the plasticity of categories color

8/9/2019 The Plasticity of Categories Color

1/34

The British Society for the Philosophy of Science

The Plasticity of Categories: The Case of ColourAuthor(s): J. Van BrakelSource: The British Journal for the Philosophy of Science, Vol. 44, No. 1 (Mar., 1993), pp. 103-135

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2/34

Brit.

J. Phil.

Sci. 44 (I993)

I03-I35

Printed n

Great

Britain

The

Plasticity

of Categories:

The

Case

of

Colour

J. VAN

BRAKEL

ABSTRACT

Probably

olour

s thebest

worked-out

xample

f

allegedly

europhysiologically

innateresponse

ategories

etermining

ercepts

nd

percepts

etermining

on-

cepts,

andhence

biology ixing

hebasic

ategories

mplicit

n the

useof

language.

In this

paper

I

argue against

this

view and

I

take C.

L.

Hardin's

Color or

Philosophers

1988]

as

my main

target.

I start

by

undermining

he

view that

fourunique

hues

stand

apart

rom

all other

colour

shades

Section

2) and

the

confidence

hat

the solar

spectrum

s naturally

divided

nto

four

categories

(Section

3).

Forsuch

categories

o be truly

universal,

hey have

to be true

for

all peoples nd n Section4 I showthatBerlinand Kay's 1969] widelyquoted

theory

of basic

colour

categories

s

not sufficiently

upported

o

lend

it any

credibility.

Having

disposed

f

the

view that

inspection

f language

or 'pure'

perception

unveils

the

universal

colour categories,

turn to

neurophysiological

nd

psychophysical

heories

f colour

vision

osee

whether

hey

provide

more olid

basis

for deciding

what the

innate

response

ategories

re.

In

Section

5 I show

that Hardin's

ccount

of

theopponent-process

heory

neither

upports

is

view

that

'colour-coding

takes

placeearly

n the visual

neural

pathway,

nor

his view

that

knowledge

f colour

vision

science

will

help

us solve

many

philosophical

mysteries boutcolour.

In

Section

6 I

give a

more

detailed

eview

of

what is known

today

about

he

neurophysiology

f

colour

vision

and I show

that theres

nothing

n the

brain

whichcould

be

called

a colour

module,et

alone

a module

with

homunculi

or

particular

asic

colour

ategories.

nSection

7 I show

hat

psychophysical

odels

do not

support

such

rigid

constraints

on category

formation

ither.

Hence

(Section

8), at least

in the case

of colour,

current

cience

supports

plasticity

in the formation

f

categories

hat

goes

far

beyond

he

requirements

f

those

naturalistic

hilosophers

howould

ike o

ground

rimitive

oncepts

n biology.

1 Introduction

2 The

Alleged

Natural

Primacy

of Four

Unique

Hues

3 Dividing

up the Solar

Spectrum

4

TheAlleged

Universality

f Eleven

Basic Colours

4.1

Methodological

riticism


3/34

Io4

J. Van Brakel

4.2 TheDefinition f

Colour

Term

4.3 TheDefinition f Basic ColourTerm

4.4 OtherExplanationsor TheirUniversality

4.5 UnnamedCategories

4.6 BCCsand UniqueHues

4.7 Languageswith Less ThanSix BCCs

5 Hardin'sAccountof ColourVision

5.1 Neurophysiologicalccount

5.2 Psychophysical ccount

5.3 Philosophicalmplications

6 Moreon the Neurophysiologyf ColourVision

6.1 Single-opponent ells

6.2

Double-opponentells

6.3 TheConcept f 'Colour-coded' ells

7 Moreon PsychophysicalOpponent hannels

7.1 Problemswith the SimpleModel

7.2 Chromatic-Responseurves nd UniqueHues

8 Concluding emarks

I INTRODUCTION

SeveraldisciplinesoSer theories according o which there are severe con-

straints on what concepts can be formed to categorize he experimental

world. Take or leave a few details, a number of primitiveconcepts are

assumed to be biologically nnate, wired into the brain as prototypes,

modules,or gestalts,the result of evolutionary nteractionof the organism

with its environment.As Fodor [1981], p. 312) writes about emotions:

Consideruch folk-psychologicalonceptsasANGRY,SAD, HAPPY,etc. I think

there'sno doubtthat these are acquired arly, that they must have been part

of the universalprehistory f our species,and that they are easily introduced

by ostension.

In this paper I take colour as an example to argue that the facts of

neuroscience or psychophysics) et no interestingconstraintson the cate-

gorizations r concepts mplicit n the way we use colour words.1

l The term 'constraint' Hardin 1988], p. xxii) would warrant urtheranalysis.Here it is

meant to include such formulations s: the existence of 'linguisticuniversalsbased on

pan-humanneurophysiologicalrocesses' Kayand McDaniel 1978]); 'hue naminghas a

relatively implephysiological asis' (Wernerand Wooten [1979]); 'a primary pigenetic

rule for basiccolourcategories' Lumsden 1985]); 'Psychology, natomy,and psychology

help to constructand to patternbasic categorizations f color, and there do exist natural

divisionsof the spectrum' Bornstein,n Harnad 1987], p. 291); 'the link betweenbasic

colorsensations nd theirnames s congenialand physiologically ased' Boynton nd Olson

[1987]); 'our experience f colorshapes he way we describe t; the structure f colorspace

is not established y convention' Hardin, . 202).


4/34

The

Plasticity

of Categories:The Case

of Colour

IOS

Throughout

I shall use as

a target C. L. Hardin's

Color or

Philosophers

[1988].

He states

as his goal:2

to encourage

and provoke ther

philosophers

o cometo gripswith

the relevant

scientific

material,and to promulgate

within

the philosophical ommunity

he

opinion

hat, henceforth,

discussionsabout

colour proceedingn

ignoranceof

nsual

science are intellectually

rresponsible.Hxn]

and what

we can learn from

science is that 'it is

the biological

perspective

which

is the viamediabetween

. . colors n the extradermal

hysicalworld

and . .

. the properties

f sensedata' [H58].

His method s 'to

suppose hat

phenomenalsimilarities

and

diSerencesare rooted

in and to

be explicated

by physiological

imilarities nd

diiYerences'H127].

Philosophically

his will

'provide resh approaches

o stagnant

problems' H181];

in particular:

(a) '

We are to be

eliminativistswith respect

o coloras a property

f objects,

but

reductivistswith respect

o color

experiences' H112].

(b) 'the

semantics

of ordinary olor terms

is powerfully onstrained

by

the

physiology

of the human

visual system'

[Ekxii].

Hence,

Wittgenstein

and his followers

are wide of the mark

in trying

to

findsolutions n the use of language.Forexample, he relationsbetweenthe

meanings

of colourwords can

be explainedwith

reference o

the existence

of two opponent

airs of unique

hues or primitive

olours:

red/greenand

blue/yellow.And

the cross-culturaluniversality

of the constraintson

the

ordering

of the colour

space s supported

y Berlinand Kay's

1969] theory

of basic

colour terms(to be

discussedbelow).

In this

paper I shall concentrate

on the relation

between

naming

colours and the

science of

colour vision and I shall

conclude that biology

does not

set any

interesting onstraints

on colour semantics.

am sceptical

about:

(a) theories

about pre-linguistic

or pre-conceptual

ognitive

experiences

(such

as categoricalperception),

nvoking

privileged alient

categories

innate

to the

human race;3

2 In square

brackets

I give references o Hardin's

book using

'H' followedby the

page

number.

Although

I often quote literally, he

passages so indicatedshould

be taken

as

paraphrases

f how

I interpretHardin's osition.

3

For categoricalperception

ee

Harnad[1987]; for pre-conceptual

odilyexperiences

ee

LakoW1987]. It is possible, f course, o argue hat on a pre-linguisticognitive evel there

are a

numberof primitive olours,

the presence

of which may be blurred

by 'mistaken'

conceptual

chemes

embodiedn language,but

this is not Hardin'sine. For

examples f

this

approach

ee Kayand Kempton

1984] and

Lakoff 1987], who assume

that basic colour

categoriesare cognitively

nnate,

but these cognitive capacities

may be suppressed

by

language.


5/34

Io6

J. Van Brakel

(b) theoriesabout naturalkinds which dividethe world n a fised number

of basic categories to be discoveredby science);4

but I wonst argue for that here. If any of these theories were true, say a

gene-culture heory about the pre-linguistic ategoricalperceptionof four

primitive olours(Lumsden 1985]), then the point of this paper s that the

truth of such a theory sets no interesting onstraintson colour semantics.

2 THE ALLEGED NATURAL PRIMACY OF FOUR UNIQUE HUES

Whatthen are the phenomenal imilarities nd diSerences nd the semantics

of colourwords,awaitingthe biologicalvia media7According o Hardin, he

basic fact of colour vision is the existenceof four incompatible nique hues

(red,green,yellow, and blue).5A uniquehue is a colourshade that contains

no tracesof the other uniquehues. Binaryhues (likepurpleand orange)are

equal mixtures of neighbouringunique hues. A colour consisting of two

opponent ues (green/red,blue/yellow) s impossible. n addition here are

two uniquebrightness r lightness erms:blackand white.6All other olours

can be describedn termsof these six primitive olours.Hardinhas no doubts

that the four unique hues

do have certaincharacteristics ecessarily.This s a central ruth . . One can

succeed n the task of identifying he hues with some physicalstructureonly

if that structure aptures he essentialeatures f the hues as these aredisplayed

to us in experience. . [for example:] t is impossibleor there to be a unique

orange. [H66]

4 Although he emphasis n the philosophicaliterature s on things like gold and tigers,also

coloursare often considered aturalkinds.Quinediscussed yellow' as a naturalkind term

and so does Kripke.Kripke's iew impliesthat there is an extra-cultural,metaphysically

existingnaturalkindYELLOW,hereasactualusage of the term 'yellow' n our culture or

similar erms n othercultures)may well be (partly)wrong.We must eave to the specialists

what really s yellow. This leaves room for linguisticrelativity o be explained n terms of

localcircumstances. hisnaturalkindapproach, lacingwhat is true n the world eventually

to be describedn terrns f the TrueScientificTheory), s differentromboth the Berlinand

Kay approach placingwhat is true in language)and the 'rationalWhorfianism'mentioned

in the previousnote (which placeswhat is true in innate cognitivecapacities).

5 The deaof a perceptual niqueor unitaryhue has a long history Leonardo a Vinci,Goethe,

Mach)andwas firstput on a theoreticalootingby Hering 1920]; unique ue s the translation

of Urfarbe. lreadyHeringdraws on language o support heir reality: languagehas long

since singledout red, yellow, green, and blue as the principal olors of the multiplicity f

chromatic olors' (p. 48).

6 In this paper I shall use the term 'brightness' hroughout o refer to the appearance f

darkand light. In a more narrowsense 'brightness' s only used for the intensityof lights

and surface colours viewed in aperture mode. Then the corresponding erm for the

appearance f surfacecolours s 'lightness'.The physicalproperty f light that corresponds

roughly to brightnessand lightness s called 'luminosity'.Colourscientistsdo not agree

on the relationsbetween hese concepts; ee Boynton [1988], pp. 87f) and Beck [1972].


6/34

The

Plasticity

of

Categories:

The

Caseof

Colour

Io7

Nevertheless,

his sort

of

necessity

s

apparently

f a Kripkean

ort,

which

is subject

to

scientific

revision.

Referring

o

the

experiments

of

Crane

and

Piantanida 1983], Hardin ays that having a reddishgreenexperience is

a matter

to be settled

by experiment'

[H125].

Hence,

'it is conceptually

possible

that

something

could

look

both red

and

green

all

over' [H125].

And

any necessity

in the

subdivision

of the

colour

domain

disappears

completely

when

he discusses

he

various systems

that have

beenproposed

to order

colour

space,

such

as the

Munsell

Colour

System

or the Natural

ColourSystem

(NCS).7

He

says that

'the

issueis

not that

there

cannot

be

a

consistent

scheme

of

representing

henomenal

olour,

for there

can

. . . The

point is

rather,

that

one cannot

expect

any

single

representation

o be

serviceableorall purposes' H120]. And also:'since we have no indepen-

dentphysical

criteria

or the identity

of hues,

we are

obliged

o fall

back

on

some form

of

stipulation'

[H89].

But if that

is

so, we

may

as well

extend

this

pragmatic

attitude

o the

unique hues,

and even

to

the whole

category

of colour.

Why

would

a representation

f

colour in

terms

of six

primitives

be serviceable

or

all

purposes?

Why

would

there be one

concept

of

colour

which

serves

all purposes?

Hardin

quotes

various

bitsof

'behavioral

vidence

hat

shows

the

natural

primacy

of the unique

hues' [H41,

emphasis

added].

For

example:8

it was

discovered

hat

subjects

ould

completely

escribe

ll

the

spectral ights

as well

as the purples

by using

just

the unique-hue

names,

but that they

were

unable

o give

a complete

description

f thenames

o

whichthey

wererestricted

lacked

one

of the

unique-hue

names.

[H42]

How

necessary

s

this result?

English

speakers

may

manage

quite

well

in

psychophysical

xperiments

using

six

Basic Colour

Terms(BCTs

or short),

7

TheNCS ystem

tipulates

equaldistancesbetween hefouruniquehuesandthesame0-100

per

centscale

for hesaturation

f thesefour

hues.

TheMunsell

ystem

s based

on equal-sized

perceptual

steps along

each of

the

dimensions

hue,

saturation,

and brightness,

but each

dimension

s scaled

differently.

n

orderingwith

uniform

perceptual

ntervals

betweenany

two adjacent

olours

s

of coursepossible,

but this

meansthat

we lose

the attractive

eature

of planes

of constant

hue

(Indow

[1988],

[H119]). All

these systems

are conventional

n

the

sensethat

theydefine

colour

n terms

of hue,

brightness,

ndsaturation

nly (see

Notes

9

and 21).

8

Hardin

mentions hree

morepieces

of evidence:

nfant

hue space

(see

Note10),

Rosch's

work

withthe

Dani

(seeSection

4. 5),

andratings

ofthe 'qualitative

imilarity'

f fourteen

olours.

With

regard o

the

latterhe

says:'Notice

particularly

hat

the

unique

hues.

. . are spaced

about90

degreesapart,

whichis the

spacing

hat the

opponent

heory

would

have

led one

toexpect' H42]. However,hepicturehe presentswould it thepainter's olourwheelbetter,

with

the primaries

ellow,

blue

andred

placed

120 degrees

apart.

Moreover,

ndow

[1988]

provides

data,

spacing

the five

Munsellprimaries

red,

purple,

blue,

green,

and yellow

about 72

degrees

apart.

Finally,

in the

colour hexagon

used by

printers,

six primaries

(magenta-red,

iolet-blue,

yan-blue,

green,

yellow,

and

orange-red)

re

'naturally'

placed

60 degrees

apart.


7/34

J.

Van

Brakel

Io8

naming

six Basic

Colour

CategoriesBCCs

or

short).9

But by

itself it

does

not

supportwhat

Hardincalls the

'natural

primacyof

unique

hues'.

That

would

certainlybe an

old-fashioned

iew of the

naturalnessof

the

English

language. In such experimentsspeakersmight just be displayingthe

peculiarities f the

contingent

relations

between

English

colour

words.

Even f it

were

true, as

Hardin

uggests,

hat 'the

division

between

unique

and

binary

hues is

manifestly

bound

up with

the

peculiar

characteristics

of the

human

visual

system'

[H67],

this would

be

irrelevant or

the

'natural

primacy'

on

the

phenomenal

evel, if

speakers

of

other

languages

would

employ

diSerentBCCs.

So it is

crucial

for

Hardin's

program o

substantiate

that

BCTsare

linguistic

universals.

3

DIVIDING UP

THE

COLOUR

SPECTRUM

More

han one

colourscientist

has

askedme

the

rhetorical

uestion

whether

anybody ould

doubt hat the

solar

spectrum

aturally

divides nto

fourparts:

blue,

green,

yellow

and red.

Therefore,

n

this

section, I

list some

opinions

on

the colours

that

can be

seen in the

spectrumand

in

the

rainbow.

Note

that

the

discussion

has

now

shifted rom

unique

hues to

primitiveor

basic

colours.The

first

referto

lines in

the

spectrum, he

second to bands

of

the

spectrum.

Obviouslythe spectrumis the paradigm of the scientificconcept of

colour

although

there

are many

non-spectral

olours:

black,

white,

grey,

brown,

olive, purple

and

pink, to

name just

a

few. Also

spectral ights

are

not very

representative

f the

ordinary

situation of

seeing

contextualized

surface

colours.

Nevertheless,

lmostall

scientific

esearch

on

colour

vision

is

carriedout

with

spectral

colours,

whether

t is

humans

who are

askedto

match a

spectral

light with

a

mixture of

other

spectral lights,

or the

unfortunate

monkeys

who are

anaesthetized

nd

paralysed o

that a

hole

can

be drilled

n

their eyes

to

measure the

response

of

particular

cells to

spectral ightflashesdirectedat tiny spotson theirretina.

What

are the

colours

of the

spectrum?

According o one

oft-quoted

tudy,

four-month-old

nfants see

no

problem

here. They

naturally

divide

the

spectrum

nto four

colours:red,

yellow,

green

and blue.10

However,

when

9

Althoughone

might

wonder

whether

heywould

manageas

well if

presentedwith

metallic

surfacesnstead

of

spectralights.

Kuehni [1983],

p. 42)

saysthat

metallic

coloursare

a

'groupof

colorswe

perceiveas

unique' (emphasis

dded),

althoughhe

addsthat

this is

'an

aspectof

the

appearance f

objectsnot

strictly

elated o

color'.See

also

Note 21.

For

a

review of infant

colourvision,

see Tellerand

Bornstein

1987], who

stressthat

all

pre-1975

studiesare

ofhistorical

nterestonly

because

differencesn

brightness

nd in

hue

were not clearlyseparated.Theconclusion hat four-month-oldnfants use' fourBCCso

divide he

spectrum s

basedon

one

1976

experimental

tudy, nvoked

by Hardin

H41]

to

support

he

existenceof

four

uniquehues and

also in

order o

explain hat

we

havewords

for he

binaries range

and

purple,but

not for

yellow-green

H163].

Because

our-month-old

infants

(and

adults) are

not interested

n

looking at

green-yellow

colours this

shows


8/34

The

Plasticity

of Categories:

The

Case

of Colour

IO9

they grow

up they

have

great

difficulty

earning

to use

colour

words

correctly.1l

At age

two

they use

them

in the right

context,

but

usually

produce

he wrong

name.

At age

four they

are still

making

many

mistakes

in the correctuse of words ikeblue,althoughtheirvocabularymayalready

include

such

wordsas

beige and

tan.

Even at age

twelve

they may

name

the

same

spectral

olour

blueor yellow

on diGerent

ccasions.

Moreover,

he

sequence

n which

they

learnto

use colour

words

correctly

varies

widely,

although

there

is a definite

tendency

for North

American

children

at

university

day-care

centres

to first

get orange

right

(perhaps

because

they

regularly

get oranges).12

Therefore

I shall

consider

the observations

of

four-month-old

nfants

irrelevant

or an assessment

of

how

the colours

of

the

spectrum

hould

be divided.

Whatdo adultssay aboutthe coloursof the spectrum?Manytextbooks

state

that

Newton

discovered

the spectrum

consisting

of

the following

colours:

red,

orange,

yellow,

green, blue,

indigo,

violet.

How

reliable s

this

scientific

act?

Newton

himself

did

not see seven

colours:13

I heldthe

Paper

so that the

Spectrum

niight fall

uponthis

delineated

igure,

and

agreewith it

exactly,

whilst an

Assistant,

whose

Eyesfor distinguishing

Colours

weremore

critical

han mine

. . .

note the Confines

f the

Colours,

hat

is . .

. of the

red . . . orange

.

. yellow . . .

green . . blue

. . .

indigo . .

and . .

.

blue.

As

Campbell

1983] notes:

'If

Newton's

assistant

had

not been so

eager

to

please

his

master our

current

textbooks

would be

different.

Newton's

assistant

'saw'

seven

colours because

at the time

the

harmonic

series of

Pythagoras

till dominated

mathematical

hinking

and

Newton (and

many

scientists

after him)

studied

he analogy

between

the colour

spectrum

and

(accordingo Hardin)hatit is an unpleasant olour.A moreplausible xplanationmightbe

that

a saturation

minimum s perceived

n the yellow-green

egionof the

spectrum,which

just

makes it less

colourful.

This would

also

undermine

the conclusion

that

infants

distinguish

etween

he primitive

olours

yellow

andgreen,

as distinct rom

being

sensitive

to saturation

gradients.

Tellerand Bornstein

onclude heir

review

saying:'The

topicof

infantspectral

ensitivity

hus remains

poorly

understood,

nd nature

is still

not yielding

her secrets

easily n this

area.'

For a review

of the

development

f colournaming

in

children, ee

Bornstein

1985]

and

also

Andrick nd

Tager-Flusberg

1986].

12

In severalstudies

orange'

came

out firstor

second

for two- or three-year-old

hildren.

t

alsocameout

first

as thecolour

with thehighest

memory

accuracy'

or

DaniandAmerican

adults

(Rosch

Heider[1972]).

Andrickand

Tager-Flusberg

1986]

reported

a strong

correlation etween he mothers'andchildren's se of specific olour ermsandconcluded

that 'external

&ctors,

such as

the input

and guidance

provided

by children's

mothers,

interact

with

andhelp to

shapethe concepts

whichunderlie

he

color exicon'.

13

Newton,Opticks

1952],

p. 126;

see alsothe often

reproduced

olour

circle

on p. 155.

When

he just

lookshimself,

he

only listsviolet,

blue,

green,yellow

andred (pp.

31, 114,

124).


9/34

J. Van Brakel

I I O

musical chords.l4 Newton's definitionof the spectrum n terms of seven

colourshas survivedprimarily ecausepicturesof the spectrum n textbooks

are either 'artist'srenderings' r very bad photographs.l5 have even come

across scientificencyclopaedian which the pictureof the spectrum imply

consistsof seven homogeneously olouredbands.

In fact, it is not easy to assess the colours of the spectrum.Firstly, he

colourswe see in a solar spectrumdependon many factors: he materialof

the prism, the distance of the prism from the screen, the size and shape

of the aperture, he intensity of the light source, the manner of viewing,

etc. Secondly, the observationof colour bands may be enhanced by the

Frauenhoferines.

What other observationsdo we have, apart iom Newton's assistant?

ThomasYoungdivided he spectrum nto three olours(presumablyn order

to supporthis trichromaticheoryof colourvision); irst nto red,yellow, and

blue, changing t to red, green, and violet a few years later (becauseof data

reportedby Wollaston).According o Helmholtz,a spectrum hort enough

to be viewed in its entiretyall at once consists of four colours (red, green,

blue, violet) and he notes further [1911], p. 117):

Newton'sdivision nto seven principal olourswas perfectly rbitraryrom he

beginningand deliberatelyoundedon the musicalanalogies . . Indeed, here

are no real boundariesbetween the coloursof the spectrum.These divisions

are more or less capriciousand largely the result of a mere love of calling

things by name.

Mostrecent encyclopaedia have consulted ist five or six colours.It is still

a matterof disputewhetheryellow can be seen in a finelyresolved pectrum

(Campbell1 983]).

But can't we all see that yellow must be includedby looking at a good

rainbow('whose most prominent eature s that it consistsof a small set of

clearlydiSerentiatedoloredregions' [H156])7 Surely, f we concentrateon

seeing yellow, we'll see it (provided he circumstancesare right); but

the same appliesto pink or orange or turquoise if the circumstancesare

4 Theperfect umber even s stillwith us. Paritsis nd Stewart 1983] write(p. 109): 'When

we look at the analysednarrowband of sunlight hrougha prismas Newtondid, we see

that seven colours are emphasized . . The above phenomenamay be considered s an

indication hat, at the cortical evel, colours are classified nto seven classes of cells' and

data are provided o support his claim.

l5 Campbell1983]: 'I have examinedmany coloureddisplaysof the spectrum n dozensof

text-books f physics,photography nd visualpsychology ncluding ome very recentones

such as Hurvich 1981) . . . It is difficulto photograph spectrum orthe dyeschosenhave

a narrower pectral ensitivity omparedwith the eye . . . The only illustrated pectrum

could find that was nearly correctwas that of R. A. Houston 1923) a very experienced

spectroscopist.


10/34

The

Plasticity

of Categories:

The

Case of Colour

I I I

right).16

Newton

usually

describes

a rainbow

as

consisting

of red,

yellow,

green

and blue;

originally

he

identified

ive

colours(including

orange)

and

officially

ettled for

seven.

Munsell

refers o

the rainbow

in

support

of the

five primary

hues on

which his

now

widely used

Munsell

ColourSolid is

based:

red,

purple,blue,

green, yellow.17

The Luri

(Iran)

call the

rainbow

'red-green'.

Arawakspeakers

Surinam),

when asked

aboutthe colours

of

the rainbow,

were at a

loss what

to say.

WhenDe

Goeje

[1928],

p. 173)

pressed

bilinguals

to translate

'The

rainbow

has

many diiCerent

olours',

they

translated

t

by to yawale

abalokodiako

ka-ya-n-da,

lossed

as 'this

rainbow

different

upon with-image'.

I leave

it to the reader

o decide

how

manycolours

they saw

in the

rainbow.18

Nothingvery

much follows

rom his

brief

surveyof disagreements

n

the

coloursof the spectrumand the rainbow.Andthat is precisely he point. It

just

is

not a very

reliableprocedure

o rely on

'pure'

perception

o establish

that

the spectrum

s madeup

of four primitive

BCCs.

4 THE

ALLEGED

UNIVERSALITY

OF ELEVEN

BASIC

COLOURS

In

support f

the universality

f BCCsHardin

efers

o Berlin

and

Kay[1969],

in

which it

is argued

that,

although

diSerent

anguages

encode

in their

vocabularies

diSerent

numbers

of BCCs,

a

universal inventory

of exactly

elevenBCCs xists.BCCs re characterized y theirfoci:the bestexampleof

a colour

category.

Boundaries

between

colour categories

luctuate

widely

between

languages,

but

if we ask

people

about

best

examples,

there is

(according

o

Berlinand

Kay)cross-cultural

greement.

Moreover,

he

order n which

BCCs

merge

n the languages

of the world

follows

a definite

pattern: irst

white

and black,

then red, next

green

and

yellow,

followed

by blue,

then brown,

and finally

purple,pink,

orange

and

grey (the

latter

in no

specific order).

This evolution

is associated

with

technological

development.

Accordingto Hardinthe work of Berlinand Kay 'has by and large

successfully

passed the

critical

scrutiny

of linguists

and

anthropologists'

[H156].

All

peoples employ

the 'natural,

biologically

nduced set

of

hue

categories'

H156], because

the basic

linguisticcategories

hemselves

have

been

induced

by

perceptual

aliencescommon

to the human

race' [H168].

16

Again,colour

photographs

ould

seem

to be unreliable.

na photograph

f a rainbowabove

Newton's

birthplace

Campbell

1983])

I see five bands:

violet,

green,

white orange,

ilac.

17

According

o his diary

of

13 April1900,

as reported

y Indow

[1988].

18

In Arawak

here s

no separate

olour

domain,although

here

arewords

ikecolour

words.

Thereare threetermscovering he brightness r intensityof light:karimetodark/black),

harrirato

light/white),

ubuletovarious

mediumbright

colours,

ncluding

yellowand

light

blue).In addition

t

designateshue

aspects

via a vegetation

metaphor,

lso

withthree

basic

terms:

moroto

unripe,mmature,

reen,pale

yellow),kereto

ripe,

mature, ed,orange,

deep

yellow),

andbunaroto

overripe,

verdone,

brown,buff,

an,

purple).


11/34

J. Van Brakel

I I

2

Hence: biologydeterminesphenomenology nd, in consequence,a piece of

semanticstructure' H156].

Hardin'sappeal o Berlinand Kay is paradigmatic f the enthusiasticbut

uncriticalway in which philosophers ngaged in naturalizingphilosophy

sometimesdrawon SCIENCE.shall therefore pellout a numberof criticisms

of the Berlinand Kay theory of eleven BCCs nd the way Hardinwants to

have it supporthis view that biologysets strongconstraintson language.19

4.1 Methodologicalriticisms

In reviewsof Berlinand Kay[1969] theirworkwas described s an outdated

form of science, hastily conducted, gathering data in a slapdash way,

containing many ethnographic rrorsand uncriticallyacceptingaccounts

by writerswho had theoreticalaxes to grind.20

Furthermore, ll subsequentwork n the Berlinand Kaytraditionhas been

carriedout with

Munsell olour hips

nd standardized rocedures o elicit

BCTs. t has been estimated hat in doing this 95 per cent of the world's

colour words are eliminated.The decontextualization lso eliminates all

aspectsof semantic or symbolicdepth. If colour is stronglyembedded n a

culturallysalient semanticnetwork,measuringBCCswill of course mirror

the properties f this structure.For example,eight BCTsare found in the

Khmer anguage (Cambodia).nsteadof assigninga particular volutionary

stage to this culture on the basis of there being eight BCCs, t is obviously

more crucial o note that all Khmer peakersknow variousmyths about the

origin of colours such as the story of 'Eight-Colours-Crystal-Woman

Similarly,having a three-colour-symbolismmany African cultures) or a

five-colour ymbolism forexample,Turkish,MandarinChinese)will strongly

influencethe 'salience' of colour words in the particular anguage, if not

predeterminehe numberof BCTs hat will be found.

More echnicalcriticisms f using a fixed et of 320 colourchips nclude:

(a) In elicitingthe foci data the 320 chips are shown togetheron a chart

(with hue changing horizontallyand brightnessvertically).It is well

documented hat the appearance f colour dependson its environment

l9 In the next subsections give examples rommany differentanguagesdrawingon a few

hundred publications,all of which it is not practicalto mention here. More detailed

surveys, ncluding ull bibliographiesan be found in Saunders 1992] and van Brakel

[forthc.].Manyof the relevant eferences an also be found n Berlinand Kay [1969], Kay

and McDaniel 1978], Kay and Kempton 1984], MacLaury1987], Saundersand van

Brakel 1988], Tornay 1978], see also van Brakel 1992a, 1992b].

20 The original heory was based on 98 languages: or 20 languagesactual colour-naming

experimentswere carriedout with speakers f those languages n the San FranciscoBay

area (with the exceptionof Tzeltal); or 12 languagesdata were obtained rom personal

contacts with linguists and anthropologists;or the remaining66 languagesdata were

extracted romdictionaries nd ethnographies.


12/34

The Plasticity

of Categories:

The Case of Colour

I I 3

and when subjects

are presented

with the same

chips ordered

diSerently

diSerent

oci

are chosen.

(b) Only hue and

brightness

s varied.All chips

are at maximumpossible

saturation,

but this maximum

s very diSerent

n diSerent

egionsof the

chart.

This excludes inding

BCCs ike

beige.

(c) Most importantly,

what

people tend to do

when asked for the

best

exampleof a

colour s to point to the

most saturated

hip of that colour.

This

would supportthat

human beings

universallyagree

that in

the

domainof colour

'best example'

means'most

saturated',but it does

not

support he universality

of particularolour categories.

4.2 TheDefinitionof Colour Term

Of course,

nobodydenies that

there is

a wide rangeof symbolic

and other

uses of

colour terms.But, the

argument

runs, Berlinand Kay

measured he

referencef colour

terms. However,

there remains

a strong scientistic

and

ethnocentric

bias in the way

the reference

of the foci of the

BCCs s fixed,

because

it is assumedthat colour

constitutes

a separatedomain

of abstract

colour categories,

where colour

is measured on

three dimensions:

hue,

brightness,saturation.

But there are

serious problems

with taking

this

three-dimensional

patial metrics as the

properpsychological

imensions

of

colourperceptionsBurnsand Shepp[1988]).21

Although

the

320 chips 'define' colour,

often

in experiments60-80

per cent

of the chips remain

unnamed.

Many people when

presented

with the chips get

confused and give

inconsistent

answers or they

find

the naming tasks

simply absurd, not

to mention

the potential racist

implicationsof coming

along to measure

a culture's

evolutionarystage

via colour

chips.

Ichkari women (Uzbekistan)

efused to do classifica-

tion experiments

with coloured hreads

of their own

making), aying things

like 'This

is like calf's dung,

and this

is like a peach; you

can't put them

together '.Suchdata are discarded ecause t doesn'tproduceBCCs.Onthe

otherhand, if the

Jorai Vietnam) ome

up with having

23 BCTs, his can't

be accepted ither

and the definingcriteria

or BCTs

have to be applied

more

strictly.

In western

anguages, he

domainof

colour s clearlyseparated

romother

categories

and there is a bias

towards

hue at the expenseof

brightness

and

saturation.

n other cultures,

the hue

aspect of colourmay,

as it were,

be

subsumed

under diSerentcategories,

so

that it is not really

present as a

21 Coloursmay have

many other

characteristicsesideshue,

brightness nd

saturation Beck

[1972]):

size, shape,

location,fluctuation flicker,

parkle,glitter), exture,

transparency,

lustre (glossiness),

glow, fluorescence,metallic

appearance

iridescence),nsistence,

pro-

nouncedness,

ndpossiblymore.


13/34

J. Van

Brakel

I4

separate

domain;

still

there

will be

wordslike

olour

words.22

The domain

of

colour

may

overlapwith

the

domain

of form,

with

the domain

of

ritual

or the domain

of evaluatory

erms.

Further,

here

may be

different

ets

of

BCTs or animate and inanimateobjectsas in Uzbek(Afghanistan)and

Comaltepec

Mexico);

or daily

and

symbolic

usage (Mandarin

Chinese

and

several

Polynesian

anguages);

or natural

and

man-made

objects

Turkish);

or ordinary

colour

words

may

not be

applicable

o

particular

classes

of

objects,

orexample,

many

languages

have

separate

ocabularies

orthe

skin

colours

of

animals.

4.3 The

De.finition

f

Basic

ColourTerm

A detailed

discussion

of

the

original

definition

of

BCT and

subsequent

alternative roposalss outside he scopeof thisarticle.23 achof theproposed

criteria

has

been criticized

because

of vagueness,

nternal

consistency,

and

for

mixing

up linguistic

and psychological

riteria.24

Even

when applied

n

such

a way

that

lends general

support

or the Berlin

and

Kay theory,

there

are many

possible

exceptions

or theirbeing

exactly

eleven

BCTs.

n

English

andGerman

urquoise

might

be a

BCT.

Frenchand

Russian

may

have two

BCTs

for

brown.

Russian

has two

BCTs

for

blue; Hungarian

two for

red.

There

s an extensive

iterature

deliberating

whether

Russian

has zero,

one, two or

threeBCTs

or

purple. n

Coast

Croatian

live is

definitely

BCT.

Andwe haven'teven leftEurope.25

Perhaps

the most

telling

of the

sort

of methodology

that

went into

22

Foran example,

see Note

18 on Arawak.

There

are many

languages

which

emphasize

brightness

nstead

ofhue. Paliyan

India)

has

five BCTsor

degrees

ofbrightness,

ut none

fordifferences

n

hue.Similarly,

heproblem

n

translating

Greek

colour' erms

s thatthey

havemuch

more

to dowith

aspects

of brilliance

ndtone

(lustre)

hanwith

hue or

tint.In

theoretical

ccounts,

Greek

writers reat

colour

as a linear

seriesof which

white

andblack

arethe end

points

asdid Goethe).

nsteadof our

colourcircle

which

doesnot

contain

black

or

white, they

use conceptual

models

ike: n

the conversion

of

purefire (='white')

into

water(=dark')

the

whole

colour-scale

s run

through Plato,

Timaeus).

23

TheBCT-definitionfBerlin ndKay[1969] canbesummarizeds follows:i)Themeaning

of a

BCTmust not

bepredictable

rom

hemeaning

of its parts. ii)

Thereference

f

the BCT

must

notbe included

n

thatof another

olour

erm. iii)

Itsapplication

mustnotbe restricted

to

a narrowclass

of

objects. iv)

A BCTmust

be a

commonword

with

a stablereference

acrossspeakers.

24

The

originaldefinition

has been criticized

n

several

publications.

One

alternative

s given

in

Kayand

McDaniel

1978]. Evaluating

othdefinitions,

Mervis ndRoth

[1980]

conclude

that

by the criteria

of Berlin

and

Kay 'noneof

the eight

putative

colors[studied

by

Mervis

and

Roth]

areactually

basic

, while virtually

verycolour

will beconsidered

asicaccording

to K&McD's

riteria'.

25

Languages

with

morethan

one BCT or

red

(i.e. two BCTs

nearer

o red than

to orange,

brown,pink

orpurple)

nclude:

everalSalish

anguages

Canada),

rabela

Peru),

Behinemo

(PapuaNew Guinea),Bodi(Ethiopia), juka Surinam), aqaru Peru),TikopiaPolynesia).

A

BCTfor

light blue

is found

in Spanish

(Guatemala,

Peru), a few

Salish

languages

(Canada),

epali Nepal),

Mongol Mongolia),

hinook

argon

Canada/USA),

ncient

Greek,

Japanese,

nd other

anguages.

English

peakers

ften

volunteer

wo focifor

blue (one

darl

and

one light).


14/34

The

Plasticity of

Categories:The

Case of

Colour

I I 5

extracting

eleven

universal BCCs

rom

the world'slanguages

is the

way

in

which implicit

rules

were used to assign

meaningsto BCTs

n a parti-

cular

anguage.These

rules

almostguarantee

hat the

evolutionary

equence

will be confirmed.Given a list of BCTsin a language, first the BCTs

meaning

white and

black

are selected.

If one

of them is

not listed it is

assumed

that

it exists

anyway

(Berlin and

Kay [1969],

p. 80).

The

next one to

be selectedhas

to be

RED,even if

it is glossed

in the

original

source

as

yellow (p. 58).

In Arunta

(Australia) ierga,

lossed

as 'yellow,

green,blue'

is assignedthe

BCT-value

YELLOW

p. 67),

becausethat's

the

next

one to

appear.Similarly

n Mazatec

Mexico),sase,

glossed

as

'blue,

blue-greens,

blue-violets,

is assigned

GREEN,

ecause

GREENas o

appear

beforeBLUE

p. 78).

4.4 Other

Explanations

or the

Universality

f BCCs

Even

if it were true

that

opinions about

colour

foci around

the world

exemplify

leven

BCCsor

a specificsubset

of them,

this universality

could

have many

reasons. It could

be

that all peoples

of the

worldare endowed

with the same

eleven

Platonicbasic

colour

forms,which

they draw

on to a

greateror

lesser extent.

But there

are other possibilities

s well:

(a) Languages

may

havesimilar

ets of BCCs ecause

of

(former) eographical

proximity.

This

pointapplies

primarilyo the

validity

of theevolutionary

part of the theory.)

(b)

Cross-language

tabilityof

particular

olour saliences

might

be related

to the stability

of certainkinds

of coloured

objects

occurring

universally,

for example,

blood and

fire for red.26

(c)

The

most plausible

explanation for

the

ubiquityof common

colour

meanings n twentieth-century

anguages

s, I believe,

hat

it reflects he

spreadof cultural

mperialism

nd common

echnology, n

particular he

inventionof artificial

yes.

Moreover,

n the twentieth

century

hereare

very few

monolingual

speakers eft

who

don't use loan

words

from

western

anguages.27

26

However,one can

never be

carefulenough

in takingwhat seems

natural

at face value.

For example,

he sky is known

in

numerous anguages

as 'prototypically'

lue

(or light

blue), but

in a survey of

Italian dialects

answersto

the questionabout

the

colour of

the

sky included

descriptions

ike 'knows

no colour

for the sky' and

'great embarrass-

ment'.

27

Consider,or example,Khmer Cambodia)ukulaand GujaratiIndia) hoklati,.e. brown,

which somehow

got there from

Spanish

perhaps ia

Tagalog n the Philippines),

whereas

the

Spanishgot the

wordfromNahuatl

Mexico)

hokolatlfood

madefrom

cacaoseeds).In

return

Nahuatl

has kafentik

or brown,

fromSpanish

cafe(coffee).

Kilivila Melanesia)

as

kwinin yellow),

rom

quinine'(a yellow

anti-malaria

rug),and

so on.


15/34

II6

J.

Van

Brakel

4.5

Unnamed

ategories

Berlin

and

Kay

relate

the

evolutionary

development

f

the

number

of

BCTs

to a culture's echnologicaldevelopment.However, he factthat we do not

have

Basic

Odour

Terms

does

not

mean

that

the

Western

Flavours

and

Flagrances

Syndicate

s

underdeveloped.

he

fact

that

there

are

no

words

for

certain

categories

does

not

say

very

much

about

the

cultural

significance

of

the

category,

et

alone

the

general

evel

of

technological

development.

n

Ancient

Egypt

people

managed

for

thousands

of

years

without

a

word

for

blue,

but

blue

was

the

most

prestigious

painted

colour.

Of

course,

the

absence

of

linguistic

categories

or

certain

BCCs

gives

an

ideal

opportunity

o

check

whether

at

a

pre-linguistic,

ognitive

level

the

BCCs rethereanyway.Probablyhe workof Roschis the one single-most

complete

eSort

to

show

that

the

eleven

BCCs

are

universal

cognitive

ate-

gories.28

However:

(a)

All

Rosch's

work

is

concerned

with

establishing

the

existence

of

eleven

CCs,

which

is

not

directly

relevant

to

the

issue

of

four

unique

hues.

(b)

She

did

several

types

of

experiments

o

test

the

evolutionary

order

of

the

Berlin

and

Kay

sequence.

In

all

cases

the

sequence

was

not

confirmed.

(c) What was

confirmed

n

most

of

her

experiments

was

the

universal

primacy

of

focal

colours.

They

are

the

most

preferred

olours;

he

best

remembered;

he

easiest

to

learn;

and

so

on.

However,

as

pointed

out

in

Section

4.1,

this

result

only

attests

the

primacy

of

the

most

saturated

exemplar

within

a

colour

category,

not

the

existence

of

particular

universal

colours.29

(d)

Hardin

refers

specficially

o

her

work

with

the

Dani

(New

Guinea).

t's

therefore

f

interest

o

note

that

Rosch

[1973:

340]

reports

hat

the

Dani

'were

unwilling

to

designate

one

of

the

color

chips

as

the

most

typicalmember'.

28

Hardin

H41,

117,

168]

quotes

t

to

support

he

universality

f

the

unique

hues.

There

s

a

large

number

of

original

publications

y

Rosch

formerly

Rosch

Heider),

ncluding

1972,

1973].

For

a

review

and

references

ee

Lakoff

1987],

ch.

2.

Several

of

her

results

have

later

been

disputed

ecause

hey

couldn't

be

replicated.

Her

work

on

colour

ormed

he

basis

of

'prototype

heory'

(fora

critique

of

this

theory

see

van

Brakel

1991]).

29

In

fact

Rosch

[1972]

herself

writes:

the

most

saturated

olors

were

the

best

examples

of

basic

color

names

both

for

English

speakers

and

for

speakers

of

the

other

10

languages

represented'.

Furthermore,

he

distinction

of

best

example

n

terms

of

conspicuousness,

familiarity,

leasantness,

tc.

is

a

matter

of

dispute.

There

s a long-standingraditionofresearch n colourpreferences, hichhas

not

yet

led

to

any

clear

conclusions,

xcept

hat

saturated

olours

are

generally

considered

more

attractive/better

nd

the

order

of

colour

preferences

s

definitely

not

the

same

cross-culturally.

See,

for

example,

Martindale

nd

Moore

1988],

Schwanenflugel

nd

Rey

[1986],

Wiegersma

nd

van

Loon

[1989],

Zold

et

al.

[1986].)


16/34

ThePlasticity

of Categories:

The Case of Colour

I I 7

4.6 BCCsnd

UniqueHues

Assumethat all the

above criticisms an

be countered.30

Assumethat there

is no doubt that

there really are

eleven

niversal BCCs although

not

all

peoplesemploythem

all). There

s still a problem

o present

his as support

for their

being

four

nique hues,

which

are biologicallynnate.

What about

the otheruniversal

CCsBerlin

and Kay

have foundto exist?

Ironically,had

Hardin

been awareof subsequent

publications

f Kayand collaborators

Kay

and McDaniel

1978],

Kay and Kempton

1984],

MacLaury1987]),

he

might

have found even better

support

for his belief that BCCs

are neuro-

physiologically

wired in. Kay

and McDaniel

1978] draw on

the same

six

primitive

opponent colours

as Hardin,

i.e. they argue that

there is

a

physiological ase

for six primitive

BCCs nd, derivatively,

or

five secondary

ones.

Thereare some problems

n taking

the Kayand McDaniel

modelas

an

extensionof the

originalBerlin

and Kaytheory, but

let's not dwell on that.

Therestill remain

two more

generalproblems.

Firstly,

t is assumed

hat the four unique

hues

correspondo the foci

of

the red,

green, yellow and blue

BCCs.

However, ociare as easily

elicited or

secondary

BCCs

r any othercolour term.

So how can we be

sure that

the

foci measure

biologically

basedunique

hues in some cases, but

not in other

cases?

Moreover,

although it is concluded

hat foci

are universallyagreed

upon,

this law has to be taken

with a pinch

of salt. In actual fact

everypoint

along

the spectrum

has beenchosen as

a focal point for some

BCCby some

speakers.

The apparent

orderin the

publishedcolour maps

simply arises

because

there is

a universal endency o

choose the most saturated

hips

as

foci and

not to placefoci on

very light

or very darkpatches.

Secondly,how

are we going to explain

the many

languages that have

less than

six BCCs,combining

two or more primitive

colours

into one

category?

There

are hundreds of languages

mapping blue and green

together

under one

BCT.31 huswap speakers

on

the N.W. Pacificcoast),

use the

wordkwaalt

o name a yellow-green

ategory(i.e.

ncludingyellow

30 The

examples n Notes 314 (and

also 25) should

be seenin this light.

When I describe

language

as having,

say, one BCT overingyellow

and green,

his is not a factof the matter,

but subject o the

criticisms utlined n Sections

4.14.3.

31 Forexample,speakers

of some

Italiandialectsuse verde o

refer o both

green and blue.

Hence,

they'll use a minimum

of three words

to name the coloursof the

spectrum.Also

Zulu

has only one

BCT or blueand greentogether.

When

they want to makesure it's

one

or the

other they'll

say 'grue like the sky'

or 'grue like

grass', which isn't the same

as

recognizing

lue and

greenas BCCs.English-speaking

eople

often nsiston makinga

clear

distinction

betweenapple-green

nd lime-green,but it doesn't

follow that

both are BCCs.

One

reasonfor there

being manylanguages

which map green

and bluetogethermight

be

that there'sa stronger endency o distinguish olour according o brightnessn this part

of the

spectrum.

For example,Nahuatl and

Tlapanec (both Mexico)

seem to employ

separateBCTs or

green, turquoise,blue and

violet, but in

fact refer o different egrees

of

brightness

n the blue-green egion

and may

say in Spanish using 'standard'

ranslations)

that

the sky is green

or violet.


17/34

I I8

J.

VanBrakel

and green).32

Much to the amazement

of MacLaury

1987] reporting

his

fact,

it 'contradictspresent

physiological

knowledge'.

Couldit really

be

possible hat the

meaning of a word

in a faraway

culture contradicts

our

physiologicalnowledge?33

Evenmore serious

a problem s

the fact that

there are many

languages

who have BCTs

for some

secondarycolours,

but not for

all primitiveBCCs.

For example,

a Quichespeaker

Central

America)may

use BCTs

for each of

orange,

grey,purple,

brownand pink,

but only

one termcovering

both green

and blue.34A similar

difficulty

s the occurrence

fBCTscovering

a primitive

and

a secondary colour

and focusing

in the non-primitive

colour, for

example,

a blue-purple ategory

with focus in

purple.

Hence

I conclude hat the

languages

of the worldprovide

ittle

support or

there

beingfour

uniquehuesor six

primitiveBCCs,which

are psychologically

elementary

and

naturalreferents n

the domain of colour.

Let

us now see

what

colour vision

scienceitself can

tell us about there

being three

pairsof

opponent

colours.

5 HARDIN

S ACCOUNT

OF COLOUR

VISION

In his book Hardin

gives

a surveyof the state

of the

art in colourscience,

which is presently

dominated

by the psychophysical

heory of

'opponent-

processes'. In

this section

I summarizeseparately

the

parts of Hardin's

account

that drawon neurophysiology

nd

psychophysics,

lthoughHardin

himself s not very

concerned

with this distinction.

Next I discuss

his claim

32 In the

Berlin and Kay tradition

the occurrence

of a yellow-green

category is considered

more

threatening

because it combines

a ' warm'

and a 'cool' colour. Other

languages

which have

one term covering

both green and yellow

include: Ancient

Greek,Sanskrit, at

least 13 Salish

languages,

most Wakashan

languages,

a Haida dialect and both

Tsimshian

languages (all

Canada),

several Ainu dialects

(Japan),

Aguaruna (Brazil), Klamath

(USA),

two Numic

languages

(Mexico),

Natchez (USA), Creek

(USA), Jicaque

(Honduras),Fanti (Ghana),

several

languages in/near Australia (Arunta, 'FitzroyRiver', Murinbata, Martu Wangka, 'Queens-

land',

'Seven Rivers').

33 There

are also a

number of reportson languages

which

have one BCTcovering

two opponent

colours:

Ainu (Japan),

Daza (Nigeria),

Proto-Slavic,

Pukapuka (Samoa). This

information

may be less reliable,

but the

explanations offered are

not implausible.

For example, in the

vegetative domain

green =

fresh red. Occurrences

of yellow

and blue under the same

dictionary entry

may arise

because of the suppression

of the brightness

domain: light blue

and

yellow may

go together as bright

colours, whereas

dark blue would go

with 'black'.

(Of

course, on the

Berlin and Kay theory

this is rendered as YELLOW

nd

BLACKpresent,

but

not BLUE.)

34 Languages

with one BCT for

blue + green

(or, much less common,

one term

for green +

yellow)

and at

least one BCTfor (something

like) purple, orange,

brown,

or pink include

Angaatiha (Papua

New Guinea),

Bodi (Ethiopia),

Cofan (Ecuador),

Chayahuita (Peru),

Chinantec

(Mexico),Didinga

(Sudan), Haisla

(Canada),Huastec (Mexico),

Kapsiki

Cameroon),

Makah

(USA),Menye (New

Guinea), Mikasuki

(USA),Mixtec (Mexico),

Mono (USA), Navaho

(USA),Ocaina (Peru),

Paiute

(USA), Papago (USA),

Tikopia (Polynesia), Tlapanec

(Mexico),

Vietnamese, Wester

Apache

(USA), Yupik (Alaska),

Yucuna

(Columbia). Compare also

Note

31.


18/34

The

Plasticity

of

Categories:

The

Case

of

Colour

I

I 9

that

knowledge

of

colour

vision

science

helps

to

dissolve

various

philosophi-

cal

worries

about

colour.

5.1

Neurophysiological

ccount

In

the

retina

of

the

eye

there

are two

types

of

photoreceptors

ensitive

to

visual

stimuli:

ods

and

cones.

Visual

stimuli

reaching

he eye

consist

of light

which,

for

the

present

purpose,

will

be

characterized

y

wavelength

and

intensity

only.

Rods

are

specialized

or

perceiving

achromatic

contrast

at

night.

Cones

operate

under

daytime

ight

levels

and

produce

both

chromatic

and

achromatic

perceptions.

They

differ

n their

absorption

spectra:

the

efficiencywithwhichtheyabsorbight

of diSerent

wavelengths.

The L-cones

are

most

sensitive

to

lon:g

wavelengths,

M-cones

to medium,

and S-cones

to short

wavelengths.35

Colour

ensations

depend

upon

the

relative

rates

of

absorption

f light

in

the

L-,

M-

and

S-cones.

However,

he

signal

passed

on

by an

individual

one

preserves

no

information

bout

the

wavelength

of

the

light

that

is

being

absorbed:

ingle

cones

are

colour-blind.

Also

a particular

stimulus

pattern

of

the receptors

an

be

caused

by

more

than

one

wavelength

distribution

f

the

incoming

light.

This

explains

the

phenomenon

of meta-

mers,the

fact that

objects

which

reflect

diSerent

pectra

may

have

the

same

phenomenal

colour.

In fact,

this

description

of

the

cone

mechanism

is

already

tendentious,

assuming

a strictly

deterministic

timulus-response

model

of perception.

The

following

alternative

might

be

slightly

better:

perception

f

colour

n

normal

circumstances

depends

somehow

on

the

combined

timulation

of

the three

types

of cones,

i.e.

colour

perceptions

usually

depend

on the

proportions

n

which

the

three

cone types

are

activated

by

an

object

and

its

surrounding;

this

activity

s

a function

of

how

the

cones

were stimulated

n the

past

and

is

not

always

processed

n the

same

way

at

higher

levels

in

the

brain.

Cones

(and

rods)

connect,

inter

alia,

to

retinal

ganglion

cells,

which

have

opponent

properties.

This

means

the

following:

wo

sets

of receptors

are

connected

o a single

ganglion

cell.

One

set

subserves

he centre

of

the

cell's

receptive

ield

and another

ts

surround.

The

cell

is

called

an opponent

cell

because

simultaneous

stimulation

of

the

centre

and

surround

leads

to

no

response

(e.g.

when

the

whole

receptive

field

of

the

cell is

filled

with the

same

light),

but

a spot

on

either

the

centre

or

the

surround

xcites

the

cell.

35

Becauseof the predominance f the trichromatic olour theory in the firsthalf of the

twentieth

century,

the

cones

are still

often

called

the

blue,green

and

red

cones.

The

trichromatic

heory

of

colour

vision

was

firstproposed

t

the

beginning

of

the

nineteenth

century

by

Thomas

Young

and

found

support

when

Maxwell

and

Helmholtz

emonstrated

that

allthe

spectral

olours

we

seecan

be

completely

matched

by

mixtures

f

three

suitable

spectral

ights.


19/34

J.

Van

Brakel

20

This

conceptof

opponentcells

lends

tselfvery

well

to

explaininga

variety

of

phenomena, or

example:

(a) It can explainwhy we are good at observingedges and other abrupt

changes in

space or time.

(b) It

provides a

theoretical

formatfor

talking

about

various

aspects

of

contrast;

or

example,

darkness

blackness) rises

from

contrast

only.

And

Hardin

reportson

these

matters

at some

length in

orderto

explain

the

idea

f

opponency.

However,at

this

stage

there is

no

reference o

colour

or hue.

Colour-opponent

ells are

introducedby

Hardin

only

much

later

[H52], after

he has

outlined the

attractiveness

of the

psychophysical

opponent-process

heory.

5.2

Psychophysical

ccount

The

psychophysical

heory

of

opponent-processes

hich

Hardin

presents

consistsof

two

parts.36

(1)

Certain oloured

ights when

mixed

cancel

each other,

for

example

red

and

green

ight

mixed n the

right

proportion

ields

white

light,

whereas

it is

impossible o

obtain a

reddish

green.

Apparently ed

and green

are

somehow

antagonistic.

To explain

this

it is

assumed

that

brightness

(white) is the resultof some sort of summing of cone outputs,while

perceived ues

are

the resultof

some sort

of

diSerencing

f

cone

outputs.

The

diSerencing or

subtracting

mechanism

can

also

explain why

humans

have a

sharp

colour

discrimination,

lthough the

absorption

curves

of the

three

cone types

overlap

considerably.

(2) This

general dea is

then

worked

out by

assuming

that

thereare

three

colour-opponent

hannels,

includingone

achromatic

hannel,

yielding

six

BCCs:

(a) The

summed

output

of the L

and

M cones

gives the

achromatic

channel: L+ M

> O

codes for

whiteness, L

+ M < O

codes for

blackness.

36 This

s basically

he theory

proposed y

Hurvichand

Jameson n

the 1950s

as

reviewedn

Hurvich

1981]. Theidea

of

opponencyas a

basis

of a theory

of colour

vision

stemsfrom

Hering

1920].

During he

firstpart of

the

twentieth

century

Helrnholtz's

1911]

trichro-

matic

heory

dominated

ecause

Hering's

heorywasbased

on the

phenomenology

fcolour

appearances. t could

be revived

because

wavelength

dependent

opponency n

cells

was

discovered,

and

relying on

subjects'

qualitative

udgements

gained new

respectability.

Notwithstanding

Hardin's

laimthat

Hurvich

and

Jameson

broughtabout a

revolution

n

colourscience,

there

are many

similar

approaches

hat took

into

account

post-receptor

subtractive ombinations f coloursignals.For a reviewof earlyzone-theories,ee Judd

[1979].

As was

already

acknowledgedby

Helmholtz

and proven

more

elegantly

by

Schrodinger,

aken as

calculi

i.e. as

instruments or

predicting

henomenal

olourdata),

the

trichromaticand

tetrachromatic

heories are

to a

very great

extent

functionally

equivalent Niall

[1988]).


20/34

The

Plasticity of

Categories:

The Case of

Colour

I2I

(b) The diSerenced

utput of

the L

and M cones

generates

a red-green

opponentchannel:

L-M > Ocodes

for

redness,L-M

< Ocodesfor

greenness.

(c) Similarly,

L +

M-S generates

a yellow-blue

opponent channel:

L + M-S

> O codes

for yellowness,

L +

M-S <

O codes for

blueness.

In order

for the

formulaeto

be read as

linear

equations, weighting

coefficients

have to be added.

Por

example,aL-M

> O codes

for redness,

where

a is

a measureof

the relative

contribution

of the L and

M cones

to

the red/green

channel.

Using this psychophysical

model,which

is hoped o

fit the

neurophysio-

logicalhardware,Hardinexplainsvariouscolour phenomena:

(a) The fact

that

certain colours

(red/green,

yellow/blue)

seem

to exclude

one another.

For example,

he

explanation

uns,

the red/green

channel

either

gives a positive

response

or a negative

response.

So we

cannot

have

a red and green

experience

at the same

time.

But as the

colour

circle

shows, there is

an infinite

number

of opponent

colours,

so why

single

out red/green

and blue/yellow

as special?

(b)

He uses

the model to

discuss

varioussimultaneous/successive

ontrast

phenomena, orexample,yellowgives a blueafter-image.However,very

little is

explained

with explicit

reference

o the opponent-process

heory

and he

does not explain

why the older

explanations

n terms

of the

trichromatic

olour theory

are less good.

5.3

Philosophical

mplications

The

psychophysical

opponent-process

heory

does not support

Hardin's

materialistic

program

because

there is

no evidence

that the

three psycho-

physical

channels

correspond

o

particularneurophysiological

at)zways

see

next section).Secondly,as a functionalmodel it covers the whole colour

channel,

from the

light

rays entering

the

eye all the

way up to the

psychological

olour

experience.

Hence,

t has

the statusof a

psychophysical

bridge

law

(connecting

physical

and mental

events). That

one

kind of

psychophysical

model

s better uited

o

explain he phenomena

hananother

would seem

to

be of little relevance

for Hardin's

goal of showing

that

reductivism

s the right

philosophical

pproach.

Hardin ritically

discusses

variousphilosophical

heoriesabout

colour,but

particular

knowledge

about our

biological

make-up

does not play

any

significantrole in his account.37For example, I am sympatheticto his

37 He dismisses

bjectivism

ecause: here

are at

least 15 (physical)

ausesof the colours

we

experience

H2J; hereare

no standard

onditionsor

measuring

pectralransmittances

r

reflectances

of translucent

materials

[H69]; objectivism

cannot solve

the problem

of

metamers

H7] or why there

are fourunique

hues

[H66]; and finally

the setting-off

f


21/34

J.

Van Brakel

22

arguments

against

taking

indistinguishability s an

all

or nothing

aSair:

perceptual

hresholds renot

absolute,but

statistical

properties

H169-82],

but

we do

not

need the

statistical

nature of

neuron

firings,

let alone

a

full-fledged

olour-opponent

heory to

makethis

point.

In

setting up an

argument

against the

possibilityof

spectral

nversions

[H13442],

Hardin

suggeststhat

there is a

straight

analogy

between,

on

the

one hand,

the

phenomenologyof

colours and

the

neurophysiology f

opponent cells

and,

on the

other,

thermodynamics

and

the

kinetic gas

theory.

However,

irstly,

phenomenal olour

does

not

correspondo

tempera-

ture in

'phenomenal'

hermodynamics,

ut to

feelinghot

or

cold.

Secondly,he

argues

that it

is as

implausible

o

assume

that

'the heat

of a gas

should

not be

constitutedby

the motion

of

its

molecules'

tH136]

as it is to assume that seeing orange

s

constituted

by the

fact that

'the

r-g

channel

codes for r,

whereas

the

y-b

channel

fires at its

base

rate'

(which

represents

perceiving

red).

However, he

forgets

that the

point

at

which

the 'y-b

channelfires

at its

base

rate' has

simply

been fixed

as

the

point

where

people

say

they are

perceivingred

(see

Section

7.2).

So,

obviously, he

philosophical

worry

that they

might be

experiencing

range

is not

aSected

by the

coding

story.

On the

otherhand,

if the

goal is

to

show

that

if

two

brain states

in two

observersare

identical

hen they

must

have

the same

experience,we

do not

need all

the

scientific

details.

Hence I concludethat Hardinhas not shown that

knowledgeof

colour

science,

and the

opponent-process

heory n

particular,

rovides

naturalistic

solutions

o old

philosophical

roblems.

f

anything, t is

the other

way

round:

the

opponent-process

heory s

built

upon a

particular

hilosophical

recon-

ceptionthat

the

phenomenal

essence of

colouris

three

pairsof

opponent

colours.

6

MORE ON

THE

NEUROPHYSIOLOGY

OF

COLOUR-OPPONENT CELLS3 8

The

neurophysiological

ore

Hardin

appeals

o is the

existence

of

opponent

cells.

Thereare,

however,a

number

of

problemswith

the

conceptof

opponent

colour llusions

romother

perceived olours s

not

grounded

H72, 82,

91f].

Hence'our

common-sensenotion

that

objects

have colour

simpliciter cannot

withstand

scientific

scruti

the plasticity of categories color

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