PSY 101L: Introduction to Psychology
Lab
Lecture:1
Introduction to the psychological
experiment
Ms. Ashma Rahman
Lecturer
Department of History and Philosophy
Nature of Science
Science follows the orderly and consistent
method to investigate the natural world
around us, gather evidence and adequately
explain the evidences.
Nature of Science
Order & Consistency
Natural
World
Investigation
Tentative
Evidence
Evaluation
Explanation
“a systematically organized body of knowledge about the
universe obtained by the experimentation and observation.”
- by McGuigan
Psychology as a science
Psychology must fulfill the properties of science to
qualify as a field of science.
1) It has to be empirical and objective: Testable &
free from personal biases.
2) Deterministic: Must follow the causal-effect law.
3) Systematic exploration: Must follow orderly way
to investigate and to analyze.
4) Reliability: The investigation result should be
consistent under similar circumstances.
5) Predictability: It should attempt to predict for
similar events.
https://www.youtube.com/watch?v=xzCrc6eRRIk
History of Psychology as a Science
• Long rooted history in the Greek philosophy
• Emergence as a field of science during the 19th
century by Wilhelm Wundt in 1879 and by
William James in U.S in the next year.
• The introduction to experimental methods
gave psychology the status of a scientific field
of study.
Psychology is the scientific study of behavior
and mental process. - By Feldman
Behavior & Mental Process
• Behavior is any kind of activity a living being or an
organism that can be observed, recorded and
measured. It includes what the organisms do in
their space. It even includes the physiological or
the bodily changes. E.g. changes in the blood
pressure or brain waves.
• Types of Behavior
A) Voluntary & involuntary behavior
B) Overt & covert behavior
https://www.youtube.com/watch?v=QSXzzszM93Q
• Mental processes are all the things that
individuals can do with their mind. It includes
thoughts, memories, emotions, motivations,
dreams, perception, feelings.
• The behavior and mental process are interrelater. One causes the other. Psychologists
believe that mental process can be studied by
observing changes in behavior. e.g. individual’s
level of alertness can be studied by measuring
the changes in the electrical signals generated by
brain. Or stress can be inferred by measuring
changes in the blood pressure and perspiration.
Overt Behavior
Mental Processes
Body Functions ( covert)
•
•
•
•
•
•
•
•
•
•
• Nervous system (Brain
and Body)
• Internal functions of
the body organs e.g.
heart, liver, kidneys
• Voluntary, involuntary
muscle activities
• Genetics
How we communicate
How we eat
How we look
Verbal and non-verbal
behavior
• Expressions, Gesturespostures e.t.c.
Thinking
Perceiving
Memory
Learning
Problem solving
Reasoning
HIGHER MENTAL
PROCESSCOGNITION
Measuring Behavior and Mental
process
Experimental method and non-experimental
method.
The key difference between experimental and nonexperimental research lies in the extent to which
the environment is controlled and manipulated by
the researcher. In experimental studies the
researcher sets up the environment and carefully
controls the variables of interest and, on the other
hand, in non-experimental method, the researcher
simply measure variables as they naturally occur.
What is Psychological Experiment?
The experiment is a well defined, systematic and
controlled procedure for identifying the causal
relationship between two (or more) variables by:
 deliberately producing a change in one variable
and
 observing the effects of that change on other
variable
Variables:
Behaviors, events or any other characteristics
that can be changed or vary somehow in an
experiment is called the variable. e.g. age,
gender, sound, light, response etc.
Variables are the central core of any
experimental research of psychology. In any
experiment psychologists establish the causeeffect relationship by manipulating these
variables. The causal effect relation is studied
by deliberately producing change in one
variable to see its effect on the other. e.g. to
see the effect of noise on attention.
• Independent variable (IV) and
• Dependent variable (DV).
Independent variable (IV) : The variable that is
manipulated in an experiment is called the IV.
e.g. the intensity of sound. These are the factors
in an experimental setting whose effect defines
the outcome of the research.
e.g. Researcher may increases and decries the
intensity of sound to investigate whether it
effects the attention in a classroom. Here the
amount of attention depends on the intensity of
sound. So the sound here is the IV.
Dependent Variable (DV)
The variable that is measured and is expected to
change as a result of changes caused by the
experimenter’s manipulation of the independent
variable.
It shows the effect of manipulation and change
in independent variable. In other words, the
variation in the dependent variable depends on
the variation in the independent variable.
• The result of an experiment is the changed
condition of the dependent variables that is
produced by the direct effect of the
independent variable.
Extraneous Variable:
Conditions or factors that an experimenter wants
to prevent from affecting the outcomes of the
experiment.
EV are those factors in the research environment
which may have an effect on the dependent
variable(s) but which are not controlled.
Extraneous variables are dangerous. They may
damage a study's validity, making it impossible to
know whether the effects were caused by the
independent or some extraneous factor.
e.g. the light effect in a cloth store
Hypothesis Testing
 Hypothesis: a tentative statement about the
relationship between two or more variables.
 A specific, clear, testable prediction about the
outcome of the experiment or research
---Example – “sleep-deprived people will
perform worse on a test than individuals who
are not sleep deprived.”
 Research Hypothesis
A hypothesis derived from an in-depth review of
the existing literature or theories.
Experimental Manipulation:


Experimental manipulation- the change that
an experimenter deliberately produces in a
situation.
Treatment
 Manipulation implemented by the
experimenter
 Randomization –
The procedure which assures that each member of population has equal probability of
being selected in the experiment.
 each level of an extraneous variable has an equal
chance to be occurred in all conditions of
observation.
So that, the extraneous variable does not confound with
our manipulated variable
Experimental Group
A group of subjects (participating in an
experiment) are exposed to the treatment
(receive non-zero values of the IV)
Also called the experimental condition in
some situation
The group is studied for comparing with the
control group
Control Group
 A group of subjects (participating in an
experiment) are not exposed to the treatment
(receive a zero value of IV).
The control group is compared to those of the
experimental group on dependent variable
Also called the control condition
Basic Characteristics of an Experiment
 Control over extraneous variables
holding constant
 randomizing effects
• A causal relationship can be established
between the independent and dependent
variables by the process of manipulation.
• Randomization is done in every step of a
psychological experiment.

Steps in Experimental Method
Steps involved are:
1) Label the experiment: Title must be specific,
clear and to indicate the content.
2) Identify Research problem: By definition; a
research problem is a statement about an
area of concern that needs to be improved or
answered. e.g. Whether paracetamol should
be banned?
• It arises from the gap of knowledge.
That is, we may not have enough information
about concerned question or the existing
knowledge may be disordered. e.g. the lack of
knowledge about the side effect of paracetamol
leads to the research on whether it should be
banned or not?
There are time when different studies on the similar
topic provides contradictory results, which
further create research problems to investigate
on. e.g. One study may find that paracetamol is
harmful for kidney whereas another could found
that it is not.
Selection of research problem
• Testable & practical
• Relevant
• True Statement
3) Propose a hypothesis: A clear specific hypothesis
needs to be undertaken before conducting an
experiment.
4) Identification and control of variable: The
independent and dependent variables need to be
specified clearly prior to the conduction of the
experiment and at the same time all sources of
extraneous variables need to controlled.
5) Collection
6)analysis of data
7) Generalize the findings
The Ethics of Experiment /Research
 Protecting Participants as The Aim of The Ethical
Guidelines
 APA (American Psychological Association, 2002) Ethical
Guidelines:
 Assurance that participation is completely voluntary
 Protect from physical and mental harm


Participants’ right to privacy regarding behavior
Informing participants about the nature of procedures
prior to participation
Informed Consent: One of Key
Ethical Principles

A document signed by participants affirming that
they know:





the basic outlines of the study
what their participation will involve
the risks the experiment may hold
that their participation is purely voluntary
they may terminate the study at any time