Notes on Clark Chapter 4
("Collective Wisdom: Slime-Mold Style")
Econ 308: Agent-Based Computational Economics

Last Updated: 16 June 2006

Latest Course Offering: Spring 2006

Course Instructor:

Professor Leigh Tesfatsion

tesfatsi AT iastate.edu

Syllabus for Econ 308

Basic Reference:

Andy Clark, Being There: Putting Brain, Body, and World Together Again, MIT Press, Cambridge, MA, 1998 (paper), ISBN: 0-262-53156-9

• Basic Concepts

• Key Issues

• Questions Arising from In-Class Discussion

Basic Concepts

• Self-Organization and Emergence (Clark, p. 73)
  "A self-organizing system is one in which some kind of higher-level pattern emerges from the interactions of multiple simple components without the benefit of a leader, controller, or orchestrator."

  Direct Emergence (Clark, p. 73-75)

  "(D)irect emergence... relies largely on the properties of (and relations between) the individual elements, with environmental conditions playing only a background role."

  Examples: (1) Traffic jams; (2) The compression of the molecules of a gas in a container, leading to the emergence of the macro properties "temperature" and "pressure."

  Indirect Emergence (Clark, p. 73-75)

  "(I)ndirect emergence... relies on the interactions of individual elements but requires that these interactions be mediated by active and often quite complex environmental structures."

  Example 1 (pp. 75-76): Nest-building behavior of termites, in which arches are slowly constructed as a result of the propensity of each individual termite to make mudballs (incorporating its chemical trace) and to drop them where chemical traces from other termites are strongest.

  Example 2 (pp. 76-77): Ship navigation -- an overall system of artifacts, agents, natural world, and spatial organization coming together to solve the problem of keeping the ship afloat and headed in the desired direction. "The overall (ship-level) behavior is not controlled by a detailed plan in the head of the captain."

  Rational Reconstruction (Clark, p. 80)

  "(T)he practice of casting each problem immediately in terms of an abstract input-output mapping and seeking an optimal solution to the problem thus defined."

  Embodied Active Cognition (Clark, p. 81-82)

  Clark describes three key features of this methodology: (a) Real-world real-time focus; (b) Awareness of decentralized solutions and the possibility of emergent solutions; (c) An extended vision of cognition and computation spread out in space and time.

  Classical Cognitivism (Clark, p. 83)

  "(D)epiction of the mind in terms of a central logic engine, symbolic databases, and some peripheral `sensory' modules. Key characteristics of this vision include these ideas: (1) memory as retrieval from a stored symbolic database; (2) problem solving as logical inference; (3) cognition as centralized; (4) the environment as (just) a problem domain; and (4) the body as input device."

  Connectionist (Artificial Neural Network) Revolution (Clark, p. 83-84)

  Replaces first three tenets of classical cognitivism with the following: (1)* memory as pattern re-creation; (2)* problem solving as pattern completion and pattern transformation; and (3)* cognition as increasingly decentralized. However, Clark claims that this radical rethinking of the nature of the inner cognitive engine has been marred by "residual classicism" because it has been largely accompanied by a tacit acceptance of the classical marginalization of body and world.

  Emergentist Perspective (Clark, p. 83-84)

  "To see adaptive success as inhering as much in the complex interactions among body, world, and brain as in the inner processes bounded by skin and skull." The emergentist perspective thus augments connectionist views by "a vision of the environment as an active resource whose intrinsic dynamics can play important problem-solving roles and the body as part of the computational loop."

Key Issues

1. Role of self-organization and emergence in human affairs?

(Clark, p. 73): "Collectives of humans, too, exhibit forms of emergent adaptive behavior. The biological brain, which parasitizes the external world... so as to augment its problem-solving capabilities, does not draw the line at inorganic extensions. Instead, the collective properties of groups of individual agents determine crucial aspects of our adaptive success."

2. Importance of distinction between direct and indirect emergence?

(Clark, p. 74): "The difference ... concerns the extent to which we may understand the emergence of a target phenomenon by focusing largely on the properties of the individual elements (direct emergence), versus the extent to which explaining the phenomenon requires attending to quite specific environmental details."

3. How does harmonization of brains, bodies, and worlds come about?

(Clark, Section 4.4, pp. 77-80): "...an important part of the answer is clearly `through evolution.'" Examples: Ship navigation team facing an unexpected challenge; Optimal placement of footpaths to connect a complex of already-constructed buildings.

4. What's wrong with "rational reconstruction"?

(Clark, Section 4.5, pp. 80-81): Clark argues that rational reconstruction can "mislead in several crucial ways," paraphrased as follows: (a) It can obscure opportunistic strategies that involve acting upon or otherwise exploiting the real world as an aid to problem solving; (b) it invites a view of cognition as passive computation in which the important role of epistemic action falls through the cracks; and (c) it obscures the role of history in constraining the space of biologically plausible solutions.

5. What challenges are posed by the "embodied active cognition" alternative to rational reconstruction?

(Clark, p. 82): "(T)he study of embodied active cognition clearly presents some major conceptual and methodological challenges.

• The problem of tractability: How are we to isolate tractable phenomena to study?
• The problem of advanced cognition: How far can we (should we) hope to go with a decentralized view of the mind? Surely there is some role for central planning in advanced cognition.
• The problem of identity: Where does all this leave the individual person? Does it imply that the individual brain and the individual organism are not proper objects of scientific study?

6. How can we respond to these concerns?

(Clark, p. 83) "The key to integrating the facts about advanced cognition with the vision of embodied active cognition lies, I shall suggest, in better understanding the roles of two very special external props or scaffolds: language and culture."

Questions Arising from In-Class Discussion

1. Comparing and contrasting the termite and navigation cases as examples of indirect emergence