The Need for Psychological Science Psychologists, like all scientists, use the scientific method to construct theories that organize observations and imply testable hypotheses

The Need for Psychological Science  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

The Need for Psychological Science The biases and errors of people’s everyday judgments illustrate the need for: 1. Skepticism 2. Humility 3. Critical Thinking

The Need for Psychological Science  Critical Thinking  thinking that does not blindly accept arguments and conclusions  examines assumptions  discerns hidden values  evaluates evidence The Amazing Randi--Skeptic

Goals of Psychology Describe Explain Predict Control behavior and mental processes

Scientific Method Formulate testable questions  Develop hypotheses Design study to collect data  Experimental  Descriptive Analyze data to arrive at conclusions  Use of statistical procedures  Use of meta-analysis Report results  Publication  Replication

The Need for Psychological Science

Experimentation

Description Psychologists describe behavior using case studies, surveys, Psychologists describe behavior using case studies, surveys, and naturalistic observation and naturalistic observation

Defined as a thorough, exhaustive study of a person. It includes personal, educational, family and work histories. Advantage : A wealth of background information about one person Disadvantages : Information cannot be generalized to others; also, researcher’s biases can influence subject’s behavior. The Case Study Method

Description Case Study  Psychologists study one or more individuals in great depth in the hope of revealing things true of us all Is language uniquely human?

The Survey Method Defined as asking questions of a carefully selected group of people and tabulating their answers. Information can be gathered about feelings, opinions, and behavior patterns. Interpretation difficult; sample may not be representative. Advantage: Disadvantages:

Description  Survey  technique for ascertaining the self-reported attitudes or behaviors of people  usually by questioning a representative, random sample of people  Wording Effects  Even subtle changes in the order or wording of questions can have major effects.

Samples and Sampling Sample Sample selected segment of the population Representative sample Representative sample closely parallels the population on relevant characteristics Random selection Random selection every member of larger group has equal change of being selected for the study sample

Evaluating Media Reports Be skeptical of sensationalist claims Be skeptical of sensationalist claims Goal of “shock” media is ratings Goal of “shock” media is ratings Look for original sources Look for original sources Separate opinion from data Separate opinion from data Consider methodology and operational definitions Consider methodology and operational definitions Correlation is not causality Correlation is not causality Skepticism is the rule in science. Skepticism is the rule in science.

Description

Description  If marbles of two colors are mixed well in the large jar, the fastest way to know their ratio is to blindly transfer a few into a smaller one and count them

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

The Naturalistic Observation Method Defined as observing behaviors in their natural settings. Disadvantages: Researcher cannot interact with the subject. Researcher may interpret subject’s responses incorrectly.

Description  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

Correlation  Correlation 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 direction of relationship (positive or negative) Indicates strength of relationship (0.00 to 1.00) r = +.37

Coefficient of Correlation Numerical indication of magnitude and direction of the relationship between two variables –Positive correlation— two variables vary systematically in the SAME direction –Negative correlation— two variables vary systematically in OPPOSITE directions

Correlation Perfect positive correlation (+1.00) No relationship (0.00)Perfect negative correlation (-1.00) Scatterplots, showing patterns of correlations

Correlation Scatterplot-- a graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the degree and direction of the relationship between the two variables. Correlation Coefficient-- a statistical measure of how strongly related any two sets of scores are. It can range from (a perfect correlation) through 0.00 (the scores are unrelated) to (a perfect negative correlation). Scores with a positive correlation increase and decrease together. A negative correlation coefficient indicates that one score falls as the other rises. Regression toward the mean— falling back to the norm. It can fuel the illusion that uncontrollable events correlate with out actions.

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 suggests the strength of the correlation  little scatter indicates high correlation  also called a scattergram or scatter diagram

Correlation Three Possible Cause-Effect Relationships (1) Low self-esteem Depression (2) Depression Low self-esteem Depression (3) Distressing events or biological predisposition could cause or and

Correlation Scatterplot of Height and Temperament Temperament scores Height in inches

Correlation Height and Temperament of 20 Men Subject Height in Inches Temperament Subject Height in Inches Temperament

Illusory Correlation  Illusory Correlation  the perception of a relationship where none exists ConceiveDo not conceive Adopt Do not adopt disconfirming evidence confirming evidence disconfirming evidence confirming evidence

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

Experimentation  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

The Need for Psychological Science  Theory  an explanation using an integrated set of principles that organizes and predicts observations  Hypothesis  a testable prediction  often implied by a theory

X amount of sleeping pills helps the healthy person with insomnia to sleep better. Sleeping pills Experimental Group # of people who had restful nights Placebos Independent Variable Groups Dependent Variable # of people who had restful nights The hypothesis proves to be incorrect. People taking the sleeping pill over a period of days had more insomnia than before. They had less restful sleep than the people in the control group. Hypothesis Control Group

The Need for Psychological Science  Operational Definition  a statement of procedures (operations) used to define research variables  Example-  intelligence may be operationally defined as what an intelligence test measures  Testing the effects of vitamin C on the health of students could be measured by the number of colds experienced during the month.

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

Experimental Design Random sample— every member of the population being studied should have an equal chance of being selected for the study Random sample— every member of the population being studied should have an equal chance of being selected for the study Random assignment— assigning subjects to experimental and control conditions by chance. Random assignment— assigning subjects to experimental and control conditions by chance. Randomization helps avoid false results Randomization helps avoid false results

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  commonly used in drug-evaluation studies

Experimentation  Experimental Condition  the condition of an experiment that exposes participants 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

 Basic Ethical Guidelines for Psychological Researchers Do no harm. Accurately describe risks to potential subjects. Ensure that participation is voluntary. Minimize any discomfort to participants. Maintain confidentiality. Do not unnecessarily invade privacy. Remove any misconceptions caused by deception (debrief). Provide results and interpretations to participants. Treat participants with dignity and respect.

The Need for Psychological Science  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

Research Strategies  Design of the subliminal tapes experiment Subliminal tape content Self-esteemMemory Self-esteem Tape label

Distributions Percentile Rank--the percentage of scores that fall below a particular score. You can never have a percentile rank of 100 because you are part of that 100. (You can’t exceed yourself!) Bar Graphs (histograms)-- Percentile ranks and distributions can be represented in bar graphs or histograms. Bar Graphs (histograms)-- Percentile ranks and distributions can be represented in bar graphs or histograms.

Frequency Distribution Frequency Distributions 1. What are they? – Tables – Graphs Bar Histogram

Histogram

Statistical Reasoning Our Brand Brand Brand Brand X Y Z 100% Percentage still functioning after 10 years Brand of truck

Statistical Reasoning Our Brand Brand Brand Brand X Y Z 100% Percentage still functioning after 10 years Brand of truck

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

Median Separates the upper and low half of distribution Separates the upper and low half of distribution 1) mean and median not necessarily equal 2) median much less sensitive to extremes

Mode Most common value Most common value Always present in the distribution Always present in the distribution May be more than one mode May be more than one mode Used mainly with nominal data Used mainly with nominal data Plays minor role in statistical inference Plays minor role in statistical inference

Statistical Reasoning A Positively Skewed Distribution Mode Median Mean One Family Income per family in thousands of dollars

Skewed Distributions Positive Mean > Median Negative Mean < Median

Statistical Reasoning  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

Variation Normal Curve--a bell-shaped curve that describes the normal distribution of many types of data. Most scores fall near the mean and fewer and fewer fall near the extremes. In a normal curve the mean, median and mode are all near the middle. Normal Curve--a bell-shaped curve that describes the normal distribution of many types of data. Most scores fall near the mean and fewer and fewer fall near the extremes. In a normal curve the mean, median and mode are all near the middle.

Statistical Inference When is it safe to generalize from a sample? 1.Representative Samples are better than biased samples. 2.Less-variable observations are more reliable than those that are more variable. 3.More cases are better than fewer. Larger samples are better than smaller ones. 4.As the size of a sample increases, the size of the standard deviation is most likely to decrease

When is a difference significant? When sample averages are reliable and the difference between them is large we say the difference has statistical significance (it reflects a real difference not due to chance or variation between samples). When sample averages are reliable and the difference between them is large we say the difference has statistical significance (it reflects a real difference not due to chance or variation between samples).

Longitudinal studies Longitudinal studies

Frequently Asked Questions about Psychology Is psychology free of value judgments? Is psychology free of value judgments? *Topic of investigation *Research methods *Explanatory theories

Frequently Asked Questions about Psychology Can laboratory experiments illuminate everyday life? Can laboratory experiments illuminate everyday life?

Frequently Asked Questions about Psychology Does behavior depend on ones culture? Does behavior depend on ones culture?  Culture--the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next

Frequently Asked Questions about Psychology Does behavior vary with gender? Psychologists report gender differences in our risk of: 1. Alcoholism 2. Depression 3. Eating disorders

Frequently Asked Questions about Psychology Why do psychologists study animals? Why do psychologists study animals? Is it ethical to experiment on animals? Is it ethical to experiment on animals? Coile & Miller’s analysis of animal research revealed that psychologists DID NOT: 1. Shock animals with extremely painful shocks that caused them to die 2. Allow animals to die slowly from hunger and thirst 3. Place animals in isolation chambers until they were driven insane

Ethical Guidelines Is it ethical to experiment on people? Informed consent and voluntary participation Informed consent and voluntary participation Students as participants Students as participants Use of deception Use of deception Confidentiality of records Confidentiality of records Information about the study and debriefing Information about the study and debriefing

Frequently Asked Questions about Psychology Is psychology potentially dangerous? Is psychology potentially dangerous?