Written by 4:09 am article writing

Eye Tracking and The Impact on Readability

There is much interest in rumors that Apple has licensed a Tobii Technology eye tracking platform to be used in a tablet, confidentiality agreements mean that I can’t comment on that. But I do know Apple users will not be getting eye tracking as an input device anytime soon, if indeed ever, because of one inalienable fact; Eye Tracking is not as good as multi touch:

Eye tracking is no more accurate than your finger

Your eye is constantly moving, tiny movements, that you don’t even notice, just in the same way that when you run, the World looks stable, you don’t notice that you are moving up and down as well as forward. But when Kate Adie’s standard issue BBC camera man runs away from a ‘contact’ in Basra the picture bounces around so as to be largely indecipherable. Your brain smoothes out the movement, cameras don’t have brains so they can’t.

The tiny movements I refer to are necessary for you to see properly: When a beam of light hits the back of your eye a chemical reaction happens that sends a signal to the brain allowing you to see. Once the chemical reaction has happened it takes a few seconds for the chemicals to recharge before that part of the eye can see again in full detail.

Allow me to give you a practical demonstration, please keep your head still and look at the centre cross on this optical illusion.

After watching it for a few moments the lilac spots will disappear – you have (temporally!) become blind to lilac on part of your eye. To overcome this problem the eye is constantly making tiny movements so you don’t notice you have become blind. This movement induces a margin of error into all eye trackers meaning that it is not possible to make an eye tracker any more accurate than a finger.

It’s worth noting that a finger is less accurate than a mouse because the point of contact is about 1 centimeter square. With a mouse you can be millimeter accurate. Do you ever hit ‘A’ by mistake whilst searching for contacts when using your iPhone? Imagine doing that kind of thing, a lot.

Multi touch is better than single touch

Eye tracking is a single touch interaction, you can only look in one place at any one time. Fingers allow single touch and multi touch interaction. Who would go back to single touch interaction once they have experienced the benefits of multi touch?

Eye tracking is expensive in comparison to multi touch screens

The current price of an integrated Tobii eye tracker is as low as $9,000. This will fall as eye tracking hardware becomes commoditized but it’s unlikely to fall below $200 and that is significantly more than a multi touch screen costs.

Eye tracking is a good user input device for some users

Eye tracking as a user input device can be useful, indeed life changing for people with impaired or no motor control and for people without the ability to use a mouse, keyboard or multi touch surface.

Eye tracking will become a main stream user input device

But it won’t be for anything as mundane as an Apple Mac Pro (no offence meant Steve). It will be an input device for you, yes, you. Wearable eye tracking, integrated with augmented reality is the way that eye tracking will becomes a main stream user input device. It will automatically feed you information about people, places and things you look at in real time. James Cameron showed the usefulness of eye tracking and augmented reality to great effect in the original Terminator movie in 1985.

Last modified: July 23, 2021