Catherine L. Caldwell-Harris in Scientific American:
Does the language you speak influence how you think? This is the question behind the famous linguistic relativity hypothesis, that the grammar or vocabulary of a language imposes on its speakers a particular way of thinking about the world. The strongest form of the hypothesis is that language determines thought. This version has been rejected by most scholars. A weak form is now thought to be obviously true, which is that if one language has a specific vocabulary item for a concept but another language does not, then speaking about the concept may happen more frequently or more easily. For example, if someone explained to you, an English speaker, the meaning for the German term Schadenfreude, you could recognize the concept, but you may not have used the concept as regularly as a comparable German speaker.
Scholars are now interested in whether having a vocabulary item for a concept influences thought in domains far from language, such as visual perception. Consider the case of the “Russian blues.” While English has a single word for blue, Russian has two words, goluboy for light blue and siniy for dark blue. These are considered “basic level” terms, like green and purple, since no adjective is needed to distinguish them. Lera Boroditsky and her colleagues displayed two shades of blue on a computer screen and asked Russian speakers to determine, as quickly as possible, whether the two blue colors were different from each other or the same as each other. The fastest discriminations were when the displayed colors were goluboy and siniy, rather than two shades of goluboy or two shades of siniy. The reaction time advantage for lexically distinct blue colors was strongest when the blue hues were perceptually similar.