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The scientific method. Why psychology is a science. How do we know things. Think of something about the world that you just know is correct. Tornados never happen during the winter. Cooking at home is cheaper than eating out in a restaurant. - PowerPoint PPT Presentation
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How do we know things
Think of something about the world that you just know is correct
Cooking at home is cheaper than eating out in a restaurant
It’s better to punt on 4th down and long than try to get the 1st down
Tornados never happen during the winter
How we know things• Sources of declarative knowledge• Authority
9/10 dentists say flossing daily prevents cavity formation
Your mom tells you that you need good grades to get into college…
How we know things• Sources of declarative knowledge• Authority• Common sense/common knowledge
Swimming immediately after eating causes cramps
Playing violent video games causes violent behavior
How we know things• Sources of declarative knowledge• Authority• Common sense/common knowledge• Intuition
Food poisoning attributed to new/novel foods
Your cat ruins your stuff because he is mad at you
How we know things• Sources of declarative knowledge• Authority• Common sense/common knowledge• Intuition• Empiricism
How we know things• Sources of declarative knowledge• Authority• Common sense/common knowledge• Intuition• Empiricism
Not mutually exclusive
What is empiricism?• Knowledge must be grounded in observations• These observations are gathered through the use of the scientific method
Set of techniques that allow for the evaluation of ideas based on evidence
What is empiricism?• Knowledge must be grounded in observations• These observations are gathered through the use of the scientific method
Application of the scientific method
Generate theory
Articulate
hypothesis
Make predictio
nDesign study
Interpret results
Gather data
Share findings
theoretical
experimental
analytical
The scientific method
Generate theory
Articulate
hypothesis
Make predictio
nDesign study
Interpret results
Gather data
Share findings
theoretical
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena• Does NOT mean that the explanation is lacking evidence• Has different meanings in science compared to everyday language
The ‘theory’ of evolution
The ‘theory’ of gravity
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena• Does NOT mean that the explanation is lacking evidence• Has different meanings in science compared to everyday language
The ‘theory’ of gravity
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena
The burning sensation on your tongue after eating spicy foods is caused by chemicals in the peppers that bind to your taste buds
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena
• Hypothesis: idea about how the world operates that follows directly from a theory• Suggests some systematic, predictable pattern between phenomena
Ingesting foods that cause these chemicals to ‘let go’ of your taste buds will soothe the burning feeling on your
tongue
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena
• Hypothesis: idea about how the world operates that follows directly from a theory
• Prediction: forecast of how data will come out in a particular study• Specific only to the study in question, not generalized to other
situations
Theories, hypotheses, and predictions• Main components of the scientific method• Theory: a model that potentially explains a set of
observations/phenomena• Does NOT mean that the explanation is lacking evidence• Has different meanings in science compared to everyday language
• Hypothesis: idea about how the world operates that follows directly from a theory• Suggests some systematic, predictable pattern between phenomena
• Prediction: forecast of how data will come out in a particular study• Specific only to the study in question, not generalized to other
situations
general
specific
Theories, hypotheses, and predictions• Parental Investment Theory• Theory: The sex with smaller obligate parental investment will compete
for access to the sex with larger obligate investment
Trivers, 1972
Theories, hypotheses, and predictions• Parental Investment Theory• Theory: The sex with smaller obligate parental investment will compete
for access to the sex with larger obligate investment
Trivers, 1972
Theories, hypotheses, and predictions• Parental Investment Theory• Theory: The sex with smaller obligate parental investment will compete
for access to the sex with larger obligate investment
• Hypothesis: The higher investing sex will be more selective in choosing mating partners than the lower investing sex
• Prediction: men will be more likely to agree to sleep with a stranger than will women
Trivers, 1972 Clark & Hatfield, 1986
“Will you go to bed with me tonight?”
“Will you go out on a date with me tonight?”
Theories, hypotheses, and predictions
Women
Men
Go on a date tonight Go to bed with me tonight
~50% 0
~50% 75%
Theories, hypotheses, and predictions• The most important property of theories, hypotheses, and
predictions is that they are falsifiable• Must be some data that can disconfirm prediction
✔ ✖Get better
Too far gone for treatmentDieDie
Theories, hypotheses, and predictions• The most important property of theories, hypotheses, and
predictions is that they are falsifiable• Must be some data that can disconfirm prediction
Get what you imagine Don’t get what you imagine
✔ ✖Don’t get what you imagine
Didn’t believe hard enough
The scientific method
Generate theory
Articulate
hypothesis
Make predictio
nDesign study
Interpret results
Gather data
Share findings
experimental
Testing predictions• Need tools to measure the dimensions that are of interest
Imagine you are testing the hypothesis that stronger people are quicker to anger than weaker people
How would you measure strength? How would you measure anger?
Testing predictions• Need tools to measure the dimensions that are of interest• Require operational definitions – concrete, measureable descriptions of
the dimensions of interest in a study
• Good operational definitions:• do not rely on subjective judgments• make it easy for others to exactly replicate• have high reliability• have high construct validity
ReliabilityDoes a measure produce the same results when repeated under the same conditions?
“consistency”
Construct validityDoes a measure actually measure the dimension you want it to?
“accuracy”
• Reliability vs. validity
Operational definitionsCould be survey, physiological measurement, reaction time
task, etc
• Reliability vs. validity
240 lbs.(actual weight) average = 220.6
Mon Tues Weds Thurs Fri
221 219 220 221 222
Operational definitions
☐ validity
☐ reliability✗✓
• Reliability vs. validity
240 lbs.(actual weight) average = 240.8
Mon Tues Weds Thurs Fri
230 241 231 248 254
Operational definitions
☐ validity
☐ reliability✗✓
• Reliability vs. validity
240 lbs.(actual weight) average = 240.2
Mon Tues Weds Thurs Fri
240 241 241 240 239
Operational definitions
☐ validity
☐ reliability✓✓