Affordances

A

Anton Flügge, Hannes Schulz

University of Osnabrück, Department of Cognitive Science

December 21st 2005

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Gibson’s Concept Types Later Definitions Aspects Application

J J G

b 1904, McConnelsville, OH

d 1979, Ithaca, NY

Ph.D. Psychology, Princeton, 1928

Worked at Cornell University,Ithaca, NY

Main contribution: The Perceptionof the Visual World (1950)

Claims perception is direct

Invented influential term“Affordance”

Founded School of EcologicalPsychology

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E P

E P

“It’s not what is inside the headthat is important, it’s what thehead is inside of”

Animals stand in a relationto the environment

To explain behaviours it isnecessary to study theenvironment in whichbehaviours take place

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D P

D P

Perception is gatheringinformation from meaning-ladenenvironment without performinginferences on the sensations

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G’ A-D

D (A)

The affordances of the environment are what it offers the animal,what it provides or furnishes, either for good or ill. The verb toafford is found in the dictionary, but the noun affordance is not. Ihave made it up. I mean by it something that refers to both, theenvironment and the animal in a way that no existing term does.

Animal Environment

Nutrition

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E: B A

DyingNutrition

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E: P A

Drive-on Affordance

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E: P A

Stove-Top-Control

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E: C A

Cognitive Affordances are provided by cultural conventions

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E: M A

Knowledge (Semantic Affordance)

Ties (Physical Affordance)

Mixed Affordance

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A B S

Warren (1984): Used “affordance” as ratio between size ofbody-parts and environment

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D

D (D)

Tendency to any action or state resulting from natural constitution

Dispositions are always actualized if certain circumstances occur

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T’ (1992) F

D (A)

p is Affordance⇔ ∃Wpq : Wpq = j(Xp ,Zq) (1)

p Disposition of theEnvironment

q Disposition of the Animal

X Environment

Z Animal

j Juxtaposition

Wpq Entity with (new)property r

Environment X Animal Z

p q

j

Wpq

r

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S’ (2003) C

1 Affordances should describe what can bedone, not what has to be done.

2 In any situation many actions arepossible, most aren’t actualized.

3 Dispositions must be actualized in theright circumstances (Turvey’s def), but jfilters them: Inconsistent.

4 Based on Turvey the property r cannot bedirectly perceived, it must be inferred

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S’ (2003) D

D (A)

An Affordance r is an emergent property of theanimal-environment system Wpa = (Xp ,Za).

p Disposition of theEnvironment

a Ability of the Animal

X Environment

Z Animal

Wpa Entity with emergentproperty r


p a

Wpa

r

Emergence

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C (2003)

N U

Affordances are relations, not properties of entities

Relation TallerThan(Averell, Joe)

The relation is not inherent in eitherof the objects but depends on bothof them

The relation is not an extra “thing”,yet it exists and is perceivable

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C’ A D

D

An Affordance is a relation between a feature f of the environmentand an ability a of the animal: Affords-Φ(f , a)

Φ Behavior

Affords-ΦRelation/Affordance

f Feature of Environment

a Ability of Animal

X Environment

Z Animal


f a

Affords-Φ

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A E

Reed (1996): Affordances are offered by Environment

Affordances exist independently of animals

Affordances exert selection pressure during evolution

Observed complementarity is an epiphenomenon

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A R A E

According to previousdefinitions a matchinganimal must exist forsomething to be called“affordance”.

Analogous to Dennett(1998): Female hipposdepend for loveliness onpotential observer,suspiciousness needs anactual observer

Affordances are “lovely”,not “suspicious”.

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T M P

Indirect View of Perception

Direct View of Perception

Direct Perception of Affordances

Affordances can be a solution tothe problem how our minds canbe private when we assumeperception to be direct.

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E

D (E)

An Event is a change in the layout of affordances (Chemero 2000)

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N

D (N)

A niche is a set of affordances (Gibson, 1979)

Nutrition

Housing

Gibson Bruce

Environment

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A: H C I

User interface affordances in a planning representation(Amant 1999)

U A C

Affordances are used todetermine the costs for

execution of operatorsgeneration of operators

Affordances used to modelusability of user interfaces

Allows “search” for optimaldesign in problem space

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A: S D

Affordance Theory for Improving the Rapid Generation,Composability, and Reusability of Synthetic Agents and Objects(Cornwell 2003)

I amattackable U A C

Objects in Env’t tell agentswhat they are useful for

Easy adding of new agents

Enhanced reusablitiy

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S

“Affordance” is a terminvented by James J. Gibson

The concept is intuitivelyappealing

There is an ongoing debateabout a formal definition

Even without a consensousvarious fields of researchhave been stimulated

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Technology

Affordances