What's the difference between telling people they shouldn't do something and telling them they shouldn't do something? If you have dysprosody, nothing. People with dysprosody can't control the stresses in their speech, and it makes a world of difference.
Those who have studied poetry will be familiar with, and perhaps exasperated by, the concept of prosody. Prosody is the rhythm, intonation, and stress of speech. Most people study it, however briefly, in school when they cover a poetry unit - mapping out the pauses and stresses in sonnets and other rhythmic poems. Prosody isn't a strictly artistic invention. The way we stress and intone words in everyday speech conveys a great deal of meaning.
This is never more apparent than when people are struck by dysprosody. Generally the product of brain disease or injury, dysprosody robs people of control over how they stress their speech. Some people get a very strange form of it called foreign accent syndrome. Technically this isn't a special kind of dysprosody. It's just a dysprosody that forces people into the kinds of tones and stresses that happen to sound like a specific accent. It can force a Japanese-speaker to have a Korean accent, a Norwegian-speaker to have a German accent, or an English-speaker to have a Chinese accent.
Other dysprosody sufferers simply sound bizarre or robotic. Dysprosody can be linguistic, forcing people to give odd stresses and tones to their words but leaving some of their other intentional stresses intact. Sometimes, though, it takes away a person's ability to convey emotion. All kinds of emotions are conveyed by stress and tone - sarcasm, enthusiasm, accusation, interrogation. This is especially true in languages in which a correctly stressed word means the difference between a question and a statement.
One particularly interesting case of dysprosody showed that the condition can vary from language to language, even when those languages are spoken by the same person. A Spanish-English translator, fluent in both languages from adolescence, came down with a neurodegenerative disorder. The first signs were the loss of her Spanish accent. For forty years, no one talking to her in Spanish had known that she was a native English speaker. Suddenly she was unable to correctly pronounce Spanish words, and pronounced them as an English speaker would. She also lost all ability to convey emotion in Spanish. She spoke, and even sang, in a monotonous robotic voice. Although her English also became noticeably more monotonous, she was still able to convey emotion if she made an effort.
Those whose dysprosody was the result of injury or temporary sickness can heal. For those who have degenerative diseases, it can get continuously worse. Sufferers can lose the ability to hear stresses, or emotion, in other people's voices. Only treatment for the underlying problem could make it possible for them to regain their abilities.
The fact that dysprosody exists reminds us how many different ways we convey meaning. Words alone aren't enough.
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