Innateness of colour categories is a red herring: insights from computational modelling

1
Innateness of colour categories is a red herring
insights from computational modelling

• Tony Belpaeme
• Artificial Intelligence Lab
• Vrije Universiteit Brussel

2
Colour categories

• The colour spectrum is continuous
• Still, we divide it into colour categories
• What are the origins of colour categories?(Insigh
  ts might be applicable to other perceptual
  categories as well)

3
Importance for language

• this may at first appear to be a comparatively
  trivial example of some minor aspect of language,
  but the implications for other aspects of
  language evolution are truly staggering.
• (Deacon, 1997)

4
Universalism

• Berlin and Kay (1969) used naming experiments to
  extract colour categories

5
Universalism

• This universal character has been hailed by many
  and has been reconfirmed by some. (among others
  Rosch-Heider, 1972 Kay and McDaniel, 1978
  Durham, 1991 Shepard, 1992 Kay and Regier,
  2003)

6
Three positions

• Supposing we accept a certain universality of
  colour categorisation, what mechanisms could
  underlie this?
• Nativism genetic makeup.
• Empiricism interaction with the environment.
• Culturalism cultural interaction with others.

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Nativism

• Colour categories are directly or indirectly
  genetically specified.
• Regularities in human early visual perception,
  especially the opponent character of colour
  vision. (Kay and McDaniel, 1978)
• Regularities in the neural coding of the brain.
  (Durham, 1991)
• Genetic coding of colour categories. (Shepard,
  1992)

8
Empiricism

• Our ecology contains a certain chromatic
  structure which is reflected in our colour
  categories.
• We extract colour categories by interacting with
  our environment.(e.g. Elman et al., 1996
  Shepard, 1992 Yendrikhovskij, 2001)
• This all happens without the influence of culture
  or language.

9
Culturalism

• Colour categories are culture-specific.
• They are learned with a strong causal influence
  of language and propagate in a cultural
  process.(e.g. Whorf, 1954 Davidoff et al.,
  2001 Roberson, 2005 Belpaeme and Steels)

10
Nativism, empiricism or culturalism?

• The discussion has been held on many different
  fronts
• Neurology.
• Psychology.
• Anthropology.
• Linguistics.
• Ophthalmology.
• Philosophy.
• We will tackle the discussion from artificial
  intelligence and computer modelling.

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How can Artificial Intelligence help?

• Artificial Intelligence allows us to create
  models of natural phenomena, of which we then
  observe their behaviour.
• Different premises can be implemented in the
  models, allowing us to get an insight into the
  validity of the premises.
• E.g. traffic modelling.

12
Studying empiricism

• Procedure
• Collect chromatic data.
• Extract colour categories. For this we use a
  clustering algorithm.
• Compare extracted categories with each other and
  with human colour categories.
• If empiricism holds, we would expect a high
  correlation between the extracted categories and
  human categories.

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Chromatic data

• Three data sets natural, urban and random

14
Extracting categories
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Quantitative comparison

• 11 categories extracted from natural and urban
  data
• Correlation with human colour categories

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Reflections on empiricism

• The claim that human colour categories are
  specified by the distribution of chromatic
  stimuli in the world is not supported by our
  data.
• However, there does seem to be a twofold
  influence by
• The structure of the perceptual colour space.
• The properties of perceptual categories.

17
Studying culturalism

• Procedure
• Take a population of simulated individuals that
  learn colour categories and communicate about
  colour.
• If culturalism holds, we expect linguistic
  interactions to cause sharing of colour
  categories.

18
The simulations

• Agent-based simulations
• An agent is a simulated individual, with
  perception, categorisation, lexicalisation and
  communication.
• Perception maps spectral power distribution onto
  an internal colour space.
• Categorisation maps percepts onto categories,
  categories have prototypical behaviour.
• Lexicalisation connects categories to words.
• Communication takes care of uttering word forms.
• The agents have no way to access the internal
  state of other agents there is no telepathy!

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Results

• Colour categories of two agents
• Agents arrive at colour categories that are
  shared.

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Results (2)

• Influence of linguistic interactions on
  categories.
• But as language is culture-specific, cultural
  evolution cannot explain universalism.

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Summary

• Empiricism is not a good candidate to explain
  universalism
• There is not enough ecological pressure.
• Culturalism can explain the sharing of categories
  in a culture, but not universalism.
• Nativism can explain universalism, but is to slow
  to follow ecological changes.
• Also, recent neurophysiological and molecular
  studies point out many differences in colour
  perception between individuals.

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Conclusion

• A blend of all three positions is needed to
  explain universalism.
• But language and culture play a crucial role as
  the catalysts which binds the perceptual
  categories of individuals.
• Read the full story at http//arti.vub.ac.beStee
  ls Belpaeme (2005) Coordinating Perceptually
  Grounded Categories through Language A Case
  Study for Colour. Behavioral and Brain Sciences.
  To appear.