People often pronounce a word differently when asked to read written material aloud than when speaking spontaneously. These differences may cause problems for those who develop computers that recognize speech. Usually the developers "train" the computers by using samples of written material read by the people who will be using the computer. The observations above provide most evidence for the conclusion that ['computers may be less reliable in decoding spontaneous speech than in decoding samples that have been read aloud', 'it will be impossible to develop computers that decode spontaneous speech', 'computers are now able to interpret oral speech without error', 'a "trained" computer never correctly decodes the spontaneous speech of a person whose voice sample was used to train it']