Vision 04 00018.Pdf (3.374Mb)

vision Article The Influence of Typography on Algorithms that Predict the Speed and Comfort of Reading Arnold Wilkins 1,* , Katie Smith 1 and Olivier Penacchio 2 1 Department of Psychology, University of Essex, Wivenhoe Park, Essex, Colchester CO4 3SQ, UK; [email protected] 2 School of Psychology and Neuroscience, University of St. Andrews, St Mary’s Quad, South Street St Andrews, Fife KY16 9JP, UK; [email protected] * Correspondence: [email protected] Received: 21 January 2020; Accepted: 9 March 2020; Published: 12 March 2020 Abstract: 1. The speed with which text can be read is determined in part by the spatial regularity and similarity of vertical letter strokes as assessed by the height of the first peak in the horizontal autocorrelation of the text. The height of this peak was determined for two passages in 20 fonts. The peak was unaffected by the size of the text or its content but was influenced by the font design. Sans serif fonts usually had a lower peak than serif fonts because the presence of serifs usually (but not invariably) resulted in a more even spacing of letter strokes. There were small effects of justification and font-dependent effects of font expansion and compression. 2. The visual comfort of images can be estimated from the extent to which the Fourier amplitude spectrum conforms to 1/f. Students were asked to adjust iBooks to obtain their preferred settings of font and layout. The preference was predicted by the extent to which the Fourier amplitude spectrum approximated 1/f, which in turn was jointly affected by the design of the font, its weight and the ratio of x-height to line separation. Two algorithms based on the autocorrelation and Fourier transformation of text can be usefully applied to any orthography to estimate likely speed and comfort of reading. Keywords: font; spatial periodicity; discomfort; reading speed; autocorrelation; Fourier amplitude spectrum 1. Introduction There have been many studies of the effects of typographic variables on reading [1,2] including the effects of letter size (x-height)[3], line spacing (leading)[4] and typeface (e.g., serif vs. sans serif [5]. Text is a complex stimulus in which the effects of typographic variables interact together and with other variables such as familiarity [6] to determine the speed and comfort of reading. In this paper, it is shown that despite this complexity, simple algorithms that measure the shape of text are able to predict both reading speed and choice of font. They do so by registering the extent to which the spatial periodicity of text interferes with vision, and may have relevance for both normal and low-vision reading. One algorithm measures the periodicity from letter strokes, whereas the other measures aspects of the periodicity from lines of text. 2. Horizontal Spatial Periodicity Weaver [7] reported the case of a lady who experienced seizures when reading. She found that the seizures occurred only when she was reading material printed in Times or Palatino, and not when reading the same material printed in Arial or Verdana. Her observations were confirmed electrophysiologically. Times and Palatino are fonts with serifs, whereas Arial and Verdana are sans serif fonts. Serifs have little effect on reading [5]. However, the fonts differ not only with respect Vision 2020, 4, 18; doi:10.3390/vision4010018 www.mdpi.com/journal/vision Vision 2020, 4, 18 2 of 16 Vision 2020, 4, x FOR PEER REVIEW 2 of 16 toserifs serifs but but in inthe the periodicity periodicity of ofthe the letter letter strokes, strokes, as asillustrated illustrated in Figure in Figure 1. 1In. InArial Arial and and Verdana, Verdana, the thespace space between between the the strokes strokes within within a aletter letter is is greate greaterr than than that that between between letters, letters, whereas inin TimesTimes andand Palatino,Palatino, thethe letterletter strokesstrokes areare evenlyevenly spaced,spaced, givinggiving thethe typefacetypeface aa spatialspatial regularityregularity referredreferred toto byby typographerstypographers as asrhythm rhythm. Figure 1. The horizontal periodicity in the letter strokes for the word minimum printed in Times, Figure 1. The horizontal periodicity in the letter strokes for the word minimum printed in Times, Palatino, Arial and Verdana. The font size has been chosen to equate the x-height. The pattern beneath Palatino, Arial and Verdana. The font size has been chosen to equate the x-height. The pattern beneath each word is that formed by the central part of the letter strokes. each word is that formed by the central part of the letter strokes.. The rhythm of a typeface can be assessed using horizontal autocorrelation, the correlation of anThe image rhythm with of aa secondtypeface versioncan be assessed of itself, using displaced horizontal horizontally autocorrelation, by a small the correlation amount (lag).of an Theimage mathematical with a second technique version can of be itself, understood displaced by imagininghorizontally text byprinted a small on amount the transparency (lag). The ofmathematical an overhead projector.technique When can be two understood identical transparencies by imagining are text superimposed printed on andthe intransparency register, the of light an transmittedoverhead projector. through When them istwo at itsidentical maximum transparen (the correlationcies are superimposed is 1.0). When and the topin register, transparency the light is movedtransmitted horizontally through across them theis at lower its maximum one, the lag(the increases correlation and is the 1.0). transmitted When the lighttop transparency decreases (the is correlationmoved horizontally decreases). across It reaches the lower a minimum one, the when lag aincreases majority and of letter the transmitted strokes on the light top decreases transparency (the arecorrelation in the spaces decreases). between It reaches letters on a minimum the lower transparency.when a majority As of the letter top strokes transparency on the istop moved transparency further, andare in the the lag spaces increases between further, letters the on transmitted the lower lighttransp increasesarency. As (and the the top correlation transparency increases), is moved reaching further, aand maximum the lag increases when the further, majority the of transmitted letter strokes light on increases one transparency (and the correlati lie on theon neighbouring increases), reaching letter strokesa maximum on the when other. the majority of letter strokes on one transparency lie on the neighbouring letter strokesThe on height the other. of the first peak in the horizontal autocorrelation is therefore a measure of the spatial periodicityThe height of the of typeface, the first dependentpeak in the onhorizontal both the autocorrelation shape and spacing is therefore of neighbouring a measure letter of the strokes. spatial Wilkinsperiodicity et al. of [ 8the] showed typeface, that dependent the height on of both the firstthe shape peak in and the spacing horizontal of neighbouring autocorrelation letter of astrokes. word determinedWilkins et al. how [8] stripedshowed in that appearance the height the of wordthe firs wast peak judged in the to horizontal be. More importantly, autocorrelation they of showed a word thatdetermined the height how of thestriped peak in predicted appearance the speedthe word with was which judged the word to be. could More be importantly, read aloud. they Words showed with highthat peakthe height were readof the about peak 10%predicted more slowlythe speed than with those which with the low. word The could peak alsobe read predicted aloud. the Words speed with of silenthigh peak visual were search read through about a10% paragraph more slowly of text. than Reducing those with the autocorrelationlow. The peak also by compressingpredicted the words speed nearof silent the middle visual andsearch expanding through them a paragraph at the edges of text. (leaving Reducing their length the autocorrelation unchanged) increased by compressing reading speed,words even near thoughthe middle readers and preferred expanding to them read anat undistortedthe edges (leaving version their of the length text [ 8unchanged)]. One of the increased reasons forreading the eff speed,ects of spatialeven though periodicity readers on readingpreferred speed to read concerns an undistorted the ways inversion which of the the eyes text move [8]. One across of textthe whenreasons reading. for the effects of spatial periodicity on reading speed concerns the ways in which the eyes moveDuring across a text rapid when eye movementreading. (saccade), one eye generally leads and the other follows, resulting in a misalignmentDuring a rapid of theeye eyesmovement that requires (saccade), correction one eye when generally the eyes leads come and to the rest other [9]. Jainta,follows, Jaschinski, resulting andin a Wilkinsmisalignment [10] measured of the eyes saccades that requires and vergence correction movements when the eyes when come their to participants rest [9]. Jainta, read Jaschinski, German sentences.and Wilkins When [10] themeasured words hadsaccades a high and first vergence peak in themovements horizontal when autocorrelation, their participants the eyes read rested German on eachsentences. word forWhen longer the duringwords had the vergencea high first eye peak movements in the horizontal that corrected autocorrelation, the misalignment the eyes (vergence rested on error).each word The realignmentfor longer during took the longer vergence with a eye

Load more