This stems from a column in The New Republic in which its senior editor tells readers he stopped speaking Hebrew to his young daughter because “My Hebrew self turns out to be much colder, more earnest, and, let’s face it, less articulate. In English, my natural sensibility is patient and understated.”
This is not unusual. A number of studies have shown that people can wear different personalities depending on the language there are speaking.
Obviously, there are implications here for the importance of context and whether there really is such a thing as a “true self.”