Document Type


Date of Degree

Summer 2014

Degree Name

PhD (Doctor of Philosophy)

Degree In

Second Language Acquisition

First Advisor

Slabakova, Roumyana

First Committee Member

Hurtig, Richard

Second Committee Member

Gavruseva, Elena

Third Committee Member

Fagan, Sarah

Fourth Committee Member

Davison, Alice

Fifth Committee Member

Shea, Christine


Linguists studying language acquisition often assume that once a first language is fully acquired, its mental linguistic representation remains constant and stable. Observations of native language attrition due to the influence of a dominant second language have led researchers to rethink the nature of the first language and consider the possibility that the mental representation of our first language may not be completely stable.

The purpose of this dissertation is to investigate specific areas of the first language that may be particularly vulnerable to L1 attrition if exposed to a dominant L2. I test Sorace's (2003) Vulnerable Interface Hypothesis, and propose and test the Structural

Overlap Hypothesis.

The Vulnerable Interface Hypothesis for first language attrition claims that linguistic properties located in the interfaces between the linguistic computational system and external domains (e.g. discourse or pragmatics) are particularly vulnerable to attrition, while internal interfaces (e.g. the syntax-semantics interface) are only somewhat vulnerable to attrition. The domain of narrow syntax is assumed to remain stable unless the L1 begins to attrite in childhood (Montrul, 2008). The Structural Overlap Hypothesis assumes that properties which exhibit structural overlap between the L1 and L2 are more vulnerable to L1 attrition.

The predictions of both hypotheses are tested using 15 L1 German adult attriters whose dominant L2 is English, in order to observe the degree of stability of the linguistic system in adult onset bilinguals. Four linguistic properties of German are examined, which are grouped in two pairings of a purely syntactic property with a grammatically related interface property. 15 monolingual L1 German speakers and 15 monolingual L1 English speakers serve as controls.

The data obtained also shed light on a frequently debated question of attrition research, viz. whether L1 attrition is due to transfer from the L2, or a decrease in the linguistic processing capacity due to competition of a dominant L2, or both.


Applied Linguistics, German, Interface Hypothesis, Language Attrition, Second Language Acquisition, Syntax


xi, 219 pages


Includes bibliographical references (pages 211-219).


Copyright 2014 Vera K. Grabitzky