Topics in Cognition and Language:

Theory, Data and Models

*Perceptual scene analysis: • extraction of meaning • events, causality, intentionality, Theory of Mind*Representation of meaningOperations on meaning representations • reasoning, induction, analogySensorimotor Interaction • joint attentlon, imitation*Mapping Language to meaning

Introduction

Central issues of language acquisition• Outline two approaches to explaining language acquisition• Highlight the property of “recursivity”• Discussion: identify studies that can help choose between competing hypotheses• Briefly discuss future events• Prepare the next meeting

Language Acquisition

Learning the associations <sentence, meaning>• Two problems • Extracting meaning from the world (by vision, audition, touch etc.) • Learning the sentence-meaning relations

ConceptualRepresentatio

n(Meaning)

Sentence Scene

(Some) Data to account for:

Most of children's early language is grammatical from the adult point of view- simplified- follows adult grammatical conventions fairly well• Children can generalize to use verbs in ways they have not heard before- produce some creative yet canonical utterances that they could not have heard from adults

The "Poverty of the stimulus"Obstacle

The possible mappings of sentence to meaning are uncountable• Language acquisition is an indeterminate problem• The training data is underspecified

How to approach this question?

What is the “initial state” or architecture of the learning system?• How does it learn?• Data to account for• Specify requirements for an artificial system that can learn language*

Two ExplanationsNativist: Chomsky, Pinker: • Children do not learn abstract syntactic structures at all, but rather • they already possess them as a part of their innate language faculty (UG). • Usage Based Learning: Tomasello, Goldberg: • Early utterances organized around particular concrete words and (idiom-like) phrases, not system-wide syntactic schemas. • Abstract and adult-like syntactic categories and schemas emerge only gradually and in piecemeal fashion during the preschool years.

How they account for the Data:

Most of children's early language is grammatical from the adult point of view • Nativist: because the structure is already there • Usage-based: Because they are performing “idiomlike” copy and paste.• Children can generalize to use verbs in ways they have not heard before • Nativist: because they exploit the innate adult syntax • Usage-Based: This generalization does occurs later in development, suggesting learning.

Types of Generalization:

Lexical categories (e.g. Nominal substitution): Take ___. Eat ___. Draw ___ on ___. • Re-use of Grammatical constructions: new verb learned in intransitive form generalized to transitive form• Creative constructions recursivityPredictions about transfer of grammatical forms: • Nativist - once a gramatical form (e.g. transitive) is present it should be fully available • Usage-based - transitive is element-soecific, theu becomes generalized

Transfer is progressiveProductive transitive utterances in different studies. Percentage of children (or responses in some cases – see Table 1) that produced transitive utterances of a novel verb that was heard in some other sentence frame. The data points correspond to the studies listed in Table 1 (Tomasello 2000)

Usage-Based Learning

1. Item based imitation2. Generalization • Across types (e.g.concrete nouns) • Across structures (e.g. Transitive)3. Creative Re-combination *

* What principles govern the ways in which children combine established linguistic constructions with one another creatively? Recursivity

Source of Recursivityin LanguageChomsky:

• Syntax is source of recursive structure in semantics

Jackendoff:• Syntax and semantics are parrailel recursive systems• Meaning has complex combinatorial structure that is not derived from syntax

Extreme alternative:• Semantics is the source of recursive structure

Parallel Recursive Structure

Major IssuesHow does the system

• Extract meaning from the world (by vision, audition, touch etc.)• Learn the sentence-meaning relations1. Item based imitation2. Generalization

• Across types (e.g.concrete nouns)• Across structures (e.g. Transitive)

3. Creative Re-combination *

Language Acquisitio

n Test-Bed

Upcoming Meetings

1. June: "Vision and Language: A Robotlcs Perspective"2. September: Mehler + Tomasello: Debate3. Next Meeting:• Data to accounz for?• Recursion in language and meaning- Hauser et al. 2002 Science- Goldberg 2003 TICS

References• Ray Jackendoff. Parallel constraint-based generative theories of language, Trends in Cognitive Sciences, Volume 3, Issue 10, 1 October 1999, Pages 393-400• Michael Tomasello. The item-based nature of children's early syntactic development, Trends in Cognitive Sciences, Volume 4, Issue 4, 1 April 2000, Pages 156-163