Hong Kong bilingual-Chinese managers who responded to a values questionnaire in English displayed means closer to a group of American managers in the US than did the bilingual-Chinese managers who responded to the same questionnaire in Chinese (Ralston et al., 1995).The explanation, which the authors of the linked study (two of whom I know pretty well personally, and still had never heard of this stuff) attribute to "Cultural Frame Switching" or "cultural accomodation," is that the language primes the culture that goes with it, and the cultures values and atitudes are thus primed as well. You know, I can almost buy that.
But for social psychologists, the mere priming of values and attitudes is not sexy enough. They need something bigger; they need to show that switching between languages causes personality changes. Of course, this requires showing something equally sexy, namely that differences in personality exist between Spanish and English speakers in the first place. So the paper is, like, doubly sexy ("sexy" is, of course, a technical term in social psychology, and doesn't refer to anything related to actual sex... I hope).
In the first study, they administered the Big Five Inventory, which measures the Big Five personality dimensions, to 168, 451 (yes, that's a lot) English-speaking participants in the United States, and 1031 Spanish-speaking participants living in Mexico. They found small, but statistically different differences on all 5 dimensions (with samples that large, it's no wonder), such that the English-speakers scored higher on the Extraversion, Agreeableness, Conscientiousness, and Openness dimensions, while the Spanish-speakers scored higher on the Neuroticism dimension.
Using this finding, they then predicted that if bilinguals take the BFI in both languages, they will score higher on Extraversion, Agreeableness, Conscientiousness, and Openness when they take it in English, and higher on Neuroticism when they take it in Spanish. In three studies, with a combined sample of 249 English-Spanish bilinguals in Mexico and the United States, they found differences in the predicted directions on four of the five dimensions, with the difference on the Openness dimension being in the opposite direction, though not statistically significant. The difference between the scores on the Spanish and English versions on the Neuroticism dimension, while in the predicted direction, was also not statistically significant.
Once again, the authors interpret these results in terms of Cultural Frame Switching. They also make it clear that, while they found small changes in personality within individuals, the correlation between scores on the English and Spanish tests, across all participants, was 0.8. This implies that the differences between the scores for a single individual on the two versions of the test were relative. If one person takes the test in English and scores higher on the Extraversion dimension than another person did on the English version, it's likely that the first person will also score higher on the Extraversion dimension on the Spanish version than the second will on the Spanish version. Thus, switching languages isn't really altering your personality all that much. It's just tweaking the levels a little. And switching between Spanish and English doesn't seem to change your level of openness at all. I guess openness isn't as prone to priming effects as, say, extroversion. So, if you're an overly close-minded Spanish speaker, I'm afraid that learning English and speaking it exclusively probably won't help. But if you're an introverted Spanish speaker with a messy bedroom (Conscientiousness), and you want to have more fun at parties and finally clean that room, then by all means, learn English.