In a previous post I talked about the ClearType improvement in word recognition. Lee Gugerty and Rick Tyrrell at Clemson University found that ClearType improves word recognition accuracy by 17%. One of the other studies in the same publication looked at the effect of ClearType on reading sentences. If ClearType improves the accuracy of word recognition then we should see speed and/or comprehension improvements when reading full sentences.
They used a methodology that psychologists have long used to measure sentence comprehension. The participants in the study would read pairs of sentences and determine if the sentences belonged together. Half of the sentence pairs belonged together and half did not make sense together.
Sentences that belong together: Drew picked up the starfish from the sea floor. He was very happy to be scuba diving again.
Sentences that do not belong together: Drew picked up the starfish from the sea floor. He was very happy to be sky diving again.
Participants were presented pairs of sentences like the ones above, and pressed one button if the sentences belonged together and another if they didn’t belong together. The computer measured the time from sentences being presented until a button was pressed, as well as the accuracy of the responses. 46 Clemson university students read 144 sentence pairs each.
Overall, the study participants read the ClearType sentences statistically reliably faster than the sentences rendered in black & white (called aliased here). The magnitude of effect is approximately 5%. From the figure it’s clear that while ClearType improves both italic and normal (Roman), ClearType has a larger improvement on the italic text.
Additionally, the participants made more correct responses when the text was presented in ClearType. This is important because it’s very common to see speed improvements at the expense of accuracy, but we’re not seeing that here. There was a statistically reliable accuracy improvement ClearType with a smaller effect magnitude of about 2%.
This sentence comprehension study nicely extends the earlier word recognition finding. ClearType works by making each word easier to recognize, and easier to recognize words results in faster sentence reading and improved comprehension.
Gugerty, L., Tyrrell, R. A., Aten, T. R. & Edmonds, K. A. (2004). The effects of subpixel addressing on users’ performance and preferences during reading-related tasks. ACM Transactions on Applied Perception, 1(2), 81-101.
Edit: Update Image Reference