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University of Toronto Scarborough
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Psychology
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PSYA01H3
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Steve Joordens
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Chapter 2

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Psychology

PSYA01H3

Steve Joordens

Fall

Description

Chapter 2: (pgs. 40 – 73)
Methods in Psychology
1) Empiricism: How to Know Stuff (pgs 40 – 43)
Empiricism: The belief that accurate knowledge can be acquired through observation.
The Scientific Method (pgs 40 – 41)
Scientific method: A set of principles about the appropriate relationship between ideas and
evidence.
Theory: A hypothetical explanation of a natural phenomenon.
Hypothesis: A falsifiable prediction made by a theory.
The Art of Looking (pgs 41 – 43)
Empirical method: A set of rules and techniques for observation.
Method: Technologies that enhance the powers of the senses.
What three things make people difficult to study?
1) Complexity: The human brain is complicated. Scientists can barely begin to say how the 500
million interconnected neurons that constitute the brain give rise to the thoughts, feelings, and
actions that are psychology’s core concerns.
2) Variability: People are as varied as their fingerprints. No two individuals ever do, say, think, or
feel exactly the same thing under exactly the same circumstances, which means that when
you’ve seen one, you’ve most definitely not seen them all.
3) Reactivity: People often think, feel, and act one way when they are being observed and a
different way when they are not. When people know they are being studied, they don’t always
behave as they otherwise would.
Summary:
Empiricism is the belief that the best way to understand the world is to observe it firsthand. It is
only in the last few centuries that empiricism has come to prominence.
Empiricism is at the heart of the scientific method, which suggests that our theories about the
world give rise to falsifiable hypotheses, and that we can thus make observations that test
those hypotheses. The results of these tests can disprove our theories but cannot prove them.
Observation doesn’t just mean “looking.” It requires a method. The methods of psychology are
special because more than most other natural phenomena, human beings are complex,
variable, and reactive. 2) Observation: Discovering What People Do (pgs 43 – 51)
Measurement (pgs 43 – 48)
Defining and Detecting
Operational definition: A description of a property in concrete, measurable terms.
Measure: A device that can detect the condition to which an operational definition refers.
Electromyograph (EMG): A device that measures muscle contractions under the surface of a
person’s skin.
Validity, Reliability, and Power
Validity: The extent to which a measurement and a property are conceptually related.
Reliability: The tendency for a measure to produce the same measurement whenever it is used
to measure the same thing.
Power: The ability of a measure to detect the concrete conditions specified in the operational
definition.
Demand Characteristics
Demand characteristics: Those aspects of an observational setting that cause people to behave
as they think they should.
Naturalistic observation: A technique for gathering scientific information by unobtrusively
observing people in their natural environments.
Observer Bias
Double-blind: An observation whose true purpose is hidden from both the observer and the
person being observed.
Descriptions (pgs 48 – 51)
Graphic Representations
Frequency distribution: A graphical representation of the measurements arranged by the
number of times each measurement was made.
Normal distribution: A mathematically defined frequency distribution in which most
measurements are concentrated around the middle. Also known as Gaussian distribution and
bell-curve. Descriptive Statistics
Mode: The value of the most frequently observed measurement.
Mean: The average value of all the measurements.
Median: The value that is “in the middle”– i.e., greater than or equal to half the measurements
and less than or equal to half the measurements.
Skewed distribution: When a frequency distribution is (a) normal the mean, median, and mode
are all the same. But when a frequency distribution is (b) positively skewed, or (c) negatively
skewed the three measures of central tendency are quite different.
Range: The value of the largest measurement in a frequency distribution minus the value of the
smallest measurement.
Standard deviation: A statistic that describes the average difference between the measurements
in a frequency distribution and the mean of that distribution.
Summary:
Measurement involves defining a property in terms of a concrete condition, and then
constructing a measure that can detect that condition. A good measure is valid (the concrete
conditions it measures are conceptually related to the property of interest), is reliable (it
produces the same measurement whenever it is used to measure the same thing), and is
powerful (it can detect the concrete conditions when they actually exist).
When people know they are being observed, they may behave as they think they should.
Demand characteristics are features of a setting that suggest to people that they should behave
in a particular way. Psychologists try to reduce or eliminate demand characteristics by observing
participants in their natural habitats or by hiding their expectations from the participant.
Observer bias is the tendency for observers to see what they expect to see or cause others to
behave as they expect them to behave. Psychologists try to eliminate observe bias by making
double-blind observations.
Psychologists often describe the measurements they make with a graphic representation called
a frequency distribution, which often has a special shape known as the normal distribution. They
also describe their measurements with descriptive statistics, the most common of which are
descriptions of central tendency (such as the mean, median, and mode) and descriptions of
variability (such as the range and the standard deviation). 3) Explanation: Discovering Why People Do What They Do (pgs 52 – 68)
Correlation (pgs 52 – 55)
Patterns of Variation
How can we tell if two variables are correlated?
1) You measured a pair of variables. You measured one variable whose value could vary from not
insulted to insulted, and you measured a second variable whose value could vary from refused
to agreed.
2) You did this again. And then again. And then again. That is, you made a series of measurements
rather than making just one.
3) You tried to discern a pattern in your series of measurements. If there is a pattern; one column
will have a particular pattern of variation. If you compare the third column with the second, you
will notice that the patterns of variation in the two columns are synchronized. This synchrony is
known as a pattern of covariation or a correlation (as in “co-relation”).
Variable: A property whose value can vary across individuals or over time.
Correlation: Two variables are said to “be correlated” when variations in the value of one
variable are synchronized with variations in the value of the other.
Measuring Correlation
Correlation coefficient: A measure of the direction and strength of a correlation, which is
signified by the letter ‘r’. The value of ‘r’ can range from -1 to 1.
How can correlations be measured?
o If every time the value of one variable increases by a fixed amount the value of the
second variable also increases by a fixed amount, then the relationship between the
variables is called a perfect positive correlation and r = 1.
o If every time the value of one variable increases by a fixed amount the value of the
second variable decreases by a fixed amount, then the relationship between the
variables is called a perfect negative correlation and r = −1.
o If every time the value of one variable increases by a fixed amount the value of the
second variable does not increase or decrease systematically, then the two variables are
said to be uncorrelated and r = 0. What does it mean for a correlation to be strong?
Two variables can have a perfect correlation (r = 1),
o A strong correlation (for example, r = .90)
o A moderate correlation (for example, r = .70)
o A weak correlation (for example, r = .30).
Causation (pgs 55 – 64)
The Third-Variable Problem
Natural correlation: A correlation observed in the world around us.
Third

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