Rule

Learning

by

Seven-Month-Old

Infants

G.

F.

Marcus

et

al.

Science

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DOI

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and

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activation

of

the

lacZ

reporter

gene

in

yeast

strain

H.-C

Kornau

L.

T.

Schenker

M.

B.

Kennedy

P.

H.

Seeburg

Science

-LRB-

-RRB-

F.

M.

Ausubel

et

al.

Eds.

Current

Protocols

in

Molecular

Biology

-LRB-

Wiley

New

York

-RRB-

G.

von

Heijne

Nucleic

Acids

Res

-LRB-

-RRB-

J.

Kyte

and

R.

F.

Doolittle

J.

Mol

Biol

-LRB-

-RRB-

S.

F.

Altschul

W.

Gish

W.

Miller

E.

W.

Myers

D.

J.

Lipman

ibid

-LRB-

-RRB-

J.

Garnier

D.

J.

Osguthorpe

D.

J.

Robson

ibid

-LRB-

-RRB-

R.

Kuner

G.

Kohr

S.

Grunewald

G.

Eisenhardt

A.

Bach

H.-C

Kornau

data

not

shown

The

DNAs

encoding

the

COOH-terminal

amino

acids

to

-LRB-

-RRB-

and

to

-LRB-

-RRB-

of

were

inserted

into

-LRB-

Pharmacia

-RRB-

in-frame

with

GST

-LSB-

D.

B.

Smith

and

K.

S.

Johnson

Gene

-LRB-

-RRB-

-RSB-

The

constructs

were

expressed

in

Escherichia

coli

and

the

fusion

proteins

-LRB-

GST

and

-RRB-

and

GST

alone

were

purified

on

glutathione-Sepharose

beads

The

loaded

beads

were

incubated

with

cytoplasmic

extracts

of

cells

-LRB-

-RRB-

expressing

fusion

proteins

of

the

Flag

epitope

with

either

amino

acids

to

of

or

with

amino

acids

to

of

and

processed

as

described

-LRB-

-RRB-

except

that

the

antibody

-LRB-

Kodak

-RRB-

was

used

for

probing

the

immunoblot

-LRB-

hour

C

-RRB-

Immunoblots

were

analyzed

by

incubation

with

an

antimouse

secondary

antibody

conjugated

to

horseradish

peroxidase

-LRB-

Jackson

ImmunoResearch

Laboratories

min

C

-RRB-

followed

by

incubation

with

SuperSignal

substrate

-LRB-

Pierce

-RRB-

and

exposure

to

HyperFilm

ECL

-LRB-

Amersham

Pharmacia

Biotech

-RRB-

Total

RNA

was

isolated

from

the

respective

rat

organs

separated

and

blotted

according

to

standard

procedures

-LRB-

-RRB-

A

base

pair

-LRB-

bp

-RRB-

cDNA

probe

of

was

labeled

with

-LSB-

P

-RSB-

deoxycytidine

triphosphate

with

a

random

primed

labeling

kit

-LRB-

Boehringer

Mannheim

-RRB-

The

blot

was

hybridized

with

QuikHyb

solution

-LRB-

Stratagene

-RRB-

washed

-LSB-

sodium

chloride/sodium

citrate

-LRB-

SSC

-RRB-

C

-RSB-

and

exposed

to

x-ray

film

Digoxigenin

-LRB-

Dig

-RRB-

uridine

triphosphate

labeled

complementary

RNA

-LRB-

cRNA

-RRB-

probes

were

synthesized

from

linearized

template

DNA

-LRB-

Boehringer

Mannheim

-RRB-

The

open

reading

frame

of

-LRB-

-RRB-

was

used

for

generating

sense

-LRB-

bp

-RRB-

and

antisense

-LRB-

bp

-RRB-

cRNA

probes

codetecting

transcripts

of

and

Sense

-LRB-

bp

-RRB-

and

antisense

-LRB-

bp

-RRB-

cRNA

probes

detecting

the

message

were

synthesized

from

the

untranslated

region

of

In

situ

hybridization

was

performed

on

frozen

brain

sections

-LRB-

m

-RRB-

from

Wistar

rats

as

described

-LSB-

M.

J.

Rossner

J.

Dorr

P.

Gass

M.

H.

Schwab

K.

A.

Nave

Mol

Cell

Neurosci

-LRB-

-RRB-

-RSB-

with

to

ng

of

cRNA

probes

overnight

at

C

-LRB-

formamide

SSC

-RRB-

Nonspecific

binding

of

probes

was

eliminated

by

sequential

washes

in

SSC

and

in

SSC

at

room

temperature

and

at

C

and

the

single-stranded

probe

was

removed

by

treatment

with

ribonuclease

A

-LRB-

g/ml

C

min

-RRB-

Bound

Dig-labeled

cRNA

probes

were

detected

with

alkaline

phosphatase

conjugated

antibody

to

Dig

-LRB-

to

hour

-RRB-

and

standard

reagents

-LRB-

Boehringer

Mannheim

-RRB-

N.

G.

Bowery

A.

L.

Hudson

G.

W.

Price

Neuroscience

-LRB-

-RRB-

D.

C.

M.

Chu

R.

L.

Albin

A.

B.

Young

J.

B.

Penny

ibid

-LRB-

-RRB-

W.

J.

Woicik

and

N.

H.

Neff

Mol

Pharmacol

-LRB-

-RRB-

D.

R.

Hill

Br

J.

Pharmacol

-LRB-

-RRB-

A.

R.

Knight

and

N.

G.

Bowery

Neuropharmacology

-LRB-

-RRB-

Transiently

transfected

cells

or

untransfected

controls

were

incubated

in

serum-free

medium

containing

mM

for

min

at

C.

Cells

were

harvested

washed

and

resuspended

in

Krebs-tris

buffer

-LRB-

-RRB-

We

treated

cells

per

sample

in

quadruplicates

with

either

GABA

-LRB-

mM

-RRB-

or

-LRB-

R

-RRB-

baclofen

-LRB-

M

-RRB-

or

respective

vehicles

for

min

followed

by

incubation

with

forskolin

-LRB-

M

-RRB-

or

dimethyl

sulfoxide

-LRB-

vehicle

-RRB-

for

min

at

C.

Cells

were

pelleted

and

boiled

for

min

in

tris-EDTA

buffer

-LRB-

Amersham

Pharmacia

Biotech

-RRB-

and

cell

extracts

were

assayed

for

cAMP

centrations

with

a

standard

cAMP

assay

kit

-LRB-

Amersham

Pharmacia

Biotech

-RRB-

P.

Dutar

and

R.

A.

Nicoll

Nature

-LRB-

-RRB-

P.

W.

Gage

Trends

Neurosci

-LRB-

-RRB-

C.

Luscher

L.

Y.

Jan

M.

Stoffel

R.

C.

Malenka

R.

A.

Nicoll

Neuron

-LRB-

-RRB-

W.

Jarolimek

J.

Baurle

U.

Misgeld

J.

Neurosci

-LRB-

-RRB-

Transfected

cells

-LRB-

-RRB-

on

cover

slips

were

transferred

to

the

stage

of

an

inverted

microscope

and

were

continuously

perfused

with

a

solution

containing

mM

NaCl

mM

KCl

mM

mM

mM

Hepes

and

mM

glucose

-LRB-

pH

adjusted

with

NaOH

-RRB-

The

whole-cell

configuration

of

the

patch-clamp

technique

was

applied

at

room

temperature

with

pipette

solutions

containing

mM

K-gluconate

mM

KCl

mM

Hepes

mM

EGTA

mM

adenosine

triphosphate

-LRB-

salt

-RRB-

and

mM

guanosine

triphosphate

-LRB-

salt

-RRB-

-LRB-

pH

adjusted

with

KOH

-RRB-

GABA

-LRB-

M

-RRB-

or

-LRB-

R

-RRB-

baclofen

-LRB-

M

-RRB-

was

dissolved

in

the

extracellular

solution

and

was

applied

steadily

to

single

lifted

cells

by

a

double-barreled

application

pipette

The

inward

rectifier

currents

were

activated

with

voltage

ramps

Membrane

potentials

were

corrected

for

the

liquid

junction

potential

-LRB-

mV

-RRB-

Data

collection

and

analysis

were

performed

as

described

-LSB-

G.

Kohr

and

P.

H.

Seeburg

J.

Physiol

-LRB-

-RRB-

-RSB-

N.

G.

Bowery

Annu

Rev.

Pharmacol

Toxicol

-LRB-

-RRB-

G.

Bonanno

and

M.

Raiteri

Trends

Pharmacol

Sci

-LRB-

-RRB-

cells

-LRB-

American

Type

Culture

Collection

-RRB-

were

cultured

in

minimal

essential

medium

with

Earles

's

salts

supplemented

with

L-glutamine

fetal

calf

serum

and

Pen/Strep

-LRB-

Gibco-BRL

-RRB-

transiently

transfected

with

standard

calcium

phosphate

transfection

procedures

-LRB-

-RRB-

with

g

of

combined

cytomegalovirus

-LRB-

CMV

-RRB-

expression

plasmids

-LRB-

-RRB-

per

million

cells

and

used

for

analysis

at

hours

after

transfection

The

coding

regions

for

-LRB-

-RRB-

-LSB-

Y.

Kubo

E.

Reuveny

P.

A.

Slesinger

Y.

N.

Jan

L.

Y.

Jan

Nature

-LRB-

-RRB-

-RSB-

and

-LSB-

M.

Stoffel

et

al.

Biochem

Biophys

Res

Commun

-LRB-

-RRB-

-RSB-

were

amplified

from

rat

brain

cDNA

with

gene-specific

primers

The

amplicons

and

the

cDNA

for

were

subcloned

into

pBluescript

-LRB-

Stratagene

-RRB-

and

also

into

a

CMV

expression

vector

-LSB-

T.

J.

Schall

et

al.

Cell

-LRB-

-RRB-

-RSB-

for

transfection

in

cells

-LRB-

-RRB-

The

amino

acid

sequences

were

aligned

by

the

clustal

method

-LRB-

Lasergene

DNAStar

Madison

WI

-RRB-

Amino

acid

abbreviations

are

as

follows

A

Ala

C

Cys

D

Asp

E

Glu

F

Phe

G

Gly

H

His

I

Ile

K

Lys

L

Leu

M

Met

N

Asn

P

Pro

Q

Gln

R

Arg

S

Ser

T

Thr

V

Val

W

Trp

and

Y

Tyr

We

thank

K.

Hirschfeld

and

A.

Hesselschwerdt

for

expert

technical

assistance

our

colleagues

at

BASFLYNX

Bioscience

AG

for

discussions

and

help

and

P.

H.

Seeburg

and

colleagues

for

suggestions

discussions

and

support

Supported

by

the

Bundesministerium

fur

Bildung

Wissenschaft

Forschung

und

Tech

nologie

-LRB-

grant

-RRB-

November

accepted

December

Rule

Learning

by

Seven-Month-Old

Infants

G.

F.

Marcus

S.

Vijayan

S.

Bandi

Rao

P.

M.

Vishton

A

fundamental

task

of

language

acquisition

is

to

extract

abstract

algebraic

rules

Three

experiments

show

that

infants

attend

longer

to

sentences

with

unfamiliar

structures

than

to

sentences

with

familiar

structures

The

design

of

the

artificial

language

task

used

in

these

experiments

ensured

that

this

discrimination

could

not

be

performed

by

counting

by

a

system

that

is

sensitive

only

to

transitional

probabilities

or

by

a

popular

class

of

simple

neural

network

models

Instead

these

results

suggest

that

infants

can

represent

extract

and

generalize

abstract

algebraic

rules

What

learning

mechanisms

are

available

to

infants

on

the

cusp

of

language

learning

One

learning

mechanism

that

young

infants

can

exploit

is

statistical

in

nature

For

example

Saffran

et

al.

-LRB-

-RRB-

found

that

the

looking

behaviors

of

infants

indicated

a

sensitivity

to

statistical

information

inherent

in

sequences

of

speech

sounds

produced

in

an

artificial

language

for

example

transitional

probabilities

which

are

estimates

of

how

likely

one

item

is

to

follow

another

In

the

corpus

of

sentences

The

boy

loves

apples

The

boy

loves

oranges

the

transitional

probability

between

the

words

the

and

boy

is

G.

F.

Marcus

S.

Vijayan

S.

Bandi

Rao

Department

of

Psychology

New

York

University

Washington

Place

New

York

NY

USA

P.

M.

Vishton

Department

of

Psychology

Amherst

College

Amherst

MA

USA

To

whom

correspondence

should

be

addressed

Email

gary.marcus@nyu.edu

but

the

transitional

probability

between

the

words

loves

and

apples

is

It

has

been

suggested

that

mechanisms

that

track

statistical

information

or

connectionist

models

that

rely

on

similar

sorts

of

information

-LSB-

for

example

the

simple

recurrent

network

-LRB-

SRN

-RRB-

-LRB-

-RRB-

-RSB-

may

suffice

for

language

learning

-LRB-

-RRB-

The

alternative

possibility

considered

here

is

that

children

might

possess

at

least

two

learning

mechanisms

one

for

learning

statistical

information

and

another

for

learning

algebraic

rules

-LRB-

-RRB-

open-ended

abstract

relationships

for

which

we

can

substitute

arbitrary

items

For

instance

we

can

substitute

any

value

of

x

into

the

equation

y

x

Similarly

if

we

know

that

in

English

a

sentence

can

be

formed

by

concatenating

any

plural

noun

phrase

with

any

verb

phrase

with

plural

agreement

then

as

soon

as

we

discover

that

the

three

blickets

is

a

well-formed

plural

noun

phrase

and

that

reminded

Sam

of

Tibetan

art

is

a

well

SCIENCE

VOL

JANUARY

Downloaded

from

on

May

REPORTS

formed

verb

phrase

with

plural

agreement

we

can

infer

that

The

three

blickets

reminded

Sam

of

Tibetan

art

is

a

well-formed

sentence

To

date

however

there

has

been

no

direct

empirical

test

for

determining

whether

young

infants

can

actually

learn

simplified

versions

of

such

algebraic

rules

A

number

of

previous

experiments

drawn

from

the

literature

of

speech

perception

-LRB-

not

aimed

at

the

question

of

rule

learning

-RRB-

are

consistent

with

the

possibility

that

infants

might

learn

algebraic

rules

but

each

of

these

prior

experiments

could

be

accounted

for

by

a

system

that

extracted

only

statistical

tendencies

For

example

infants

who

are

habituated

to

a

series

of

two-syllable

words

attend

longer

when

confronted

with

a

three-syllable

word

-LRB-

-RRB-

An

infant

who

attended

longer

to

a

three-syllable

word

might

have

noticed

a

violation

of

a

rule

-LRB-

for

example

all

the

words

here

are

two

syllables

-RRB-

but

an

infant

could

also

have

succeeded

with

a

statistical

device

that

noted

that

the

three-syllable

word

had

more

syllables

than

the

average

number

of

syllables

in

the

preceding

utterance

Similarly

Gomez

and

Gerken

-LRB-

-RRB-

found

that

infants

who

were

habituated

to

a

set

of

sentences

constructed

from

an

artificial

grammar

-LRB-

VOT-PEL-JIC

PEL-TAM-PEL-JIC

-RRB-

could

distinguish

between

new

sentences

that

were

consistent

with

this

grammar

-LRB-

VOT-PEL-TAM-PELJIC

-RRB-

from

new

sentences

that

were

not

consistent

-LRB-

VOT-TAM-PEL-RUD-JIC

-RRB-

Such

learning

might

reflect

the

acquisition

of

rules

but

because

all

the

test

sentences

were

constructed

with

the

same

words

as

in

the

habituation

sentences

-LRB-

albeit

rearranged

-RRB-

in

these

test

sentences

it

was

possible

to

distinguish

the

test

sentence

on

the

basis

of

statistical

information

such

as

transitional

probabilities

-LRB-

for

example

in

the

training

corpus

VOT

was

never

followed

by

TAM

-RRB-

without

recourse

to

a

rule

We

tested

infants

in

three

experiments

in

which

simple

statistical

or

counting

mechanisms

would

not

suffice

to

learn

the

rule

that

was

generating

the

sequences

of

words

In

each

experiment

infants

were

habituated

to

three-word

sentences

constructed

from

an

artificial

language

-LRB-

-RRB-

and

then

tested

on

threeword

sentences

composed

entirely

of

artificial

words

that

did

not

appear

in

the

habituation

The

test

sentences

varied

as

to

whether

they

were

consistent

or

inconsistent

with

the

grammar

of

the

habituation

sentences

Because

of

the

test

words

appeared

in

the

habituation

phase

infants

could

not

distinguish

the

test

sentences

based

on

transitional

probabilities

and

because

the

test

sentences

were

the

same

length

and

were

generated

by

a

computer

the

infant

could

not

distinguish

them

based

on

statistical

properties

such

as

number

of

syllables

or

prosody

We

tested

infants

with

the

familiarization

preference

procedure

as

adapted

by

Saffran

et

al.

-LRB-

-RRB-

if

infants

can

abstract

the

underlying

structure

and

generalize

it

to

novel

words

they

should

attend

longer

during

presentation

of

the

inconsistent

items

than

during

presentation

of

consistent

items

Subjects

were

infants

who

were

younger

than

those

studied

by

Saffran

et

al.

but

still

old

enough

to

be

able

to

distinguish

words

in

a

fluent

stream

of

speech

-LRB-

-RRB-

In

the

first

experiment

infants

were

randomly

assigned

to

either

an

ABA

condition

or

an

ABB

condition

In

the

ABA

condition

infants

were

familiarized

with

a

speech

sample

-LRB-

-RRB-

containing

three

repetitions

of

each

of

three-word

sentences

that

followed

an

ABA

grammar

such

as

ga

ti

ga

and

li

li

In

condition

ABB

infants

were

familiarized

with

a

comparable

speech

sample

in

which

all

training

sentences

followed

an

ABB

grammar

such

as

ga

ti

ti

and

li

-LRB-

-RRB-

In

the

test

phase

we

presented

infants

with

sentences

that

consisted

entirely

of

new

words

such

as

wo

fe

wo

or

wo

fe

fe

-LRB-

-RRB-

Half

the

test

trials

were

consistent

sentences

constructed

from

the

same

grammar

as

the

one

with

which

the

infant

was

familiarized

-LRB-

an

ABA

test

sentence

for

infants

trained

in

the

ABA

condition

and

an

ABB

sentence

for

infants

trained

in

the

ABB

condition

-RRB-

and

half

the

test

trials

were

inconsistent

sentences

that

were

constructed

from

the

grammar

on

which

the

infant

was

not

trained

-LRB-

-RRB-

We

found

that

of

infants

showed

a

preference

for

the

inconsistent

sentences

-LRB-

-RRB-

which

was

indicated

by

their

looking

longer

at

the

flashing

side

light

during

presentations

of

those

sentences

-LRB-

-RRB-

-LRB-

Table

-RRB-

Although

each

of

the

test

words

in

experiment

was

new

the

sequence

of

phonetic

features

in

the

test

overlapped

to

some

extent

with

the

sequence

of

phonetic

features

in

the

habituation

items

For

example

in

the

ABA

condition

three

habituation

sentences

contained

a

word

starting

with

a

voiced

consonant

followed

by

a

word

starting

with

an

unvoiced

consonant

Each

of

these

three

sequences

ended

with

a

word

that

contained

a

voiced

consonant

An

infant

who

was

thus

expecting

the

sequence

voiced-unvoicedvoiced

would

be

surprised

by

the

inconsistent

tests

items

-LRB-

each

of

which

was

voiced-unvoiced-unvoiced

-RRB-

but

not

by

the

consistent

items

-LRB-

each

of

which

was

voiced-unvoicedvoiced

-RRB-

To

rule

out

the

possibility

that

infants

might

rely

on

learning

sequences

of

particular

phonetic

features

rather

than

deriving

a

more

abstract

rule

we

conducted

a

second

experiment

with

the

same

grammars

as

in

the

first

experiment

but

with

a

more

carefully

constructed

set

of

words

In

experiment

then

the

set

of

phonetic

features

that

distinguished

the

test

words

from

each

other

did

not

distinguish

the

words

that

appeared

in

the

habituation

sentences

-LRB-

-RRB-

For

example

the

test

words

varied

in

the

feature

of

voicing

-LRB-

for

example

if

the

A

word

was

voiced

the

B

word

was

voiced

-RRB-

whereas

the

habituation

words

did

not

vary

on

the

feature

of

voicing

-LRB-

they

were

all

voiced

-RRB-

Thus

the

habituation

items

provided

no

direct

information

about

the

relationship

between

voiced

and

unvoiced

consonants

the

same

holds

for

each

of

the

phonetic

features

that

varied

in

the

test

items

As

in

experiment

of

infants

looked

longer

during

the

presentation

of

the

inconsistent

items

than

during

the

presentation

of

the

consistent

items

-LRB-

-RRB-

-LRB-

Table

-RRB-

Rather

than

encoding

the

entire

ABA

or

ABB

rule

the

infants

could

have

habituated

to

a

single

property

that

distinguishes

these

grammars

Strings

from

the

ABB

grammar

contain

immediately

reduplicated

elements

-LRB-

for

example

ti

ti

-RRB-

whereas

strings

from

the

ABA

grammar

do

not

In

a

third

experiment

we

compared

sentences

constructed

from

the

ABB

grammar

with

sentences

constructed

from

an

AAB

grammar

-LRB-

-RRB-

because

reduplication

was

contained

in

both

grammars

the

infants

could

not

distinguish

these

grammars

solely

on

the

basis

of

information

about

reduplication

-LRB-

-RRB-

As

in

the

first

two

experiments

infants

-LRB-

this

time

of

-RRB-

looked

longer

during

presentation

of

the

inconsistent

items

than

during

presentation

of

the

consistent

items

-LRB-

-RRB-

-LRB-

Table

-RRB-

Our

results

do

not

call

into

question

the

existence

of

statistical

learning

mechanisms

but

show

that

such

mechanisms

do

not

exhaust

the

child

's

repertoire

of

learning

mechanisms

A

system

that

was

sensitive

only

to

transitional

probabilities

between

words

Table

Mean

time

spent

looking

in

the

direction

of

the

consistent

and

inconsistent

stimuli

in

each

condition

for

experiments

and

and

significance

tests

comparing

the

listening

times

Mean

ages

of

the

infants

tested

were

months

days

-LRB-

median

months

days

-RRB-

in

experiment

months

day

-LRB-

median

months

-RRB-

in

experiment

and

months

-LRB-

median

months

days

-RRB-

in

experiment

Mean

listening

time

-LRB-

s

-RRB-

-LRB-

SE

-RRB-

Consistent

sentences

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

Inconsistent

sentences

-LRB-

-RRB-

-LRB-

-RRB-

-LRB-

-RRB-

Repeated

measures

analysis

of

variance

F

-LRB-

-RRB-

F

-LRB-

-RRB-

F

-LRB-

-RRB-

P

P

P

Exp

JANUARY

VOL

SCIENCE

Downloaded

from

on

May

REPORTS

could

not

account

for

any

of

these

results

because

all

the

words

in

the

test

sentences

are

novel

and

hence

their

transitional

probabilities

-LRB-

with

respect

to

the

familiarization

corpus

-RRB-

are

all

zero

Similarly

a

system

that

noted

discrepancies

with

stored

sequences

of

words

could

not

account

for

the

results

in

any

of

the

three

experiments

because

both

the

consistent

items

and

the

inconsistent

items

differ

from

any

stored

sequences

of

words

A

system

that

noted

discrepancies

with

stored

sequences

of

phonetic

features

could

account

for

the

results

in

experiment

but

not

those

in

experiments

and

A

system

that

could

count

the

number

of

reduplicated

elements

and

notice

sentences

that

differ

in

the

number

of

reduplicated

elements

could

account

for

the

results

in

experiments

and

but

it

could

not

account

for

infants

performance

in

experiment

Likewise

we

found

in

a

series

of

simulations

that

the

SRN

is

unable

to

distinguish

the

inconsistent

and

consistent

sentences

because

the

network

which

represents

knowledge

in

terms

of

a

set

of

connection

weights

learns

by

altering

network

connection

weights

for

each

word

independently

-LRB-

-RRB-

As

a

result

there

is

no

generalization

to

novel

words

Such

networks

can

simulate

knowledge

of

grammatical

rules

only

by

being

trained

on

all

items

to

which

they

apply

consequently

such

mechanisms

can

not

account

for

how

humans

generalize

rules

to

new

items

that

do

not

overlap

with

the

items

that

appeared

in

training

-LRB-

-RRB-

We

propose

that

a

system

that

could

account

for

our

results

is

one

in

which

infants

extract

abstract

algebra-like

rules

that

represent

relationships

between

placeholders

-LRB-

variables

-RRB-

such

as

the

first

item

X

is

the

same

as

the

third

item

Y

or

more

generally

that

item

I

is

the

same

as

item

J.

In

addition

to

having

the

capacity

to

represent

such

rules

our

results

appear

to

show

that

infants

have

the

ability

to

extract

those

rules

rapidly

from

small

amounts

of

input

and

to

generalize

those

rules

to

novel

instances

If

our

position

is

correct

then

infants

possess

at

least

two

distinct

tools

for

learning

about

the

world

and

attacking

the

problem

of

learning

language

one

device

that

tracks

statistical

relationships

such

as

transitional

probabilities

and

another

that

manipulates

variables

allowing

children

to

learn

rules

Even

taken

together

these

tools

are

unlikely

to

be

sufficient

for

learning

language

but

both

may

be

necessary

prerequisites

J.

Saffran

R.

Aslin

E.

Newport

Science

-LRB-

-RRB-

J.

L.

Elman

Cogn

Sci

-LRB-

-RRB-

E.

Bates

and

J.

Elman

Science

-LRB-

-RRB-

M.

S.

Seidenberg

ibid

-LRB-

-RRB-

N.

A.

Chomsky

Rules

and

Representations

-LRB-

Columbia

Univ.

Press

New

York

-RRB-

S.

Pinker

and

A.

Prince

Cognition

-LRB-

-RRB-

S.

Pinker

Science

-LRB-

-RRB-

G.

F.

Marcus

U.

Brinkmann

H.

Clahsen

R.

Wiese

S.

Pinker

Cogn

Psychol

-LRB-

-RRB-

G.

F.

Marcus

The

Algebraic

Mind

-LRB-

MIT

Press

Cambridge

MA

-RRB-

in

press

R.

Bijeljac-Babic

J.

Bertoncini

J.

Mehler

Dev

Psychol

-LRB-

-RRB-

R.

L.

Gomez

and

L.-A

Gerken

in

Boston

University

Conference

on

Language

Development

E.

Hughes

M.

Hughes

A.

Greenhill

Eds

-LRB-

Cascadilla

Press

Somerville

MA

-RRB-

p.

We

leave

open

the

question

of

whether

infants

interpreted

our

materials

as

genuinely

linguistic

and

thus

also

leave

open

the

question

of

whether

the

mechanisms

that

acquire

abstract

rules

are

specific

to

language

learning

or

are

more

generally

used

in

many

domains

P.

Jusczyk

and

R.

N.

Aslin

Cogn

Psychol

-LRB-

-RRB-

Infants

sat

in

a

three-sided

booth

on

the

laps

of

their

parents

-LRB-

parents

wore

headphones

playing

classical

music

so

that

they

could

not

hear

the

stimulus

materials

-RRB-

and

listened

to

sounds

generated

off-line

by

a

speech

synthesizer

The

booth

had

a

yellow

bulb

on

the

center

panel

each

side

panel

had

a

red

bulb

A

speaker

was

behind

each

of

the

red

bulbs

The

speakers

were

connected

to

a

Power

Macintosh

computer

that

presented

the

stimuli

and

controlled

the

lights

During

the

familiarization

phase

the

yellow

light

flashed

to

draw

the

infant

's

attention

to

the

center

panel

of

the

testing

booth

while

the

familiarization

speech

segment

played

from

both

speakers

After

the

familiarization

ended

the

infant

was

presented

with

test

trials

At

the

beginning

of

each

test

trial

the

central

light

was

flashed

Once

an

observer

-LRB-

who

also

wore

headphones

playing

music

to

mask

the

stimuli

-RRB-

indicated

that

the

infant

had

fixated

on

the

flashing

light

the

central

light

was

turned

off

and

one

of

the

two

side

lights

began

flashing

When

the

observer

indicated

that

the

infant

had

turned

toward

the

side

light

the

computer

played

a

three-word

test

sentence

from

the

speaker

that

was

hidden

behind

the

light

which

repeated

the

test

sentence

over

and

over

-LRB-

with

a

to

pause

between

presentations

of

the

test

sentence

-RRB-

until

either

the

infant

had

turned

away

for

two

continuous

seconds

or

until

s

had

elapsed

The

dependent

measure

was

the

total

time

that

the

infant

spent

looking

at

the

light

associated

with

the

speaker

Infants

who

became

fussy

prior

to

completion

of

at

least

four

test

trials

were

not

included

in

the

statistical

analyses

The

first

six

subjects

-LRB-

three

in

each

condition

-RRB-

were

familiarized

with

speech

samples

The

sentences

that

followed

an

ABA

pattern

were

ga

ti

ga

ga

ga

ga

gi

ga

ga

la

ga

li

li

li

ti

li

li

gi

li

li

la

li

ni

gi

ni

ni

ti

ni

ni

ni

ni

la

ni

ta

la

ta

ta

ti

ta

ta

ta

and

ta

gi

ta

The

sentences

that

followed

the

pattern

ABB

were

ga

ti

ti

ga

ga

gi

gi

ga

la

la

li

li

ti

ti

li

gi

gi

li

la

la

ni

gi

gi

ni

ti

ti

ni

ni

la

la

ta

la

la

ta

ti

ti

ta

and

ta

gi

gi

Vocalizations

of

the

words

used

in

the

above

sentences

were

created

with

a

speech

synthesizer

which

is

available

at

The

vocalizations

were

then

combined

to

form

the

sentences

listed

above

by

using

a

sound

editor

A

pause

was

placed

between

consecutive

words

in

each

sentence

The

sentences

were

presented

in

random

order

and

separated

by

pauses

of

s

The

test

trials

which

were

randomly

ordered

included

three

repetitions

of

each

of

four

test

sentences

two

following

the

ABB

pattern

-LRB-

wo

fe

fe

and

de

ko

ko

-RRB-

and

two

following

the

ABA

pattern

-LRB-

wo

fe

wo

and

de

ko

de

-RRB-

Similar

stimuli

were

used

in

a

study

of

children

's

memory

and

attention

-LSB-

J.

V.

Goodsitt

P.

A.

Morse

J.

N.

Ver

Hoeve

Child

Dev

-LRB-

-RRB-

-RSB-

That

study

does

not

however

answer

our

question

about

rules

because

it

tested

only

how

well

an

infant

could

remember

target

B

in

the

context

of

sequences

ABA

versus

AAB

versus

ABC

and

not

whether

infants

familiarized

with

one

of

those

sequences

could

distinguish

it

from

another

Results

for

the

ABA

and

ABB

conditions

were

combined

because

there

was

no

significant

interaction

between

them

F

-LRB-

-RRB-

Similar

results

involving

transfer

from

one

finite

state

grammar

to

another

with

the

same

structure

but

different

words

have

been

reported

for

adult

subjects

-LSB-

A.

Reber

J.

Exp

Psychol

-LRB-

-RRB-

-RSB-

and

for

infants

-LRB-

R.

L.

Gomez

and

L.-A

Gerken

paper

presented

at

the

Annual

Meeting

of

the

Psychonomics

Society

Philadelphia

PA

November

-RRB-

These

researchers

whose

focus

was

not

on

rule

learning

did

not

include

the

phonetic

control

we

introduce

in

experiments

and

The

habituation

sentences

that

followed

the

ABA

pattern

were

le

di

le

le

je

le

le

li

le

le

we

le

wi

di

wi

wi

je

wi

wi

li

wi

wi

we

wi

ji

di

ji

ji

je

ji

ji

li

ji

ji

we

ji

de

di

de

de

je

de

de

li

de

de

we

de

ABB

items

were

constructed

with

the

same

vocabulary

The

test

trials

were

ba

po

ba

ko

ga

ko

-LRB-

consistent

with

ABA

-RRB-

ba

po

po

and

ko

ga

ga

-LRB-

consistent

with

ABB

-RRB-

Results

for

the

ABA

and

ABB

conditions

were

combined

because

there

was

no

significant

interaction

between

them

F

-LRB-

-RRB-

In

principle

an

infant

who

paid

attention

only

to

the

final

two

syllables

of

each

sentence

could

distinguish

the

AAB

grammar

from

the

ABB

grammar

purely

on

the

basis

of

reduplication

but

they

could

not

have

succeeded

in

the

experiment

of

Saffran

et

al.

-LRB-

-RRB-

We

thank

an

anonymous

reviewer

for

suggesting

this

comparison

The

vocabulary

used

to

construct

the

test

and

familiarization

items

was

the

same

as

in

experiment

hence

as

in

experiment

the

phonetic

features

that

distinguished

the

test

words

from

each

other

did

not

vary

in

the

habituation

items

The

ability

to

extend

reduplication

to

novel

words

appears

to

depend

on

an

algebraic

rule

To

recognize

that

an

item

is

reduplicated

a

system

must

have

the

ability

to

store

the

first

element

and

compare

the

second

element

to

the

first

the

storage

retrieval

and

inferential

mechanisms

that

are

involved

may

appear

simple

but

are

outside

the

scope

of

most

neural

network

models

of

language

and

cognition

Conversely

adults

are

strongly

sensitive

to

the

presence

of

reduplication

and

its

location

in

phonological

constituents

-LSB-

I.

Berent

and

J.

Shimron

Cognition

-LRB-

-RRB-

-RSB-

For

further

discussion

see

references

cited

in

-LRB-

-RRB-

Results

for

the

AAB

and

ABB

conditions

were

combined

because

there

was

no

significant

interaction

between

them

F

-LRB-

-RRB-

The

sort

of

generalizations

that

such

models

can

draw

are

dictated

by

the

choice

of

input

representations

If

input

nodes

correspond

to

words

the

model

can

not

generalize

the

abstract

pattern

to

new

words

if

the

input

nodes

correspond

to

phonetic

features

the

model

can

not

generalize

to

words

containing

new

phonetic

features

-LSB-

G.

F.

Marcus

Cognition

-LRB-

-RRB-

Cogn

Psychol.

in

press

-RSB-

An

appropriately

configured

SRN

that

represented

each

word

by

a

set

of

nodes

for

phonetic

features

if

it

were

trained

that

a

voiced

consonant

followed

by

an

unvoiced

consonant

was

always

followed

by

a

voiced

consonant

could

use

memorized

sequences

of

features

as

a

basis

to

distinguish

the

test

items

in

experiment

However

such

a

model

could

not

account

for

the

results

of

experiments

and

because

in

those

experiments

the

feature

sequences

that

the

network

learned

about

in

the

familiarization

phase

would

not

distinguish

the

test

items

An

enhanced

version

of

the

SRN

-LSB-

Z.

Dienes

G.

T.

M.

Altmann

S.

J.

Gao

in

Neural

Computation

and

Psychology

L.

S.

Smith

and

P.

J.

B.

Hancock

Eds

-LRB-

Springer-Verlag

New

York

-RRB-

-RSB-

aims

to

model

how

speakers

who

are

trained

on

one

artificial

language

are

able

to

learn

a

second

artificial

language

that

has

the

same

structure

more

rapidly

than

a

second

artificial

language

that

has

a

different

structure

This

model

would

not

be

able

to

account

for

our

data

however

because

the

model

relies

on

being

supplied

with

attested

examples

of

sentences

that

are

acceptable

in

the

second

artificial

language

whereas

our

infants

succeeded

in

the

absence

of

such

information

The

problem

is

not

with

neural

networks

per

se

but

with

the

kinds

of

network

architectures

that

are

currently

popular

These

networks

eschew

explicit

representations

of

variables

and

relationships

between

variables

in

contrast

some

less

widely

discussed

neural

networks

with

a

very

different

archi

References

and

Notes

SCIENCE

VOL

JANUARY

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from

on

May

REPORTS

tecture

do

incorporate

such

machinery

and

thus

might

form

the

basis

for

learning

mechanisms

that

could

account

for

our

data

-LSB-

J.

E.

Hummel

and

K.

J.

Holyoak

Psychol

Rev.

-LRB-

-RRB-

-RSB-

Our

goal

is

not

to

deny

the

importance

of

neural

networks

but

rather

to

try

to

characterize

what

properties

the

right

sort

of

neural

network

architecture

must

have

Supported

in

part

by

an

Amherst

College

Faculty

Research

Grant

to

P.M.V.

We

thank

L.

Bonatti

M.

Brent

S.

Carey

J.

Dalalakis

P.

Gordon

B.

Partee

V.

Valian

and

Z.

Zvolenszky

for

helpful

discussion

and

P.

Marcus

and

F.

Scherer

for

their

assistance

in

construction

of

the

test

apparatus

We

also

thank

Bell

Labs

for

making

available

to

the

public

the

speech

synthesizer

that

we

used

to

create

our

stimuli

Some

subjects

in

experiment

were

tested

at

Amherst

College

all

other

subjects

were

tested

at

New

York

University

The

parents

of

all

participants

gave

informed

consent

September

accepted

November

Assembly

and

Analysis

of

Conical

Models

for

the

Core

Barbie

K.

Ganser

Su

Li

Victor

Y.

Klishko

John

T.

Finch

Wesley

I.

Sundquist

The

genome

of

the

human

immunodeficiency

virus

-LRB-

HIV

-RRB-

is

packaged

within

an

unusual

conical

core

particle

located

at

the

center

of

the

infectious

virion

The

core

is

composed

of

a

complex

of

the

NC

-LRB-

nucleocapsid

-RRB-

protein

and

genomic

RNA

surrounded

by

a

shell

of

the

CA

-LRB-

capsid

-RRB-

protein

A

method

was

developed

for

assembling

cones

in

vitro

using

pure

recombinant

CA-NC

fusion

proteins

and

RNA

templates

These

synthetic

cores

are

capped

at

both

ends

and

appear

similar

in

size

and

morphology

to

authentic

viral

cores

It

is

proposed

that

both

viral

and

synthetic

cores

are

organized

on

conical

hexagonal

lattices

which

by

Euler

's

theorem

requires

quantization

of

their

cone

angles

Electron

microscopic

analyses

revealed

that

the

cone

angles

of

synthetic

cores

were

indeed

quantized

into

the

five

allowed

angles

The

viral

core

and

most

synthetic

cones

exhibited

cone

angles

of

approximately

degrees

-LRB-

the

narrowest

of

the

allowed

angles

-RRB-

These

observations

suggest

that

the

core

of

HIV

is

organized

on

the

principles

of

a

fullerene

cone

in

analogy

to

structures

recently

observed

for

elemental

carbon

assembly

is

initially

driven

by

polymerization

of

the

Gag

polyprotein

which

forms

a

spherical

shell

associated

with

the

inner

membrane

of

the

budding

particle

The

three

major

regions

of

Gag

all

perform

essential

roles

in

viral

assembly

the

MA

-LRB-

matrix

-RRB-

region

binds

the

membrane

the

central

CA

-LRB-

capsid

-RRB-

region

mediates

important

Gag-Gag

interactions

and

the

COOHterminal

NC

-LRB-

nucleocapsid

-RRB-

region

packages

the

viral

RNA

genome

-LSB-

reviewed

in

-LRB-

-RRB-

-RSB-

As

the

particle

assembles

the

viral

protease

cleaves

Gag

producing

discrete

MA

CA

and

NC

proteins

which

subsequently

rearrange

to

form

the

mature

infectious

viral

particle

During

maturation

MA

remains

associated

with

the

inner

viral

membrane

while

CA

and

NC

condense

about

the

viral

RNA

to

form

an

unusual

conical

structure

at

the

center

of

the

virus

-LRB-

the

core

-RRB-

The

interior

of

B.

K.

Ganser

S.

Li

V.

Y.

Klishko

W.

I.

Sundquist

Department

of

Biochemistry

University

of

Utah

Salt

Lake

City

UT

USA

J.

T.

Finch

Structural

Studies

Division

UK

Medical

Research

Council

Laboratory

of

Molecular

Biology

Hills

Road

Cambridge

UK

These

authors

contributed

equally

to

this

work

To

whom

correspondence

should

be

addressed

Email

wes.sundquist@hsc.utah.edu

the

core

is

composed

of

an

RNA/NC

copolymer

and

is

surrounded

by

an

outer

shell

composed

of

copies

of

CA

The

conical

core

appears

to

be

essential

because

Gag

mutations

that

disrupt

proper

core

formation

invariably

inhibit

viral

infectivity

-LRB-

-RRB-

The

core

probably

organizes

the

viral

RNA

genome

-LRB-

and

its

associated

enzymes

-RRB-

for

uncoating

and

replication

in

the

new

host

cell

although

these

processes

are

not

yet

well

understood

Our

initial

goal

was

to

develop

a

model

system

for

studying

viral

core

structure

and

assembly

in

vitro

The

assembly

properties

of

pure

recombinant

Gag

protein

fragments

have

been

investigated

in

several

laboratories

-LRB-

-RRB-

Pioneering

work

by

Campbell

and

Vogt

demonstrated

that

fragments

of

and

Rous

sarcoma

virus

-LRB-

RSV

-RRB-

Gag

proteins

that

encompass

the

CA

and

NC

domains

can

assemble

into

long

hollow

cylinders

in

the

presence

of

RNA

-LRB-

-RRB-

Building

on

this

we

screened

for

conditions

that

would

support

the

assembly

of

conical

-LRB-

rather

than

cylindrical

-RRB-

structures

Initially

we

employed

an

RNA

template

that

spanned

sites

required

for

genomic

RNA

packaging

-LRB-

-RRB-

and

dimerization

-LRB-

DLS

-RRB-

because

some

models

for

the

viral

core

have

suggested

that

the

genomic

RNA

dimer

dictates

the

cone

morphology

-LRB-

-RRB-

The

protein

construct

included

both

the

CA

and

NC

domains

of

Gag

because

viral

core

morphology

can

be

disrupted

by

mutations

in

either

of

these

domains

or

in

the

short

spacer

peptide

that

connects

them

-LRB-

-RRB-

Finally

solution

assembly

conditions

were

varied

because

cylinder

formation

is

sensitive

to

protein

and

RNA

concentrations

salt

and

pH

-LRB-

-RRB-

Cone

formation

was

assayed

by

transmission

electron

microscopy

-LRB-

TEM

-RRB-

of

negatively

stained

samples

A

mixture

of

cones

-LRB-

Fig.

arrows

-RRB-

and

cylinders

formed

spontaneously

upon

incubation

of

a

pure

recombinant

CA-NC

fusion

protein

with

a

purified

-LRB-

nt

-RRB-

RNA

template

in

mM

NaCl

-LRB-

pH

-RRB-

-LRB-

-RRB-

Cone

cylinder

ratios

as

high

as

were

observed

under

these

optimized

conditions

Cones

also

formed

under

physiological

conditions

-LSB-

that

is

mM

NaCl

-LRB-

pH

-RRB-

-RSB-

albeit

at

reduced

efficiencies

The

synthetic

cones

were

capped

at

both

ends

and

many

appeared

strikingly

similar

to

authentic

cores

-LRB-

Fig.

-RRB-

Cones

formed

in

vitro

varied

between

and

nm

in

length

Viral

cores

are

typically

nm

long

-LRB-

-RRB-

however

this

can

also

vary

considerably

because

virions

range

between

to

nm

in

diameter

-LRB-

-RRB-

These

similarities

Fig.

CA-NC/RNA

complexes

spontaneously

assemble

into

cones

in

vitro

-LRB-

A

-RRB-

TEM

image

of

a

representative

field

of

negatively

stained

particles

formed

by

the

CA-NC

protein

on

a

RNA

template

Conical

structures

are

denoted

by

arrows

Scale

bars

in

Figs.

and

are

nm

-LRB-

B

-RRB-

Selected

thin-sectioned

TEM

images

of

an

authentic

virion

grown

in

culture

-LRB-

bottom

-RRB-

and

a

synthetic

CA-NC/RNA

cone

assembled

in

vitro

-LRB-

top

-RRB-

Electron

microscope

preparations

of

virions

and

synthetic

cores

were

identical

and

the

two

objects

are

shown

at

the

same

magnification

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O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O B O O O O B O O O O O B O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O B O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O B O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

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EDITORIALS NATURE | Vol 436 | 25 August 2005 Join a social revolution Your bookmarks make your web life manageable . But we can all benefit by sharing them . s the big challenge in the Internet era information overload or underload ? Those who complain about the former may simply be inadequately organized . Many tools now exist for taming the flow of scientific information on the web , but scientists have been slow to adopt them and are no doubt missing out on gems as a result . Take , for example , the need to manage the results of a web search . Storing the items selected so that you can easily find them again is often critical . A new generation of ` social bookmarking ' services now allow a user to post an article or web page with a single click to a personal web collection and to automatically group them under keyword tags . The ` social ' element arises from the fact that these bookmarks can easily be shared over the web , either selectively or publicly . Three leading examples of such services are del.icio.us -LRB- http://del.icio.us -RRB- , CiteULike -LRB- www.citeulike.org -RRB- and Connotea -LRB- www.connotea.org -RRB- . The last of these is an open-source service produced by Nature 's publishers , the Nature Publishing Group , and will be used in the following examples , but CiteULike is also tailored for scientists . There is no implication here that one service is better than another . The intention is simply to highlight ways by which readers can make more efficient use of the web and spread their knowledge at the same time . Users of Connotea say how easy it is to post and tag an article as they are looking at it on , say , Pubmed . And once a user clicks in their browser to send an article to Connotea , the software looks up the various metadata for the article , such as authors , journal volume and page numbers , and adds these to the entry . Kevin Olbrich , a researcher at Duke University Medical Centre in I Durham , North Carolina , is one enthusiast . A key difference from personal desktop reference software is that many of Olbrich 's bookmarks can be viewed by anyone -LRB- http://www.connotea.org/ user/kco -RRB- , as can those of any user . Some researchers are reluctant to use such services because they do not want their competitors to see what they are reading . But users can opt to make a bookmark private if they wish . Or they can create a ` group ' with other users , and make their bookmarks available only to members of that group . There is added value here . Whereas a PubMed or Google search will bring back everything that `` There 's no greater sign matches a keyword , the fact that a researcher considers an article that an article is important important enough to post to than when a colleague his or her collection implicitly e-mails `` Hey , you should says something about the likely see this . '' Connotea takes value of the article . There 's no greater sign that an article the same principle but is important than when a colbroadens the benefit . '' league e-mails you to say `` Hey , you should see this . '' Connotea takes the same principle but broadens the group who benefit . Other researchers can be alerted by an RSS feed -LRB- http://en.wikipedia.org/wiki/RSS_ -LRB- protocol -RRB- -RRB- . Such social collections share the effort that people have put into searching . Suppose you are contemplating introducing electronic laboratory notebooks -LRB- ELNs -RRB- to your laboratory . Search on Google for ELN and you may well find that a Connotea collection is the number one hit . You can thus save effort by using the collection of Connotea links on electronic laboratory notebooks -LRB- www.connotea.org/tag/ELNS -RRB- discovered by a Nature journalist while researching a feature article . These are early days and suppliers of these services have plenty to learn . But readers are urged to try them out , provide feedback and join the quiet social revolution . Who owns your work ? A case in the Kansas Supreme Court reflects a lack of clarity in US copyright law . decade ago , US universities , infected with the internet mania of the early nineties , convinced themselves that there was a large amount of money to be made in distance education . The online course materials were not subject to patents , which the university typically owns , but to copyright , which traditionally rests with its academics . So a number of schools made attempts to wrest copyright away from the researchers under the doctrine of ` work for hire ' . Under work-for-hire , if you create something for your employer , copyright belongs to the employer . Academics have not traditionally been included in this category because although everyone agrees that they must publish or perish , and that teaching courses is part of the job , the head of a department does not typically request a specific paper or lecture on a specific subject . `` Have a 20-page review of A isopod parasites on my desk by Monday '' is not the order of the day . Besides , if the university owns the scholarly output of its faculty , it is also responsible for that output , and might be tempted to shape it , for example when threats of litigation or bad PR loom . Almost all universities who `` Tradition hands tried to claim copyright have copyright to academics backed off . In those cases where work-for-hire seems to be parin most cases , but the law ticularly applicable -- when a is unclear . The time has faculty member is asked to procome to tidy it up . '' duce a specific document , for instance -- an agreement is often signed waiving the university 's right to the copyright . But an exception in Kansas -LRB- see page 1072 -RRB- has highlighted the uncertainties over ownership of intellectual property in current US law . If the Kansas Supreme Court rules that work-for-hire should apply to academics , this will muddy the waters more . If it does not , it will hardly clarify matters . Tradition hands copyright to academics in most cases , but the law is unclear . The time has come to tidy it up . 1066 2005 Nature Publishing Group

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