The eyes are the window to the soul, so says the old adage. And for companies developing eye-tracking technology, they're becoming the ultimate Peeping Toms.

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Front-facing cameras are certain to become standard on all devices, and they'll be equipped to not only monitor what we read online, but how we read it. They'll watch how long you linger on a word or image, how your pupils dilate, how fast you blink. Why? Because those details provide a wealth of important information about their favorite customer: you. And that means big bucks for them in terms of advertising revenue.


Slate's John Villasenor recently ruminated on this very subject:

"Did our eyes linger for a few seconds on an advertisement that, in the end, we decided not to click on? How do our eyes move as they take in the contents of a page? Are there certain words, phrases, or topics that we appear to prefer or avoid? In the future, will we be served online ads based not only on what we’ve shopped for, but also on the thoughts reflected in our eye movements?"

Of course, the bodhisattva pacesetters of modern technology at Apple have already filed a patent application for a 3-D eye-tracking graphical user interface for personal electronic devices like the iPhone and iPad. And European company Senseye is slated to have eye-tracking software built into its smartphones next year.

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While most contemporary computers and personal electronic devices aren't powerful enough to accommodate the complex computations that are required for eye-tracking software, it's only a matter of time before they are.

Villasenor put a nicely placed "cherry on top" at the end of his post when he wrote the following:

"Today, when we read something online, our thoughts are still our own. We should enjoy it while it lasts."