Chapter 2 Scientific Methods in Psychology

Chapter 2Scientific Methods in Psychology

Scientific Methods in Psychology • Science is a word derived from Latin roots: • Scientia meaning “knowledge” Scientific practice helps psychologists to know that they have obtained the most accurate and useful knowledge of mental processes and human behavior.

Module 2.1 • Science and the Evaluation of Evidence

Science and the Evaluation of Evidence Psychology is a science. This chapter is about how we utilize scientific methods in evaluating claims and theories in psychology.

The Scientific Method • Why do we need it? • The scientific method provides guidelines for scientists in all fields, including psychology, to use in evaluating discrete claims (called hypotheses) and broader theories.

The Scientific Method • Why do we need it? • It is almost impossible to prove with utter certainty that any individual claim or theory is true beyond a doubt. • The scientific method allows us to declare our conclusions to be probable to the point where it is reasonable to treat them as factual.

The Scientific Method • How do we support claims scientifically? • Scientists want to know the evidence that will support or disprove a claim. • The scientific word for a claim is hypothesis. • A hypothesis is a testable prediction of what will occur under a stated set of conditions.

The Scientific Method • What’s the hypothesis? • Claim: There Is a relationship between televised violence and aggressive behavior.

Figure 2.1 A hypothesis leads to predictions. An experimental method tests those predictions; a confirmation of a prediction supports the hypothesis; a disconfirmation indicates a need to revise or discard the hypothesis. Conclusions remain tentative, especially after only one experiment. Most scientists avoid saying that their results “prove” a conclusion.

The Scientific Method • How do we test the hypothesis? • Some possible methods: • Measure how much time a sample of children watch violent television programs and compare that to how much violent behavior the children exhibit (a correlational study.) • Have a group of children watch violent programs and another group watch non-violent programs, and then record the differences in amount of violent behavior between the two groups (an experimental study.)

The Scientific Method • How do we measure the results? • It is tricky to measure phenomena such as “violent behavior.” • We need to operationally define concepts such as this one; clearly stating which behaviors will represent the phenomenon of interest (verbal threats, hitting, etc.). • We need to apply the definitions consistently.

The Scientific Method • What do our results mean? • If the results support the original prediction, it may mean the hypothesis is valid, but that does not eliminate other possible explanations for the outcome. • If the results contradict the original prediction, the hypothesis may need to be modified or abandoned (at least under certain circumstances.) • Scientists generally do not make any dramatic alterations to their conclusions based on one study only.

The Scientific Method • The importance of replication • The standards in the scientific community demand that researchers report their methods in enough detail so that any other scientist could feasibly repeat the study to confirm or contradict the validity of the findings. • Replicable results are those that anyone can obtain, at least approximately, by following the same procedures.

The Scientific Method • A good example of an interesting non-replicable result in psychology is the much-ballyhooed “Mozart effect.” • Based the results of a single study, researchers claimed that listening to classical music could improve cognitive functioning. • Several other studies have failed to replicate the results of the original one.

The Scientific Method • The method of meta-analysis • Because we sometimes find predominance of small to medium effects in most studies of a particular phenomenon (such as sex differences in aggressive behavior) we may compile the results of a large number of studies and treat them for all intents and purposes as one very large research study. • A meta-analysis also provides us with more information about the circumstances that will increase or decrease the likelihood of the predicted effect occurring.

Scientific Theories • What is a theory? • A theory is a comprehensive explanation of observable events and conditions. • A good theory makes precise and consistent predictions while relying on a small number of underlying assumptions.

Figure 2.2 A good theory makes precise (falsifiable) predictions

Scientific Theories • The importance of falsifiability and parsimony • A theory that makes precise predictions is falsifiable because it is easy to think of evidence that would confirm or contradict the theory. • Reliance on the fewest and simplest possible assumptions is called parsimony, and is considered an essential strength of good scientific theory.

Scientific Theories • Example of a Parsimonious and Falsifiable Scientific Theory: • Gravity is a force that pulls objects in the universe towards each other. • According to the theory of gravity, larger and more massive objects pull smaller objects towards them.

Can you think of examples of evidence that would confirm or contradict this theory? • Does the theory rely on assumptions other than the existence of the force itself and the effects of size on the workings of the force? EASILY. It is falsifiable. NO. It is parsimonious.

An example of a claim that is NOT falsifiable: • The telephone psychic says “Next year, you will go through a big change.” • This is not falsifiable because it is too vague.

An example of a claim that is NOT parsimonious: • The sun goes around the earth. Little gnomes push it around the sky every day. We can’t see them because they are invisible to the human eye. • This is not parsimonious because too many assumptions must be made in order for the claim to be accepted as fact.

Concept Check • Is this claim falsifiable? • “You will encounter new challenges in your travels this week.” NO It is vague.

“An oversupply of dopamine in the human central nervous system will eventually result in a decline in the number of receptors available for that neurotransmitter.” YES

“On March 19th, 2005, you will meet a 30-year-old millionaire who will offer you an exciting entry-level job in a growing high-tech company in Austin, TX.” YES Think – why do horoscopes never get this specific?

“Children whose parents divorce will eventually have serious emotional and relationship problems.” • NOT AS SUCH • We need to operationalize the terms “emotional problems” and “relationship problems”.

“There are unseen powers at work in our lives that scientists will never be able to fully explain.” NO This is vague – What powers? How do they work?

Parsimony and Degrees of Open-mindedness • You might ask - • “Shouldn’t we remain open-minded to new possibilities?”

Scientific open-mindedness: • It is the willingness to consider proper evidence. • It is NOT unquestioning acceptance of any possibility in the absence of evidence. This is known as “gullibility.” In other words, your degree of open-mindedness should have some relationship to the quality of the evidence presented.

What about anecdotal evidence? • People often use personal accounts of isolated events to bolster their beliefs in phenomena (such as ESP.) • Because this sort of evidence is not systematically gathered, it is prone to “selective memory” (called confirmation bias) on the part of the reporter. • We tend to remember when our hunches come true, and forget when they do not. We like to be right.

Research on ESP (“Extrasensory Perception”) • Because of the problems described above, anecdotal evidence is not considered to be acceptable as good evidence of the existence of ESP. • Experiments done in controlled settings, such as the Ganzfeld procedure, along with careful observation of some famous professional psychics, have shown results that were non-replicable, or easily explainable by techniques of slight-of-hand known well to experienced magicians.

Psychology as a Science • Science does not deal with proof or certainty. • The history of science is one of constant revision in the face of new and compelling evidence. • Yet in psychology and all other sciences, we apply the rigorous and systematic methods of scientific study – hypothesis, methods, results, and interpretation, to ensure that our claims are firmly grounded and our revisions reflect an improved understanding of the phenomena under scrutiny.

Module 2.2 • Conducting Psychological Research

General Principles of Research • It is essential to your learning in psychology, and perhaps to your knowledge in general, to be able to evaluate the quality of the evidence presented in psychological research. What information do you need to know to be a good interpreter of psychological research?

General Principles of Research • Definitions of Psychological Terms • The Problems of Measurement • We need to measure the phenomena we are studying. • Sometimes what we study in psychology is not tangible. It is not as we are measuring weight or length of time.

General Principles of Research • Definitions of Psychological Terms • The problems of Measurements • In order to accurately measure these concepts and phenomena, we develop behavioral or observable definitions of them. • We call these definitions operational definitions. • An operational definition is one that specifies the operations or procedures used to produce or measure something. It’s a way to give an intangible idea a numerical value.

General Principles of Research • Definitions of Psychological Terms • So if we are investigating the effect of watching violence on television on children’s aggressive behavior: • We need to operationalize “violence” on television. • We need to operationalize “aggressive behavior.”

General Principles of Research • Definitions of Psychological Terms • Violence might be operationalized as “the number of times in a one-hour show that one person threatens or injures another person.” • Aggressive behavior might be operationalized as “the number of insults, threats and assaults by the subject over a 24-hour period after watching a particular television program.” • (There are other versions of these operational definitions that would work well.)

Concept Check • Operational definitions • Which of the following might be used as an operational definition of “attraction?” • A feeling of affection when two people are together. (1) • The number of minutes during which two people are touching each other over a four-hour period. (2) (2)

Which of the following might be used as an operational definition of “assertiveness?” • The number of times a person makes requests or states his or her feelings over the course of a one-hour interaction. (1) • An appearance of confidence and ease in social situations. (2) (1)

General Principles of Research • Population Samples • Usually in research we are asking questions that are pertinent to a large population of interest such as: • Seven to ten-year-old children • People diagnosed with depression

General Principles of Research • Population Samples • But it is not practical to study all the individuals in the population. • We take a relatively small number of observations or individuals from the population, and we generalize from that small number. • The small number of individuals or observations is called a sample.

General Principles of Research • Population Samples • There are several types of samples and sampling procedures: • A convenience sample is a group chosen because of its ease of availability and study. • A representative sample closely resembles the population in its percentage of males and females, ethnic or racial groups, age levels, or whatever other characteristics might have some relevance to the results.

General Principles of Research • Population Samples • A random sample is one in which every individual in the population has an equal chance of being selected. • A cross-cultural sample is one that contains groups of people from at least two distinct cultures.

General Principles of Research • Population Samples • How we go about obtaining a sample has to be carefully assessed in terms of our resources and goals. Sometimes it is acceptable and appropriate to rely on a convenience sample, other times this strategy will produce results that are useless in helping us understand and interpret the “real world.”

Concept Check • Population Samples • Suppose I am interested in the attitudes of college students towards using the Internet in their studies. I survey my students in one Introductory Psychology class at my college. • Population Samples • Suppose I am interested in the attitudes of college students towards using the Internet in their studies. I survey my students in one Introductory Psychology class at my college. • Can I assume that their attitudes are representative of the attitudes of all college students in general? • Not a safe assumption – why?

General Principles of Research • Experimenter Bias • Because (fallible) humans do the research, we need to keep in check the various tendencies that can work to create erroneous research findings or erroneous interpretations of findings. • Experimenter bias is the tendency of an experimenter to unintentionally distort the procedures or results of an experiment based on the expected or desired outcome of the research.

General Principles of Research • Experimenter Bias • For example, if you were a researcher testing the hypothesis that children who have been diagnosed with learning disabilities are on average more creative than children who have no diagnosis, you may find it hard to “ignore your hypothesis” as you observe the children with an LD diagnosis going about whatever tasks you have devised to operationalize “creativity.”

General Principles of Research • Experimenter Bias • Methods have been devised to help counteract these normal human tendencies that create bias: • Using blind observers who record data without knowing what the researcher is studying. • Using a placebo control. A placebo is a pill or other sham treatment that makes it very difficult for the subjects (single-blind) or the subjects and experimenter (double-blind) to know who has received the treatment and who has not.

Table 2.1 Single-Blind and Double-Blind Studies

Chapter 2 Scientific Methods in Psychology