Reading and the Eye

Reading in the Brain by Stanislas Dehaene explains at length how we read. The first chapter starts with the eye. I was surprised that:

“The fovea, which occupies 15 degrees of the visual field is the only part of the retina that is genuinely useful for reading.”

Just 15 degrees of the visual field is useful for reading? No wonder then:

“Our eyes do not move continuously across the page… They move in small steps.”

In steps of 15 degrees coverage, that is.

 

McConkie and Rayner’s experiment proves this window is real. The setup involves a special device that tracks eye movement of the wearer. It then changes the visual display on the screen accordingly. In real time. It shows only a few characters to the left and right of the center gaze, the rest it fills with x’s.

            We the pexxx xx xxx xxxxxxx xxxxxx xx xxxxxx xx

When the eye moves, the screen gets updated to align where the gaze has moved:

            Xx xxx people of the xxxxxxx xxxxxx xx xxxxxx xx

            Xx xxx xxxxxx xx the United xxxxxx xx xxxxxx xx

            Xx xxx xxxxxx xx xxx xxxxxed States xx xxxxxx xx

The startling finding?

“They found that the participant did not notice the manipulation. As long as enough characters are presented left and right of fixation, a reader… believes that he is looking at a perfectly normal page of text.”

 

This 15 degree window also explain why this seemingly paradoxical point holds:

“Small letters should be harder to read than larger ones. Oddly enough, however, that is not the case.”

Because the larger the character, the more room it uses of the fovea. Which means one’s eyes have to jump to see the next character. And reading character by character (or just 2-3 characters at a time) is woefully slow. (Of course, there is a minimum character size below which the fovea can’t focus).

 

How long do characters need to be seen to register?

“A computer can be programmed so that, after a given duration, all of the letters are replaced by a string of x’s, even in the fovea. The experiment reveals that fifty milliseconds of presentation are enough for reading to proceed at an essentially normal pace.”

 

We’ve heard of speed-reading techniques. There are indeed ways to achieve that.

“If a full sentence is presented word by word, at the precise point where gaze is focalized, thus avoiding the need for eye movements, a good reader can read at a staggering speed – a mean of eleven hundred words a minute, and up to sixteen hundred words per minute… (that is) three to four times faster than normal reading.”

 

No wonder the first chapter is titled “The Eye: A Poor Scanner”!

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