Experimental Result: For a while now, psychologists have known that being bilingual correlates with improved performance in certain perceptual situations.
Consider a situation where you are asked to indicate whether the arrow in the centre of the following two arrays is pointing to the left or right: 1) »»»»» 2) ««»««. Results show that bilingual people are better at this task; they aren't as thrown off, we could say, by the arrows pointing in incongruent directions.
A recent article, "On the Bilingual Advantage in Conflict Processing: Now You See It, Now You Don't" (Cognition 113(2009) 135-149), probes this "bilingual advantage" in more detail, with experimental results that indicate that the relative advantage of bilinguals over monolinguals is apparent when tasks of the sort illustrated in 1) and 2) are presented in relatively rapid alternation ( vs. when blocks of the 1) task are followed by blocks of the 2) task). Also the advantage is more in response time than ability to perform the task. The discussion focuses on why this is the case: why does bilingualism confer this advantage? Is it based in some better ability to resolve conflicting information, or in better ability to attentively monitor situations, so as to apply the right kind of attention to it? The authors incline to the latter, although they can't settle the issue.
On their view, bilinguals who are able to switch between one language and another quickly, sometimes even within a conversation, need to develop an ability to monitor their linguistic/auditory context and attend to it in the right way, e.g., not listen to conversations in other languages that are going on in the background, listen to this conversation as in language X, not Y.
Discussion: This raises interesting questions about the relation between language, perception, and inhabiting the world in different ways. Putting aside questions of underlying mechanisms, this result and the phenomenon are interesting for several reasons.
First, the issue of perceptual flexibility/plasticity. Merleau-Ponty, "In the Child's Relation With Others" talks about experiments in which children are shown a cartoon in which a dog, say, gradually turns into a cat; some children are able to see that this has happened, others not. The issue being probed in the above experiments is a related one, namely ability to look at and see things in different ways, e.g., to not be caught up by certain elements in a context (surrounding arrows pointing a certain way) such that they preclude seeing other elements (the central arrow pointing in another direction). What's interesting here is the connection between perceptual flexibility, and perception in general, and language. Merleau-Ponty would especially be interested to see this connection between the linguistic and the perceptual, since he sees language as elaborating our motor-perceptual engagement with the world.
Second, this reminds us that language is part of the domain of perception--it's something we in the first instance hear (or see or touch, in the case of sign language). The sort of monitoring that's under discussion can be nicely illustrated by the phenomenon of having your ear 'captured' by a particular voice, whisper or tone, of the diner at the other table, or (perhaps you've had this happen to you) overhearing a language that you know spoken in a restaurant where you don't expect to hear it, and finding all you can hear is that conversation in the other language. (There's a lot going on in our ability to hear just this one conversation amongst all the others at a party or in a restaurant, and the phenomena just mentioned are no doubt of a piece with this ability.) And being grabbed by the overheard, other language gets you to inhabit the world in a different way, to orient to the world according to that language and its ways of conceptualizing and bearing towards things. If you can really speak French and English, you find yourself being a little bit different speaking French than English, not just making different sounds; someone hearing their native language spoken, will tune to it and can get pulled along with it into being in their 'native'/home way. If you've ever talked to someone grabbed in this way, you may notice them responding to you differently.
Perhaps an underlying issue here is that people used to switching between one language and another are use to switching between different ways of being in the world (as the phenomenologist would put it). We're always moving, varying our way of being in the world--that's what emotion is, e.g.--but language switches, I think, are formalized, deepened, overall versions of that. Perhaps the bilingual has a cultivated talent for 'biworldism', which means cultivating a talent for attending to situations in multiple or shifting ways--and this helps her/him cultivate a talent for switching back and forth, say, between discerning the direction of an arrow as part of a block all pointing the same way, vs. discerning the direction by looking at each arrow individually. Bilinguals are tuned to the ways that various situations call for different modes of attunement. Which is not to say that only bilinguals have this capacity. We might think of a child caught between conflicting world views of the two different parents or caregivers, learning to see/respond to the world differently in the presence of these two different people.
Third, underneath this all is a really interesting point about attention that calls for further thinking: the way in which, in the experiment as discussed above, and in the linguistic situations described, the 'perceptual data' has two complexly intertwined roles: prompting paradigms of interpretation, and showing up as interpreted. There is, e.g., the sound that prompts us to hear it as not being of the language that we are listening for, the sound that is heard as: not-to-be-heard-as-language-that-makes-sense; and sound that is heard as sound that is to be heard as language, and is then/also heard as a language that makes sense. This also points to the dynamics of givenness.