Thomas Kuhn (1922-1996)

Paradigms, normal science and revolution

Zoltán Dienes, Philosophy of Psychology

Paradigm : The entire constellation of beliefs, values and techniques shared by members of a scientific community.

(Includes: universally recognized scientific achievements that provide model problems and solutions to a community of practitioners. Hence the name “paradigm”)

E.g. Newtonian dynamics.

Paradigm : The entire constellation of beliefs, values and techniques shared by members of a scientific community.

Example in Psychology:

Behaviourism:

An analysis of e.g. dogs salivating to a bell in terns of classical conditioning provides a model problem and solution

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

(Contrast Donovan, Laudan and Laudan, 1992)

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”

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? Contrast Donovan et al)

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 Donovan et al)

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:

When paradigms enter into a debate about paradigm choice, their role is necessarily circular: Each groups uses its own paradigm to argue in that paradigm’s defence.

The protagonists provide a clear exhibit of what scientific practice will be like for those who adopt the new view of nature.

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 paradigm choice there is no standard higher than the assent of the relevant community.”

Two different ways of practicing psychology:

Connectionism

Build a network to solve a learning or constraint satisfaction problem: How many layers? How connected? What learning rule?

Two different ways of practicing psychology:

Connectionism Information processing psychology

Build a network to solve a learning or constraint satisfaction problem: How many layers? How connected? What learning rule?

Find experimental dissociations to determine how many boxes to draw and how to connect them; what rules transform representations in each box

In 1980s when connectionism was taken up enthusiastically, networks were shown to behave a little bit like people in e.g. learning past tense of verbs

But many things they could not do

Fodor and Pylyshyn (1988) provided arguments that it was impossible for them to do the things cognitive psychologists were really interested in, like language

In 1980s when connectionism was taken up enthusiastically, networks were shown to behave a little bit like people in e.g. learning past tense of verbs

But many things they could not do

Fodor and Pylyshyn (1988) provided arguments that it was impossible for them to do the things cognitive psychologists were really interested in, like language

But many people started using networks, including to model language: It was a way of practicing psychology that had promise. Who knows how the arguments of Fodor and Pylyshyn would stand the test of time.

Note information processing psychology had not solved the problems of language either.

No logical argument for why a researcher must choose one or the other

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?)

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 ?)

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?