Businesses selling courses and manuals on speed reading claim that it is possible to increase the rate of reading to beyond 1000 words per minute with full comprehension, provided the course is followed and that the exercises are constantly practiced. However, a good deal of these courses and manuals are conflicting as to why and how speed reading should be adopted as a method. Some courses claim that reading at over 1000 wpm is advantageous for all types of reading material, whereas others say that it is best only for novels. Some say that speed reading is not appropriate for reading poetry and others say that it is [citation needed]. Some sources go even further, claiming that speed reading will increase IQ, memory, and comprehension ability. Other sources claim that it will only improve rate and comprehension.
One point of contention between the various speed reading courses is the assertions concerning sub vocalization. Some courses claim that the main obstacle to speed reading is any form of sub vocalization. Other courses claim that sub vocalization. can be used on keywords in order to speed up learning and reading. And some proponents of speed reading claim that sub vocalization. can be broken down into two levels, only one of which will reduce reading speed.
Speed reading courses and books take a variety of approaches to the concept of reading comprehension. Some courses and books claim that good comprehension is essential to speed reading, and that comprehension will improve with speed reading. Special non-standardized reading comprehension questionnaires are provided in order to convince the reader of the effects of the program. Some courses advise that while comprehension is important, it should not be measured or promoted above the speed of reading. Other courses and books argue that 90% of reading material is irrelevant and so comprehension should simply be ignored.
Speed reading courses variously claim that not all information in text needs to be covered while speed reading. Some claim that speed reading involves skipping text (exactly as has been measured during studies on skimming), whereas other speed reading promoters claim that all of the text is processed, but with some or most becoming subconsciously processed. Similarly, some courses claim that text should be serially processed whereas others say that information is processed in a more haphazard or ad hoc fashion. Terminology such as vision span and sub vocalization. are often used as explanations, but findings of research into these terms is not presented.