something beyond the capabilities of typical personal computers. Legibility research has been published since the late nineteenth century. Although there often are commonalities and agreement on many topics, others often create poignant areas of conflict and variation of opinion. For example, Alex Poole asserts that no one has conclusively answered which typeface style, serif or sans serif, is more legibile, although strong opinion exist. Other topics, such as justified vs. unjustified type, use of hyphens, and proper typefaces for people with reading difficulties such as dyslexia, have continued to be debated. Legibility is usually measured through the speed of reading, with comprehension scores used to check for effectiveness (that is, not a rushed or careless read). For example, Miles Tinker, who published numerous studies from the 1930s to the 1960s, used a speed of reading test that required participants to spot incongruous words as an effectiveness filter. The Readability of Print Unit at the Royal College of Art under Professor Herbert Spencer with Brian Coe and Linda Reynolds did important work in this area. It was one of the centres that revealed the importance of the saccadic rhythm of eye movement for readability—in particular, the ability to take in (i.e., recognise the meaning of groups of) about three words at once and the physiognomy of the eye, which means the eye tires if the line required more than 3 or 4 of these saccadic jumps. More than this is found to introduce strain and errors in reading (e.g., doubling). The use of all-caps renders words indistinguishable as groups, all letters presenting a uniform line to the eye, requiring special effort for separation and understanding. These days, legibility research tends to be limited to critical issues or the testing of specific design solutions (for example, when new typefaces are developed). Examples of critical issues include typefaces for people with visual impairment, typefaces and case selection for highway and street signs, or for other conditions where legibility may make a key difference. Much of the legibility research literature is atheoretical—various factors were tested individually or in combination (inevitably so, as the different factors are interdependent), but many tests lacked a model of reading or visual perception. Some typographers believe that the overall word shape (Bouma) is essential in readability and that the theory of parallel letter recognition is wrong, less important, or not the entire picture. Word shape differs by outline, influenced