Abstract
Purpose Letter transpositions (the reversal of pairs of adjacent letters) result in slower reading speed (Rayner et al, psychol Sci 2006). The reduction is greatest for initial letters ('turtle' to 'utrtle'), intermediate for ending letters ('turtel'), and least for middle letters ('tutrle'). Of relevance to some forms of low vision, letter transpositions might have less impact for reading with peripheral vision because of increased spatial uncertainty for letter positions in the periphery. Our study investigated how letter transpositions affect reading performance (speed, critical print size and reading acuity) in both central and peripheral vision. Method Sixteen normally-sighted native English speakers performed computer-based versions of the MNRead test in central vision, and a rapid serial visual presentation (RSVP) test of reading speed in both central and peripheral (10° lower field) vision. The tests included separate blocks with letter transpositions in initial (INIT), middle (MID) and end (END) positions. Approximately 40% of the words in each sentence had a transposition. Results For MNREAD testing in central vision, there were significant reductions in maximum reading speed for all three transposition conditions—INIT (25.6±2.4%), MID (9.0±2.5%) and END (22.0±3.5%). Critical print size (CPS) was only affected in the INIT condition by 0.16±0.05 logMAR. Reading acuity was not affected by the transposition conditions. For RSVP reading in central vision, there were significant reductions in reading speed for all three conditions—INIT (40.8±5.4%), MID (22.8±6.1%) and END (27.1±5.4%). The RSVP speed reduction in peripheral vision was significantly less, and only the INIT condition showed a significant drop of reading speed by 20.2±9.5%. Conclusion Our results in central vision confirmed Rayner's finding that letter transpositions reduce reading speed, but only weak effects were found for CPS and reading acuity. Peripheral reading is less affected than foveal reading by transpositions, possibly due to higher spatial uncertainty in the periphery.
Meeting abstract presented at VSS 2018