SCIENZE. IL TEST SUI NEONATI CHE DÀ RAGIONE A KANT:
«PRESTANO PIÙ ATTENZIONE A SUONI E OGGETTI CORRELATI»
Quantità, tempo e spazio sono innati e non
derivati dall’esperienza L’esperimento: ai bimbi del reparto maternità sono
stati mostrati stimoli visivi e sonori con un grande schermo, mentre gli
scienziati misuravano la durata del loro sguardo
Non capita tutti i giorni, anzi nemmeno tutte le settimane
e nemmeno tutti i mesi, che una tesi filosofica fondamentale sia confermata
sperimentalmente. Eppure questo è appena successo, grazie a un lavoro appena
uscito sull’ultimo numero dei Proceedings
of the National Academy of Sciences of the Usa (in breve PNAS) co-firmato
da una delle piu’ note e autorevoli psicologhe cognitive: Elisabeth Spelke di Harvard. Insieme alle colleghe Véronique Izard,
Coralle Sann e Atlette Streri del Laboratorio di Psicologia della Percezione
del CNRS e dell’Università di Parigi Descartes, hanno confermato la tesi Kantiana che spazio, tempo e numero sono
innati. La Spelke
ha indagato per anni e riportato in numerose pubblicazioni le radici cognitive
dell’aritmetica e della nostra percezione dello spazio. Me lo conferma in un’intervista
in esclusiva. Mi dice, infatti: «Le mie collaboratrici ed io avevamo
recentemente scoperto che i neonati sono sensibili ai numeri e che bimbi appena
più grandi, a cinque mesi, notano la correlazione tra numeri crescenti o
decrescenti e spazi, rispettivamente, più o meno grandi. Volevamo, quindi,
meglio indagare l?origine di questa capacità. Ovviamente, nel mondo che ci
circonda, numeri, lunghezze e durate vanno insieme. Serie più numerose di
oggetti occupano maggior spazio e sequenze più numerose di suoni durano più a
lungo. Ci siamo chieste se queste correlazioni sono apprese o invece innate.
Ora lo abbiamo fatto studiando i neonati, che ancora non hanno potuto avere
esperienze di queste correlazioni».Effettuare esperimenti di natura cognitiva
su bimbi molto piccoli, in particolare su neonati a solo due o tre giorni dopo
la nascita, sembrerebbe presentare formidabili difficoltà. Chiedo alla Spelke
come hanno fatto. «Arlette Speri ha condotto questi esperimenti pionieristici a
Parigi, in un reparto maternità, quando i bimbi sono svegli e attenti. Si pone
loro di fronte un grande schermo e si fanno loro udire sequenze di suoni più o
meno numerose, ciascuno di durata più o meno lunga, per uno o due minuti, prima
che sullo schermo appaiano gruppi di oggetti più o meno numerosi, oppure linee
di diverse lunghezze. La durata del loro sguardo viene rigorosamente misurata,
mentre le serie di suoni continuano. Come noi, i neonati prestano maggior
attenzione, cioè guardano più a lungo, eventi tra loro correlati, in questo
caso, sequenze di suoni più numerosi, o che durano più a lungo, abbinate a un
numero corrispondente di oggetti, oppure a linee più lunghe».Vale la pena, per
rendere questi esperimenti a noi palpabili, precisare che i numeri delle
ripetizioni di sequenze acustiche (tipo tu-tu-tu... oppure ra-ra-ra-ra...,
oppure tuuuu-tuuuuuu... oppure raaaaa-raaaa-raaaa...) variano tra quattro e
diciotto e sullo schermo appaiono, in corrispondenza, o senza corrispondenza,
quattro triangolini gialli, oppure sei o dieci cerchietti rosa e così via.Faccio
l?avvocato del diavolo e chiedo alla Spelke perché questi risultati mostrano
che spazio, tempo e numeri sono innati. Risponde: «I suoni sono udibili, seppur
distorti, già in utero, quindi in astratto è possibile che l’abbinamento tra
suoni e durate sia stato appreso prima della nascita. Ma certo non l’abbinamento
tra durate e stimoli visivi. Dormire, guardare il soffitto e guardare mamma,
papà e parenti occupano totalmente i primi tre giorni di vita. Non vengono
loro, ovviamente, dati giocattoli, né hanno alcuna esperienza di linee che si
allungano o si accorciano né di figure geometriche colorate. Quindi ci sentiamo
autorizzate a concludere che non possono aver anticipato, sulla base della loro
precedente esperienza, l’abbinamento tra linee più lunghe, oggetti più numerosi
e sequenze uditive di maggior durata. Assai più plausibilmente, la mente e il
cervello di un essere umano sono pre-organizzati alla nascita per fare tali
abbinamenti fondamentali».Le chiedo, infine, quali saranno i prossimi esperimenti
del suo gruppo. «Vogliamo sapere se queste capacità, presenti alla nascita,
aprono la strada al susseguente progresso di concetti e intuizioni in
matematica. Stiamo studiando, nel mio dipartimento a Harvard, bimbi più grandi
e adulti. Vedremo come questi primordi si innestano su ulteriori sviluppi
cognitivi di tipo matematico».Riaffioreranno in alcuni di noi, penso, ricordi
di filosofia del liceo. Gli empiristi inglesi amavano il motto: niente nell’intelletto
se prima non è passato attraverso i sensi. Emanuele Kant obiettò: tranne l’intelletto
stesso. Appunto, ora lo abbiamo constatato. Peccato che Liz Spelke non possa
averlo come collega, in una cattedra di psicologia a Harvard.© RIPRODUZIONE
RISERVATA
Piattelli
Palmarini Massimo
Pagina 25
(06 aprile 2014) - Corriere della Sera
(06 aprile 2014) - Corriere della Sera
----------------------------------------------------------------------
The New
York Times
CAMBRIDGE, Mass. — Seated
in a cheerfully cramped monitoring room at the Harvard
University Laboratory
for Developmental Studies, Elizabeth S. Spelke, a professor of psychology and a
pre-eminent researcher of the basic ingredient list from which all human
knowledge is constructed, looked on expectantly as her students prepared a
boisterous 8-month-old girl with dark curly hair for the onerous task of
watching cartoons.
The video clips
featured simple Keith Haring-type characters jumping, sliding and dancing from one group to another.
The researchers’ objective, as with half a dozen similar projects under way in the lab,
was to explore what infants understand about social groups and social
expectations.
Yet even before
the recording began, the 15-pound research subject made plain the scope of her
social brain. She tracked conversations, stared at newcomers and burned off
adult corneas with the brilliance of her smile. Dr. Spelke, who first came to
prominence by delineating how infants learn about objects, numbers, the lay of
the land, shook her head in self-mocking astonishment.
“Why did it take
me 30 years to start studying this?” she said. “All this time I’ve been giving
infants objects to hold, or spinning them around in a room to see how they
navigate, when what they really wanted to do was engage with other people!”
Dr. Spelke, 62,
is tall and slim, and parts her long hair down the middle, like a college
student. She dresses casually, in a corduroy jumper or a cardigan and slacks,
and when she talks, she pitches forward and plants forearms on thighs, hands
clasped, seeming both deeply engaged and ready to bolt. The lab she founded
with her colleague Susan
Carey is strewed with toys and festooned with children’s T-shirts, but the Elmo
atmospherics belie both the lab’s seriousness of purpose and Dr. Spelke’s
towering reputation among her peers in cognitive psychology.
“When people ask
Liz, ‘What do you do?’ she tells them, ‘I study babies,’ ” said Steven Pinker,
a fellow Harvard professor and the author of “The Better Angels of Our Nature,”
among other books. “That’s endearingly self-deprecating, but she sells herself
short.”
What Dr. Spelke is really doing, he said, is what Descartes, Kant and
Locke tried to do. “She is trying to identify the bedrock categories of human knowledge.
She is asking, ‘What is number, space, agency, and how does knowledge in each
category develop from its minimal state?’ ”
Dr. Spelke
studies babies not because they’re cute but because they’re root. “I’ve always been fascinated by questions about human cognition and the
organization of the human mind,” she said, “and why we’re good at some tasks
and bad at others.”
But the adult
mind is far too complicated, Dr. Spelke said, “too stuffed full of facts” to
make sense of it. In her view, the best way to determine what, if anything,
humans are born knowing, is to go straight to the source, and consult the
recently born.
Decoding
Infants’ Gaze
Dr. Spelke is a
pioneer in the use of the infant gaze as a key to the infant mind — that is,
identifying the inherent expectations of babies as young as a week or two by
measuring how long they stare at a scene in which those presumptions are
upended or unmet. “More than any scientist I know, Liz combines theoretical
acumen with experimental genius,” Dr. Carey said. Nancy
Kanwisher, a neuroscientist at M.I.T., put it
this way: “Liz developed the infant gaze idea into a powerful experimental
paradigm that radically changed our view of infant cognition.”
Here, according
to the Spelke lab, are some of the things that babies know, generally before
the age of 1:
They know what an
object is: a discrete physical unit in which all sides move roughly as one, and
with some independence from other objects.
“If I reach for a
corner of a book and grasp it, I expect the rest of the book to come with me,
but not a chunk of the table,” said Phil Kellman, Dr. Spelke’s first graduate student, now at the University
of California , Los Angeles
A baby has the
same expectation. If you show the baby a trick sequence in which a rod that
appears to be solid moves back and forth behind another object, the baby will
gape in astonishment when that object is removed and the rod turns out to be
two fragments.
“The visual
system comes equipped to partition a scene into functional units we need to
know about for survival,” Dr. Kellman said. Wondering whether your bag of four
oranges puts you over the limit for the supermarket express lane? A baby would
say, “You pick up the bag, the parts hang together, that makes it one item, so
please get in line.”
Babies know, too,
that objects can’t go through solid boundaries or occupy the same position as
other objects, and that objects generally travel through space in a continuous
trajectory. If you claimed to have invented a transporter device like the one
in “Star Trek,” a baby would scoff.
Babies are born
accountants. They can estimate quantities and distinguish between more and
less. Show infants arrays of, say, 4 or 12 dots and they will match each number
to an accompanying sound, looking longer at the 4 dots when they hear 4 sounds
than when they hear 12 sounds, even if each of the 4 sounds is played
comparatively longer. Babies also can perform a kind of addition and
subtraction, anticipating the relative abundance of groups of dots that are
being pushed together or pulled apart, and looking longer when the wrong number
of dots appears.
Babies are born
Euclideans. Infants and toddlers use geometric clues to orient themselves in
three-dimensional space, navigate through rooms and locate hidden treasures. Is
the room square or rectangular? Did the nice cardigan lady put the Slinky in a
corner whose left wall is long or short?
At the same time,
the Spelke lab discovered, young children are quite bad at using landmarks or
décor to find their way. Not until age 5 or 6 do they begin augmenting search
strategies with cues like “She hid my toy in a corner whose left wall is red
rather than white.”
“That was a deep
surprise to me,” Dr. Spelke said. “My intuition was, a little kid would never
make the mistake of ignoring information like the color of a wall.” Nowadays,
she continued, “I don’t place much faith in my intuitions, except as a starting
place for designing experiments.”
These core mental
modules — object representation, approximate number sense and geometric
navigation — are all ancient systems shared at least in part with other
animals; for example, rats also navigate through a maze by way of shape but not
color. The modules amount to baby’s first crib sheet to the physical world.
“The job of the
baby,” Dr. Spelke said, “is to learn.”
Role
of Language
More recently,
she and her colleagues have begun identifying some of the baseline settings of
infant social intelligence. Katherine
D. Kinzler, now of the University
of Chicago, andKristin
Shutts, now at the University of
Wisconsin, have found that infants just a few weeks old show a clear liking for
people who use speech patterns the babies have already been exposed to, and
that includes the regional accents, twangs, and R’s or lack thereof. A baby
from Boston not only gazes longer at somebody speaking English than at somebody
speaking French; the baby gazes longest at a person who sounds like Click and
Clack of the radio show “Car Talk.”
In guiding early
social leanings, accent trumps race. A white American baby would rather accept
food from a black English-speaking adult than from a white Parisian, and a
5-year-old would rather befriend a child of another race who sounds like a
local than one of the same race who has a foreign accent.
Other researchers
in the Spelke lab are studying whether babies expect behavioral conformity
among members of a group (hey, the blue character is supposed to be jumping
like the rest of the blues, not sliding like the yellow characters); whether
they expect other people to behave sensibly (if you’re going to reach for a
toy, will you please do it efficiently rather than let your hand meander all over
the place?); and how babies decide whether a novel object has “agency” (is this
small, fuzzy blob active or inert?).
Dr. Spelke is
also seeking to understand how the core domains of the human mind interact to
yield our uniquely restless and creative intelligence — able to master
calculus, probe the cosmos and play a Bach toccata as no bonobo or New
Caledonian crow can. Even though “our core systems are fundamental yet
limited,” as she put it, “we manage to get beyond them.”
Dr. Spelke has
proposed that human language is the secret ingredient, the cognitive catalyst
that allows our numeric, architectonic and social modules to join forces, swap
ideas and take us to far horizons. “What’s special about language is its
productive combinatorial power,” she said. “We can use it to combine anything
with anything.”
She points out
that children start integrating what they know about the shape of the
environment, their navigational sense, with what they know about its landmarks
— object recognition — at just the age when they begin to master spatial
language and words like “left” and “right.” Yet, she acknowledges, her ideas
about language as the central consolidator of human intelligence remain
unproved and contentious.
Whatever their
aim, the studies in her lab are difficult, each requiring scores of parentally
volunteered participants. Babies don’t follow instructions and often “fuss out”
mid-test, taking their data points with them.
Yet Dr. Spelke
herself never fusses out or turns rote. She prowls the lab from a knee-high
perspective, fretting the details of an experiment like Steve Jobs worrying
over iPhonepixel density. “Is this car seat angled a little too far back?” she
asked her students, poking the little velveteen chair every which way. “I’m
concerned that a baby will have to strain too much to see the screen and decide
it’s not worth the trouble.”
Should a student
or colleague disagree with her, Dr. Spelke skips the defensive bristling,
perhaps in part because she is serenely self-confident about her intellectual
powers. “It was all easy for me,” she said of her early school years. “I don’t
think I had to work hard until I got to college, or even graduate school.”
So, Radcliffe Phi
Beta Kappa, ho hum. “My mother is absolutely brilliant, not just in science,
but in everything,” said her daughter, Bridget, a medical student. “There’s a
joke in my family that my mother and brother are the geniuses, and Dad and I
are the grunts.” (“I hate this joke,” Dr. Spelke commented by e-mail, “and
utterly reject this distinction!”)
Above all, Dr.
Spelke relishes a good debate. “She welcomes people disagreeing with her,” said
her husband, Elliott M. Blass, an emeritus professor of psychology at the University of Massachusetts
When Lawrence H.
Summers, then president of Harvard, notoriously suggested in 2005that
the shortage of women in the physical sciences might be partly due to possible
innate shortcomings in math, Dr. Spelke zestily entered the fray. She combed
through results from her lab and elsewhere on basic number skills, seeking
evidence of early differences between girls and boys. She found none.
“My position is
that the null hypothesis is correct,” she said. “There is no cognitive
difference and nothing to say about it.”
Dr. Spelke laid
out her case in an acclaimed debate with her old friend Dr. Pinker, who
defended the Summers camp.
“I have enormous
respect for Steve, and I think he’s great,” Dr. Spelke said. “But when he
argues that it makes sense that so many women are going into biology and
medicine because those are the ‘helping’ professions, well, I remember when
being a doctor was considered far too full of blood and gore for women and
their uncontrollable emotions to handle.”
Raising Her Babies
For her part, Dr.
Spelke has passionately combined science and motherhood. Her mother studied
piano at Juilliard but gave it up when Elizabeth
When her children
were young, Dr. Spelke often took them to the lab or held meetings at home. The
whole family traveled together — France ,
Spain , Sweden , Egypt ,
Turkey
Scaling the
academic ranks, Dr. Spelke still found time to supplement her children’s public
school education with a home-schooled version of the rigorous French
curriculum. She baked their birthday cakes from scratch, staged elaborate
treasure hunts and spent many days each year creating their Halloween costumes:
Bridget as a cave girl or her favorite ballet bird; her younger brother, Joey,
as a drawbridge.
“Growing up in my
house was a constant adventure,” Bridget said. “As a new mother myself,” she
added, “I don’t know how my mom did it.”
Is Dr. Spelke the
master of every domain? It’s enough to make the average mother fuss out.
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