A friend of mine recently posed the question on social media: Does everyone change their personality a little when they speak another language? My response is a resounding "yes." There's a saying, "You are who you hang out with," and while that is not referring to language or cultural delineation whatsoever, I find when we spend time with English speakers, we act more American, and when we spend time with Spanish speakers, we act more Guatemalan. Although it may not be a dramatic difference, our personalities do change a little depending on what language we are speaking.
Languages have their own personalities that reflect the cultures of those who speak them. According to research, your personality can change depending on the language you speak, probably because our perceptions of the culture associated with a given language can impact our behavior. A study in 2006 asked bilingual Mexican Americans to take a personality test in both English and Spanish, and their responses to questions were actually quite different, depending on what language they were being tested in. In English, their responses reflected the individualistic culture of the US, and in Spanish, their responses represented the collectivist culture of Mexico. So it is very possible for a bilingual, bicultural person to see themselves through the cultural values of the language they are speaking.
It could also be the context in which you learn a language that develops your sense of self. Depending on how, where, and why you develop your new language skills, the firsthand observations you make about the people and culture during that period will be built into your sense of identity as a speaker. If you’re learning a new language in a classroom, along with vocabulary, grammar, and syntax, it's also possible you’ll internalize your instructor’s beliefs and associations with the culture.
Linguists have studied linguistic relativity, or the idea that language reflects the fundamental values of the given culture and at the same time forms them.
But personality changes might not be specific to the language we speak whatsoever. It could have more to do with country and culture. Self-help guru Jim Rohn said, "You are the average of the five people you spend the most time with," so it only makes sense that as you traverse different language, culture, and country boundaries, your personality and self might also evolve to fit the different settings. Different contexts trigger different behaviors, attitudes, and responses. What is taken as a personality shift due to a change of language may have little, if anything, to do with language itself. Language, culture, and identity, however, are so intricately interconnected, research finds it hard to pinpoint. All we have is the qualitative experiences of bilingual or multilingual speakers and learners.
The way we learn language is through imitation. Whether it is an infant mimicking the sounds and intonations of the parents, or a middle-age ESL students copying the tongue and lip placement of a teacher to reproduce the illusive "th" sound. When we echo the language of our teachers, we are also impersonating aspects of their culture and identity, and in doing so, internalize a bit of it ourselves. It's also a strategy of assimilation, because the main purpose of learning any language is to be able to connect and communicate with the people who speak that language.
So whether you find yourself more collectivist or individualist depending on the language you are speaking, I would say embrace every new part of your self you might happen to discover. Just like the Czech proverb states, "Learn a new language and get a new soul."