Most of us hardly notice the surveillance cameras watching over the grocery store or the bank. But lately those lenses have been looking for far more than shoplifters.

Engineers at IBM’s Almaden Research Center in San Jose, CA, report that a number of large retailers have implemented surveillance systems that record and interpret customer movements, using software from Almaden’s BlueEyes research project. BlueEyes is developing ways for computers to anticipate users’ wants by gathering video data on eye movement and facial expression. Your gaze might rest on a Web site heading, for example, and that would prompt your computer to find similar links and to call them up in a new window. But the first practical use for the research turns out to be snooping on shoppers.

BlueEyes software makes sense of what the cameras see to answer key questions for retailers, including, How many shoppers ignored a promotion? How many stopped? How long did they stay? Did their faces register boredom or delight? How many reached for the item and put it in their shopping carts? BlueEyes works by tracking pupil, eyebrow and mouth movement. When monitoring pupils, the system uses a camera and two infrared light sources placed inside the product display. One light source is aligned with the camera’s focus; the other is slightly off axis. When the eye looks into the camera-aligned light, the pupil appears bright to the sensor, and the software registers the customer’s attention.

BlueEyes has set off warning bells at the American Civil Liberties Union. “Soon you won’t only be able to capture how many people stopped by, but who they were,” says Barry Steinhardt, associate director of the ACLU. “Once identity is established it will be cross-referenced to capture that person’s income and buying preferences. It’s only a matter of time.” Not surprisingly, IBM’s retail customers unanimously requested that the firm not reveal their names to the press, or the locations where BlueEyes has been implemented.