Dyslexia is characterized by persistent difficulty in learning to read. One prevalent myth is that people with dyslexia perceive or write letters and numbers backwards. However, this is not the case. Dyslexia encompasses a larger range of reading impairments. Some individuals with dyslexia may experience no problems at all when it comes to reading and writing words and sentences, while for others, reading can be extremely difficult or impossible. People with dyslexia often report having had trouble with reading since they began school. Typically, they will say that they "didn't get" the material being taught, that teachers didn't explain things well, or that there was too much work to do. Many who learn about their diagnosis as adults say they knew something was wrong, but nobody would believe them. Dyslexics often perform better on tests of visual perception and memory than they do on reading comprehension tests. This is because they usually understand what is expected of them when taking a test, whereas when reading for information's sake they often make mistakes due to not understanding the content. The main problem for people with dyslexia is that decoding (the process of breaking words down into their components) takes more time than for most people. This is because people with dyslexia have to think about each letter of the word separately instead of processing the whole word at once.