomly assigned to the different levels of the independent variable.

Unfortunately, because of the researcher's desire to control as much of the experimental situation as

possible in order to properly assign causality, an air of artificiality may exist in the lab (Gosling, 2004;

Rozin, 2001).

Making Experiments Real

Experimenters recognize two types of realism

Experimental realism

Does the experimental situation feel real to the participants in that situation?

Mundane realism

Does the experiment have the look and feel of situations in the outside world?

Table 1 illustrates the relationship between internal and external validity, as well as between both forms of

realism.

Experimental Designs

Independent measures

designs

Repeated-measures

designs

Counterbalancing

applied to reduce order

effect

same

individuals exposed to

2 or more conditions

called ABBA design:

Changing the sequence

of conditions for the

participants;

Source: Brechler et al. 2006, Social Psychology Alive

advantages are less

subject variability, and more strong conclusions about causality

Matched participants

Conclusion: There is no one best method in all research settings. In each investigation, social

psychologists must decide what method provides the best opportunity of meeting the study's goals.

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