A Study of Braille Reading: 2. Patterns of Hand Activity in One-Handed and Two-Handed Reading

Abstract

Video recordings of the hands of 24 blind adults reading aloud prose, statistical approximations and scrambled words with either hand alone and with two hands were analysed. Hand activity involved forward scanning movements, regressions and returns to the next line. In two-handed reading, most readers resorted to mixed movement patterns, where a first segment of the line was explored by the left hand alone, a second segment by the two hands conjointly and a third segment by the right hand alone, each hand returning to the line while the other one was reading. In subjects who dissociated the hands to a great extent, the left hand generally started scanning the new line before the right hand had reached the end of the preceding line. This simultaneous disjoint exploration occurred with little slowing down of forward scanning, and involved parallel collection of textual information by the two hands. There were large and reliable individual differences in the relative sizes of the segments explored using the different hand combinations. Hand dissociation was correlated positively with individual reading speed in both two-handed and one-handed reading, and reductions in the degree of contextual constraint induced the adoption of more conjoint patterns of exploration. Total reading time was analyzed into components corresponding to regressions, line transitions and forward scanning. The main part of the gain from two-handed reading resulted in most subjects from savings in line transition time, but the most conjoint readers gained also on forward scanning and on regressions. The lower overall speed of conjoint readers was due not only to longer transition times but also to slower forward scanning and more time spent regressing.