Reading with letter transpositions in central and peripheral vision.

We used a letter transposition (LT) technique to investigate letter position coding during reading in central and peripheral vision. Eighteen subjects read aloud sentences in a rapid serial visual presentation task. The tests contained a baseline and three LT conditions with initial, internal, and final transpositions (e.g., "reading" to "erading", "raeding", and "readign"). The four reading conditions were tested in separate blocks. We found that LT had a smaller cost on peripheral (10° lower field) than on central reading speed, possibly due to the higher intrinsic position uncertainty of letters in the periphery. The pattern of cost (initial > final > internal) was the same for central and peripheral vision, indicating a similar lexical route for both. In the periphery, LT only affected transposed words, while in central vision it also affected untransposed words. This spread of the LT effect in central vision could not be accounted for by increased attention or memory load, or by decreased sentence context.