The perception of complex patterns by touch

Two experiments are reported on matching Braille characters in dot pattern and outline shape formats by congenitally blind subjects. In a third experiment subjects' drawings of Braille shapes were analysed. Experiment 1 showed that normal and retarded readers differed significantly when outline shapes 'cued' identical dot patterns, but did not differ when the dot patterns preceded outlines. However, normal as well as retarded readers were faster and more accurate in judging identical pairs in dot-pattern format than in any other condition. In experiment 2 dot patterns and outline shapes were matched at three levels of reading proficiency. Faster readers made fewer errors in matching identical pairs, but all subjects were more accurate and faster with dot patterns than with outline shapes. Experiment 3 showed that blind subjects' drawing of outline shapes is not affected by reading proficiency. Most common were errors of alignment, including 'rotation' from vertical to horizontal axes, suggesting that sources of confusion were spatial position of dots and major axes of alignment rather than mirror-image reversals. It is argued that the results are not compatible with the hypothesis that Braille letters are perceived as global outline shapes by faster readers.