DESIGN FOCUS
Mathematics for the blind
Solve the following equation: 3(x − 2) + 4 = 7 − 2(3 − x).
Did you do it in your head or use a piece of paper? When an equation is even slightly complex the
instant response of a sighted person is to reach for paper and pencil. The paper acts as an external memory,
allowing you to record and recall previous steps in a calculation. Blind children learning mathematics
have to perform nearly all such calculations in their head, putting them at a severe disadvantage.
Mathtalk is a system developed as part of a European project to create a mathematics workstation
for blind people [330]. It uses speech synthesis to speak formulae, and keyboard input to navigate
and manipulate them. The first stage, simply speaking a formula out loud, is complex in itself. Given the
spoken equation ‘three x plus four equals seven’, how do you know whether this is ‘3x + 4 = 7’ or
‘3(x + 4) = 7’? To make it unambiguous one could say the latter as ‘three open bracket x plus four close
bracket equals seven’, but this soon becomes very tedious. In fact, when reading mathematics people
use several cues in their speech: longer and shorter gaps between terms, and prosody: rising and
falling pitch (see Figure 10.6). The Mathtalk system includes a set of rules for generating such patterns
suitable for most equations.