For many people today, reading is no longer relaxation. To keep up their work they must read letters, reports, trade publications, interoffice communications, not to mention newspapers and magazines: a never-ending flood of words. In getting a job or advancing in one, the ability to read and comprehend quickly can mean the difference between success and failure. Yet the unfortunate fact is that most of us are poor readers. Most of us develop poor reading habits at an early age, and never get over them. The main problem lies in language itself—words. Single words have little meaning until they are combined into phrases, sentences and paragraphs. Unfortunately, however, the untrained reader does not read groups of words. He reads one word at a time, often regressing to reread words or passages. Regression, or looking back over what you have just read, is a common bad habit in reading. Another habit which slows down the speed of reading is vocalization—sounding each word either orally or mentally as one reads. To overcome these bad habits, some reading clinics use a device called accelerator (加速器), which moves a bar down the page at a predetermined speed. The bar is set at a slightly faster rate than the reader finds comfortable, in order to “stretch” him. The accelerator forces the reader to read fast, making word-by-word reading, regression and vocalization virtually impossible. At first, comprehension is sacrificed for speed. But when you learn to read ideas, you will not only read faster, but your comprehension will improve. Many people have found their reading skills improved a lot after some training.What does “At first, comprehension is sacrificed for speed” (Para. 2) mean?