The five senses have traditionally been viewed as distinct yet complementary. Each sense is thought to have its own range of stimuli that are incapable of stimulating the other senses. However, recent research has discovered that some people taste a banana and claim that they are tasting blue, or see a color and say that it has a specific smell. This shows that such people, called synesthesiacs, have senses that do not respect the usual boundaries between the five recognized senses. Which one of the following statements, if true, most seriously weakens the argument? ['Recent evidence strongly suggests that there are other senses besides sight, touch, smell, hearing, and taste.', 'Synesthesiacs can be temporarily rid of their synesthetic experiences by the use of drugs.', 'The particular ways in which sensory experiences overlap in synesthesiacs follow a definite pattern.', 'Synesthesiacs demonstrate a general, systematic impairment in their ability to use and understand words.']