EMPIRICISM: HOW TO KNOW STUFF
- Dogmatists thought the best way to understand illness was to develop theories about the body’s functions
- Empiricists thought that the best way to understand illness was to observe sick people.
- Today the word dogmatism is used to describe the tendency for people to cling to their assumptions
- And the word empiricism is sued describe the belief that accurate knowledge can be acquired through
THE SCIENTIFIC METHOD
- Empiricism is the essential element of the scientific method, which is a set of principles about the appropriate
relationship between ideas and evidence.
- Overall, the scientific method suggests that when we have an idea about the world we should gather empirical
evidence relevant to that idea and then modify the idea to fit with the evidence.
o Most scientists refer to an idea of this kind as a theory which is a hypothetical explanation of a natural
- When scientists set out to develop a theory they start with the simplest one, and refer to this as the rule of
o This rule of parsimony is often credited to the 14 century logician William Ockham, who wrote
“Plurality should only be posited when necessary,” which is essentially the way people in the Middle
Ages said, “Keep it simple, stupid.”
- Theories are ideas about how and why things work the way they do.
- So how do we decide if a theory is right? Most theories make predictions about what we should and should not
be able to observe in the world.
- A hypothesis is a falsifiable prediction made by a theory. The word falsifiable is a critical part of that definition.
- The scientific method suggests that the best way to learn the truth about the world is to develop theories,
derive hypotheses from them, test those hypotheses by gathering evidence, and then use that evidence to
modify the theories.
THE ART OF LOOKING
- As wonderful as eyes may be, there are a lot of things they cannot see and a lot of things they see incorrectly.
o For instance, the debate of whether all four of a horse’s feet ever leave the ground at the same time.
- As Muybridge knew, we have to do more than just look if we want to know the truth about the world.
- Empiricism is the right approach, but to do it properly requires an empirical method which is a set of rules and
techniques for observation.
- Three things that make people especially difficult to study are the following:
o COMPLEXITY – no galaxy, particle, molecule, or machine is as complicated as the human brain. 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.
o VARIABILITY – No two individuals ever do, say, think, or feel exactly the same thing under exactly the
o 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
- The fact that human beings are complex, variable, and reactive presents a major challenge to the scientific study
of their behaviour, but psychologists have developed two kinds of methods that are designed to meet these
o Methods of observation: allowing them to determine what people do
o Methods of explanation: allowing them to determine why people do it.
OBSERVATION: DISCOVERING WHAT PEOPLE DO
- To observe means to use one`s senses to learn about the properties of an event or an object.
- This kind of informal observation is fine for buying objects but not for doing science because of the following: o Casual observations are notoriously unstable.
o Casual observations can`t tell us about all of the properties that might interest us
- Measurement is the basis not just of science, but of modern life.
- What does measurement require?
o Whether we want to measure the intensity of an earthquake, the distance between molecules, or the
attitude of a registered voter, we must always do two things: DEFINE the property we wish to measure
and then find a way to DETECT it.
DEFINING AND DETECTING
- Every unit of time has an operational definition which is a description of a property in concrete, measurable
- A measure is a device that can detect the condition to which an operational definition refers.
- The steps we take to measure a physical property are the same steps we take to measure a psychological
- An electromyography(EMG) is a device that measures muscle contractions under the surface of a person’s skin.
- Having an operational definition that specifies a measurable event and a device that measures that event are
the two keys to scientific measurement.
VALIDITY, RELIABILITY, AND POWER
- Good measures have THREE properties: validity, reliability, and power
- Validity refers to the extent to which a measurement and a property are conceptually related.
o For instance the frequency of smiling is a valid way to define happiness in comparison to the number of
friends one may have.
- Reliability is the tendency for a measure to produce the same measurement whenever it is used to measure the
o For example if a person’s facial muscles produced precisely the same electrical activity on two different
occasions, the EMG should also produce the same readings on those two occasions, if not it would be
referred to as unreliable
- Power is the ability of a measure to detect the concrete conditions specified in the operational definition.
o For instance if a person’s facial muscles produced different amounts of electrical activity on two
occasions, then an EMG should detect those differences and produce two different readings, and if it
produced the same reading then it would be powerless.
- Valid, reliable, and powerful measures consistently detect concrete conditions that are conceptually related to
the property of interest when and only when those conditions actually exist.
- While we are trying to measure how people behave, they may be trying to behave as they think we want them
to or expect them to.
- Demand characteristics are those aspects of an observational setting that cause people to behave as they think
- They are called demand characteristics because they seem to “demand” or require that people say and do things
that they normally might not.
- Demand characteristics make it hard to measure behaviour as it normally unfolds.
- One way that psychologists avoid the problem of demand characteristics is by observing them without their
- Naturalistic observation is a technique for gathering information by unobtrusively observing people in their
o For instance it was shown that the biggest groups leave the smallest tips in restaurants that hungry
shoppers buy the most impulse items at the grocery store.
o This conclusion is the result of measurements made by psychologists who observed people who didn’t
know they were being observed.
- Some of the things psychologists want to observe simply don’t occur naturally. o For instance if we wanted to know whether people who have undergone sensory deprivation perform
poorly on motor tasks, we would have to hang around the shopping mall for a very long time before a
few dozen blindfolded people with earplugs just happened to wander by and start typing.
- Some of the things that psychologists want to observe can only be gathered from direct interaction with a
o For example, by administering a survey, giving tests, conducting an interview, or hooking someone up to
- There are other ways to avoid demand characteristics
o People are less likely to be influenced by demand characteristics when they cannot be identified as the
originators of their actions, and psychologists often take advantage of this fact by allowing people to
respond privately (questionnaires) or anonymously.
- Another technique that psychologists often use to avoid demand characteristics is to measure behaviours that
are not susceptible to demand.
o For instance, a person’s behaviour can’t be influenced by demand characteristics if that behaviour isn’t
under the person’s voluntary control.
- Behaviours are also unlikely to be influenced by demand characteristics when people don’t know that the
demand and the behaviour are related.
o For instance, you may want a psychologist to believe that you are concentrating on a task, but you
probably don’t know that your blink rate slows when you are concentrating thus you probably won’t
fake a slow blink.
- One of the best ways to avoid demand characteristics is to keep the people who are being observed from
knowing the true purpose of the observation.
- When people are blind to the purpose of an observation, they can’t behave the way they think they should
behave because they don’t know how they should behave.
o For example, if you didn’t know that a psychologist was studying the effects of music on mood, you
wouldn’t feel obligated to smile when the music is played.
- When psychologists don’t tell people the purpose of their observations, people generally try to figure it out for
- That’s why psychologists sometimes use cover stories, or misleading explanations that are meant to keep people
from discerning the true purpose of an observation.
o For example, if the psychologist wanted to know how music influenced your mood, he or she might
falsely tell you that the purpose of the study was to determine how quickly people can do logic puzzles
while music plays in the background.
- In addition, the psychologist might use filler items, or pointless measure that are designed to mislead you about
the true purpose of the observation
- When psychologists measure behaviour, it is all too easy for them to see what they want to see or expect to see.
- Expectations can influence observations
- It is easy to make errors when measuring the speed of a rat, and expectations often determine the kinds of
errors people make.
- Expectations can influence reality.
- Observers’ expectations, then, can have a powerful influence on both their observations and on the behaviour
of those whom they observe.
- Psychologists use many techniques to avoid these influences, and one of the most common is the double blind
observation, which is an observation whose true purpose is hidden from both the observer and the person being
- Due to this, measurements are often made by research assistants who do not know what is being studied or
why, and who thus don’t have any expectations about what the people being observed will or should do.
- Psychologists often create graphic representations of the measurements they collect. - The most common kind is the frequency distribution which is a graphic representation of measurements
arranged by the number of times each measurement was mad.
- Although a frequency distribution can have any shape, a common shape is the bell curve, which is technically
known as the Gaussian distribution or the normal distribution, which is a mathematically defined frequency
distribution in which most measurements are concentrated around the middle.
- A frequency distribution depicts every measurement and thus provides a full and complete picture of those
- In psychology, brief summary statements that capture the essential information from a frequency distribution
are called descriptive statistics.
- There are two important kinds of descriptive statistics: those that describe the central tendency of a frequency
distribution and those that describe the variability in a frequency distribution.
- Descriptions of central tendency are statements about the value of the measurements that tend to lie near the
center or midpoint of the frequency distribution.
o For instance, when a friend says that she’s been “doing pretty well” she is describing the central
tendency (or approximate locations of the midpoint) of the frequency distribution of her happiness.
- The three most common descriptions of central tendency are the mode – the value of the most frequently
observed measurement; the mean – the average value of all the measurements; and the 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
- In a normal distribution, the mean, median, and mode all have the same value, but when the distribution is not
normal, these three descriptive statistics can differ.
- When distributions become skewed, the mean gets dragged off toward the tail, the mode stays home at the
hump, and the median goes to live between the two.
- When distributions are skewed, a single measure of central tendency can paint a misleading picture of the
- Descriptions of central tendency are statements about the location of the measurements in a frequency
distribution, descriptions of variability are statements about the extent to which the measurements differ from
- The simplest description of variability is the range which is the value of the largest measurement in a frequency
distribution minus the value of the smallest measurement.
- When the range is small, the measurements don’t vary as much as when the range is large.
- Other descriptions of variability aren’t quite as susceptible to this problem.
o The standard deviation is a statistic that describes the average difference between the measurements
in a frequency distribution and the mean of that distribution.
EXPLANATION: DISCOVERING WHY PEOPLE DO WHAT THEY DO
- Although scientific research always begins with the measurement of properties, its ultimate goal is typically the
discovery of casual relationships between properties.
o For instance, it is interesting to know that happy people are healthier than unhappy people, but what
we really want to know is whether their happiness is the cause of their good health.
o Another example is that, it is interesting to know that attractive people earn more money, but what we
really want to know is whether being attractive is a cause of higher income.
- Measurements tell us what happened, but not why.
- By measuring we can learn how much happiness and health or attractiveness and wealth a particular group of
people has, but we still cannot tell whether these things are related, and if so, whether one causes the other.
- Consider the example of insulting someone and then asking for the time.
- The conclusion with this study was that specifically, every person who was not insulted would give you the time
of day, and every person who was insulted would refuse. - Results such as these would probably convince you that being insulted causes people to refuse requests from
the people who insulted them.
- You would conclude that two events – being insulted by someone and refusing to do that person a favour – have
a casual relationship.
PATTERNS OF VARIATION
- Measurements can only tell us about properties of objects and events, but we can learn about the relationships
between objects and events by comparing the patters of variation in a series of measurements.
- When performing the imaginary study of insults and requests, three things were done:
o First, we measured a pair of variables which are properties whose values can vary across individuals or
over time. For instance, in algebra we measured one variable whose value could vary from not insulted
to insulted, and we measured a second variable whose value could vary from refused to agreed.
o Second, we made a series of measurements rather than making just one.
o Third, we tried to discern a pattern in our series of measurements. For example, if we were to look at
the second column of Table 2.1 (page 52) we will see that it contains values that vary as our eyes move
down the column. This column has a particular pattern of variation. And if we were to compare the third
column with the second, we 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. Two variables are
said to “covary” or to “be correlated” when variations in the value of one variable are synchronized with
variations in the value of the other.
- By looking at the synchronized patterns of variation, we can use measurement to discover the relationships
o This is the only way anyone has ever discovered the relationship between variables, which is why most
of the facts you know about the world can be thought of as correlations.
For example we know that adults are generally taller than children, but this is just a shorthand
way of saying that as the value of age varies from young to old, the value of height varies from
short to tall
Or that people who eat a pound of spinach everyday generally live longer than people who eat a
pound of bacon every day.
- Correlations are the fundamental building blocks of knowledge.
- Correlations not only describe the past, but also allow us to predict the future.
o When two variables are correlated, knowledge of the value of one variable allows us to make
predictions about the value of the other variable.
- Every correlation can be described in two equally reasonable ways.
o A positive correlation describes a relationship between two variables in “more-more” or “less-less”
When we say that more spinach is associated with more longevity or that less spinac