I am not a huge follower of the affective computing trend, but once in a while I read stuff about it, just to keep me updated about progress in that area. There is a piece in the Christian Science monitor entitled What if your laptop knew how you felt?, which deals with this issue. Some parts I found relevant. First about the main principles:

Computers can now analyze a face from video or a still image and infer almost as accurately as humans (or better) the emotion it displays. It generally works like this:

1. The computer isolates the face and extracts rigid features (movements of the head) and nonrigid features (expressions and changes in the face, including texture); 2. The information is classified using codes that catalog changes in features; 3. Then, using a database of images exemplifying particular patterns of motions, the computer can say a person looks as if they are feeling one of a series of basic emotions - happiness, surprise, fear - or simply describe the movements and infer meaning.

Now, in terms of applications:

"Mind Reader" [MIT] uses input from a video camera to perform real-time analysis of facial expressions. Using color-coded graphics, it reports whether you seem "interested" or "agreeing" or if you're "confused" about what you've just heard. (...) Researchers interviewed for this story concur that emotion recognition appeals to the security industry, which could use it in lie detection, identification, and expression reading. [Quite scary, isn't it] (...) there is peril in working with "fake data" if this technology is used in security. Yes, machines may be able to read fear, but fear is not necessarily an indicator of bad intentions [Phew...]

Why do I blog this? well, as I said, I am not very well versed into this domain so it's good to discover the main principles of such applications for pure cultural background. It's also curious to think about the underlying cultural assumptions of such an approach to interacting with machines. And finally, I am looking forward to see how this could be tinkered/hacked by artists in curious ways.