Copyright © Allyn & Bacon 2006 by Pearson Education. Reproduced by permission of the publisher. Further reproduction is prohibited without written permission from the publisher. This multimedia product and its contents are protected under copyright law. The following are prohibited by law: Any public performance or display, including transmission of any image over a network; Preparation of any derivative work, including the extraction, in whole or in part, of any images; Any rental, lease, or lending of the program. The Science of Psychology
Copyright © Allyn & Bacon 2006 What Makes Psychology a Science? Two premises of modern-day science 1. Empiricism Acquiring information through careful observation 2. Theory development A psychological theory is a collection of interrelated ideas and observations that describe, explain, and predict behavior and mental processes
Copyright © Allyn & Bacon 2006 What Makes Psychology a Science? A. Three scientific principles 1. Objectivity Evaluating research and theory on their own merits 2. Systematic Observation Having a plan for gathering data 3. Replication Confirming findings through repeated observations
Copyright © Allyn & Bacon 2006 What Makes Psychology a Science? B. Scientific Method in Psychology 1.State the problem 2.Develop a hypothesis An educated guess 3.Design a Study Identify variables and responses to examine Decide how to define and measure the variables of interest
Copyright © Allyn & Bacon 2006 Scientific Method in Psychology 1. State the problem 2. Develop a hypothesis 3. Design a Study 4. Collect and Analyze Data 5. Draw Conclusions and Report Results
Copyright © Allyn & Bacon 2006 What Research Methods do Psychologists Use? A. The Experimental Method –Systematically manipulating variables and observing the effects Can establish a cause and effect relationship
Copyright © Allyn & Bacon 2006 The Experimental Method Two types of variables 1. Independent variable (IV) Intentionally manipulated by the experimenter 2. Dependent variable (DV) Behavior or response that is expected to change because of the IV – this is the factor that is being observed and studied Outcome that depends on the IV
Copyright © Allyn & Bacon 2006 The Experimental Method Operational Definition –How will the variable be measured? Participants in the study must be alike on all variables except the IV Participants are randomly assigned to groups –Experimental group receives the treatment –Control group does not receive the treatment Also known as the comparison group
Copyright © Allyn & Bacon 2006 The Experimental Method If the groups are comparable, you can conclude that the manipulation of the independent variable caused changes in the dependent variable If the groups are not comparable, extraneous variables may “confound the results”
Copyright © Allyn & Bacon 2006 What Research Methods Do Psychologists Use? B. Descriptive Methods –Describe relationships and events –Do not manipulate variables –Therefore, can NOT make inferences about cause and effect
Copyright © Allyn & Bacon 2006 Descriptive Methods: 5 Types 1.Case studies –Intensive study of one case 2.Naturalistic Observation –Observation of behavior in a naturally occurring situation 3.Surveys –Interviews and questionnaires –Sample must be representative of the population
Copyright © Allyn & Bacon 2006 Descriptive Methods 4.Correlational Studies –Looks for relationships between two variables –Because the variables are not controlled, you can NOT infer causation from correlational studies
Copyright © Allyn & Bacon 2006 Descriptive Methods 5.Ex Post Facto Studies –Describe differences between groups of participants that differ naturally on a variable such as ethnicity or gender Variable is NOT manipulated, so these are not experiments
Copyright © Allyn & Bacon 2006 How Do Psychologists Evaluate Research Findings? Using statistics –Statistics is a branch of mathematics that deals with classifying and analyzing data –Psychologists use two types: –Descriptive and Inferential
Copyright © Allyn & Bacon 2006 Using Statistics 1. Descriptive Statistics Averagei.Mean ii.Median iii.Mode Middle Score Most common score a.Measures of Central Tendency
Copyright © Allyn & Bacon 2006 Descriptive Statistics Measures of Variability Range Highest minus lowest score
Copyright © Allyn & Bacon 2006 STANDARD DEVIATION A measure of the variability of the scores. How closely do the scores cluster around the mean?
Copyright © Allyn & Bacon 2006 Descriptive Statistics Correlation Coefficients –Numerical way to describe the relationship between two variables –Ranges from –1 to +1 –Positive correlation coefficients indicate that As one variable increases, the other increases As one variable decreases, the other decreases
Copyright © Allyn & Bacon 2006 Correlation Coefficients Negative correlation coefficients indicate that –As one variable increases, the other decreases Closer to |1| (-1 or +1), the stronger the relationship Closer to 0, the weaker the relationship
Copyright © Allyn & Bacon 2006 Using Statistics 2. Inferential Statistics –Used to determine if research results are significant –Significant differences are statistically unlikely to occur because of chance alone
Copyright © Allyn & Bacon 2006 How Do Psychologists Evaluate Research Findings ? Avoiding Bias in the Research Process –Several different types of bias: 1. Ethnocentrism –A tendency to believe one’s group is the standard against which other groups should be judged –Implies the superiority of one’s own group –Leads to distortion and prejudice
Copyright © Allyn & Bacon 2006 Avoiding Bias 2.Race, ethnicity, culture, and social class –Ethnicity is a more valuable construct than race –Behavior must be viewed as occurring in a cultural context –Cultures can be individualist or collectivist Individualist cultures stress personal goals and value individual freedom Collectivist cultures stress group needs –Social class (education, income, and occupational status or prestige) also affects behavior
Copyright © Allyn & Bacon 2006 Avoiding Bias 3. Gender –Women and men may react differently in the same situation 4. Sexual orientation –Differs from sexual behavior –Three sexual orientations are recognized –Homosexual –Heterosexual –Bisexual –Unrelated to psychological maladjustment –Homophobia –Heterosexism
Copyright © Allyn & Bacon 2006 Avoiding Bias 5. Age –Older people are a growing percentage of the population 6. Disability
Copyright © Allyn & Bacon 2006 Avoiding Bias 7. Diversity Within and Between Groups –There are usually more differences within a group than between groups –Generalizations are virtually impossible –Therefore, psychologists emphasize individuals
Copyright © Allyn & Bacon 2006 Ethical Principles Rules concerning proper conduct in research Human participants: –Must give informed consent –Cannot be coerced –Can decline to participate at any time Information is kept confidential Debriefing: A post-experimental interview that explains the study Deception can only be used if it has overriding scientific, educational, or practical value
Copyright © Allyn & Bacon 2006 Point – Counterpoint Should Nonhuman Animals Be Used in Research? No Animals are subjected to painful treatments under the assumption they are “lesser” than humans Information may not be generalizable to humans Yes Research with animals has allowed for important studies that would be impossible with humans The information from such studies is directly relevant for improving people’s lives What do you think?