Indirect tactual discrimination of heights by blind and blindfolded sighted subjects.

The ability of blind and blindfolded sighted subjects to discriminate cubes of different heights was measured using the method of constant stimuli. Five male blind and 5 male blindfolded sighted students, ages 22 to 28 years, were subjects. All blind subjects had undergone orientation and mobility training at a school for the blind. The cubes, made of wood, were explored using a long cane. Subjects were presented the standard cube and a comparison cube and required to judge whether the comparison cube height was taller, the same, or shorter than the standard. Analysis showed that the difference thresholds of blind and blindfolded sighted subjects were 1.93 and 2.14 cm, respectively. No significant difference in accuracy of discrimination was found between the two groups. The blind subjects showed significantly better performance than the blindfolded sighted subjects on the discrimination task. The blind subjects performed the task significantly faster than the blindfolded sighted subjects. The results suggest that braille reading, use of a long cane, and daily physical activities which required prolonged haptic or proprioceptive learning, may enhance nonvisual motor skills.