Perceptual and task factors in fluent braille

Hypotheses that fluent braille depends (i) on coding letters by global outline shape for all task and speed levels, or (ii) on lateral dot-gap density scanning in fast reading for meaning were tested with three groups of fluent braillists who differed in reading speeds. In experiment 1, 90 degrees-rotated (near to far) texts under vertical and horizontal finger orientation were used. Hypothesis (i) was not supported. Finger orientation interacted significantly with Speed and Task. Vertical finger orientation, which disrupts lateral scanning, slowed reading for comprehension more than for letter search, and differentially more for faster readers. Horizontal finger orientation, which instead disrupts the familiar finger-body relation, did not have differential effects. The findings support hypothesis (ii). In experiment 2, normal texts and texts containing a degraded dot in some letters were used. These are felt in searching for individual letter patterns, but would disrupt lateral scanning of expected dot-gap density patterns in reading for meaning. The results supported the predictions from hypothesis (ii), that degraded texts slow reading for meaning significantly more than for letter search, and more in the case of faster readers than for the slowest group. Findings were not consistent with hypothesis (i), which predicts that text degradation affects tasks equally, and affects the slowest rather than the fastest readers. The results suggest that perceptual coding in reading differs with task demands and speed.