Research Methodology

Wundt’s laboratory in Leipzig

Overview

• What is a scientific inquiry?• What are the types of studies in

psychology?• How is data collected?• How is data analyzed?

Why do we need a method?

• Allows– Common ground– Comparison between studies– Replication

What is a scientific inquiry?

4 basic principles– Description

• What is it?

– Prediction• When does it happen?

– Causality• What causes it no happen?

– Explanation• Why does it happen?

Theories, Hypotheses, and Data

Theory

Hypothesis

Data

Overview: stages in research

Formulate Hypothesis

Design Study

Collect Data

Analyze Data

Disseminate Results

Major Study Designs

• Experimental Design– Manipulate conditions

• Correlational Design– Study the relationships between

variables

• Descriptive Study– Observe and describe a phenomenon

• Manipulate independent variables• Measure dependent variables• Rule out confounds and alternative

interpretations

• Establish causal relationships

The Experiment

Operational definitions

• Explains how a variable will be manipulated and measured

• Example: an operational definition for the hypothesis ‘television leads to increased aggression’ is – the variable ‘television’ will be studied by exposing children to a horror film or a family film; aggression will be measured as the number of times a child hits another child during the 60-minute play period following the film. Alternatively, in a survey we can ask parents how many hours/week their kids watch TV and ask them to rate their aggressiveness. This is a different set of definitions

Hypothesis: Gum is bad for your teeth

• Gum: – the number consumed weekly by a

person

• Bad for teeth:– Option I: number of annual visits to the

dentists– Option II: number of dents/fillings

Hypothesis: Males are angry more often than females

• Gender– Ask respondents to indicate whether

they are males or females

• Angry– Expose them to an annoying situation

and measure facial expressions of anger

Hypothesis: Noise is bad for your hearing

• Noise– Average level of noise in work place– Number of hours/week spent in

environments louder than 90 dB-SPL

• Hearing– Thresholds for frequencies 250-8000 Hz

measured with an audiometer

Major components of an experiment

• Independent Variables (IV’s)• Dependent Variables (DV’s)• Random Sampling from

Representative Populations• Random Assignment to Conditions

or Treatments• Efforts to “Control” or minimize

extraneous/irrelevant factors

The correlational design

• Correlational studies tell us how variables are related or associated

• A correlation reflects the degree of association between two variables

Correlations are expressed with scatter plots

0 10 20 300

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0 10 20 300

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0.5

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1.5

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0 10 20 300

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X

Y

r = 1 r = -1

r= 0 r = 0.85

Correlations in ‘real life’

0

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0 2 4 6 8 10

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0 2 4 6 8 10

Working memory (score)

Fre

quen

cy d

iscr

imin

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n w

ith s

tand

ard

(JN

D,

%)

Fre

quen

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iscr

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nw

ithou

t st

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rd (

JND

, %

)

r = 0.73 r = -0.17

Problems with inferences based on correlations

• The third variable problem• The directionality problem

Example

• Directionality:– Does poor working

memory cause poor frequency discrimination of vice versa?

• Third Variable:– Both could be

affected by another factor (e.g. I.Q.)

0

20

40

60

80

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0 2 4 6 8 10

Working memory (score)

Fre

quen

cy d

iscr

imin

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n w

ith s

tand

ard

(JN

D,

%)

r = 0.73

Correlation ≠ Causation

יוני רוצה להיות יותר גבוה. כל יום אחרי •הלימודים הוא מתמתח ומתמתח בתקווה

חודשים הוא אכן גבוה יותר...6שיגבה. אחרי

האם המתאם בין התמתחות וגובה הוא חיובי •או שלילי?

מהי ההשערה המיחסת סיבתיות למתאם?•

אילו גורמים אחרים יכולים היו לגרום ליוני •לגבוה?

Correlation ≠ Causation

חוקר מעביר לכל תושבי חיפה מבחן •במתמטיקה. הוא מגלה שלאנשים גבוהים

יותר, יש ציונים גבוהים יותר.

האם המתאם בין גובה וציון במבחן הוא חיובי •או שלילי?

מהי ההשערה המיחסת קשר סיבתי למתאם?•

אילו גורמים אחרים יכולים להסביר את •המתאם?

Descriptive Studies

• Observe and classify behavior (observational studies)

• Natural observation• Participant observation

Data Collection Methods

• Observing• Asking questions• Case studies• Measures of performance

– RT, JND, score…

• Measures of brain activity• Research in animals• Ethical issues are involved in each

type!

Observing in natural settings

• Unobtrusive• Often used to study

– Primate behavior– Infants– Social situations (?)

Questionnaire Studies

• Open ended• Scales of measurement

Strongly agree --------------------------------------- Strongly disagree

Positive ------------------------------------------------ Negative

Often --------------------------------------------------- Never

Case Studies

Measures of Performance

• Researchers can measure performance to infer underlying mechanisms– Reaction time (RT)– Response accuracy (e.g. % correct)– Detection or discrimination threshold

Example I: Stroop

red

green blue

In what color is the word printed?

red

green blue

<Congruent Incongruent

? מודפסת כל מילהצבעבאיזה

אדום ירוק אפור כחול שחור צהוב ירוק כחול אדום

אדום כחול צהוב אפור ירוק כחול שחור אדום צהוב

שחור אדום צהוב אפור ירוק שחור כחול צהוב ירוק

? מודפסת כל מילהצבעבאיזה

אדום ירוק אפור כחול שחור צהוב ירוק כחול אדום

אדום כחול צהוב אפור ירוק כחול שחור אדום צהוב

שחור אדום צהוב אפור ירוק שחור כחול צהוב ירוק

Neutral Condition

▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲

▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲▲

Measuring brain activity non-invasively

• Direct measure of neural activity– EEG/ERP

• Indirect measures of neural activity– PET– fMRI

EEG/ERP

PET/MRI/fMRI – measures of metabolic activity

PET

MRI

Ethical issues in research

• Issues in conducting the study – informed consent etc’.

• More general issues – does the goal justify the means? Is it likely that those participating in the study are representative of those that stand to benefit from the outcomes?

Analyzing Data

• Evaluating the quality of the data– Reliability, validity and accuracy

• Summarizing the data– Descriptive statistics and correlations

• Determining if the results confirm a hypothesis– Inferential statistics

Reliability, Validity and accuracy

• Accuracy – the extent to which a measurement is free from error.

• Reliability – the extent to which a measure is stable and consistent over time and similar conditions

• Validity – the extent to which the data address the hypothesis in the way intended.

Descriptive statistics

• Central tendency• Variation• Correlation

Inferential statistics

• Do differences exist between two sets of numbers?

• Are these differences occurring by chance?