SCIENCE OF PSYCHOLOGY
Wilhelm Wundt is considered the founder of psychology. He established the
first laboratory in 1879. Wundt relied on an early method of investigating
psychology called introspection.
 The founding of psychology is associated with the founding of
laboratories, so the founding of psychology begins with the scientific
study of psychology.
Science is a process. It is a way of knowing. It follows a series of steps.
Psychology has adopted this process, such that psychology is best defined as a science of
thought, feeling, and behavior.
Quest: When did psychology get established as an official discipline? What does this tell us
about the role of science in psychology?
Step #1: Formulate a hypothesis
A hypothesis is a tentative prediction about the relationship between two or more variables.
outcome of a specific discipline. A theory is an explanation of data. It generates predictions.
Quest: What’s the difference between a theory and a hypothesis? Which one comes first?
Step #2: Operationally define variables and design a method appropriate to the research
question.
The next step is to operationally define the variables identified in the hypothesis. An operational
definition refers to the operations used to define the variable; more specifically, it is the
measurement procedure or observations used to identify the variable. Simply said, it is the way
the variable “looks.”
Once the variables are translated into something that is measurable or observable, the researcher
designs the research design to test the hypothesis. The challenge is applying the appropriate
method. The simplest way to grasp about the various research methods is to place them into two
categories:
1. Descriptive Methods are those used to systematically describe behavior.
 One example of this type of method is naturalistic observational methods, in which the
researcher observes behavior in a natural context without interfering.
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 Another example of this type of method is correlational studies, in which two variables
are measured (perhaps through surveys or other measurement techniques), and then
statistical techniques are applied to see how much the variables co-vary (or go together).
 The advantage of these designs is that they provide a good estimate of what occurs in the
real-world. The disadvantage is that they do not establish cause-and-effect.
 These designs do not tell us the direction of the effect. This is known as the
directionality problem, in which the co-variation of these variables does not tell us
whether variable X is causing Y or Y is causing X. The designs also do not rule out thirdvariables or unmeasured variables that may be the cause of the measured variables of X
and Y.
2. Experimental Methods are those methods that allow researchers to establish a cause-andeffect relationship by systematically manipulating the presence or absence of one variable to
determine its effect on the other variable. A true experiment must have the following elements:
a) Independent Variable is a variable that is manipulated by the researcher. It is the
potential “cause” in the cause-and-effect relationship under investigation.
 The independent variable, then, essentially creates at least two groups. In the
Treatment or Experimental Group, the participants in the study receive the
active agent—the thing proposed to be the cause. In the Control Group,
participants do not receive the active agent or the thing proposed to be the cause.
It acts as the comparison group or the group that operates under standard
conditions.
b) Dependent Variable is the outcome variable being measured. It is the potential “effect”
in the cause-and-effect relationship under investigation.
c) Random Assignment is the process by which the sample (the group of people selected
or who volunteered for the study) is assigned to condition by a random procedure (e.g., a
coin toss). The idea here is that everyone in the study has an equal chance of being in the
treatment or control group. Do not confuse this with random selection, which is a
process by which participants are selected for the study in a random fashion. Random
assignment is needed for experiments; random selection is not.
d) Experimental Control refers to the fact that all the variables in the study must remain
constant, other than the independent variable. In particular, the researcher wants to ruleout any other systematic change across conditions. Do not confuse this with the control
group.
Step #3: Analyze the data and draw conclusions.
At this point, the researcher must summarize the data using descriptive statistics, which is the
process by which researchers summarize data with things like means or averages and standard
deviations or the spread of the data) and then determine whether the differences or relationships
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found are statistically reliable, using inferential statistics. The details of the latter process will
be left out of this course, but it is important that students begin to develop skills in summarizing
their data.
When conclusions are drawn, they are assessed in terms of a few things. Throughout this course,
students will practice these skills.
1. Primarily, the researcher evaluates the extent to which the evidence provides support for
the hypothesis.
2. The other thing the researcher must do is determine how strong and what kind of
conclusions can be drawn from the data. This latter part is done using two indices:
 Internal Validity describes how well the features of the research allow for causal
inferences,
 External Validity describes how well the features of the research allow for making realworld inferences (or how well it applies beyond the bounds of the particular study).
Quest: Look at the designs discussed in the notes. How well do the designs meet the criteria of
internal and external validity?
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