Consider how MP3 players--or at least the appearance of ear buds-function when used in public spaces.

Writing about the technology of his time, Shuhei Hosokawa describes a "Walkman Effect" (1984) through which music listened to via headphones allows for the user to gain more control over their environment.

Whereas your attention is fair game while simply walking down the street, riding on the subway, or sitting on a bench to rest, when you do the same activities while listening to music, you are multitasking. You appear busy and fully engaged already, making any attempt at communication effectively an interruption. Those who might otherwise be willing to interrupt may be further deterred from interaction by the fact that there's a good chance they won't even be heard...and that even if they are heard, it's easy for you to act as if they weren't.

Headphones enable users to actively tune in or tune out who or what they want. Awkward exchanges with acquaintances are less obligational, solicitors are less likely to bother you, and the cacophony of traffic can be subdued by a Bjork song. Mobile music listening also provides a personalized soundtrack to your life, customizable for optimum affect to make you feel good and give you a sense of confidence as you roam the streets. In all these ways, MP3 players allow you to float through public areas inside a protective bubble, commanding full autonomy in the management of chance encounters. They allow us to be more selective about who or what we engage with.

There are many critics of this trend who say that communities suffer when people disengage from the space they inhabit. Communities suffer both in the sense that "communities" as commonality-based solidarities don't develop and in the sense that the lived space is neglected. They suffer because individuals alienate or isolate themselves from other individuals.

There are a number of articles about the loss of manners due to portable technologies--the Walkman, cell phone, iPod, and now BlackBerry--that distract us from our physically immediate interactions.

One thing that I have not seen addressed is how a constant "separation" from other people effects how we monitor our own voices and words. Increasingly, I find that I don't think about the possibility of other people hearing what I'm saying--or the potential repercussions thereof.

Portable music and cell phones have gotten us so accustomed to being an exclusive audience and being excluded from the aural experiences of co-present others that I think we may forget to turn on the filter we all use to varying extents when talking about sensitive subjects.

The impetus for all this? I just had a phone conversation with my girlfriend about our downstairs neighbors' kittens, which effectively live with us. In detail, I described a scene, which I had only caught the very end of so wasn't entirely sure if what I thought happened did, that led me to believe we should talk to the neighbors about now being a good time to have the brother and sister cats spayed and neutered if they were going to do so.

The conversation took place just outside of a crowded computer lab, with a flow of people walking by and a couple dozen people within earshot. It wasn't the quietest place in the world, so I had to speak somewhat loudly.

If I'm using language well (that is, effectively and appropriately), I don't really like to self-censor to meet societal norms except in certain circumstances, but it's gotten to the point that I don't even think about the presence of people in crowds (it's different if I'm alone with a stranger on the elevator--I know I have their complete attention should I do anything).

Apologies to eavesdroppers and to helpless, headphoneless, alert passerbys.

[Some of this text taken from a paper I wrote in December about augmented reality.]