LINGUIST List 13.1637

Mon Jun 10 2002

Review: Psycholinguistics: Bloom (2002)

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  1. Katharine Beals, Bloom (2002) How Children Learn the Meanings of Words

Message 1: Bloom (2002) How Children Learn the Meanings of Words

Date: Sun, 09 Jun 2002 13:55:26 +0000
From: Katharine Beals <vze2shs6verizon.net>
Subject: Bloom (2002) How Children Learn the Meanings of Words


Bloom, Paul (2002) How Children Learn the Meanings of Words. 
MIT Press, paperback ISBN 0-262-52329-9, vii+300pp, $19.95, A Bradford book. 

Book Announcement on Linguist:
http://linguistlist.org/issues/13/13-1592.html

[The hardback edition ISBN 0-262-02469-1 (2000) was reviewed at
http://linguistlist.org/issues/11/11-1511.html]


Katharine Beals, full time stay-at-home mom

SYNOPSIS

In How Children Learn the Meanings of Words, Paul Bloom argues that
word learning occurs not through mental faculties dedicated to this
task, but through various abilities that exist for other, not
specifically linguistic, purposes.

He begins by reviewing the mysteries of word learning, citing Quine's
"Gavagai!" riddle, in which a linguist immersing himself in an
unfamiliar language overhears this outburst after a rabbit scurries
by. Quine points out that there is an infinity of possible meanings
for "gavagai". It might refer only to a part of the rabbit, or to a
specific type of rabbit, or to a more general category of animal, or
to some property the rabbit has, or to a time slice of the rabbit that
exists only while "gavagai" is being uttered. It might not be a
single word, or a word at all. And even if "gavagai" does
specifically refer to the whole rabbit as such, how do we know that
its actual meaning doesn't encompass one of an infinite number of
bizarre but logically possible generalizations, for instance
"rabbits-but only on Tuesdays; otherwise carrots."

Augmenting the mystery is empirical evidence about how, and how many,
words are learned. Estimates show that American children, by the time
they graduate from high school, have acquired at least 60,000 "minimal
free forms," or words and idioms whose meanings cannot be predicted by
their morphological components. But most of the word meanings
children learn are not explicitly demonstrated to them; many words,
like verbs and abstract nouns, are typically not, or simply cannot be,
spoken at the same time that their referents are observable; and even
in the case of words denoting concrete objects, between 30% and 50% of
the time the child is not attending to the referent of the word as it
is spoken-when asked "Do you want a cookie?" she may be looking at her
parent's face. Nor do children in many cultures receive any explicit
feedback about their own uses of words.

The first word learning tool Bloom discusses is fast mapping. This
involves the ability to grasp, fairly quickly, "aspects of the meaning
of a new word on the basis of a few incidental exposures, without any
explicit training." (p. 26). Bloom notes that mapping speech to
current circumstances is not limited to word learning, or to children,
but also applies when we acquire factual information. He also
debunks, through an examination of longitudinal data, the notion that
a critical period for word-learning occurs during childhood, wherein a
child's first few words are followed by a vocabulary spurt. What
differences there are between how children and adults learn words
stem, rather, from a gradual maturation of general learning
mechanisms-memory, attention, conceptual awareness, ability to
recognize a speaker's referential intentions-as well as our increasing
familiarity with the language, which means that there are, over time,
more context clues out there, but fewer new words to learn.

Bloom next addresses how children map words to their intended
referents. Emphasizing again how rarely the utterance of a word
co-occurs with its intended referent, and how poorly other animals
that are capable of associative learning acquire words, he debunks the
popular notion that word learning emerges from statistical
correlations between words and their contexts of use. Does this show
that humans have a unique word-learning mechanism? No, for there is
another ability, unique to humans but not specific to word learning,
that we use in mapping words to their intended referents: our Theory
of Mind, or ability to infer the intentions of others. When a child
hears an adult use a new word, studies show, he checks to see what the
adult is looking at rather than assuming that the adult is referring
to whatever he himself has been attending to. Autistic children,
whose core deficit is an absent or defective Theory of Mind, make the
wrong assumption; their vocabularies are often much smaller than
normal, and riddled with precisely this kind of associative error.

Two other mapping abilities that have been treated as specific to word
learning can be derived from Theory of Mind: the principle of lexical
contrast, which tells a child that a new word probably does not have
the same meaning as a word he already knows, and the principle of the
linguistic sign, which tells him that the words he hears others use
are bidirectional symbols that he himself can use in the same way.
Bloom views lexical contrast as a principle about speakers rather than
about words, namely that speakers tend not to use terms
interchangeably, and as a consequence of our naïve theories of human
psychology. He points out that this assumption applies in any
interpersonal communication system, not just one involving single
words, and doesn't just stem from a general preference for one-to-one
mappings, for children will allow that two different speakers might
describe a given object in different ways.

The child's recognition that linguistic signs are bidirectional, a
notion that other intelligent animals never master, stems from her
more general ability to infer a person's goal from his behavior and to
reason that she herself can achieve the same goal if she successfully
imitates this behavior. As Bloom puts it (p. 76), "Once a child
believes that the adult's use of the word DOG was used with the intent
to refer to a dog, she can infer that if she herself has the same
intent (to refer to a dog), then she could use the same means (saying
"dog") to satisfy this goal."

Having addressed this half of how children map words to their intended
referents, Bloom turns to how they learn what a word's possible
referents are, given what the speaker is looking at. In other words,
how can they reasonably suppose that "Gavagai!" in Quine's example
might refer to the whole rabbit? As many studies show, babies, like
adults, see the world as composed of whole objects, i.e. cohesive
stretches of matter, and deem all other properties as secondary. This
object bias is apparent before children learn their first words, and
is not specific to word learning, for it also helps them track and
count objects. Children, thus, are predisposed to view a new word as
referring to whatever whole object the speaker is looking at, rather
than, say, its color or materials.

This creates another mystery: how do children learn words for these
other properties? As Bloom points out, a number of circumstances can
override the object bias. Sometimes there aren't any object-like
candidates around-for example when the speaker refers to a non-solid
substance like water. In other cases the principle of lexical
contrast applies: if a new word is used in reference to an object that
the child already knows a word for, he may conclude that it refers to
one of the object's properties. As the child becomes more familiar
with syntax, he may also rule out object reference on the basis of a
word's part of speech.

What about entities that aren't objects? Some of these, while lacking
the core property of bounded cohesion, still have some object-like
properties. Object parts, like eyes and legs, are internally
connected, and some can move independently. Collections, like flocks
or families, are spatially bounded, and can appear cohesive if, like
schools of fish, they move in concert. Also bounded and connected are
negative spaces like holes; if we shift from space to time, so are
sounds and actions. But Bloom argues that not everything can be viewed
as a metaphorical extension of concrete objects. Sometimes what
parses motion and matter and their metaphorical extensions into
individuals is, rather, our Theory of Mind, or our "understanding of
goal, function, and intent." (p. 114). This accounts for our
individuation of entities like conferences, fights, and parties, and
more abstractly, chapters, stories and jokes. It explains why we view
a bikini as a single entity, since "it is created and used for a
single purpose." (p. 112).

Having sketched out the second half of the mapping of words to
intended referents, Bloom turns to how children deduce from this
mapping the actual meanings of words, or range of potential reference.
He begins with two word categories at either extreme. Personal
pronouns, he suggests, have a referential range so vast that, as
studies indicate, children can learn them only by attending to the
conversations of others. This is particularly true of the second
person pronoun: "Only when a child hears other people called YOU can
she... reasonably infer that it is not her name." (p. 125). Once
again, thus, Theory of Mind is key, and, accordingly, autistic
children find pronouns especially difficult. Proper names, with their
much narrower ranges of reference, also involve Theory of Mind. Young
children know that things conceived of as having mental states, or as
being personal pets, can have proper names even if they are inanimate.
Also key is lexical contrast: if the child already knows the common
noun, a new word that refers to the same thing may be its proper name.

Since different objects generally get different proper names, learning
these also means appreciating object identity. Underlying this is a
sensitivity to spatio-temporal continuity. This sensitivity, in turn,
is not specific to word learning, but, as with our parsing the world
into objects, also applies when we track things, count them, and
record their individual histories--in the case of people, who owes you
what, and who has demonstrated what kind of personality.

Bloom turns next to the concepts and categories that underlie the
meanings of other words, particularly nouns, verbs and adjectives.
Here he argues against the popular notion that concepts and categories
emerge from a "perceptual similarity space," modified through
experience, wherein clusters of objects (those that share many
observable properties) are assigned the same category. This account
meshes nicely with the tendency of children to classify solid objects
by shape. But it fails to explain how abstract concepts, with no
observable properties, arise, or how people, children and adults
alike, classify things not just by their superficial properties, but,
as studies show, also according to presumed essential properties that
may not be observable. The ability to classify objects by criteria
other than superficial appearance, Bloom points out, is highly
adaptive, and not just for language learning, because it permits
classifications by chemical or biological properties that, in turn,
allow predictions about how particular members of a class behave.
This raises the possibility that such essentialist thinking is innate.

Unlike many philosophers who assume that only natural kinds have
essential properties, Bloom argues that we also view artifacts this
way. Their essences aren't chemical or biological, but social and
psychological. A chair is not defined solely by its appearance (what
about a beanbag chair or a doll's chair?), or by its function (one can
sit on the floor) or even by its intended function (what about a chair
that was never intended to be sat in?). Rather, whether adults view
something as a chair depends on the "creator's intent and how it
relates to the design of the object," where the intent is "to create
something that falls into that kind." (p. 161), and some studies
suggest that even young children use this criterion. Representations
of objects, e.g. drawings, are also categorized by children and adults
alike according to their creators' intentions, as Bloom shows in a
following chapter specifically devoted to how we name representations.

Next, Bloom discusses the role of linguistic context in word learning,
focusing on syntactic clues. Part of speech can filter possible word
meanings; so does the distinction between count and mass nouns, and
the correspondence between the syntactic structure of predicates and
their conceptual structure-- i.e., how many entities participate in
the action a verb denotes. But for specific meanings that are hard to
otherwise deduce (for example that of "nightmare"), more general
linguistic context clues, not specifically syntactic, are key.

Bloom turns next to how we learn number words, addressing why so much
time elapses between when children understand both the concepts of
small numbers such as twoness, threeness, and the principle of
counting, and when they grasp the precise meanings of larger numbers.
He proposes two discrete mechanisms: one an innate, non-recursive
"accumulator" that underlies the awareness that babies, and other
animals, have of small numbers (and is also involved in measuring
duration), and the other a generative, recursive system of number that
children grasp only after sufficient exposure to the similarly
recursive counting system of their language. This is the first example
Bloom entertains of language influencing conceptual development.
Young children vary cross-linguistically in how well they understand
number, in a way meshes with differences among counting systems. But
this sort of influence is not specific to language: with reference to
notation systems for music and chess, Bloom observes that "an
inspection of the properties of a symbolic system that refers to the
domain can lead to insights about the domain itself." (p. 238).

Aside from this, however, the main way in which language affects
concept formation, Bloom argues, is as a vehicle for conveying ideas.
While vocabulary and linguistic structure can call attention to
different properties, ways of construing something, or ways of carving
up space and time that are already available to us, there is little
evidence, he says, that language per se actually structures the way we
view reality. One exception may be within the domain of subordinate
kinds: learning the names of types of wine might help you "organize
the 'flux of impressions' that you experience into discrete categories
and to appreciate the ways in which wines differ." (p. 253). But in
general, Bloom concludes, the abilities that many scholars have
claimed are products of language learning-the object bias,
essentialist thinking, aspects of the Theory of Mind-are, rather, its
prerequisites.

DISCUSSION 

How Children Learn the Meanings of Words is a well-written,
even-handed account, full of thought-provoking insights. It is
generally well-organized, though in such a way as to recapitulate,
somewhat confusingly, certain issues: e.g., when Bloom criticizes a
competing theory after reviewing all the evidence for his own, or when
he treats objects and individuals, which occasion many of the same
issues, in separate chapters. His careful review of experimental
methodology and results, of competing claims, and of possible
objections to his own accounts, however, make Bloom's conclusions
highly convincing. Where there are gaps in data, ambiguous results,
or open questions, we can generally trust him to say so. For all the
praise that scholars heap on falsifiability in the abstract, it is
rare to see someone so clearly demonstrate, as Bloom does in his
concluding chapter, how his particular theory may be proved wrong.

I was, however, struck with some unaddressed questions. One of the
first facts that Bloom notes about language learning is that it
involves internalizing a series of arbitrary facts that is longer than
any other list we memorize (at least 60,000 word-meaning
correspondences for the average high school graduate). It's hard to
believe that we are even capable of retaining an equivalent number of
other arbitrary facts-consider, for example, the extreme difficulty
that most of us have with all the names and dates in history or
paleontology. Furthermore, as Bloom notes, "while the recovery of
most arbitrary facts is slow and hard, access to words and their
meanings is fast and effortless." (p. 6). But then where does the
almost universal ability to memorize and rapidly recall so many facts
about word meaning come from, especially if, as Bloom's account
implies, it is not specific to language learning?

Bloom's account of essentialist thinking in categorization also raises
questions. Given that essences are often hidden, how are we able to
categorize according to them and thus learn words that denote these
categories? One possibility is that children are verbally informed of
an individual's essential properties, as they are in the study of
dinosaur categorization Bloom discusses (where the property in
question is "cold blood"). But is this typically how children learn
about category membership? That is, in order to understand what is
and isn't a dinosaur, must the child be told, for each type of
dinosaur, that it has cold blood? The dinosaur study, however,
demonstrates an alternative clue: here children learn that the
triceratops has cold blood by hearing it described as a dinosaur. But
this result conflicts with Bloom's later claim that words don't affect
category creation-unless he intends a distinction between category
creation and category membership, and would allow that words can
affect our learning of the latter. In any case, there appears to be a
complex, poorly understood interaction between words, essences and
categories that underlies the learning of each.

As the mother of an autistic child with impaired language, I was
particularly struck by Bloom's insights about Theory of Mind and word
learning. My son does not notice what others are looking at, does not
attend to their conversations, and doesn't infer referential intent
unless it is extremely obvious. He has, accordingly, required an
explicit demonstration of the meaning of each of his many
words. Pronouns remain elusive. As for proper names, I have long
noticed that he overextends these according to personal appearance, as
if he sees people as belonging to different sub-categories of person.
My assumption had been that, because he thinks of people as mere
objects rather than as sentient beings, and because individual
identity is generally more important with the latter than the former,
he simply doesn't notice people as individuals. Bloom's analysis of
how normal children learn proper names raises another possibility:
perhaps my son individuates people more than we think he does, but
doesn't understand the proper use of proper names. If proper names
are specifically reserved for sentient entities, then those who don't
recognize anything as sentient, if they use proper names, use them not
as such but as common nouns.

Further study of differences among autistic children would help
illuminate what Bloom takes to be one of the biggest factors, and
mysteries, in word learning: Theory of Mind. Do autistic children
with different degrees of Theory of Mind impairment have different
patterns of word learning? How aware are they of the principle of
lexical contrast and of the bidirectionality of the linguistic sign?
To what degree do they classify artifacts by the creator's intent?
And what do they take to be the function of proper names?

ABOUT THE REVIEWER 

Katharine Beals received her Ph.D. in linguistics from the University
of Chicago in 1995. From 1995 to 2000 she worked as a Senior Software
Engineer with the Natural Language Group at Unisys. She is currently
at home with her baby daughter and at work on a book about her deaf,
autistic son, which explores such issues as language modality,
cochlear implants, and language and consciousness in autistic people.
 
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