On the Culture and Cognition blog, Nick Enfield's absorbing review of a book by Guy Deutscher: Through the Language Glass - Why the World Looks Different in Other Languages. It also provides a good overview of the work of numerous scholars who have tackled the question of how language shapes thought. Enfield is a professor of Ethnolinguistics and is affiliated with the Max Planck Institute for Psycholinguistics.
[The preceding text] suggests a prima facie argument for a form of cultural relativity grounded in differences between languages. Given that concepts provide a basis for categorization and decision-making, and given that different languages supply their speakers with different concepts, then different languages provide their speakers with different bases for decision-making, and, subsequently, different patterns of behaviour. It's a captivating possibility. We are members of a single species, but could it be that the different linguistic systems we inherit from different cultural histories cause us to think and act in fundamentally different ways? Or that as bilinguals, when we switch languages, we switch cognitive personalities? This is what linguistic relativity suggests....
A version of relativity more likely to succeed begins with the observation that we cannot determine facts independently from the measuring instruments that are used. In life, our measuring instruments are our bodies. Why can dogs hear sounds we can't? Because dogs have different bodies from us. For humans with human ears, those ultrasonic noises may as well not be real (though we are able to infer their existence using other means, from hi tech instruments like spectrograms to low tech measures like naked-eye observations of dogs' behaviour). The body defines an individual's horizons, both limiting and licensing our possible perceptions and actions. If you have the body of a bat, a pitch-dark cave will seem like a good place to be. But with the body of an earthworm, you will feel at home in a stretch of turf. If these are not different worlds they are certainly different worldviews.
Along similar lines, you can think of each language as a kind of body for thinking and acting, and this is not meant metaphorically. Thinking is a dynamic, active thing, and seldom wholly internal. Philosopher of mind Gilbert Ryle advocated a focus on the public side of cognition, defining it not by putative internal states but by the 'assemblage of performances' that such states enable. To perceive or understand the world is to relate to it, interpret it, and react to it. The reasoning involved draws on categories in a range of ways, and many of our categories are supplied by the languages we speak. The mind, including its learnt linguistic components, is a purpose-built tool kit for cognitive action, just like a body is a tool kit for physical action. And because languages are so differently structured, each one is like the body plan of a different species, affording its users different ranges of possibility. A language, then, doesn't imprison your mind, it equips it. It's not a straitjacket, it's an action suit.