Reading in the dark: effects of age and contrast on reading speed and comprehension

To explore the effects of contrast reduction on younger and older adults' reading behavior and to examine whether readers rely on word predictability to compensate for poor contrast.

Poor contrast can degrade text and may influence reading behavior. Readers may compensate for visual degradation of text by taking advantage of word predictability.

In Experiment 1, 5 younger and 5 older adults read sentences presented with 10 levels of contrast. In Experiment 2, 40 younger and 40 older adults read high-, medium-, and low-contrast sentences that varied in target word predictability (high vs. low).

Relative to those of younger adults, older adults' reading rates were more slowed by low contrast; comprehension was less influenced by contrast (i.e., not significantly). Older adults read high-predictability words faster and comprehended them better than low-predictability words, significantly so for high- and medium-contrast sentences. Younger adults comprehended high-predictability words significantly better than low-predictability words for high- and low-contrast sentences.

Low contrast was more detrimental for older adults. High-predictability words benefited older adults by significantly reducing their reading times and benefited all readers by significantly increasing their comprehension.

The current findings demonstrate the benefit of adequate contrast and word predictability for optimal text design to facilitate both reading times and reading comprehension.