Transcript Document

Thomas Kuhn (1922-1996)
Paradigms, normal science and
revolution
Zoltán Dienes, Philosophy of Psychology
Paradigm :
Narrow definition:
Universally recognized scientific achievements that provide model
problems and solutions to a community of practitioners.
(“Paradigm” is Greek for model, pattern.)
Broad definition:
The entire constellation of beliefs, values and techniques shared by
members of a scientific community
(because they were all trained on the same paradigm examples of
good practice)
E.g. Newtonian physics.
Example in Psychology:
Behaviourism:
Narrow:
An analysis of e.g. dogs salivating to a bell in terns of classical
conditioning provides a model problem and solution
Broad Beliefs and values include:
Theories must only refer to stimuli and responses, not internal states;
all learning can be conceptualised as conditioning, etc
Normal science: research firmly based on such a paradigm (the
coming of maturity of a science)
Pre-normal science: there exists a range of different schools, not
united by a common paradigm
Normal science:
An attempt to force nature into the preformed and rigid box that the
paradigm provides. The aim is to stay within the box.
Kuhn:
Normal science is puzzle solving. If the puzzle is not solved, the
failure reflects on the scientist not on the paradigm.
The person who blames the paradigm will be seen as the carpenter
who blames his tools.
The man who succeeds proves himself an expert puzzle solver, and
the challenge of the puzzle is what drives him on.
Contrast Popper – experiments test theories not people
Kuhn:
A common paradigm frees the scientific community from having to
constantly re-examine first principles;
community is free to concentrate exclusively on the subtlest and most
esoteric of phenomena that concern it
“To turn Sir Karl’s view on its head, it is precisely the abandonment of
critical discourse that marks the transition to a science”
Popper:
“The ‘normal’ scientist, as described by Kuhn, has been badly
taught. He has been taught in a dogmatic spirit: he is a victim of
indoctrination. He has learned a technique which can be applied
without asking for the reason why … He is merely content to
solve ‘puzzles’.
I admit that this kind of attitude exists … But I can only say that I
see a very great danger in it and … the possibility of its becoming
normal… a danger to science and, indeed, to our civilisation.”
Kuhn:
Failure with a new problem is disappointing but not surprising:
problems do not often yield to the first attack. Scientists do not
renounce the paradigm.
Difficult anomalies can be set aside for future work.
(It is OK to provisionally ignore an apparent falsification of your
favourite theory!)
The scientist who pauses to examine every anomaly he notes will
seldom get significant work done.
Are anomalies simply ignored by scientists?
Dunbar 1997
Spent a year in four highly productive molecular biology labs:
Anomalies, especially those challenging core assumptions, were
especially closely attended to and used to generate new
hypotheses
In 19th century, Mercury’s orbit was not fully explained by
Newton’s theory.
A scientist at the time says that no planet had “extracted more
pain and trouble” and “awarded [astronomers] with so much
anxiety”
How do psychologists respond to “anomalies”?
Kuhn:
Crisis: build up of anomalies that resist solution. Creates a growing
sense that the paradigm has ceased to function adequately in the
exploration of nature.
Kuhn:
Crisis: build up of anomalies that resist solution. Creates a growing
sense that the paradigm has ceased to function adequately in the
exploration of nature.
Having achieved the status of a paradigm, a scientific theory is declared
invalid only if an alternative candidate is available to take its place.
“The methodological stereotype of falsification by direct comparison
with nature does not exist in actual science”
The decision to reject one paradigm is always simultaneously the
decision to accept another: a comparison between paradigms occurs.
(Do scientist only treat difficulties as acute if there is a rival? Contrast
the report on Mercury)
Incommensurability between paradigms
Kuhn: There is a sense in which work in different paradigms cannot be
compared (or are difficult to compare).
1. Disagreement over the list of problems to be solved.
“What causes conscious awareness?”
“How fast can mental images be rotated?”
were not legitimate problems for behaviourists.
Information processing psychology de-emphasized learning;
connectionism brought it back to the fore
2. Disagreement over how to describe basic observations
A hypnotherapist might literally see a subject going into trance, while
an academic researcher might just see someone relaxing.
“Sam is an extrovert” means different things depending on your theory
of extroversion and how the extroversion scale was developed
The actual data are different when seen through the lense of
different paradigms.
Must they necessarily be?
Same theory of telescope could be used for providing data to test
big bang and steady state cosmology paradigms;
Same data on children’s reading errors can be used for testing
connectionist and information processing accounts of reading
Kuhn:
When two scientific schools disagree about
what are the problems
what counts as a solution
what the data actually are
they will talk past each other in debating their respective paradigms.
So how can one choose between different paradigms?
Kuhn:
Paradigm choice can never be settled by logic and experiment alone.
It is an act of faith: Despite all the problems a new paradigm
currently has, is it a way of practicing science that is likely to be
fruitful in providing solutions to the puzzles it defines?
“In paradigm choice there is no standard higher than the assent of the
relevant community.”
Relativism: Different theories are equally true, it’s all
relative to what a group believes
“In paradigm choice there is no standard higher than the
assent of the relevant community.”
So the community could not be mistaken?
Does truth lie in power?
Does truth change when the community changes its mind?
Need to distinguish:
Description of world
from
world
In order that one could be wrong.
The fact and the representation of a fact can be different!
(If you partner says “I did/did not sleep with your best friend”
Is either answer just as true?)
Yet Kuhn says when paradigms change scientists literally live in
a different world.
Kuhn inspired (with regret) a domination of relativism in the
humanities and social sciences (e.g. post-modernism, science
studies, social constructionism)
Consider this quote from training material for teachers:
“For many centuries it was considered to be a fact that the Sun
revolves around the Earth. The appearance of another theory, such
as the diurnal rotation of the earth, entailed the replacement of the
fact just cited with another: the Earth rotates on its axis each day.”
If facts change when we change what we think, does it matter who
we convict for a rape?
Can you jump from a plane and fly if you believe you can?
Kuhn:
To go between paradigms, cannot be done step by step; it happens
all at once like a Gestalt switch.
The transfer of allegiance from paradigm to paradigm is a
conversion experience.
Converting people is difficult. Typically new paradigms are
introduced by a person new to the field.
Max Planck: “A new scientific truth does not triumph by
convincing its opponents and making them see the light, but rather
because its opponents eventually die, and a new generation grows
up that is familiar with it”.
Is that true?
Diamond 1992
Tiny non-significant correlations between actual or
professional age of 100 chemists and whether or not they
supported the radical theory of polywater
Physicists of all ages came to adopt quantum theory and
relativity rather than Newtonian dynamics as closer to the
truth in a very short period of time.
Kuhn:
Revolution: the change of a paradigm in a discipline
Revolution is a transformation of vision, crises are terminated not
be deliberation but by a gestalt switch.
After a revolution the data themselves change and the scientists
work in a different world.
Gestalt switch: the data changes
(Implications:
One way of looking at the data is not more true than another ?
One cannot simultaneously consider the data from the point of
view of two different theories ?)
The later Kuhn (1970, 2000):
There is a rational basis to theory choice. The shared core basis for
theory choice amongst all scientists is:
Simplicity, accuracy, scope, consistency and fruitfulness.
In a revolution, theories will vary according to satisfaction of these
criteria.
Hence, it is rational for scientists to pursue different theories at this
point (to hedge their bets as a community).
When the dust has settled, one theory may be a clear victor over
another on all criteria: Extreme relativism is avoided.
Are there objective reasons for why scientists should favour one
theory over another?
Does science tend to move closer to the truth?
Do scientists try to falsify fundamental theories?
Can they rationally reject fundamental theories?