processing and font information during reading : beyond distinctiveness , where vision meets design

Letter identification is a critical front end of the reading process. In general, conceptualizations of the identification process have emphasized arbitrary sets of distinctive features. However, a richer view of letter processing incorporates principles from the field of type design, including an emphasis on uniformities across letters within a font. The importance of uniformities is supported by a small body of research indicating that consistency of font increases letter identification efficiency. We review design concepts and relevant literature, with the goal of stimulating further thinking about letter processing during reading. Letter identification, fonts, and reading 3 Motivated by the increasing realization that letter perception is an important but overlooked stage in the reading process (e.g., Finkbeiner & Colheart, 2009, Grainger, 2008, Massaro & Schmuller, 1975, Pelli et al., 2006), there has been a resurgence of interest in letter perception in relation to reading. It is now clear that letter perception provides a critical front end for reading because letters are functional units — they are independent pieces of the word code (e.g., McClelland, 1976, Oden, 1984, Pelli, Farell, & Moore, 2003). The visual forms of letters exist within a larger structural design, a family of objects known as the type font. This idea has implications for perceptual identification that we begin to develop here. In previous research and theory, a core concept is distinctiveness — the properties that make one letter easy to discriminate from its alternatives in the alphabet. This has led to the central concept of feature detection in the literature (e.g., Gibson, 1969, Massaro & Schmuller, 1975, Fiset et al., 2009). Letters are defined by sets of features whose membership is determined by distinctiveness. If distinctiveness is indeed critical, then increasing it through alphabet design should increase legibility. This logic has been recently advocated (e.g., Fiset et al., 2008, Gosselin & Tjan 2008).1 However, if letter distinctiveness is an incomplete basis for understanding letter processing during reading, then calls to redesign letters are premature. A richer view of letter processing incorporates structural relations between letters and originates in the field of type design. Type designers have long been concerned with letter form and its impact on reading. Text fonts are designed for reading continuous paragraphs of text, and the main goal in their design is to produce optimally legible letterforms. Type designers recognize the importance of distinctiveness but they also emphasize the uniformity of letters (e.g., Carter, Day, & Meggs, 1985, Cheng, 2005). The 1 The idea of improving legibility through research and design is not new. Modifications to increase distinctiveness have been explored by Kolers (1969) and Lockhead and Crist (1980) and more recently Beier and Larson (2010). A modification that was actually used (mainly to increase spelling regularity, but distinctiveness was also increased) was the Initial Teaching Alphabet (Pittman & St. John, 1969); this modification was not successful (e.g., Downing, 1967). Spencer (1968) cites proposals for new designs going back to 1881. Letter identification, fonts, and reading 4 classical goal of type design is to achieve harmony and balance between individual forms. Within words, a letter should never stand out; it should cohere with neighboring letters, in order to better form a word unit, and sublexical units as well.2 In type design, there is a tension between considerations of distinctiveness and uniformity that is essential to the design process. “Individual characters must be distinct, yet related, in their form and construction” (Cheng, 2005, p. 6). Uniformity is achieved through commonalities in the shape, proportions and other stylistic attributes of letters within a font. Type designers constrain the shape of individual letters within a font so that they are related in weight, contrast, and stress or axis of the letter. Figure 1 illustrates these parameters. When type designers create letterforms, they develop a consistent treatment of part primitives and strokes (Adams, 1989). From a psychological perspective, the consistent and coherent appearance of fonts can be described as the application of rules, by the type designer, for “translating the prototypical structural features of every letter of the alphabet into a printed surface form” (Walker, 2008, p. 1024). Figure 1. Examples of 3 parameters that distinguish among fonts while relating letters within a font. Thus, commonalities within and between letters are a design feature of high quality text fonts. Type designers incorporate commonalities because they believe they are important for legibility, based on their data. Their data are judgments refined through training, aimed at understanding the structural relations that constitute a legible font. Type design 2 In general, type designers (mistakenly) assume that words are the functional units of reading. Psychological research, however, indicates that readers also form units at sublexical units such as letters, syllables, and perhaps bigrams (e.g., Grainger, 2008). Fortunately, designers work with letters and attend to how well letters form word units. We suggest that well-designed letters form functional sublexical units while also forming good word units, which are most important for lexical access. Letter identification, fonts, and reading 5 results from a design process in which design possibilities (variations in visual structure) are evaluated by the designer and other educated readers by intuitively monitoring their own reading experience. The idea that commonalities are important in letter perception receives validation from a small body of psychological studies in which commonalities increase the efficiency of human letter identification. This research will be reviewed, and the importance of specific commonalities will be discussed. To anticipate, we conclude that the commonalities that have been supported most strongly are spatial parameters concerning the size of letter parts and their interrelations. In type design, letters of the same font use a systematic reference frame of ascender line, x-height, baseline and descender line, illustrated in Figure 2. This frame system constrains size proportions within the font3, e.g., the ratio of x-height to cap height, or length of ascenders and descenders, are characteristics of a particular font (Baines & Haslam, 2005). The proportions vary somewhat among fonts, but within a restricted range, making fonts of the same point size appear larger or smaller (Luna, 1992). Figure 2. Reference frame for letters. The psychological evidence that commonalities contribute to efficiency comes from advantages found in identification of letters of consistent, regular fonts relative to mixed or irregular fonts (Gauthier, Wong, Hayward, & Cheung, 2006, Sanocki, 1987, 1988, 3 This is not done in a precise (mathematical) way. In fact, some shapes are given different heights in order to appear equivalent in height (e.g. to match the perceived height of a curved versus straight line, rounded letters such as lower case a, c, e, o are usually slightly taller than v, w, x, y, etc.). Also designers may introduce some slight irregularities to reflect their particular design style. Letter identification, fonts, and reading 6 1991a, b). The interpretation of these results is that letter processing becomes more efficient because the perceptual processing system tunes itself to exploit regularities of a font (see also Sanocki, 1991a, 1992, Walker, 2008). In contrast, in mixed font conditions, although there are often the same n alternative forms and letter identities, they are from two or more fonts instead of a single font. Note that mixing fonts increases the distinctiveness of individual letters, because differences between fonts correspond with letter identities. However, spatial and other properties are not as regular in a mixed font, and the perceptual system cannot exploit them as well. As a result, letter identification efficiency is reduced relative to same font conditions. These regularity effects imply that shared properties within a font (commonalities) are important in letter processing, in addition to distinctiveness. These commonalities are constraints that create a family of objects for identification. The ability to exploit commonalities is a hallmark of expertise with letters; non-experts (i.e. those unfamiliar with the writing system) do not exploit regularities (Gauthier et al., 2006).