Most scientists have assumed that when we read both eyes look at the same letter of a word concurrently, but research by cognitive psychologists show that our eyes look at different letters in the same word and then combine the different images through a process known as fusion.
The reading process is not as simple as one might think and the eyes rarely scan the page smoothly from left to right, or right to left depending on the alphabet being read, according Professor Simon Liversedge and his team at the University of Southampton who will present their findings at the British Association for the Advancement of Science (BA) Festival of Science in York.
Depending on what we are reading and how hard we are finding the information to digest our eyes make small jerky movements, that allow us to focus on a particularly difficult word or often re-read passages we didn’t get the first time and analysing these eye movements enables psychologists to understand how our brain processes the sentence.
With sophisticated eye tracking equipment able to determine which letter of a font-size 14 word a person is looking at every millisecond from 1 metre away, Prof. Liversedge’s team went one further and looked at the letters within the word within the sentence. They were able to deduce that when our eyes are not looking at the same letter of the word, they are usually about two letters apart.
"Although this difference might sound small, in fact it represents a very substantial difference in terms of the precise "picture" of the world that each eye delivers to the brain," Prof. Liversedge explained.
To test how the brain's fusion mechanism might work, the team chose words that could easily split in two, such as cowboy, and presented half of the word to the left eye, and half to the right eye separately and analysed readers’ eye movements when reading sentences containing these particular words presented in this way.
"We were able to clearly show that we experience a single, very clear and crisp visual representation due to fusion of the two different images from each eye," he added. "Also when we decide which word to look at next we work out how far to move our eyes based on the fused visual representation built from the disparate signals of each eye."
"A comprehensive understanding of the psychological processes underlying reading is vital if we are to develop better methods of teaching children to read and offer remedial treatments for those with reading disorders such as dyslexia," Prof. Liversedge concluded. "Our team are now measuring the range of visual disparities over which both adult and child readers can successfully fuse words."
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