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Psychological
Review
1994,
Vol. 101,
No. 2,
336-342
Copyright
1994
by the
American Psychological Association, Inc.
0033-295X/94/$3.00
Gibson's
Affordances
James
G.
Greeno
Gibson
developed
an
interactionist
view
of
perception
and
action that
focused
on
information
that
is
available
in the
environment.
He
thereby rejected
the
still-prevalent
framing
assumption
of
factoring
external-physical
and
internal-mental
processes.
The
interactionist alternative, which
focuses
on
processes
of
agent-situation interactions,
is
taken
in
ecological psychology
as
well
as in
recent
re-
search
on
conversational communication, research
on
complex, socially organized activity,
and
philosophical situation theory.
The
concepts
of
qffordance
and
ability
are key
ideas
in an
interac-
tionist account.
In
situation theory, abilities
in
activity depend
on
attunements
to
constraints,
and
affordances
for an
agent
can be
understood
as
conditions
in the
environment
for
constraints
to
which
the
agent
is
attuned.
This
broad
view
of
affordances
includes
affordances
that
are
recognized
as
well
as
affordances
that
are
perceived directly.
In
his
1954 article
on
visual perception
of
motion
and
move-
ment,
Gibson discussed several
ways
in
which perceptions
of
motion
and
movement
have
to be
understood
relationally.
As
he
remarked, citing
Kofflca
(1935),
"Just
as a
motion
for the
physicist
can be
specified
only
in
relation
to a
chosen coordinate
system,
so is a
phenomenal motion relative
to a
phenomenal
framework"
(J. J.
Gibson,
1954,
p.
310).
Most
of
the
psychology
of
perception that
had
been constructed was,
and is,
about phe-
nomena
that occur when
an
observer
is
stationary. Implicitly
in
this article,
and
more explicitly
in his
later, more comprehensive
theorizing
(1966),
Gibson argued that
a
psychology
of
percep-
tion
that
is
only
about stationary observation neglects some
of
the
crucial characteristics
of
what
it
claims
to be
about.
Another
commitment
of
Gibson's
contributions
was to a
psy-
chology
of
perception that avoids subsuming perceptual phe-
nomena
inappropriately
to an
apparently more comprehensive
theory.
I
recall
a
meeting
in
which
an
animal psychologist
was
reporting
on
observations
of the
development
of sex
differences
in
young
dogs,
and he
said that
one
function
of
urinating
by
male
dogs
was to
leave messages. Gibson
said,
"They leave
mes-
sages?
What
do
they say?" Although there
surely
is
some inter-
canine
function
of
urination involving territory, Gibson
re-
sisted
the
casual characterization
of
that process
in
terms
of
symbolic
communication.
On
another issue,
J. J.
Gibson
and E. J.
Gibson,
in
articles
also published
in
Psychological
Review
(J. J.
Gibson
&
Gibson,
1955a,
1955b), argued that perceptual learning should
not be
subsumed
by the
general
stimulus-response
theory that
was
then
at the
center
of
scientific
research
and
thinking about
ac-
tion
and
learning. They proposed that
the
psychology
of
percep-
tual
learning should
be
about learning
to
perceive more
of the
James
G.
Greeno, School
of
Education, Stanford University,
and the
Institute
for
Research
on
Learning, Palo
Alto,
California.
This research
was
supported
by the
National Science Foundation
GrantMDR-9154119.
Correspondence concerning this article should
be
addressed
to
James
G.
Greeno, School
of
Education, Stanford
University,
Stanford, Cali-
fornia
92305.
differentiating
qualities
of
stimuli
in the
environment rather
than
acquiring
associated
responses that cause greater
differ-
entiation
by
enrichment
of
stimuli
as a
result
of
past experience.
Postman
(1955)
criticized Gibson
and
Gibson's
(1955a)
discus-
sion, arguing that "descriptively, perceptual learning
is the at-
tachment
of new
responses,
or a
change
in the
frequency
of re-
sponses,
to
particular configurations
or
sequences
of
stimuli"
(Postman, 1955,
p.
441)
and
that "the need
to
account
for
changes
in
response inevitably endows
the
problem
of
percep-
tual
learning with
an
associative component" (Postman, 1955,
p.
442).
The
Gibsons were
not
convinced
by
Postman.
In
their
view,
"the main
difficulty
in the way of the
traditional enrich-
ment theory
is its
implication that learning involves
a
decreas-
ing
psychophysical
correspondence between perception
and
stimulation"
(Gibson
&
Gibson, 1955b,
p.
448). They reiter-
ated their previous contention that
"perceptual
learning
. . .
consists
of
responding
to
variables
of
physical stimulation
not
previously
responded
to. The
notable point about this theory
is
that learning
is
always supposed
to be a
matter
of
improve-
ment—of
getting
in
closer touch with
the
environment"
(Gib-
son
&
Gibson,
1955a,
p.
34).
In
their discussions
of
perception
and
perceptual learning
in
the
1950s,
J. J.
Gibson
and E. J.
Gibson
did not
present
a
broad
theoretical
framework
in
which their views were encompassed.
In
their continued work over
the
years,
however,
strong,
system-
atic theorizing
was an
important
part
of
their contributions.
In
the
1960s,
E. J.
Gibson
(1969)
proceeded
to
develop
a
general
theory
of
perceptual learning
and
development,
and J. J.
Gibson
developed
a
general
theoretical
framework
for
perception
and
sensation, which
he
presented
in The
Senses
Considered
as
Per-
ceptual
Systems
(J. J.
Gibson,
1966).
Cognitive science
was in
the
early stage
of its
development around
the
core idea
of
infor-
mation,
and the
main stream
of
cognitive science developed
a
theory
of
information processing. Gibson
differed,
and he fo-
cused
on the
question
of
what information
is
available.
In his
view,
many questions about
how
information
is
constructed
by
people
and
animals could
be
considered better
as
questions
about what sources
of
information
there
are in the
environment
that people
and
animals
use in
their activities. This
framework
is
an
alternative
to the
mainstream
view,
in
which people
and
336
SPECIAL
ISSUE:
GIBSON'S
AFFORDANCES
337
animals
are
thought
to
construct
the
world
that
they live
in and
understand.
In
Gibson's
view,
people
and
animals
are
attuned
to
variables
and
invariants
of
information
in
their activities
as
they
interact
as
participants with other systems
in the
world that
we
inhabit.
Gibson's
view
of
perception
has
been
difficult
for
many cog-
nitive
scientists (e.g., Fodor
&
Pylyshyn,
1981;
Ullman,
1980;
Vera
&
Simon,
1993)
to
understand.
I
believe this
is
because
Gibson's reasoning involves some quite general
framing
as-
sumptions about activity
and
cognition that
differ
from
those
of
mainstream cognitive science.
He
expressed
some
of
these more
general
ideas
in the
1970s
in
discussion
of the
concept
ofqffbr-
dances
(L
J.
Gibson,
1977,
1979/1986),
and the
task
of
devel-
oping
a
systematic general ecological psychology
is
being car-
ried
on by a
growing group
of
investigators (e.g.,
Shaw,
Turvey,
&
Mace,
1982;
Turvey,
1990,1992).
Situativity
and the
Concepts
of
Affordance
and
Ability
Bickhard
and
Richie (1983) argued that Gibson's thinking
evolved
from
a
view
of
perception
as
encoding features
of the
environment
toward
a
more general
view
of
perception
as an
aspect
of a
person's
or
animal's interaction with
the
environ-
ment.
The
encoding
view,
which
is
still prevalent
in
informa-
tion-processing psychology, involves analyzing cognition
in
terms
of a
factoring
assumption that supports analyses
of
different
stages
of
cognitive
processing
in
relative isolation
from
each
other.
A
claim
of
ecological psychology,
as I
understand
it, is
that
the
interactions among aspects
of
cognition
and
behavior
are
sufficiently
subtle
and
complex that
our
prevalent factoring
strategy
is
scientifically
unproductive.
As
Turvey
has put it,
"The types
of
phenomena that should lead
the way
must
be
drawn
from
perception
in the
service
of
action
and from
action
in
the
service
of
perception"
(Turvey,
1992,
p.
86). When per-
ception,
motor movement, memory, reasoning,
or
whatever,
is
studied
as a
separate
factor,
one
hopes that
the
conclusions
one
takes
from
those studies apply
in
situations where other factors
have
significant
roles. Although there
have
been occasional
ob-
jections
to the
factoring assumption (e.g.,
by
Dewey,
1896;
Lashley,
1951),
factoring
of
processes—especially
into events
occurring
outside
and
inside
the
mental
system—has
been
a
persistent methodological commitment
of
psychological
re-
search. Gibson
was
already suspicious that perception
and
the
observer's movement
did not
factor neatly
in the
perception
of
motion
when
he
wrote "The visual perception
of
objective
mo-
tion
and
subjective movement"
(J. J.
Gibson,
1954).
That lack
of
factoring
became
a
major point
of his
more general theory
of
perception
(J. J.
Gibson,
1966)
and has
been
a key
issue
in the
development
of
ecological psychology,
for
example,
in the
anal-
ysis
of
information
that
is
available
to a
person
or
animal mov-
ing
through
a
spatial environment (Cutting, Springer,
Braren,
&
Johnson, 1992; Lee,
1980).
An
important feature
of the
eco-
logical
view
involves
a
shift
in
situations that
are
taken
as
para-
digmatic
cases
of
cognition. Rather than building
a
theory
of
perception
on
analyses
of
situations with stationary observers,
and
building
a
theory
of
action
on
analyses
of
situations where
an
agent tries
to
reproduce
a
movement
of an
object
in
space,
ecological psychologists
are
working
to
build
a
theory
of
activity,
including perception
and
movement,
by
analyzing
situations
in-
volving
continuous interactions, such
as
cascade
juggling
(Beek
&
Turvey,
1992)
and
pursuit
of a
batted
fly
ball
by a
baseball
outfielder
(Michaels
&
Oudejans,
1992).
The
framing
assumptions
of
ecological psychology
are one
form
of a
general theoretical stance, which
can be
called
situa-
tivity
theory
(Greeno
&
Moore,
1993),
in
which cognitive pro-
cesses
are
analyzed
as
relations between agents
and
other sys-
tems. This theoretical
shift
does
not
imply
a
denial
of
individual
cognition
as a
theoretically important
process.
It
does,
however,
involve
a
shift
of the
level
of
primary
focus
of
cognitive analyses
from
processes that
can be
attributed
to
individual agents
to
interactive processes
in
which agents
participate,
cooperatively,
with
other agents
and
with
the
physical systems that they
in-
teract with.
If, in
analyzing those interactive processes,
one
con-
cludes that some
of
them factor conveniently into aspects that
can
be
attributed
to the
environment
and
aspects that
can be
attributed
to
individual minds, that will
be a
useful
and
produc-
tive
result. Those
of us who are
developing
situativity
theory,
however,
believe that
the
factoring assumption should
not be
taken
as a
general methodological
and
theoretical commitment.
Research
in
ecological psychology
has
focused mainly
on re-
lations
of
agents
with
physical systems
and
environments.
In
other research, processes
of
communication
and
reasoning
are
also being approached
in
ways
that
are
inconsistent with fac-
toring assumptions that
have
typically been made. Clark
and
Schaefer
(1989),
Schegloff
(1972),
and
others have analyzed
conversations
as
interactive collaborations
in
which contribu-
tions, such
as
references
to a
place,
are
considered
as
successful
joint actions rather than
as
events that occur when
one
person
uses
a
referring
term. Many studies
of
socially organized
prob-
lem
solving
and
reasoning
in
complex environments
have
been
conducted, including
a
study
by
Suchman
and her
associates
(Brun-Cottan
et
al.,
1991)
of the
ground operations
of an
air-
line,
and
studies
by
Hutchins (1991,
in
press)
of
processes
of
calculating
a
military
ship's
position
as it
enters
a
harbor
and of
remembering
to
adjust
the
wing
flaps of a
commercial aircraft
as
its
speed decreases during
a
landing. Symbolic representa-
tions
of
information
in
these situations
are
very
tangible,
and
the
theoretical analyses that turn
out to be
productive
are at the
level
of
functions that
are
accomplished
by
groups
of
people
interacting with each other rather than
of
hypothetical mental
representations constructed
by and
operated
on by
individuals.
The
view
of
problem solving that assumes
a
process
of
search
in
a
symbolic problem space consisting
of
representations
of
an
initial state,
a
goal,
and a set of
operators combined with
a
problem solver's domain-specific knowledge
and
strategy
for
planning,
has
been challenged
in
studies
of
reasoning
and
deci-
sion
making
in
activities
of
trying
to get
malfunctioning
photo-
copying
machines
to
work (Suchman, 1987),
of
grocery
shop-
ping
and
food
preparation
by
American adults (Lave,
1988);
of
selling
produce, candy,
and
other commodities
by
young Bra-
zilian
street merchants
(Carraher,
Schliemann,
&
Carraher,
1988;
Saxe, 1991);
of
making inferences about quantitative
properties
of a
physical system that behaves according
to
linear
functions
by
middle-school
and
high-school students (Greeno,
Moore,
&
Mather,
1993);
and of
solving
or
constructing expla-
nations
of
algebra word problems (Hall, 1990). These studies
have
taken
an
interactivist
view
of
reasoning, considering
it as
338
JAMES
G.
GREENO
an
interaction
of the
problem
solver with material systems that
include
meaningful
symbols
and
considering
the
interpretation
of
the
symbols' meanings
as an
important process
to be un-
derstood.
An
aspect
of
this approach
was
anticipated
by J, J.
Gibson
and E. J.
Gibson
(1955b),
who
argued, against Postman
(1955),
that study
of
learning
to
perceive symbols should
focus
on
processes
of
differentiation.
"Symbols, like natural objects,
must
be
differentiated
or
identified
in
order
to be
carriers
of
meaning.
They come
in
sets,
not
singly.
And it is
quite possible
that
the
meaning
of
a
symbol,
in the
mathematico-logical
sense,
is
given
by its
univocality
within
the
set" (Gibson
&
Gibson,
1955b,
pp.
449-450).
A
proposal
by
Neisser
(1992)
is
particularly relevant
to the
perception
of
symbols. Neisser
has
argued that
one
needs
to
distinguish
two
kinds
of
perceptual processes, which
he
calls
direct perception
and
recognition. Direct perception, which
provides information
for
orientation
and
locomotion
in
space,
occurs
in
dynamic interaction with
the
environment. Recogni-
tion, which provides information
for
identifying
and
classifying
objects
and
events,
is
more
effective
when
the
observer
can ac-
cumulate
information about
the
features
of an
object
or ar-
rangement.
If
we
choose
not to
factor behavior into
the
process categories
of
perception, memory, movement, reasoning, decision making,
and so on, one
then needs theoretical terms
for
referring
to as-
pects
of the
phenomena
and
systems
at the
level
of
agent-situa-
tion
interactions.
Gibson's
concept
of
affordance
is a key
pro-
posal.
The
idea
is
quite straightforward.
In any
interaction
in-
volving
an
agent
with
some other
system,
conditions that enable
that interaction include some properties
of the
agent along with
some
properties
of the
other system. Consistent with
his
empha-
sis
on
understanding
how the
environment supports cognitive
activity,
Gibson focused
on
contributions
of the
physical sys-
tem.
The
term
affordance
refers
to
whatever
it is
about
the en-
vironment that contributes
to the
kind
of
interaction that
oc-
curs.
One
also needs
a
term that refers
to
whatever
it is
about
the
agent that contributes
to the
kind
of
interaction that occurs.
I
prefer
the
term
ability,
although Shaw
et
al.
(1982)
preferred
to
coin
the
term
effectivity
for
that concept.
I
believe
my use of
the
term ability
is
also synonymous with Snow's
(1992)
use of
the
term
aptitude.
Affordances
and
abilities
(or
effectivities
or
aptitudes) are,
in
this
view,
inherently relational.
An
affordance
relates attributes
of
something
in the
environment
to an
interactive activity
by an
agent
who has
some ability,
and an
ability relates attributes
of
an
agent
to an
interactive activity with something
in the
envi-
ronment that
has
some
affordance.
The
relativity
of
affordances
and
abilities
is
fundamental. Neither
an
affordance
nor an
abil-
ity
is
specifiable
in the
absence
of
specifying
the
other.
It
does
not
go far
enough
to say
that
an
ability depends
on the
context
of
environmental
characteristics,
or
that
an
affordance depends
on
the
context
of an
agent's
characteristics.
The
concepts
are
codefining,
and
neither
of
them
is
coherent, absent
the
other,
any
more than
the
physical concept
of
motion
or
frame
of
ref-
erence makes sense without both
of
them.
As
Gibson's
idea
of
affordances
has
been developed
in re-
search,
it
seems most productive when
it is
treated
as a
graded
property rather than
as a
property that
is or is not
present.
A
beautifully
simple example
by
Warren
and
Whang (1987)
in-
volves
the
affordance
of an
aperture
for a
person
to
walk
from
one
side
of a
partition
to the
other.
The
affordance
provided
by
an
aperture
is a
function
of its
width,
and the
ability
of a
person