© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Abnormal Psychology, Eighth Edition by Gerald C. Davison and John M. Neale Lecture notes created by Paul J. Wellman, Texas A&M University PowerPoint  Lecture Notes Presentation Chapter 5 Research Methods in the Study of Abnormal Behavior Ch 5

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e The Scientific Method Science is the pursuit of systematized knowledge through observation –Science is both a method and a goal Scientific propositions must be –Stated clearly and precisely –Testable (allows for disconfirmation) Tests of hypotheses must be reproducible by other scientists Ch 5.1

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e The Role of Theory in Science A theory is a set of propositions meant to explain a class of phenomena –Propositions are causes, the phenomena are the effects induced by the causes Theories often lead to the generation of hypotheses that confirm or disconfirm the theory Theories are constructed by scientists Ch 5.2

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Research Methods of Abnormal Psychology A case study includes historical and biographical information on a single person Case studies are used to –provide a detailed description of a rare phenomenon –disconfirm allegedly universal aspects of a particular theoretical proposition –generate new research hypotheses Ch 5.3

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Epidemiological Research Epidemiology is the study of the frequency and distribution of a disorder in a population –Prevalence is the proportion of a population that has a disorder at any given time –Incidence refers to the number of new cases that occur during some time period –Risk factors are conditions that increase the likelihood of developing the disorder Ch 5.4

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Lifetime Prevalence Rates of Selected Diagnoses Major depressive episode Manic episode Simple phobia Antisocial personality disorder DiagnosisMaleFemaleTotal Ch 5.5

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e The Correlational Method The correlational method examines the relationship between or among two or more variables The variables are assessed as they exist in nature (no experimental manipulation) Correlational studies seek to determine the magnitude and direction of a relationship among variables –E.g. stress and body weight Ch 5.6

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e The Correlation Coefficient The relationship between values of two variables can be quantified by the correlation coefficient “r” –r can take on values between +1.0 and -1.0 –sign of r indicates direction of relationship –size of r indicates strength of relationship Ch 5.7

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Scatter Diagrams Ch 5.8

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Statistical Significance A correlation of zero implies no relationship between 2 variables –Chance factors can result in a correlation different from zero Statistical significance tests examine the likelihood that a correlation is different from zero simply because of chance variation –The probability of a chance finding is set at p < 0.05 (5 in 100 or less) Ch 5.9

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Problems of Causality in Correlational Research The directionality problem: one cannot tell the direction of causation from a correlation coefficient –Correlation does not imply causation (involvement of 3rd variable) –Causation does imply correlation (correlational research can be used to disconfirm a predicted causal relation) Ch 5.10

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e The Experiment The experiment allows for determination of a causal relation between two variables An experiment involves –random assignment of subject to experimental conditions –manipulation of an independent variable (IV: believed to be a causal variable) –measurement of a dependent variable (DV is assumed to the controlled by the IV) Ch 5.11

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Overview of an Experiment Determine the hypothesis: –Cause ----> Effect Define the variables of the experiment –IV, DV Subjects are randomly assigned to treatments Evaluate the dependent measures –Statistical significance testing: are the differences between group due to chance? Ch 5.12

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Validity Issues Internal validity assesses whether the differences between groups is due to the influence of the IV or some other factor –Experimenter uses a control group that is treated identically to the experimental group, with the exception of receiving the treatment Confounds are variables that complicate experimental interpretation –E.g. passage of time or life events Ch 5.13

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Placebo Effects A placebo effect reflects a therapy effect due to the expectations of the person rather than a treatment effect –Placebo effects can exert significant change and can endure for some time Experimenters employ double-blind procedures to control for placebo effects –Neither the subject or the experimenter know which group the subject is in; the subject is led to believe they are receiving a treatment Ch 5.14

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e External Validity External validity refers to the extent to which the results of an experiment can be generalized beyond the conditions of the experiment –Results from laboratory studies may generalize to more natural conditions –Results from animal studies may generalize to that of humans Ch 5.15

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Analogue Experiments Many key issues in abnormal psychology cannot be examined in experiments due to ethical concerns –Effects of stress on likelihood of developing schizophrenia Analogue studies examine a related phenomenon in the laboratory –Analogue is related to the disorder of interest –The participants are similar to those who have the disorder Ch 5.16

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Single-Subject Research Designs Single-subject research involves the sequential application of control and experimental variables for a single person –Reversal design involves measurement of a behavior during baseline (A), during treatment (B), during baseline (A) and again during treatment (B) ABAB design Ch 5.17

© 2000 John Wiley & Sons, Inc. Davison and Neale: Abnormal Psychology, 8e Copyright Copyright 2000 by John Wiley & Sons, New York, NY. All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission of the copyright owner.