Artificial life

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This article is about a field of research. For artificially created life forms, see synthetic life. For the mobile game developer, see Artificial Life Inc.

Artificial life (commonly Alife or alife) is a field of study and an associated art form which examine systems related to life, its processes, and its evolution through simulations using computer models, robotics, and biochemistry.[1] There are three main kinds of alife, named for their approaches: soft, from software; hard, from hardware; and wet, from biochemistry.[2] Artificial life imitates traditional biology by trying to recreate biological phenomena.[3] The term "artificial life" is often used to specifically refer to soft alife.[citation needed]

A Braitenberg simulation, programmed in breve, an artificial life simulator
A Braitenberg simulation, programmed in breve, an artificial life simulator

Contents

[edit] Overview

Artificial life studies the evolution of agents, populations of computer-simulated life forms, in artificial environments. The goal is to study phenomena found in real-life evolution in a controlled manner, hopefully eliminating some of the inherent limitations of evolutionary studies that use live bacteria or mice. The simulated nature of the organisms and environments also allows for unorthodox and previously impossible experiments, such as a comparison of Lamarckian evolution and natural selection.

Also sometimes included in the umbrella term "artificial life" are other agent-based emergent properties, such as the development of economies or societies. The common thread of all "artificial life" is the concept of an iterative population approach, generations of agents which can mutate and become fitter over time.

[edit] Philosophy

At present, the commonly accepted definition of life does not allow for any alife simulations to be considered "alive". However, different opinions about artificial life's potential have arisen:

  • The strong alife (cf. Strong AI) position states that "life is a process which can be abstracted away from any particular medium" (John von Neumann). Notably, Tom Ray declared that his program Tierra is not simulating life in a computer but synthesizing it.
  • The weak alife position denies the possibility of generating a "living process" outside of a chemical solution. Its researchers try instead to mimic life processes to understand the underlying mechanics of phenomena. That is, "we don't know what in nature generates this phenomenon, but it could be something as simple as...".[citation needed]

[edit] Techniques

  • Cellular automata were used in the early days of artificial life, and they are still often used for ease of scalability and parallelization. Alife and cellular automata share a closely tied history.
  • Neural networks are sometimes used to model the brain of an agent. Although traditionally more of an artificial intelligence technique, neural nets can be important for simulating population dynamics of higher organisms that can learn. The symbiosis between learning and evolution is central to theories about the development of instincts in higher organisms, as in, for instance, the Baldwin effect.

[edit] Related subjects

  1. Artificial intelligence has traditionally used a top down approach, while alife generally works from the bottom up.[citation needed]
  2. Artificial chemistry started as a method within the alife community to abstract the processes of chemical reactions.
  3. Evolutionary algorithms applied to optimization problems are strongly related to weak alife, yet are sometimes dismissed as "not real artificial life".[citation needed] Many optimization algorithms have been crafted which borrow from or closely mirror alife techniques. The primary difference lies in explicitly defining the fitness of an agent by its ability to solve a problem, instead of its ability to find food, reproduce, or avoid death.[citations needed] The following is a list of evolutionary algorithms closely related to and used in alife:
  4. Evolutionary art uses techniques and methods from artificial life to create new forms of art.
  5. Evolutionary music uses similar techniques, but applied to music instead of visual art.

[edit] History

Main article: History of artificial life

[edit] Criticism

Alife has had a controversial history. John Maynard Smith criticized certain artificial life work in 1994 as "fact-free science".[4] However, the recent publication of artificial life articles in widely read journals such as Science and Nature is evidence that artificial life techniques are becoming more accepted in the mainstream, at least as a method of studying evolution.[5]

Generally, the lack of biologists and abundance of computer scientists in the field has hurt the field's credibility within mainstream biology.[original research?] There is also scepticism of the field within the computer science community.[original research?]

[edit] Notable simulators

This is a list of Artificial life/Digital organism simulators, organized by the method of creature definition.

[edit] Program-based

These contain organisms with a complex DNA language, usually Turing complete. This language is more often in the form of a computer program than actual biological DNA. Assembly derivatives are the most common languages used. Use of cellular automata is common but not required.

[edit] Module-based

Individual modules are added to a creature. These modules modify the creature's behaviors and characteristics either directly, by hard coding into the simulation (leg type A increases speed and metabolism), or indirectly, through the emergent interactions between a creature's modules (leg type A moves up and down with a frequency of X, which interacts with other legs to create motion). Generally these are simulators which emphasize user creation and accessibility over mutation and evolution.

[edit] Parameter-based

Organisms are generally constructed with pre-defined and fixed behaviors that are controlled by various parameters that mutate. That is, each organism contains a collection of numbers or other finite parameters. Each parameter controls one or several aspects of an organism in a well-defined way.

  • Jeffrey Ventrella's programs Darwin Pond and Gene Pool.
  • "Cell-based" - Parameters control the expression of "genes" or "proteins" which can themselves interact in complex ways. The resulting organism's properties are largely emergent but are still encoded in the genome with a finite number of parameters.

[edit] Neural net–based

These simulations have creatures that learn and grow using neural nets or a close derivative. Emphasis is often, although not always, more on learning than on natural selection.

[edit] See also

[edit] See also

[edit] References

  1. ^ Dictionary.com definition. Retrieved on 2007-01-19.
  2. ^ Mark A. Bedau (November 2003). Artificial life: organization, adaptation and complexity from the bottom up. TRENDS in Cognitive Sciences. Retrieved on 2007-01-19.
  3. ^ Christopher Langton. What is Artificial Life?. Retrieved on 2007-01-19.
  4. ^ Horgan, J. 1995. From Complexity to Perplexity. Scientific American. p107
  5. ^ Evolution experiments with digital organisms. Retrieved on 2007-01-19.

[edit] External links

Retrieved from "http://en.wikipedia.org/wiki/Artificial_life"
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