Reasons for this phenomenon may be due to complacency or inability to overcome the obstacles to acquiring native proficiency in the target language.

I had been an enthusiastic bayonet fighter in time of peace and had acquired considerable proficiency.

She, however, devoted herself more particularly to etching, in which she acquired great proficiency.

Abauzit at an early age acquired great proficiency in languages, physics, and theology.

The Belfast Society records him as graduating in 1821 "having acquired considerable proficiency on the instrument (60 tunes)".

He acquired proficiency in French, German and various Indian languages.

This led to a passion for the Blues and she quickly acquired proficiency with the instrument.

It is usually not possible to acquire proficiency in the formal, "high" dialect without formal study of it.

In six months they acquired proficiency in the Biblical language and a strong inclination toward Judaism.

However, he was also one of numerous long-lived German missionaries who acquired great proficiency in Arabic.