What can Eye Movements tell us about Reading?
If you think about what your eyes are doing as you read this blog, you probably imagine them moving in a smooth line from left to right, line by line. You might occasionally decide to go back to re-read something. In fact, your eyes are doing something quite different. They’re moving in a series of jumps called saccades and in between the saccades are pauses, called fixations. Psychologists have learned a lot about reading by measuring the pattern of fixations and saccades as people read.
We measure people’s eye movements as they read using an eye tracker. Our eye tracker has a video camera that records exactly where the eyes are looking every millisecond. As you can see from the picture above, Adam’s chin is resting comfortably on the chin rest. The tracker is located underneath the computer monitor, looking up at his eyes. It’s completely harmless and he is able to read perfectly normally.
What has been learned about reading from measuring people's eye movements? Most of the research literature has investigated reading processes in adults who are highly skilled readers. But eye movement experiments are also beginning to teach us about children’s reading. We’ll be discussing findings in more detail in future blogs, but here are some interesting findings from the literature to get us started.
Consider these sentences:
1a. Sarah liked the picture of the prince in the storybook.
1b. Sarah liked the picture of the daisy in the storybook.
The sentences 1a and 1b differ by one word, prince or daisy; prince and daisy share the same number of letters. But, prince is higher in frequency than daisy: it occurs more often in the language and in the books children are likely to have seen. Children, like adults, spend less time looking at higher frequency words like prince than lower frequency words like daisy. Paper here **
Now consider these sentences:
2a. Nick saw the goat in the zoo.
2b. Nick saw the elephant in the zoo.
They differ by the length of one word, goat or elephant. These words are equally frequent in the language, but children and adults spend less time looking at short words than long words. Paper here **
Apart from looking at specific properties of words, it is also interesting to explore sentences that differ in terms of meaning. Think about these three sentences:
3a. John used a knife to chop the large carrots for dinner.
3b. John used an axe to chop the large carrots for dinner.
3c. John used a pump to inflate the large carrots for dinner.
Sentence 3a is plausible, sentence 3b is implausible (it is possible, but unlikely that we would use an axe to chop carrots) and sentence 3c is anomalous (we wouldn’t normally use a pump to inflate carrots). Both adults and children spend more time looking at the anomalous sentence (3c) than the plausible sentence (3a). This is probably a reflection of them trying to make sense of the meaning of the sentence. Paper here **
We can can also explore how people read sentences that are syntactically ambiguous. Such sentences can mean different things, depending on how the syntax is processed, as in this example:
4a. The boy poked the elephant with the long stick from outside the cage.
4b. The boy poked the elephant with the long trunk from outside the cage.
The only difference between sentences 4a and 4b is that one contains the word stick and the other the word trunk. The part of the sentence with the long… is temporally ambiguous. Until we have read and processed the sentence a bit further, we are not sure what it refers to. In sentence 4a, stick is attached to the boy: it is the boy who has the stick, not the elephant. In sentence 4b, trunk is attached to the elephant: it is the elephant who has the trunk, not the boy. Both adults and children spend longer reading the word trunk than the word stick. This is because they were anticipating one type of interpretation of with the long, as in with the long stick; upon reading the word trunk, they had revise their initial interpretation to arrive at the correct meaning. Paper here **
Interested in learning more about eye movements and reading?
Find out about other research on children’s reading and eye movements by visiting Holly Joseph at the University of Reading and Hazel Blythe and Simon Liversedge at the University of Southampton. Keith Rayner, who did so much to further our understanding of reading, died in 2015. This paper summarises his scientific legacy. ** To learn more about the complexity of how we process complex visual information, check out these videos.
** if you're unable to locate one of these papers but would like to read it, please let us know.
Together with our partners at Oxford University Press we have produced a video to show how we use eye tracking in our research.You can view the video here