Symbol recognition produced by points of tactile stimulation: the illusion of linear continuity.

OBJECTIVE

To determine whether tactile receptive communication is possible through the use of a mechanical device that produces the phi phenomenon on the body surface.

DESIGN

Twenty-six subjects (11 blind and 15 sighted participants) were tested with use of a tactile communication device (TCD) that produces an illusion of linear continuity forming numbers on the dorsal aspect of the wrist. Recognition of a number or number set was the goal.

MATERIAL AND METHODS

A TCD with protruding and vibrating solenoids produced sequentially delivered points of cutaneous stimulation along a pattern resembling numbers and created the illusion of dragging a vibrating stylet to form numbers, similar to what might be felt by testing for graphesthesia.

RESULTS

Blind subjects recognized numbers with fewer trials than did sighted subjects, although all subjects were able to recognize all the numbers produced by the TCD. Subjects who had been blind since birth and had no prior tactile exposure to numbers were able to draw the numbers after experiencing them delivered by the TCD even though they did not recognize their meaning.

CONCLUSION

The phi phenomenon is probably responsible for the illusion of continuous lines in the shape of numbers as produced by the TCD. This tactile illusion could potentially be used for more complex tactile communications such as letters and words.