The Need for  Psychological Science

Psychologists, like all scientists, use the scientific method to construct theories that organize observations and imply testable hypotheses

         Hindsight Bias

         we tend to believe, after learning an outcome, that we would have foreseen it

         the “I-knew-it-all-along” phenomenon

         Overconfidence

         we tend to think we know more than we do

         Critical Thinking

         thinking that does not blindly accept arguments and conclusions

         examines assumptions

         discerns hidden values

         evaluates evidence

 

Guidelines for Evaluating Reports of Psychological Research

•           Don’t confuse pseudoscience or nonscience with science.

•           Be skeptical.

•           Be aware that scientists may disagree.

•           Keep in mind that research is generally about averages.

•           Whenever possible, go to the original source.

 

The Scientific Method

•           “Scientific method” refers to

–          an abstract concept,

–          not a particular technique or method.

•           The scientific method refers to ways in which scientists ask questions and the logic and methods they use to gain answers.

         Theory

         an explanation using an integrated set of principles that organizes and predicts observations

         Hypothesis

         a testable prediction

         often implied by a theory

 

Getting Started

•           How do I develop a hypothesis to test in my research?

–          Think about deviations (oddities, exceptions) from a general trend or principle.

–          Imagine how you would behave in a task or when faced with a specific problem.

–          Consider similar problems with known solutions.

–          Make sustained, deliberate observations of a person or phenomenon (e.g., perform a “case study”).

–          Generate counterexamples for an obvious conclusion about behavior.

–          Borrow ideas or theories from other disciplines.

–          Read reports of psychological research.

Goals of the Scientific Method

•           Researchers use the scientific method to meet four research goals:

–          description

–          prediction

–          explanation

–          application

 

         Operational Definition: a statement of procedures (operations) used to define research variables

         Example: intelligence may be operationally defined as what an intelligence test measures

         Replication: repeating the essence of a research study to see whether the basic finding generalizes to other participants and circumstances

         usually with different participants in different situations

 

Description

•           Most psychology research is nomothetic rather than idiographic.

–          Nomothetic: large sample sizes, “average” performance of a group

–          Idiographic: individual case studies

–          Nomothetic researchers appreciate there are important differences among individuals; they seek, however, to emphasize similarities among individuals.

•           Most psychology research is quantitative rather than qualitative.

–          Quantitative: statistical summaries of performance

–          Qualitative: verbal summaries of research findings

 

Case Study

         Psychologists study one or more individuals in great depth in the hope of revealing things true of us all

 

Survey: technique for ascertaining the self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of people

 

Naturalistic Observation

         observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation

 

         Random Sample:  sample that fairly represents a population because each member has an equal chance of inclusion

 

         False Consensus Effect: tendency to overestimate the extent to which others share our beliefs and behaviors

         Population: all the cases in a group, from which samples may be drawn for a study

 

Measures must be valid and reliable.

–          Validity refers to truthfulness; a valid measure is one that measures what it claims to measure.

–          Reliability refers to the consistency of a measure.

–          Note that a measure may be reliable but not valid.

•           For example, a scale that consistently underreports someone’s weight is reliable but not valid.

 

Correlation Coefficient: a statistical measure of the extent to which two factors vary together, and thus how well either factor predicts the other

 

Correlation Scatterplot

         a graphed cluster of dots, each of which represents the values of two variables

         the slope of the points suggests the direction of the relationship

         the amount of scatter inversely suggests the strength of the correlation

         little scatter indicates high correlation

 

Correlation and Causation

•           Correlation does not imply causation

•           Correlation is a necessary condition for causal inference

 

Three conditions for making a causal inference

•           Covariation of events: If one event causes the other, the two events must vary together (when one changes, the other must change also).

•           Time-order relationship: The presumed cause must occur before the presumed effect.

•           Elimination of plausible alternative causes: We accept a causal explanation only when other possible causes of the effect have been ruled out.

 

Illusory Correlation: the perception of a relationship where none exists

 

Causal Inferences

•           Scientific control requires that the effects of independent variables are isolated.

•           A confounding occurs when two potentially effective independent variables are allowed to vary together simultaneously — we cannot determine which variable caused the effect on the dependent variable.

•           When an experiment is free of confoundings, we can make a causal inference regarding the effect of the independent variable on the dependent variable.

 

Experiment: an investigator manipulates one or more factors (independent variables) to observe their effect on some behavior or mental process (the dependent variable)

         by random assignment of participants the experiment controls other relevant factors

Experimentation

 

Placebo: an inert substance or condition that may be administered instead of a presumed active agent, such as a drug, to see if it triggers the effects believed to characterize the active agent

 

Double-blind Procedure: both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo

 

Experimentation

         Independent Variable

         the experimental factor that is manipulated

         the variable whose effect is being studied

         Dependent Variable

         the experimental factor that may change in response to manipulations of the independent variable

         in psychology it is usually a behavior or mental process

In a correlation study, it is better to refer to:

            The perceived cause as the predictor

            The perceived effect as the criterion

 

Statistical Reasoning

         Mode: the most frequently occurring score in a distribution

         Mean: the arithmetic average of a distribution obtained by adding the scores and then dividing by the number of scores

         Median: the middle score in a distribution, half the scores are above it and half are below it

         Range: the difference between the highest and lowest scores in a distribution

         Standard Deviation: a computed measure of how much scores vary around the mean

         Statistical Significance: a statistical statement of how likely it is that an obtained result occurred by chance

 

Statistical Reasoning

•           You can never prove your hypothesis

•           You can only disprove that your findings are due to chance

•           The Null Hypothesis: the findings are due to chance

•           If you disprove the Null Hypothesis, your hypothesis is most likely true

•           Type I error: Claiming significant findings when there is no significance

•           Type II error: Not claiming significant findings when there really is significance.

 

Application

•           Psychologists apply their knowledge and research methods to improve people’s lives.

 

Frequently Asked Questions about Psychology

• Does behavior depend on ones culture?
• Is psychology free of value judgments?
• Can laboratory experiments illuminate everyday life?
• Is psychology potentially dangerous?
• Does behavior vary with gender?