Science and Scientific Methods

  • Science = the systematic pursuit of knowledge through observation
  • Theory = a set of propositions meant to explain a class of observations o Goal to understand cause-effect relationships

o A good theory is falsifiable *allows for disconfirmation

  • Hypotheses = expectations/predictions about what should occur if a theory is true o Must be able to be systematically tested o Focus is on disproving rather than proving
  • Scientific approach requires that theory and hypothesis are stated precisely
  • Scientific observations must be replicable
  • Use assessments with strong validity and reliability to make replication possible Approaches to Research Psychopathology The Case Study
  • Case study = most familiar method of observing human behaviour, involves recording detailed info about one person at a time o Covers: developmental milestones, family history, medical history, educational background, employment history, marital history, social adjustment, peer/romantic relationships, personality, environment, etc.
  • Lack control and objectivity *validity is questionable
  • Clinician’s paradigm will shape the kinds of info reported in a case study
  • Uses: (1) provide rich description of a clinical phenomenon, (2) disprove an allegedly universal hypothesis, (3) generate hypotheses that can be tested through controlled research
  • Limitations: paradigm may influence observations, cannot rule out alternative explanations, cannot prove hypotheses
  • Case Study as a Rich Description:
    • Includes much more detail that other research methods o Provide detailed description of how a new intervention works  Case Study Can Disprove but Not Prove a Hypothesis:
    • Do not provide good enough evidence in support of a particular theory, don’t provide a way to rule out alternative hypotheses
    • Data collected from case study doesn’t allow to determine true cause of change  Using Case Study to Generate Hypotheses:
    • Helps to generate hypotheses for causes/treatments for disorders

The Correlational Method

  • Correlational method = variables are measured as they exist in nature
  • Different from an experiment during which a variable is manipulated

 

  • Rely on correlational method when cannot do an experiment for ethical reasons
  • 4 shapes: positive linear, negative linear, curvilinear, (increases in one variable have both increases and decreases in other), no relationship (straight line)  Measuring Correlation:
    • Step 1: obtain pairs of observations of the 2 variables in question o Step 2: determine correlation strength using correlation coefficient (r)

 Measures magnitude and direction of relationship  Higher the absolute value, the stronger the relationship  Statistical and Clinical Significance:

  • Statistical significance = asserts that a correlation was unlikely to have occurred by chance
    • Less than 5 in 100 (due to chance)
    • Alpha level = level of significance, p < .05
    • Higher r = less likely to have occurred by chance o Not statistically significant correlation does not provide evidence for an important relationship
  • Statistical significance influenced by size of relationship between variables AND sample size o Clinical significance = defined by whether a relationship between variables is large enough to matter
  • Problems of Causality:
    • Correlational designs do not allow determination of causality
    • Directionality problem = inability to determine which variable has causal significance o Causes must precede effects *temporal precedence
    • Longitudinal design = researcher tests whether causes are present before a disorder has developed
      • Studies participants over time o Cross-sectional design = the causes and effects are measured at the same point in time o High-risk method = only evaluates those at high risk for developing the target problem
      • Reduces the cost of longitudinal method o Third-variable problem = a third factor might have produced the correlation *confound* o Confound = a variable that produces changes in the 2 correlated variables  One Example of Correlational Research: Epidemiological Research:
    • Epidemiology = study of the distribution of disorders in a population o Data are gathered about rates of a disorder and its correlated in a large sample o Focuses on 3 features of a disorder:
      • 1) Prevalence – the proportion of people with disorder either currently or during their lifetime
      • 2) Incidence – the proportion of people who develop new cases of the disorder in some period, usually a year
      • 3)Risk factors – variables that are related to the likelihood of developing the disorder o Usually are correlational
    • Designed to be representative of the population
    • g. National Comorbidity Survey-Replication (large scale national survey, uses structured interviews to collect info on prevalence of several diagnoses)  Behaviour and Molecular Genetics:
    • Behavioural Genetics = methods to determine genetic predisposition (concordance) to psychopathology o 3 methods to uncover whether a genetic predisposition for psychopathology is inherited:  1) Comparison of members of a family, 2) comparison of pairs of twins, 3) investigation of adoptees
    • Family method = used to study genetic predisposition among family members
      • *Average number of genes shared by 2 blood relatives is known
      • 1st degree share 50%, 2nd degree share 25%
      • Concordance = co-occurrence or similarity of diagnosis
      • Index cases/probands = persons with the diagnosis in question o Twin method = monozygotic and dizygotic twins are compared
      • MZ (identical) – develop from 1 egg, genetically the same
      • DZ (fraternal) – develop from separate eggs, share 50% genes
      • When MZ concordance is higher than DZ concordance, characteristic is heritable o Adoptees method = studies children who were adopted and reared apart from their biological parents
      • Stronger evidence that a disorder is genetic if biological parents and child (who was not raised by bio parents) both have disorder
      • Cross-fostering = children are adopted and reared apart from their biological parents
    • Adoptive parent has a disorder
      • Molecular Genetics:
      • Association study = researchers examine the relationship between a specific allele and a trait/behaviour in the population *precise measurement
      • Genome-wide association studies (GWAS) = examines entire genome of a large group of people to identify variations between people
        • Require very large samples
        • Most often look for single nucleotide polymorphisms (SNPs)

The Experiment

  • Experiment = involves random assignment of participants to conditions, the manipulation of an IV and the measurement of a DV o Provides info about a causal relationship o Can evaluate treatment effectiveness o Experimental effect = differences between conditions on the DV  Internal Validity:

o Internal validity = the extent to which the experimental effect can be attributed to the IV o Control group = does not receive experimental treatment

 Shows effects in other group are due to IV o Random assignment helps ensure groups are similar on variables other than the IV  External Validity:

  • External validity = the extent to which results can be generalized beyond the study  Treatment Outcome Research:
  • Treatment outcome research = designed to address whether or not treatment works o Moderately positive effect of treatment (75% have some sort of improvement) o Treatment study should include:
    • Clear definition of the sample being studied e.g. description of diagnoses
    • Clear description of treatment being offered (in a manual)
    • Inclusion of a control/comparison treatment method
    • Radom assignment
    • Reliable/valid outcome measures
    • Large enough sample for statistical tests

o Randomized controlled trials (RCTs) = studies in which clients are randomly assigned to receive active treatment of a comparison

 IV is treatment, DV is patient outcome

  • Defining the Treatment Condition: The Use of Treatment Manuals:
    • Treatment manuals = detailed books on how to conduct a particular psyc treatment o Provide specific procedures for therapist to follow at each stage of treatment o Help therapist achieve greater uniformity in how they conduct therapy  Defining Control Groups:
    • No-treatment control group = allows researchers to test whether the mere passage of time helps as much as treatment does
    • Placebo = a pretend treatment, uses the power of suggestion, allows researchers to control for expectations of a symptom relief
    • Active-treatment control group = researchers compare new treatment against a well-tested treatment
    • Double-blind procedure = psychiatrists and patient are not told whether the patient received active medication or placebo *reduces bias in evaluating outcomes
    • Placebo effect = a physical or psyc improvement that is due to the patient’s expectations of help rather than to any active ingredient in a treatment  Defining a Sample:
    • Often there is a failure to include people from diverse cultural/ethnic backgrounds o People from minority groups are about half as likely to receive mental health treatment  Assessing How Well Treatments Work in the Real World:
    • Efficacy = whether a treatment works under the purest of conditions o Effectiveness = how well the treatment works in the real world  The Need for Dissemination of Treatment Outcome Findings:
    • Dissemination = the process of facilitating adoption of efficacious treatments in the community

 Most typically by offering clinicians guidelines about the best available treatments along with training on how to conduct those treatments  Analogue Experiments:

  • Analogue experiment = investigators attempt to create/observe a related phenomenon (an analogue) in the laboratory to allow more intensive study
  • Can obtain results with good internal validity, less external validity o Single-Case Experiments:

Single-case experiments = experimenter studies how one person responds to manipulations of the IV *high internal validity

  • Lack of external validity
  • Just because treatment works for one person doesn’t mean it will work for another

Reversal design (ABAB design) = participant’s behaviour must be carefully measured in a specific sequence (baseline, treatment intro, reinstatement of baseline, reintroduction of treatment)

  • No control group, but time period of baseline serves as control aspect

Integrating the Findings of Multiple Studies

  • Meta-analysis = thorough literature search, followed by putting together all the results into a common scale, using effect size
  • Criticism: sometimes include studies of poor quality