In an essay published on Monday, New Republic Senior Editor Noam Scheiber—who grew up speaking both Hebrew and English—explains why he stopped speaking only Hebrew to his three-year-old daughter. “My Hebrew self turns out to be much colder, more earnest, and, let’s face it, less articulate," he writes. "In English, my natural sensibility is patient and understated. My style in Hebrew was hectoring and prosecutorial.”

I understand the feeling. My not-so-fluent French “self” is most comfortable talking about classroom supplies. It’s surprising, though, that people who are actually fluent in two languages also feel their personality shifting as they switch between languages. Yet researchers have confirmed this: Between 2001 and 2003, linguists Jean-Marc Dewaele and Aneta Pavlenko asked over a thousand bilinguals whether they “feel like a different person" when they speak different langauges. Nearly two-thirds said they did.

How does that play out in day-to-day speech? In 1964, Susan Ervin, a sociolinguist at the University of California, Berkeley, set out to explore the differences in how bilinguals represent the same stories in different languages. She recruited 64 French adults who lived in the U.S. and were fluent in both French and English. On average, they had spent 12 years living in the U.S.; 40 were married to an American. On two separate occasions, six weeks apart, Ervin gave them the “Thematic Apperception Test”: She showed her subjects a series of illustrations and asked them to make up a three-minute story to accompany each scene. In one session, the volunteer and experimenter spoke only French, while the other session was conducted entirely in English.









Ervin then analyzed the stories, looking at the different themes incorporated into the narratives. When she compared the two sets of stories, she identified some significant topical differences. The English stories more often featured female achievement, physical aggression, verbal aggression toward parents, and attempts to escape blame, while the French stories were more likely to include domination by elders, guilt, and verbal aggression toward peers.

In 1968, Ervin—by this point, “Ervin-Tripp”—designed another experiment to further explore her hypothesis that the content of bilinguals’ speech would change along with the language. This time, Ervin-Tripp looked at Japanese women living in the San Francisco area, most of whom were married to American men and many of whom had American children. Most of the women were largely isolated from other Japanese in America, and spoke Japanese only while visiting Japan or talking to their bilingual friends. Ervin-Tripp had a bilingual interviewer give the women various verbal tasks in both Japanese and in English, and found—as she expected—important differences.