The document discusses the scientific foundations of psychology, emphasizing the importance of psychological science over intuition, highlighting biases such as hindsight bias and overconfidence. It explains various research methods, including experimental and non-experimental approaches, and stresses the necessity of operational definitions, random sampling, and ethical considerations in research. Additionally, it covers data analysis techniques, including measures of central tendency and variability, and the interpretation of statistical significance in research outcomes.

1. Scientific Foundations of
Psychology: Part 2

2. The Need for Psychological
Science

15. Intuition
The ability to understand something
immediately, without the need for
conscious reasoning
“Going with your gut”

16. Overestimating Our Intuition
Hindsight Bias
• The tendency to believe, after
learning an outcome, that we would
have foreseen it.
•I knew it all along

17. Hindsight Bias
After a couple breaks up, friends say “they were
never a good match.”
Think critically….
Why didn’t someone tell the couple they were a poor
match while they were dating?
Were they really a poor match?
What would we say if the couple went on to marry?
“They are perfect together?”

18. Hindsight Bias
We knew it all
along
After we lose the Friday night
football game, fans say “that
stupid move by the coach lost
us the championship!”
We knew it all
along
After we win the Friday night
football game, fans say “that
gutsy move by the coach was
a great call!”

19. Hindsight Bias
Separation weakens
romantic attraction.
When presented with the
statement above, most find
this “true” statement
unsurprising.
“Out of sight, out of mind”
Separation strengthens
romantic attraction.
When presented with the
statement above, most find
this “true” statement
unsurprising.
“Absence makes the heart
grow fonder”

20. Overestimating Our Intuition
Overconfidence
• Misjudge abilities and knowledge
• Think you know more than you do

21. Overconfidence
British expert
group
evaluating the
invention of the
telephone
“The telephone may be
appropriate for our American
cousins, but not here, because
we have an adequate supply of
messenger boys”
Popular
Mechanics,
1949
“Computers in the future may
weigh no more than 1.5 tons”

22. Overconfidence
percent confidence
80%
The degree of confidence
expressed by experts
regarding 27,000
outcomes in world events.
percent correct
40%
The amount of time those
predictions were right.

23. TRY IT
If you flip a coin 6 times… which of the following sequences
of heads (H) and tails (T) is most likely?
HHHTTT
HTTHTH
HHHHHH

24. Overestimating Our Intuition
Perceiving Patterns in Random
Events
–(Illusory correlation)
In our natural eagerness to make sense of an
unpredictable world, we are prone to perceive
patterns.

25. Perceived Order in Random Events
Most people believe HTTHTH is most likely.
Actually…
all 3 are equally likely … or unlikely.
“With a large enough sample, any outrageous thing is
likely to happen.”
Persi Diaconis and
Frederick Mosteller,1989
statisticians

26. How Do Psychologists Ask
and Answer Questions?

27. Ethics in Research (IRB)
–Informed consent (assent)
–Protect from unnecessary harm and
discomfort
–Maintain confidentiality
–Debriefing

28. Ethics in Research
–Deception/Confederates

29. The Scientific Method

30. Theory vs. Hypothesis
theory
using our observations to
explain behavior
hypothesis
predictions about behavior
that can be tested

31. Let’s consider this hypothesis:
When sleep deprived, people will remember less
from the day before.
What do we mean by sleep deprived?
2 hours fewer than usual? No sleep at all for a week?
How will we know someone “remembers less”?
Less than what? Less than whom?

32. Operational Definitions
A carefully worded statement of
the exact procedures (operations)
used in a research study.

33. Operational Definitions
Clearly explains how the variables are measured so
other researches can replicate the experiment and
get similar results..

34. Operational Definitions
How would you measure human intelligence?

35. Operational Definitions
sleep deprived
We’ll define that as 2 fewer
hours than the subject’s normal
amount of sleep.
remember less
We can compare the number of
words correctly recalled after a
normal night of sleep with that of
a shortened sleep night.

36. Operational Definitions
operational
definition
If we specifically define what we
mean by
“sleep loss” or “caffeine” or
“smiling”…
replication
…we can repeat the experiment
precisely as it was conducted the
first time.
Replication is confirmation.

37. TRY IT
Plants that are exposed to music show
increased growth.

38. TRY IT
Plants that are exposed to music show
increased growth.
What type of music will you
play?
How loud will you play the
music?
How long will the plants be
exposed to music?
What types of plants will
you use?
How will you measure
growth?
How often will you take
your measurements?

39. TRY IT
Eating junk food causes weight gain.

40. TRY IT
Eating junk food causes weight gain.
How do you define junk
food?
What brands and
products will the subjects
consume?
How much and how
often will the subjects
eat?
How will you measure
weight gain?
What weight ranges are
the subjects in at the
start of the experiment?
How active are the
participants?
Men or women?

41. Non-Experimental Research
Case Study
Naturalistic Observation
Meta-analysis
Correlation (survey)

42. Non-Experimental Research
• Provide data for further research
-Quantitative
– Central tendency (mean, median, mode)
– Variation (range, standard deviation)
– Correlation (relationships between variables)
– Qualitative
• Subjective descriptions (interviews, observations)
DOES NOT EXPLAIN BEHAVIOR (NO CAUSE/EFFECT)

43. Experimental Research
• Infer cause and effect
-Statistical significance

44. Case Study
one individual
or group is studied in-
depth

45. Case Study
one
individual
 Patient H.M.
 Phineas Gage
one group
 University of Tennessee
women’s basketball team
 Prison inmates in a group
therapy study

46. Case Study
Strengths
 Examine rare or unusual behavior.
 Large amount of qualitative data.
 Suggestions for further study.

47. Case Study
Limitations
 May not be generalizable to the larger group.
 No control group for comparison
 Researcher bias
 Cannot determine cause and effect
 Atypical cases can be misleading

48. Naturalistic Observation
• Research without interference
Observe
and record behavior in
naturally occurring situations
without trying to manipulate or
control the situation.

49. Naturalistic Observation
Strengths
 Subjects behave “normally” outside of a
lab setting.
 Data collection is unobtrusive (doesn’t
disturb the subject).

50. Naturalistic Observation
Cannot determine cause and effect.
Observations by researchers may be
subjective.
No consent
Limitations

51. Counting positive and negative words in 504 million
Twitter messages from 84 countries

52. Survey
Self-reported
attitudes or behaviors of a
particular group
Usually questioning a
representative,
random sample of the group.

53. Survey Examples
Half of all Americans reported experiencing more happiness
and enjoyment than worry
and stress on the previous day (Gallup, 2010).
1 in 5 people across 22 countries report believing that alien
beings have come to Earth and now walk among us disguised as
humans (Ipsos, 2010).
68 percent of all humans—some 5 billion people—say that
religion is important in their daily lives (Diener et al., 2011).

54. Survey
Strengths
 Able to take a “quick pulse” of
people’s beliefs, behaviors or
opinions
 Cheap; Easy; Quick

55. Survey
Limitations
 Response bias-social desirability effect
 Wording effects can skew the outcomes
 Acquiring a random sample is difficult
 Cannot determine cause and effect

56. Wording Effects
Do you support the government
providing financial aid to people
who cannot find employment?

57. Wording Effects
Do you support the government
giving assistance to people who
are too lazy to work?

58. Wording Effects
90% of the public is employed
vs.
10% of the public is unemployed

59. Wording Effects
99% fat free yogurt
vs.
1% fat yogurt

60. Survey
Population
All those in a group
being studied,
from which samples
may be drawn.
Random Sample
Each member
has an
equal chance
of inclusion.

61. Representative Sample
Roughly the same distribution
of demographic qualities in it as
the population as a whole.

62. Representative Sample
If the student population at the school is 25%
Hispanic students, 30% Asian students, 35%
African American students, and 10% Caucasian
students, your sample should reflect those
percentages.
If your school is 50% male and 50% female,
equal numbers of both sexes should be
represented in your sample.

63. Convenience Sample
Take what you can get (who’s
easily accessible)
Not a good representation of the
population

64. Sampling Bias in surveys:
Survey finds 94% of people support federal funding
of the space program.
What questions should I ask?
Where was the
survey conducted?
Who was in the
sample?

65. Why is the survey location a possible
problem?
Survey finds 94% of people support federal funding
of the space program.
Where was the survey conducted? How could each
of these survey locations change the results?
Washington
D.C.
At a
screening
of Star
Wars
In a small
Iowa town
At a
political
event

66. Why is the survey population a
possible problem?
Survey finds 94% of people support federal funding
of the space program.
Who was in the survey sample? Do these
subgroups have different goals? Priorities?
Naval
aviators
Students at
a technical
college
Prison
inmates Teenagers

67. Meta-analysis
Examines the results of multiple
studies on a topic to draw general
conclusions.
It's a way to synthesize data from many
studies to gain a more comprehensive
understanding of a subject.

68. Meta-analysis
https://graziano-raulin.com/supplements/e
xamples/meta-analysis.htm

69. Meta-analysis Pros
• By combining data from
multiple studies, meta-analysis
allows for a larger sample size,
which leads to increased
statistical power to detect
meaningful effects.

70. Meta-analysis Cons
• It can be influenced by publication bias
and heterogeneity among studies.
Publication bias refers to the tendency
of researchers and journals to publish
studies with positive results, while
suppressing or not publishing studies
with negative or inconclusive results.

71. Correlation
How well does A predict B
• Relationships
• NOT cause and effect

72. Positive Correlation
Both variables go up together or
down together

73. Positive Correlation
Ex. Hours at work increase paycheck increases.
Ex. Caffeine consumption increase alertness
level increases.
Ex. Time studying decreases grade decreases.

74. Negative Correlation
When one variable goes up the other
goes down.

75. Negative Correlation
Ex. As the minutes I spend on the elliptical
increase my weight decreases.
Ex. As my age increases the number of hairs on
my head decreases.
Ex. As temperature decreases the layers of
clothes I wear increases.

76. Correlations
The correlation coefficient: a statistical index of the
relationship between two variables.
Scatterplot of data points

77. Correlation

78. Correlation

79. Correlation

80. Correlation

81. Correlation

82. Correlation

83. Correlation

84. Correlation

85. Correlation

89. TRY IT
Which of the correlation coefficients below
expresses the strongest relationship between
two variables?
+.76
-.91
1.2
0.01

90. Correlation
• Correlation helps predict
–Does not imply cause and effect

94. 3rd
Variable/Confounding Variables

95. Illusory Correlations
Perceiving a relationship where none exists.
Or perceiving a stronger-than-actual relationship.

96. Illusory Correlations
So for instance…
A sports fan wears a blue jersey the day her team wins,
and she decides to wear that blue jersey on game days
from now on although the jersey had no impact on the
score.

97. Regression to the Mean
The tendency for extreme scores or events to fall
back toward the average.

98. Regression to the Mean
So for instance…
An athlete has an amazing game and performs
extremely well. In subsequent games, the athlete returns
to his normal performance.
A student scores much lower than normal on an exam.
On future exams, the student’s scores return to their
average.

99. Perceiving Order in Random Events
• Comes from our need to make
sense out of the world
–Coin flip
–Poker hand

100. Correlation Coefficients
• Which of the following shows the
strongest correlation? Weakest?
A) 0.02
B) 0.79
C) -0.65
D) 0.34

101. Correlation Coefficients
• Which of the following shows the
strongest correlation? Weakest?
A) 2.02
B) -0.79
C) 0.65
D) 0.34

102. Experimentation
Inferential research that can imply
cause and effect.

103. Experimentation
Pros
–Can isolate cause and effect
–Control of factors

104. Experimentation
Cons
-Can be expensive
-Hard to replicate real life in a
lab

105. Experimentation
• Independent Variable
–Input
–Thing researcher controls
• Dependent Variable
–Outcome
–What is being measured

106. Identify the IV and the DV in each instance.
Music helps plants grow.
Ginger tea helps reduce hyperactivity in
teens
Eating junk food causes weight gain.

107. Experimentation
–Experimental Group
• Receives the treatment
(independent variable)
–Control Group
• Does not receive the treatment
•Placebo
•Comparison

108. Identify the experimental group and control in
each instance.
Music helps plants grow.
Ginger tea helps reduce hyperactivity in
teens
Eating junk food causes weight gain.

109. Placebo Effect
Experimental results caused by expectation
alone

110. Placebo Effect Examples
Athletes have run faster when given a supposed
performance-enhancing drug.
(McClung & Collins, 2007)
Decaf-coffee drinkers have reported increased
vigor and alertness—when they thought their
brew had caffeine in it.
(Dawkins et al., 2011)
People have felt better after receiving a phony
mood-enhancing drug.
(Michael et al., 2012)

111. Confounding Variable
An uncontrolled factor that could affect
the dependent variable
Also called third variable or lurking
variable

112. Common Examples of
Confounding Variables
age
intelligence
level
ethnicity
sex political beliefs

113. Random Sampling
Choosing a
representative sample
of the population being
studied.
Allows the results to be
generalized to the
population as a whole.
Random Assignment
Assigning the
participants to the
experimental or control
group by chance.
Minimizes pre-existing
differences between
the two groups.

114. Single Blind
The participants in
the study are
uninformed about
the treatment, if any,
they are receiving.
Controls for subject
response bias and
placebo effect.
Double Blind
The participants and
the researcher are
uninformed about
which group
receives the
treatment and which
does not.
Controls for experimenter
and subject bias as well as
placebo effect.

115. Experiment Example
Theory: Sleep affects memory
Hypothesis: People who sleep 8 hours the night
before given a memory test will perform better
than people who sleep 4 hours the night before
given a memory test.

116. Experiment Example
Operational Definitions: How are the variables
going to be measured?
Independent Variable (input): Numbers of
hours slept at night (8 hours or 4 hours)
Dependent Variable (output): Performance on
the memory test

117. Experiment Example
Experimental group: People who only get 4
hours of sleep
Control (comparison) group: People who get 8
hours of sleep

118. Experiment Example
Random Assignment: Confounding
Variables
Double Blind: Researcher Bias

119. Comparing Research Methods

120. Comparing Research Methods

121. Comparing Research Methods

122. Comparing Research Methods

123. 123
Fred Rogers wanted to test a new sing-along
method to teach math to fourth graders (e.g. “I
Love to Multiply” to the tune of God Bless
America). He used the sing-along method in his
first period class. His sixth period students
continued solving math problems with the old
method. At the end of the term, Mr. Rogers
found that the first period class scored
significantly lower than the sixth period class on
a mathematics achievement test. He concluded
that his sing-along method was a total failure.

124. This study rated the painfulness of honeybee
stings over 25 body locations in one subject (the
author). Pain was rated on a 1–10 scale, relative to
an internal standard, the forearm. In the single
subject, pain ratings were consistent over three
repetitions. Sting location was a significant
predictor of the pain. The three least painful
locations were the skull, middle toe tip, and upper
arm (all scoring a 2.3). The two most painful
locations were the nostril and upper lip (9.0 and
8.7 respectively).

125. Statistical Reasoning in
Everyday Life

126. 126
Describing Data
A meaningful description of data is important in
research. Misrepresentation may lead to
incorrect conclusions.

127. A study showed women taking a certain birth control
pill had a 100% increased risk of developing blood
clots.
Risk of blood clots in women not taking that pill
1 in 7000
Risk of blood clots in women taking that pill
2 in 7000
Yes. There was a 100% increase in the number of women
with blood clots, but it represented 1 additional woman.

128. 128
Describing Data

129. 129
Describing Data

130. Describing Data
Measures of Central Tendency
• Mode (occurs the most)
• Mean (arithmetic average)
• Median (middle score)

131. Describing Data
Measures of Variability
• Range
• Standard Deviation

132. The following data points are the
number of games pitched by each of
the Greenbury Goblins' starting
pitchers last season:
3,2,4,7,9
Mean =
Median =
Range =

133. You have found the following ages (in years) of 5
gorillas. Those gorillas were randomly selected
from the 29 gorillas at your local zoo:
8, 4, 54, 16, 8
Based on your sample, what is the average age
of the gorillas? What is the median age? What is
the range? What is the mode?

134. Describing Data
Measures of Variability
• Normal Curve (bell shaped)

135. ~68% of scores fall 1 standard deviation from the mean
~95% of scores fall 2 standard deviations from the mean
~99% of scores fall 3 standard deviations from the mean

136. Percentile Rank
The percentage of people in a norm group
who scored lower than a particular individual
on a test or assessment.

137. Percentile Rank
For example, if you have a percentile rank of
75%, it means that you scored higher than
75% of the people in the norm group.

141. The statewide results of a standardized math test had a normal
distribution and a mean of 70. Mr. Smith’s students took the
same test and the graph above depicts their results.
A)What does the mean score of Mr. Smith’s class suggest about
how well his students are performing relative to the state
scores?

142. The statewide results of a standardized math test had a normal
distribution and a mean of 70. Mr. Smith’s students took the
same test and the graph above depicts their results.
A)What does the distribution of scores in Mr. Smith’s class
suggest about how well his students are performing relative to
the state scores?

143. The graphs depict the distribution of intelligence
test scores for two groups of students at a
middle school. Which of the following
statements is true of the graphs?

144. A) The mean and standard deviation are identical for both
distributions
B) The mean is identical for both distributions; the standard
deviation is larger for distribution B
C) The mean is identical for both distributions; the standard
deviation is larger for distribution A
D) The standard deviation is identical for both distributions;
the mean is larger for distribution B

145. Making Inferences
When Is a Difference Significant?
• Statistical significance
–Results not due to chance
–IV caused the DV
–Difference between experimental
group and control group equal to or
larger than 5% (p value)

146. Ethics in Research
• Ethics in human research
–Informed consent
–Protect from harm and
discomfort
–Maintain confidentiality
–Debriefing

147. The End