In chapter 1 I introduced two native speakers of German who had both grown up using their first language exclusively in their daily lives until age 13, when they moved to an English-speaking environment. Nearly six decades later, one of them – Albert L. – retained a fairly fluent command of German, while the other – Gertrud U. – had great difficulties expressing herself in that language.

This discrepancy raises the question of what attrition is and where it begins. Is there a clear and perceptible boundary in linguistic skills which marks the distinction between an attriter and a non-attriter? Can we define it in terms of time – can we, for example, say that it sets in after ten years? Obviously not, or not exclusively: Gertrud U. and Albert L. had both been living in an English-speaking environment for approximately the same length of time.