ENG 161: Language and Mind
The Logical Problem of Language Acquisition
Presenter: Christos Christopoulos
University of Cyprus
Date: February 27, 2025
Today's Agenda
- Learning an infinite set based on finite evidence
- Why is this a problem for language acquisition?
- How do we solve this problem?
- Take-aways
Learning an Infinite Set Based on Finite Evidence
Sets and Subsets
- Set: A collection of objects.
- Subset: A set contained within another set.
- Infinite Sets: Sets with an infinite number of elements.
- Subsets can also be infinite or finite.
Pretend Game Show: Guess the Infinite Set!
- Objective: Identify the correct infinite set using evidence.
Two Types of Evidence
- Positive Evidence: Information about items included in the set.
- Negative Evidence: Information about items not included in the set.
- Evidence gathered will always be finite.
Two Possible Strategies
- Strategy #1: Ask for items included in the infinite set (gathers positive evidence).
- Strategy #2: Inquire about specific items to gather both positive and negative evidence.
- Allows active hypothesis testing and strategic questioning to eliminate hypotheses.
Interim Conclusion
- Positive Evidence: Limited in hypothesis testing; success not guaranteed.
- Both Positive and Negative Evidence: Enables hypothesis testing; success is guaranteed if used smartly.
Why is This a Problem for Language Acquisition?
Target Language vs Input
- Languages as Infinite Sets: Can generate infinite well-formed expressions.
- Finite Input: Children have finite evidence for language acquisition.
- Success in Language Acquisition: All typically developing children succeed, unlike other skills like literacy.
- Puzzle: Children must identify the right set of expressions from finite evidence.
- Challenge: Accomplishing this without negative evidence is puzzling since success is 100%.
Children and Evidence
- Positive Evidence: Children hear and are spoken to in well-formed sentences.
- Negative Evidence: Typically indirect through parental reactions but often ignored or misinterpreted by children.
The Logical Problem of Language Acquisition
Key Points
- Languages: Infinite sets learned from finite input.
- Success: Guaranteed if using both types of evidence.
- Children's Use of Evidence: Limited reliance on negative evidence.
- Logical Problem: How do children succeed without sufficient negative evidence?
Other Names
- Plato's Problem: Questions the acquisition of knowledge not present in the environment.
- Poverty of the Stimulus: Highlights insufficient input for complete language acquisition.
How Do We Solve This Problem?
Universal Grammar (UG)
- Proposed by Noam Chomsky: Suggests innate, language-specific rules.
- Purpose of UG: Limits hypothesis space in language learning, making negative evidence less critical.
- Epistemological Approaches:
- Nativism: Knowledge is innate.
- Empiricism: Knowledge comes from experience.
Principles and Parameters Theory
- Concept: UG comprises universal principles and variable parameters.
- Principles: Shared rules across languages.
- Parameters: Language-specific settings that can vary, similar to smartphone settings.
Examples of Principles and Parameters
- Headedness: Determines the head of phrases.
- Head-Directionality: Influences phrase structure direction.
- Null-Subject Parameter: Dictates subject pronoun usage in languages.
Take-aways
- Learning Based on Finite Evidence: Not guaranteed without negative evidence.
- Language Acquisition: Children manage to learn despite limited exposure to negative evidence.
- Chomsky's Contribution: UG explains innate capabilities aiding language learning.