BioConcepts

agent

• A person who or thing which acts upon someone or something; one who or that which exerts power; the doer of an action. Sometimes contrasted with the patient (instrument, etc.) undergoing the action. (OED 2012)
  category individual

  c. 1500

  The fyrst [kind of combining] is callyd by phylosophers dyptatyve be-twyxte ye agent & ye pacyent.

  Ripley, G. (c. 1500). The Compend of Alchemy (Ashm.) l: 718.

  1995

  An agent is anything that can be viewed as perceiving its environment through sensors and acting upon that environment through effectors.

  Russell, S. & Norvig, P. (1995). Artificial Intelligence: A Modern Approach: 33.

  1995

  agent systems are systems that can initiate, sustain, and maintain an ongoing and continuous interaction with their environment as an essential part of their normal functioning

  Smithers, T. (1995). Are autonomous agents information processing systems? In: Steels, L. & Brooks, R.A. (eds.). The Artificial Life Route to Artificial Intelligence. Building Situated Embodied Agents. New Haven: 97.

  1995

  By autonomous agent, I mean any embodied system designed to satisfy internal or external goals by its own actions while in continuous long-term interaction with the environment in which it is situated

  Beer, R.D. (1995). A dynamical systems perspective on agent-environment interaction. Artificial Intelligence 72, 173-215: 173.

  2000

  Agency occurs as soon as a system is able to modify some of its boundary conditions “for its own sake”.

  Ruiz-Mirazo, K & Moreno, A. (2000). Searching for the roots of autonomy: The natural and artificial paradigms revisited. Comunication and Cognition-Artificial Intelligence 17, 209-228: 217.

  2000

  Agents are entities which engage in normatively constrained, goal-directed, interaction with their environment

  Christensen, W.D. & Hooker, C. (2000). Autonomy and the emergence of intelligence: Organised interactive construction. Communication and Cognition-Artificial Intelligence 17, 133-157: 133.

  2000

  An autonomous agent is a physical system, such as a bacterium, that can act on its own behalf in an environment.

  Kauffman, S.A. (2000). Investigations: 8.

  2005

  Behaviour defined not as physical coupling, but as its regulation, is always asymmetrical, has an intentional structure, and can be said to either succeed or fail. It is only at this stage, when the organism behaves, that we may speak of an agent […] i.e., a self-constructed unity that engages the world by actively regulating its exchanges with it for adaptive purposes that are meant to serve its continued viability.

  Di Paolo, E.A. (2005). Autopoiesis, adaptivity, teleology, agency. Phenomenology and the Cognitive Sciences 4, 429-452: 443.
  

  2009

  an agent is an autonomous organization capable of adaptively regulating its coupling with the environment according to the norms established by its own viability conditions.

  Barandiaran, X., Paolo, E. di & Rohde, M. (2009). Defining agency. Individuality, normativity asymmetry and spatio-temporality in action. Adaptive Behavior 17, 367-386: 376.