I'm a thoughtful sort of person. I like to mull things over before coming to a conclusion. I don't rant and rave. I'm not belligerent.

But German changed me.

I had been living in Germany for a year and felt comfortable in the language and culture. But that summer, a Canadian friend came to visit and was shocked at how aggressive I had become, speaking brusquely to slow waiters and queue jumpers.

The existence of my aggressive side fully hit me one night in Prague. I was with my sister, returning from a late night at the clubs. When the taxi driver quoted us the fare, I was incredulous: it sounded far too high.

From the back seat, I spouted in German (more widely understood than English at the time) that no way were we paying that price. I halved the fare and paid the driver, insisting that was more than enough. My sister later said that I was very loud, very forceful and, well, very scary. The next day, I learned the taxi driver had asked us the going rate.

Where language meets personality

I've always been fascinated by the intersection of language and personality. With the experience of my own split linguistic personalities, I was especially intrigued by a recent study that shows people who live in two cultures may unconsciously change their personality, or identity, when they switch languages.

According to researcher David Luna at Baruch College at the City University of New York, identity has traditionally been thought of as stable. But research in the past decade shows that identity is fluid, changing with the context.

People do shift between different interpretations of same events, but the study shows that bicultural people do it more readily. Language, it seems, is the trigger.

This makes sense to me. When I moved to France, I felt like I'd been split into two different people. Two containers, wine bottles if you will, represented my two personas.

The bottle for Canadian Colleen was full; wielding words and subjunctive clauses with aplomb, self-expression was my forte. The container for French Colleen, on the other hand, was empty, save for the sediment of a mediocre Merlot.

As I gradually gained vocabulary and an ear for la belle langue, the bottle filled up. It was when I achieved a sense of humour in French that I felt the bottle was finally full.

Yes, French Colleen had arrived and she was drunk on the finer things in life. I felt different when I spoke French: more joie de vivre, an ability to savour the daily pleasures of life.

Our authentic self

"Language is one of the most powerful cues to activate a culturally specific way of doing things, thereby activating a different identity," says researcher Luna, who is originally from Spain.

His study showed Hispanic women interpreted the same advertisement differently, depending on whether it was in Spanish or in English. They viewed the woman in the Spanish ad as more independent and assertive than the same woman in the English ad.

So why do people tap into different identities when they switch language and culture?

It seems one language and culture can speak more to our authentic self than another. Take the Hispanic women in the study.

The researchers note that, in Hispanic culture, women are becoming more independent and assertive, fighting for equal rights. It stands to reason the Hispanic women saw the actress in the Spanish ad as self-sufficient and extroverted.

Conversely, the Hispanic women saw the actress in English as less independent and lonely, reflecting an Anglo culture the researchers cite as becoming more traditional. So language reflects culture, which then activates identity.

A song to sing

Just as these Hispanic women interpret images based on different cultures, I find I can also interpret behaviours based on the culture I'm living in.

For example, I think it completely acceptable, even commendable, to break into song in the middle of dinner in French, but not so much in English; somehow, it's not proper, not part of the conservative British tradition I grew up with.

Pedro Sanchez notices his personality morphs not only between English and Spanish but among different dialects of Spanish.

He was born in Peru, grew up in the Dominican Republic and Colombia, and now lives in Toronto. Sanchez says his personality is different in English, a more unemotional and efficient language than Spanish, which whirls and dives, allowing him to access his more passionate side.

For Valerie LaMontagne, the language is different but the sentiment is the same. She's a francophone from Quebec but speaks English much of the time. She's split between her English academic side and her more playful French side, rooted in family. Despite the benefits of being bicultural, LaMontagne, like other multilinguists, says it can be a struggle to reconcile her different selves.

"I don't recognize my voice when I speak English. I sound like a girl from Ontario. I sound like an Anglophone, which I think deep down, I'm not."

But to me, the benefits of being bicultural or tricultural far outweigh any minuses. The value added only makes a life fuller.

I think about the millions of people who speak and live in just one language and culture and I wonder if they are somehow missing out. Maybe they're not really expressing all parts of themselves. But, then again, what you don't know, you can't miss.

As Voltaire said, "Sans variété, point de beauté."