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MACS - A Research Project
for Exploring and Exploiting the Concept of Affordances for
Robot Control
IST-2003-2.3.2.4 Cognitive Systems
Project Number: FP6-004381
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Introduction
An affordance, a concept from Ecological Psychology, denotes a specific relationship
between an animal and its environment. Perceiving an affordance means perceiving an
interaction possibility that is specific for the
animal's perception and action
capabilities (Fig. 1). The MACS project investigated how this concept can be exploited to
improve a technical system, a mobile robot with manipulation capabilities.
The perception capabilities of mobile robots comprise detection and recognition
algorithms that work on sensory data. The richest data are usually provided by
camera images, and most employed algorithms stem from the field of Computer Vision.
Appearance-based object recognition is a widely employed method for robot
perception. But given that reliable recognition of everyday things is currently
restricted to low numbers of objects, such methods seem too restrictive for
reliable robot performance in everyday environments, particularly when mobile
manipulation is involved.
But what are the alternatives? Starting from the consideration that it is most
important that a robot will get its job done, it is clear that a robot would
benefit from abilities to find alternative solutions to a given task. The role
model is the human ability to improvise, e.g. to use artefacts in ways that they
were not designed for or to use one object instead of another one, provided they
offer similar functionalities. A human could easily decide to use a mug as a drinking
vessel if a glass is not available. Glasses and mugs have quite different appearances.
But what is important in this example is their function as a drinking vessel, not the
particular appearance. Fig. 2 shows another example,
namely opportunities for a human to sit.
Transferred to a technical system, perceiving an affordance does not include
appearance-based object recognition, but rather feature-based perception of
(object) functions. The central hypothesis of MACS was that an affordance-inspired
control architecture enables a robot to perceive more interaction possibilities
than a traditional architecture that relies on appearance-based object recognition
alone.
This project web site offers you the results of
the MACS project, including the list of project
publications and public deliverables, a link to an extensive online
bibliography on affordance-related research, videos
from the experiments, a list of events that we
organized or attended, and more.
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J.J. Gibson's Concept of Affordances - Linking
Perception and Action
"The affordances of the environment are what it
offers the animal, what it provides or furnishes, either for good or
ill. The verb to afford is found in the dictionary, but the noun
affordance is not. I have made it up. I mean by it something that
refers both to the environment and the animal in a way that no existing
term does. It implies the complimentarity of the animal and the
environment." ([Gib79], p. 127)
"... If you know what can be done with a graspable
object, what it can be used for, you can call it whatever you please.
... The theory of affordances rescues us from the philosophical muddle
of assuming fixed classes of objects, each defined by its common
features and then given a name. ... But this does not mean you cannot
learn how to use things and perceive their uses. You do not have to
classify and label things in order to perceive what they afford."
([Gib79], p. 134)
[Gib79] J. J. Gibson. The Ecological Approach
to Visual Perception. Houghton Mifflin, Boston, 1979
More on affordances ...
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Online bibliography
Research on affordances is being pursued in several
research areas, including Cognitive Science, Psychology,
Robotics, Artificial Intelligence, Design, and more.
If you want to get an overview of affordance research,
you may want to visit our online bibliography on
affordance research:
Literature list of affordance-related research
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Figures
Fig. 1: The same object, here a fist-sized stone, offers different affordances to
different animals. For an adult healthy human, it offers the affordance of throwing
it, or to use it as a tool, to name just two. For a mouse, it offers the affordances
to hide behind it or to climb on top of it, and for a cat it offers the affordance
of hiding prey.
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Fig. 2: Things that afford to sit upon for
a human being.
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Acknowledgements:
The MACS project was partly funded by the European
Commission's Sixth Framework Programme. This support is
gratefully acknowledged.
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