Myers’ PSYCHOLOGY

Chapter 1 Thinking Critically with Psychological Science

James A. McCubbin, PhDClemson University

Worth Publishers

Critical ThinkingCritical thinking does not accept arguments and

conclusions blindly.

It examines assumptions,

discerns hidden values, evaluates

evidence and assesses

conclusions.The Amazing Randi

Courtesy of the Jam

es Randi E

ducation Foundation

Limits of Intuition and Common Sense

Hindsight Bias tendency to believe, after learning an

outcome, that one would have foreseen it

the “I-knew-it-all-along” phenomenonOverconfidence

we tend to think we know more than we do

Limits of Intuition

Personal interviewers may rely too much on their “gut feelings” when

meeting with job applicants.

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etty Images

How Do Psychologists Ask & Answer Questions?

Psychologists, like all scientists, use the scientific method to construct

theories that organize, summarize and simplify observations.

The Scientific Method

A theory is an explanation that integrates principles and organizes

and predicts behavior or events.

For example, low self-esteem contributes to depression.

Theory

A hypothesis is a testable prediction, often prompted by a theory, to enable

us to accept, reject or revise the theory.

People with low self-esteem are apt to feel more depressed.

Hypothesis

Research would require us to administer tests of self-esteem and

depression. Individuals who score low on a self-esteem test and high on a depression test would confirm our

hypothesis.

Research Observations

Research Process

Scientific Methods

Descriptive Method – describes something that is occurring (case studies, surveys, naturalistic observation)

Correlational Method gives information on whether there is a

relationship between two (or more) things Can NOT establish causation

Experimental Method – manipulates one variable to see if the change effects another variable Can establish causation

Description MethodsCase Study

A technique in which one person is studied in depth to reveal underlying behavioral principles.

Is language uniquely human?

Susan K

uklin/ Photo R

esearchers

SurveyA technique for ascertaining the self-

reported attitudes, opinions or behaviors of people usually done by questioning a

representative, random sample of people.

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w.lynnefeatherstone.org

Survey

Wording Effects Can change the results of a survey Should cigarette ads and pornography

be allowed on television? (not allowed vs. forbid)

False Consensus Effect tendency to overestimate the extent to

which others share our beliefs and behaviors

Survey Random Sampling

If each member of a population has an equal chance of inclusion into a sample, it is called a

random sample (unbiased). If the survey

sample is biased, its results are not valid.

The fastest way to know about the marble color ratio is to blindly transfer a

few into a smaller jar and count them.

Naturalistic Observation

Observing and recording the behavior of animals in the wild and recording self-seating patterns in a multiracial school lunch room constitute naturalistic observation.

Courtesy of G

ilda Morelli

Research StrategiesCorrelation Coefficient

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

Correlation coefficient

Indicates directionof relationship

(positive or negative)

Indicates strengthof relationship(0.00 to 1.00)

r = +.37

Scatterplots

Perfect positivecorrelation (+1.00)

No relationship (0.00) Perfect negativecorrelation (-1.00)

DataData showing height and temperament in people.

ScatterplotThe Scatterplot below shows the relationship between

height and temperament in people. There is a moderate positive correlation of +0.63.

Illusory CorrelationThe perception of a relationship where no

relationship actually exists. Parents conceive children after adoption.

Confirming evidence

Disconfirming evidence

Do not

adopt

Disconfirming evidence

Confirming evidence

Adopt

Do not conceiveConceive

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ewm

an Jr./ Photo Edit

Random Sequences

Your chances of being dealt either of these hands is precisely the same: 1 in 2,598,960.

Research StrategiesThree Possible Cause-Effect Relationships

(1)Low self-esteem

Depression

(2)Depression

Low self-esteem

Low self-esteem

Depression

(3)Distressing events

or biologicalpredisposition

could cause

could cause

could cause

or

or

and

Experimental Method

Like other sciences, experimentation is the backbone of psychological research.

Experiments isolate causes and their effects.

Exploring Cause and Effect

Many factors influence our behavior. Experiments (1) manipulate factors that interest us, while other factors are kept

under (2) control.

Effects generated by manipulated factors isolate cause and effect relationships.

Exploring Cause & Effect

Research Strategies

Operational Definition a statement of procedures

(operations) used to define research variables

Example-intelligence may be operationally

defined as what an intelligence test measures

Research Strategies

Replication repeating the essence of a research

study to see whether the basic finding generalizes to other subjects and circumstances

usually with different subjects in different situations

Research Strategies

Population all the cases in a group, from which

samples may be drawn for a studyRandom Sample

a sample that fairly represents a population because each member has an equal chance of inclusion

Research Strategies

Experiment the investigator manipulates one or more

factors (independent variables) to observe their effect on some behavior or mental process (the dependent variable) while controlling other relevant factors by random assignment of subjects

by random assignment of participants the experiment controls other relevant factors

Research Strategies

Double-blind Procedure both the subject and the research staff are

ignorant (blind) about whether the subject has received the treatment or a placebo

commonly used in drug-evaluation studiesPlacebo

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

Research Strategies

Experimental Condition the condition of an experiment that

exposes subjects to the treatment, that is, to one version of the independent variable

Control Condition the condition of an experiment that

contrasts with the experimental treatment serves as a comparison for evaluating the

effect of the treatment

Research Strategies

Random Assignment assigning subjects to experimental and control conditions by chance

minimizes pre-existing differences between those assigned to the different groups

An independent variable is a factor manipulated by the experimenter. The effect of the independent variable is the

focus of the study. For example, when examining the effects of

breast feeding upon intelligence, breast feeding is the independent variable.

Independent Variable

A dependent variable is a factor that may change in response to an independent variable. In psychology, it is usually a

behavior or a mental process.

For example, in our study on the effect of breast feeding upon intelligence,

intelligence is the dependent variable.

Dependent Variable

ComparisonBelow is a comparison of different research methods.

Statistical Reasoning

Statistical procedures analyze and interpret data allowing us to see what the unaided eye misses.

Composition of ethnicity in urban locales

Describing DataA meaningful description of data is important in research. Misrepresentation may lead to incorrect

conclusions.

Statistical ReasoningMode

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 scoresMedian

the middle score in a distribution half the scores are above it and half are below it

Statistical ReasoningA Skewed Distribution

15 20 25 30 35 40 45 50 90 475 710

70

Mode Median Mean

One Family Income per family in thousands of dollars

Normal Curve

A symmetrical, bell-shaped curve that describes the distribution of many types of data (normal distribution). Most scores fall near the mean.

Measures of VariationRange: 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 ReasoningStatistical Significance

a statistical statement of how likely it is that an obtained result occurred by chance

Making Inferences

When sample averages are reliable and the difference between them is relatively large, we say the difference has statistical significance. It

is probably not due to chance variation.

For psychologists this difference is measured through alpha level set at 5 percent.

When is a Difference Significant?

FAQQ5. Is psychology free of value judgments?

Ans: No. Psychology emerges from people who subscribe to a set of values and judgments.

© Roger Shepard

FAQ

Q4. Is it ethical to experiment on people?

Ans: Yes. Experiments that do not involve any kind of physical or psychological harm beyond normal levels encountered in daily

life may be carried out.Milgram Experiment Replication