Science and Statistics in Psychology
Lecture 1
Theory and Evidence
Dr Caleb Owens
Brennan MacCallum 453
caleb.owens@sydney.edu.au
Consultation: Wednesdays 9-10am
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Important notes about this lecture series
• Pseudo-sciences are used throughout this lecture series as examples to
emphasize the care and precision which science requires
– There is no malign intent involved in choosing particular examples of
pseudoscience. If you find yourself challenged by a particular example, you will
find dozens more given in lectures which can serve your understanding equally
well. The main purpose of these lectures is to give you the toolkit to criticize. If
you find that you can be highly critical of some things in your life but not others –
that’s fine, and a curious psychological anomaly we know well (even if we don’t
understand it). The specific aim here is to encourage you to have a strong
sceptical attitude toward all your subject areas in psychology. Psychology is a
new science, and is particularly hard for us to research objectively because it is
about us, so a high level of scientific rigour and understanding of science is
necessary.
– Any form of knowledge needs to be used responsibly. It is not recommended you
use the knowledge you gain from this series (or any other lecture series) to mock
or deride any outsider. As students sitting voluntarily in a science lecture, you are
assumed to be open to the implications of science. However in the outside world,
not everyone holds the same world view, and an insensitive approach can cause
great offence and hurt.
– If you wish to contribute to or start a debate on any of the issues raised in this
lecture series, the webCT forums for PSYC1001 are open and waiting. Use what
you learn in this lecture series to make your arguments persuasive, for example,
refer to appropriate evidence (peer reviewed research rather than anecdotes)
and avoid logical fallacies. Everyone gets to contribute to science, but not every
hypothesis can be right.
• The items posted on webCT are lecture overheads only. On many slides
however you will notice one or two ‘notes’ at the bottom which clarify or 2
reinforce particular points. Keep an eye out for them.
By the end of this lecture series:
• You should have a clear idea what distinguishes science from
pseudoscience, and be able to use this understanding to help
advance psychology
• You should feel confident in your ability to criticize and evaluate
almost all kinds of psychological research for its validity and
importance
• You should have a good understanding of the main issues which
confront psychologists attempting to both design and interpret
research
• You should understand that statistics and a grasp of it is central to
all psychology
• NB: This is NOT a mathematics course
– If you have taken a “statistics” course in mathematics and feel you can
skip these lectures, you are much mistaken
– Equally, if you are afraid of mathematics you will be surprised at how
little maths there is
– Understanding statistics in psychological research is an exercise in
empowerment, logic, and scepticism – there is very little messing
around with numbers, there is no calculator required for the final exam.
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Lecture Plan
1. Theory & Evidence : Science and pseudoscience; the
importance of a rationale
2. The power of a name : Measurement and constructs
3. Predictions : Hypotheses in science; the null
hypothesis; the importance of a disprovable hypothesis
4. A thousand zeros : Types of research design; internal
and external validity
5. The coin toss : Understanding variability in sampling
and measurement; probability and the appeal to
ignorance
6. Too much of a good thing : Statistical power; Practical
significance
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What is science ?
• An attitude – a quest for understanding
• People of science want to make sure they are not mistaken
• Continuous doubt, uncertainty, reflection, reanalysis and
scepticism
• Humility about current understanding, always hoping for
something better
• A technique for discovering the nature of the
world
• Science has taken a long time to develop and requires
training
• Structures of self-correction which (eventually)
result in valid knowledge
• Scientific structures like peer reviewed journals, research
funding mechanisms play an important role
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Current understanding of the world
No progress
whatsoever
Criticism forbidden
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Current understanding of the world
Analysis and criticism
of current theory
New theory proposed
Hypotheses proposed
about other explanations
Hypothesis #1
Not a better
explanation
Hypothesis #2
Hypothesis #3
A better*
explanation
Not a better
explanation
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*But not necessarily perfect.
Science is power
• No other system of understanding the
world comes close
• Have you heard of:
– The Eastern Science moon project with chi
powered rockets?
– An alternative chakra powered mobile phone
network?
• At most you may have heard of ‘alternative
understandings’ in fields with unclear results, and
small, hard to replicate placebo mediated effects
(e.g. “alternative” medicine)
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What science is good at
• Explanations
– Which answer questions and solve problems
• And do not lead to more questions about the same
problems
• Predictions
– Of how substances will react, structures will
perform, drug effects, technology, addictive
behaviour, consumer behaviour
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What science is bad at
• Purposes
– So we understand how to split the atom…
what do we do?
• Make nuclear weapons to destroy each other?
• Build nuclear power plants?
• Not build nuclear power plants?
• Meaning and ethics
– What was the point of all those people who
died being born in the first place?
– Is it right/good to conduct experiments on
animals?
– Science might tell us whether/which animals can feel
pain though
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Is psychology a science?
• Psychology is a challenge: a large series
of problems and issues concerning how
we understand behaviour.
• At most we could say that we want to
study the challenges psychology presents
us with in a scientific manner
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Theory and evidence
• Science needs both:
– Evidence without theory could be considered
‘blind empiricism’. We can record a vast
number of phenomena which we cannot fully
explain but progress is difficult
– Theory without considering evidence is often
a complete waste of time
• How theories and the evidence which
supports them interacts is the key to the
success of science
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Theory – mechanisms, constructs,
causal relationships
Is the theory supported by
evidence?
Scientific Knowledge –
Established theories and facts,
Previously replicated evidence
Evidence – findings from controlled
experiments, anecdotes, testimonials,
historical records, chemical evidence etc.
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What is a theory?
• A model of how something works
– E.g. the Copernican model of the revolution of
the planets around the sun
• A metaphor for the functioning of a system
– E.g. the body as electrical (1820
Frankenstein)
• An interrelation of concepts which is
supported by observations and which
leads to new predictions
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Some key theories in science
• Plate tectonic theory (from late 1960’s)
– Preceded by:
• Geosyncline theory (mid 1800’s)
• Continental drift (1912)
– Key evidence:
•
•
•
•
Continents ‘fit’ together
Age of the earth (based on cooling)
Magnetic anomalies
Seismic imaging
– Used to predict and explain
• Sea floor spreading, plates colliding forming mountain ranges
• Earthquake and volcano zones
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• Germ theory of disease
– Preceded by:
•
•
•
•
•
Spontaneous generation of disease
Evil agents inside the body (curses, negative thoughts)
Bodily imbalance (of forces, humours, energies)
Vitalistic concepts (energy, intention, purpose)
Miasmatic theory of disease (caused by pollution)
– Key evidence:
• Microscopes developed which could detect agents
– Discovery of viruses and bacteria
• Koch's (1890) postulates:
– The microorganism must be found in abundance in all organisms
suffering from the disease, but should not be found in healthy animals.
– The microorganism must be isolated from a diseased organism and
grown in pure culture.
– The cultured microorganism should cause disease when introduced
into a healthy organism.
– The microorganism must be reisolated from the inoculated, diseased
experimental host and identified as being identical to the original
specific causative agent.
– Used to predict and explain
• Effectiveness of antibiotics, hygiene, sterilization
• Led to development of vaccines, treatments, prevention
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• Modern evolutionary synthesis
– Preceded by:
• Lamarckism
– Acquired traits passed on (led to Lysenkoism in Russia)
• Orthogenesis (single direction change, e.g. bigger, more complex)
• Saltation (distinct from punctuated equilibrium)
• Evolution by natural selection
– Variation in offspring leads to differential reproduction
• Genetic drift
– Random changes in allele frequency may remove alleles when
selective pressures absent (e.g. cave animals lose pigment)
– Key evidence:
• Mendelian genetics
– Selective breeding of dominant and recessive genes
•
•
•
•
Embryology
Discovery of the structure of DNA
Palaeontology and geology
Modern genetics and genetic mapping (including population
genetics)
– Used to predict and explain
•
•
•
•
Effectiveness of antibiotics, drugs
Origins of species (futures of species)
Development and function of animal parts including the human brain
Ecosystems and ecology
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• (in Psychology) Localization of function
– Preceded by:
• Thinking with the heart
• Phrenology / Reflexology / Iridology
– Key evidence:
• Brain damage
• Lesion studies
• Brain scanning (fMRI, PET, EEG)
– Used to predict and explain
• Effects of selective brain damage
– E.g. loss of memory consolidation (hippocampus), balance
(cerebellum)
– Effects of diseases (e.g. parkinsons)
– Loss of language abilities (hearing = Wernickes; speaking =
Broca’s area)
• Operation of emotions (amygdala), and vision (V1-V4)
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• (in Psychology) Cognitive Behavioural
Therapy
– Preceded by:
• Psychoanalysis
• Behavioural therapy
– Key evidence:
• Effectiveness over a short time span
• Learning principles (e.g. reward, reinforcement)
• Cognitive principles (e.g. selective attention)
– Used to predict and explain
• Role of negative/unhelpful cognitions in coping and
anxiety
• Importance of retraining in logic, and selective
attention
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Non-scientific ‘theories’
1. Theories which cannot be tested (cannot
be disproven)
Science does not have a view on
– the ‘god’ theory
– Psychoanalysis
untestable theories because there is
nothing for it to do! If they cannot be
disproven, and new theories built to
explain even more in their place,
there is no possibility of progress.
2. Theories which contain elements which
conflict with known facts or established
theories (pseudoscience)
– Young earth creationism
– Homeopathy
Science can be hostile against
theories which make claims
which contradict well established
facts and theories.
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Avoiding pseudoscience
• Psychologists will always be tempted
– We have our own views and intuitions about why
people behave in certain ways
– We are as easily mislead as anyone else
• Have scientific knowledge
– E.g. Not having any understanding of
electromagnetism leads to a profound vulnerability
• Fear of mobile phones, mobile phone towers and power lines
– http://www.skepdic.com/emf.html
– http://mybroadband.co.za/news/Wireless/11099.html
• The use of ‘magnetic mattresses’ and bracelets to stop pain
– http://www.skepdic.com/magnetic.html
– Deaths result from misunderstanding
• Vaccination
• Drug use (e.g. alcohol and performance)
• Sexually transmitted diseases
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Avoiding pseudoscience
• Understand scientific attitudes and methods
– Never ending scepticism
– Ask for replicable evidence
– Double blind randomized trials are better than anecdotes
• Confirm that the theories are open to questions and have
been evolving
– How was the theory discovered?
– How is research being used to change/progress understanding
of the theory?
• E.g. If the theory was made up out of the blue by a particular person
at a particular time, has never been tested, and has not changed
since – it is pseudoscience
• Learn your logical fallacies! (see PSYC1001 manual,
and Carl Sagan’s “Baloney Detection Kit” from ‘Demon
Haunted World’)
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Logical errors
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Ad hominem
Argument from authority
Appeal to ignorance
Begging the question
Observational selection
Statistics of small numbers
Inconsistency
Slippery slope
Confusion of correlation
and causation
Straw man
Weasel words
The pragmatic fallacy
Excluded middle
a) Assuming an answer in the way the
question is phrased
b) Unwarranted extrapolation of the effects
c) Caricaturing (or stereotyping) a position
to make it easier to attack
d) Use of euphemisms and misleading
terminology
e) Considering only the two extremes in a
continuum of intermediate possibilities
f) Something is true because it works!
g) Drawing conclusions from inadequate
sample sizes
h) One position contradicts another
i) Counting the hits and forgetting the
misses
j) Attacking the arguer and not the
argument
k) If you are not certain about your
argument, then mine must be true
l) Something is true because the person
who said it is of high status.
m) Since two things go together, one must
have led to the other.
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What is science ?
• An attitude – a quest for understanding
• No result is ever certain – new evidence is always
welcome
• A technique for discovering the nature of
the world
• Anecdote, intuition and blind faith are not the
techniques central to science
• Structures of self-correction which
(eventually) result in valid knowledge
• If science is wrong, an open forum ensures
mistakes are corrected
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