The dynamical hypothesis is the claim that cognitive agents are dynamical systems. It stands opposed to the dominant computational hypothesis, the claim that cognitive agents are digital computers. This target article articulates the dynamical hypothesis and defends it as an open empirical alternative to the computational hypothesis. Carrying out these objectives requires extensive clarification of the conceptual terrain, with particular focus on the relation of dynamical systems to computers. Key words cognition, systems, dynamical systems, computers, computational systems, computability, modeling, time. Long Abstract The heart of the dominant computational approach in cognitive science is the hypothesis that cognitive agents are digital computers; the heart of the alternative dynamical approach is the hypothesis that cognitive agents are dynamical systems. This target article attempts to articulate the dynamical hypothesis and to defend it as an empirical alternative to the compu...

As efforts grow to develop spatio-temporal database systems and temporal geographic information systems that are capable of conveying how geographic phenomena change, it is important to distinguish the elements that are fundamental to scenarios of change. This paper presents a model based on the explicit description of change with respect to states of existence and non-existence for identifiable objects. Such changes are of concern when, for instance, modeling and reasoning about nations that are subsumed through conflict only to return once more at a later time, or about water bodies that fluctuate due to seasonal or climatic change. The basis for tracing these changes is the concept of object identity. Identity, distinct from an object's properties, values, or structure, is that unique characteristic that distinguishes one object from another. Based on a small set of primitives relating to the identity states of objects, we model the semantics associated with change and through a systematic derivation, a complete set of identity-based change operations evolves from the primitives. These operations are basic to the types of change commonly experienced by geographic phenomena and modeled by researchers studying spatio-temporal change. This approach highlights the minimum elements necessary for reasoning about change, namely, object identity, an ordering of identity states, and co-occurrence of identity states.

this paper I shall make a case for a dynamic semiotics. I list a set of phenomena that are difficult to understand in standard theories, and suggest a model borrowed from theories of complex dynamic systems. Since such theories rely on processes of self-organization that often defy analytical treatment, I use small computational models for assessing the empirical consequences of the theories.

We review several mathematical methods allowing to identify modules and hierarchies with several levels of complexity in biological systems. These methods are based either on the properties of the input-output characteristic of the modules or on global properties of the dynamics such as the distribution of timescales or the stratification of attractors with variable dimension. We also discuss the consequences of the hierarchical structure on the robustness of biological processes. Stratified attractors lead to Waddington’s type canalization effects. Successive application of the many to one mapping relating parameters of different levels in an hierarchy of models (analogue to the renormalization operation from statistical mechanics) leads to concentration and robustness of those properties that are common to many levels of complexity. Examples such as the response of the transcription factor NFκB to signalling, and the segmentation patterns in the development of Drosophila are used as illustrations of the theoretical ideas. 1

this paper is just another small step leading from the old media to the new one.

In this introductory section, I shall discuss the nature of interactive multimedia, and their present mode of development. 1.1. Multimedia are documents, music or film When new media appear they are normally treated as new versions of old media (Madsen 1994): the film posed as theatre, television as filmed radio, and video as electronic film. This is also true of interactive multimedia which are often conceived of as a book or collection of documents with more flexible ways of turning pages (Apple’s Hypercard, Allegiant’s Supercard, Netscape), as a film or piece of music that can be stopped and started (Macromind Director, Apple’s Quicktime) or as a new kind of theatre (Laurel 1991). However, all applications are computer systems, and reveal themselves as such at closer inspection, so why this playing hide-and-seek with the user? Why pose as a book when one is really an object-oriented program? The reason is the paradox inherent in creating a new medium. On the one

This report has two aims:

We review various aspects of the notion of scale applied to natural systems, in particular complex adaptive systems. We argue that scaling issues are not only crucial from the standpoint of basic science, but also in many applied issues, and discuss tools for detecting and dealing with multiple scales. We also suggest that the techniques of statistical mechanics, which have been successful in describing many emergent patterns in physical systems, can also prove useful in the study of complex adaptive systems. 1.

A quantitative measure of stability in stochastic dynamics starts to emerge in recent experiments on bioswitches. This quantity, similar to the potential function in mathematics, is deeply rooted in biology, dated back at the beginning of quantitative description of biological processes: the adaptive landscape of Wright (1932) and the development landscape of Waddington (1940). Nevertheless, its quantitative implication has been frequently challenged by biologists. Recent progresses in quantitative biology begin to meet those outstanding challenges. 1 With the successful experimental work and theoretical analysis on simple artificial gene networks [1], Acar et al [2] further explored the quantitative behaviors in a living gene regulatory network, the yeast galactose-signaling network. Their work provides a fine and new example of quantitative understanding of the stability and reversibility of cellular differentiation state in terms of the potential or energy landscape. I wish to point out here that together with the extensive, and perhaps more quantitative, study in another living genetic regulatory network not discussed by Acar et al, the phage lambda [3,4,5], where similar conclusion was obtained [6], a powerful theoretical modelling framework of stochastic dynamics