From the World in the Model to the Model in the World

From the World in the Model
to the Model in the World

Mary S. Morgan
LSE & University of Amsterdam

BA “Modelling for Policy” Conference
May 17-18th, 2012
© M.S. Morgan, 2012

Modelling creates ‘small worlds’: the
‘world in the model’
A. Scientists represent our world into small models
B. Those ‘small worlds’ become autonomous
working objects used as means of scientific
enquiry

• We enquire into the small world in the model to
help us work through our theories and hunches.
• We use the small model world to enquire with
into the big world we live in to see if the models
can help us understand that world, and intervene
(policy) in useful ways.

The qualities of small worlds as
working objects for science?

Models are representations that create
manageably small and manipulable worlds
Small does not necessarily mean simple, silly or
simplistic but rather compressed or miniature
worlds.
• Think maps: not every detail given but exhibit
relations we cannot grasp by eye.
• Think poetry: spare, but dense, expressive
prompts to imagination and understanding

The qualities of small worlds as
working objects for science?
Models are representations that create
manageably small and manipulable
worlds
• Small does not necessarily mean simple,
but rather compressed/miniature worlds.
• Manipulability: a models needs
resources that can be used as means of
enquiry and to suggest modes of action


Manipulable resources in models


Using small worlds as technologies
of enquiry
Into the world of the model and with the model
into the world the model represents

Technology = a form of experiment:
questions, model manipulations, and answers

• Eg Samuelson’s algebraic model
• Eg Tinbergen’s statistical model
• Eg Newlyn-Phillips hydraulic model

Samuelson’s
macro-economic
system (1939)


Tinbergen’s economic model for the
Great Depression (1939)


Newlyn-
Phillips
Hydraulic
macro-
economic
model (1949)

Now in London
Science Museum,
computation gallery


Technology of enquiry

Working with models = a form of experiment:
with questions, model manipulations, answers.

• Eg Samuelson: enquiry into world in model
• Eg Tinbergen: enquiry with the model into the
world
• Eg Newlyn-Phillips Machine: enquiry into the
world in the model and with the model into the
world


Experiments: seek valid inference,
not correspondent truth, between
model and world
• Lab experiments – internal validity (within the lab)
and external validity (beyond lab)
• Model experiments – internal validity (in world of
model) and parallel validity (in real world)
• External and parallel validity both problematic and
no easy solution to either!
• Statistical ‘experiments’ – rules for statistically
valid inference within and beyond the model, but
may not be sufficient for action: eg demography

So …..
• Models may be truth-makers about the small
world in the model, but not of the world that the
model represents
• Rather – learning about the world from working
with models is best conceived as an inference
problem ….
• …. which invites modest claims about how much
we can learn about the world from models, and
• ...... scepticism about action in the world
based on models, and the dangers of using
models as “engines not cameras” (Donald
Mackenzie, 2006)

With sufficient usage, models slide
from being a lens to view the world
into those things seen in world

Using small world accounts has imaginative and
cognitive aspects that alter what we see and
our ability to understand the world

• Imaginative: think poetry, we see new things in
the world because expressed in new ways
• Cognitive: think tube map, and way we start to
see world in terms of the map


‘Performativity’ of models follows
cognitive and imaginative shift

Acting on, and with, small world models has
potential to re-make the big world on the basis of
the recipes found in the small worlds
• Eg economic models and addiction (eg min.
pricing for alcohol in Scotland)
• Eg epidemiological models and vaccinations (eg
Good-night Kiss model?)
Sometimes this makes the big world behave more
like the small world in the model, sometimes less!

Model-based actions don’t always
work in big world, because model
• is a misleading/insufficient representation
• is good at description but does not give access to
behavioural/causal structures
• gives access to plausible explanations, but not to
recipes that suggest means of action
• its ceteris paribus conditions do not hold in world
• suggests modes of action that are not consistent
with other actions being taken
• is not updated with feedback from rapidly
changing situation in world ………………….. etc

Health Warnings 1 and 2:

• Model-based actions may be counter-
performative, even dangerous …think
seriously about using model to re/make
the world
• For the scientist, danger lies where there
is no distinction between the world in
the model and the model in the world


Thank
you


From the World in the Model to the Model in the World

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