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Displays 28 (2007) 60–67

The influence of line spacing and text alignmenton visual search of web pages

Jonathan Ling a,*, Paul van Schaik b

a School of Psychology, Keele University, Keele, Staffs ST5 5BG, United Kingdomb Psychology Section, School of Social Sciences, University of Teesside, United Kingdom

Received 14 December 2006; accepted 23 April 2007Available online 29 April 2007

Abstract

This research investigated the effects of text presentation on online behaviour and preferences in order to generate design guidelinesfor the production of web pages. Previous research has indicated that method of text presentation has a significant impact on usability.The present research found that varying text presentation had a significant effect on task performance, with wider line spacing leading tobetter accuracy and to faster reaction times. Left-aligned text led to better performance, although participants preferred justified text.Implications of these results for the design of web pages are discussed and recommendations given.� 2007 Elsevier B.V. All rights reserved.

Keywords: Web; Usability; Text presentation; Line spacing; Alignment

1. Introduction

With the advent of the World Wide Web, informationpresented on screen is now widespread. However, even abrief scan of the Internet will reveal that there is a widevariety in the way in which this information is presented.Some web sites may present data in a sparse and unclut-tered style, others may present similar information in acramped or cluttered fashion with little spacing betweenlines, making reading difficult. In some instances the latterapproach may be appropriate, for example when there is alarge amount of data presented in tabular form. However,the former approach is more likely to help with both visualsearch of pages and reading. Although extensive researchhas been conducted into the effect of a range of typograph-ical variables on the reading of printed material [30,34], farless has examined the relationship between typography andinformation presented on screens, and this lack is particu-

0141-9382/$ - see front matter � 2007 Elsevier B.V. All rights reserved.

doi:10.1016/j.displa.2007.04.003

* Corresponding author. Tel.: +44 (0) 1782 583447; fax: +44 (0) 1782583387.

E-mail address: j.r.ling@psy.keele.ac.uk (J. Ling).

larly noteworthy for web pages. Furthermore, the field oftypography has investigated a wide range of variablesand guidelines have been developed to indicate the bestway of presenting text on the printed page (see e.g., [12]),although this advice does not map directly on to text pre-sented on screen [4]. So it is to more recent research thatwe must turn for this advice. Dyson [6] presents a compre-hensive summary of this work. Her paper examines the evi-dence that has evaluated the many alternatives forpresenting onscreen text such as characters per line, useof columns and structure of the text. The current researchexamines the effects of two variables, line spacing and textalignment, on the visual search of web pages.

Despite the fact that there has been recognition of theimportance of how text on web pages is presented (seee.g., [24], research suggests that designers need to maketheir web sites more usable [36]), particularly because manyusers may have a degree of visual impairment or dyslexia,or be lower-literacy users [25,31]. The influence of humanfactors on interaction with screen elements should there-fore be an integral part of the design process, becausepoorly designed layouts can quickly lead to fatigue, with

J. Ling, P. van Schaik / Displays 28 (2007) 60–67 61

a resultant lowering of speed and accuracy of task perfor-mance [32]. In addition, aesthetic considerations are alsoimportant for usability [20,38] as these may be closelylinked to individuals’ motivation and satisfaction [22].

Given the wide range of options for the presentation oftext, it is perhaps surprising that there has not been moreempirical investigation of the influence of different presen-tational formats on user interaction and satisfaction withweb sites. However, there is general agreement that thereare three basic elements that must be considered whendeveloping a highly readable web page: typesize, spacing(whether down or across the page)[21], and colour [14].This paper focuses on the second of these attributes, whichto our knowledge has not been previously investigatedempirically in web pages.

In the work that has examined the influence of designparameters, including font type [3] and line length [7,19],the focus has tended to be on information retrieval. Infor-mation retrieval is a key activity in using the Web. As thisactivity involves visual search, research on the processesinvolved in visual search is essential. Visual conspicuity isone factor that influences the search process. This conspi-cuity can be defined as a combination of an object’s prop-erties, relative to its background, which attracts attentionand is therefore attended to. Conspicuity can be based oncolour, shape, size, orientation and other properties ofthe display. Research indicates that if a target object ismade visually conspicuous, search time can be up to 83%faster [26].

One way in which speed and accuracy of onscreen visualsearch – and hence usability – can be studied is through themanipulation of text presentation through altering param-eters such as line length and text spacing. However, inves-tigations of the effect of line length in both printed and on-screen formats have had differing results. For example, in acomprehension task, Duchnicky and Kolers [5] found thatblocks of text of 75–100 characters per line (cpl) were readmore quickly than when the text was presented in shorterlines. This finding contrasts with the more complex com-prehension task used by Dyson and Haselgrove [7] whofound that varying the amount of text presented between55 and 100 cpl had no effect on reading speed. However,both of these tasks were based on reading blocks of textpresented on-screen and not in the context of a realisticweb browser window. In a more recent study, Ling andvan Schaik [19] examined the effect of line length on objec-tive and subjective measures using a realistic web environ-ment. They found that line length influenced both types ofmeasure. Their results had practical implications for indi-viduals involved with web design. They suggested, first,that longer line lengths should be used when informationis presented that needs to be scanned quickly, and second,shorter line lengths should be used when text is to be readmore thoroughly, rather than skimmed. Given a choicebetween using long (85–100) and short lines (55–70),designers should opt for shorter lines, as though scanningweb pages is a major activity when finding information

on web sites [15], the majority of text-based web contentis presented to be read rather than skimmed.

Line length can also be considered in terms of align-ment, the way in which text is spread across the page. Interms of horizontal alignment, text can be presented as left-or right-aligned, which leads to uneven margins on theright or left side of text, respectively, or as justified, wherethe spaces between words are increased so that the text fitsacross the page with even margins on each side. Noresearch has examined the effect of varying text alignmenton the usability of web pages; however there is reason tobelieve that there may be differences in usage of web pagesrelated to variation in typographic style given research thathas used objective and subjective measures to inform thedesign of printed material (see e.g., [12,13]). With printedmaterial, there appears to be an advantage of greater inter-linear spacing over lesser [10], though this has also not beenverified with web pages.

Several factors impact on the usability of web pages,which can be determined using measures such as the timetaken to perform tasks or in the accuracy of task perfor-mance (see e.g., [37]). Objective measures are commonlyused to measure the usability of web sites. However,researchers have also recently begun to investigate theimplications of aesthetics for the development of visualdisplays [23,35] and web pages [28]. Users’ perceptionsof a web site may be closely linked to the length of timethey will spend on a site, as well as the probability ofthem returning to a site. Indeed, researchers have founda strong link between judgements of the aesthetic appealof interfaces and their apparent usability [17]. Attentionhas focused on subjective measures as a means of explor-ing user satisfaction [1]. Subjective or preference data helpthe development of web sites that are visually appealing.At the same time, these data can be used along withobjective data to produce better web sites, through animprovement in user satisfaction, higher levels of task per-formance or a combination of these. In addition, subjec-tive measures can be more sensitive to differences indisplay quality than performance measures [27]. Tractin-sky et al. [35] developed and validated an aesthetics eval-uation scale which they used to test the relationshipbetween the visual appeal of ATM and its usability. Theyfound strong correlations between the system’s perceivedaesthetics and its usability with a strong link betweeninterface aesthetics and ‘a priori perceptions of ease ofuse’ ([35]: 140). This scale has since been used for theevaluation of web pages (e.g., [38]).

This research therefore had three aims. First, to exam-ine the extent to which line spacing and text alignmenthave an impact on speed and accuracy of visual searchperformance. Second, to evaluate the impact of thesedesign choices on users’ aesthetic evaluations of websites. And finally, aim to explore further whether a rela-tionship exists between aesthetic considerations, prefer-ence and usability (performance) measures in use of theinternet.

62 J. Ling, P. van Schaik / Displays 28 (2007) 60–67

2. Method

2.1. Experimental design

The experiment used a two-factor mixed measuresdesign. The within-subjects factor was line spacing, withthree levels: single spacing (1), space-and-a-half (1.5) anddouble spacing (2). The between-subjects factor was textalignment with two levels: left-aligned and justified. Thedependent variables were accuracy and speed of visualsearch as well as subjective measures relating to aestheticappeal.

2.2. Participants

There were 65 undergraduate participants, 47 of whomwere female. Of these, 26 took part in the left-aligned con-dition, and 39 took part in the justified text condition (theinformation was missing from the remaining participants –check). Sample sizes were unequal because participantscompleted the tasks during lab classes and were allocatedto the between-subjects factor per class and these class sizesdiffered. A majority of participants (77%) were 25 or under;those remaining were aged between 26 and 50. All partici-pants used the Web and had been doing so for more than ayear. Frequency of using the Web varied from more thanonce a day to less than once a month, with a majority(76%) using the Web at least once a day. All participantshad normal or corrected-to-normal visual acuity.

2.3. Materials and apparatus

Sixty-six mock web pages were created in HTML anddisplayed using Microsoft Internet Explorer web browserversion 6.0. The pages were captured and saved as bitmapfiles. The web pages consisted of two frames, a smallerframe (15%, the navigation area) on the left of the screenand on the right a larger frame (85%, the content area)(Fig. 1). In the content area, hyperlinks appeared in thetext in five locations, distributed evenly down the web pagefrom top to bottom; links of approximately the same lengthwere used on each of the screens (see Fig. 1). Location ofthe target link (when present) was counterbalanced acrossthe trials, so links appeared in all the possible locationsan equal number of times. Hypertext links were presentedin bold and underlined, and were always coloured blue(colour code #0000FF). The rest of the text of the webpages was always black (colour code #000000). The back-ground in both areas was white (colour code #FFFFFF).The font used for both normal text and hyperlinks wasArial 10 point. Text presented in the content area appearedin one of 3 line spacings: single-, 1.5- or double spacing. Alltext was either left-aligned or justified depending on theexperimental condition. Each web page was created intwo versions with identical content and line spacings: onewith left-aligned text and another with justified. The textused for the content area of the web pages was taken from

a source, the doctoral thesis of one of the authors, withwhich all participants were unfamiliar.

In the experiment, the images were presented usingSuperLab experiment generator software (Cedrus, 2004)which ran on personal computers (Intel Pentium,333 MHz, 64 Mb RAM, Microsoft NT4 operating system,14 in. monitors). The screen dimensions were 800 · 600pixels. In order to ensure maximum clarity, contrast wasset to maximum level and brightness to minimum.

Four items from Tractinsky et al.’s [35] aesthetics scale(previously used by [38], for evaluating the quality of webpages) were used to rate the six types of web page usedin the visual search task; these were combinations of 3 linespacings and two text alignments. The four items wereorder, meaning, comprehension and overall. Items used7-point Likert scales, for example, ‘I judge this web pageto be:’ with scale end points ‘very ordered’ and ‘verydisordered’.

2.4. Procedure

The experiment was carried out in classrooms with 15–20 participants taking part concurrently. They first com-pleted a practice series consisting of six trials, followedby a series of 60 experimental trials presented in randomorder.

Participants were first presented with a set of on-screeninstructions. They were told that they were going to per-form in a visual search task involving mock web pagesand that they had to try to find a hyperlink in a screen oftext. If the link was present on the page, they had to pressthe ‘P’ key, and if it was absent they had to press ‘A’.

After reading the instructions, participants pressed the‘S’ key on the keyboard to proceed to a series of experimen-tal trials. In each trial a blank white screen (shown ran-domly for 1000, 1500 or 2000 ms with a mean of1500 ms) was presented, then a black target word on awhite background (always 1000 ms, in 48-point Arial inthe centre of the screen), followed by a blank white screen(shown randomly for 1000, 1500 or 2000 ms with a mean of1500 ms) and then a web page. The target word was eitherpresent in or absent from the content area.

Participants responded by pressing the appropriate keysto indicate whether the target was present or absent fromthe web page. A participant’s response triggered the startof the next trial. If a participant had not responded after5000 ms then the next trial started automatically. In thepractice trials, all 3 line spacings appeared twice and in halfthe trials the target was absent. When all participants hadcompleted the practice task, any questions were answeredby the experimenter before they went on to the main exper-iment. Participants were instructed to perform the task asquickly and as accurately as possible. As the experimentattempted to replicate the conditions under which partici-pants normally use computers, no restrictions were placedon the distance they were seated away from the screen and

Fig. 1. Typical web pages used in the experiment.

J. Ling, P. van Schaik / Displays 28 (2007) 60–67 63

they were free to move toward and away from the com-puter screens.

After completion of the final experimental trials, partic-ipants completed a series of questions presented by com-puter. The questions covered demographic details (age,sex, use of the Web), aesthetic value of pages and prefer-ence for line length and font type. Participants completed

the aesthetics scale for each type of page (24 ratings – sixscreens with all combinations of line space and text align-ment · 4 scale items). For preference, using the procedureemployed by Ling and van Schaik [18], participants werepresented with all three possible paired combinations ofline lengths and asked to choose in each pair the line lengththey preferred. This procedure for measuring preference

64 J. Ling, P. van Schaik / Displays 28 (2007) 60–67

was repeated for the single combination of the two textalignments. Questions were presented in the same orderfor all participants. Participants took approximately40 min to complete the experiment.

3. Results

The effects of line spacing and text alignment on accu-racy and speed of task performance as well as aestheticvalue and preference were analysed. A series of 2· (3) anal-yses of variance (ANOVA) assessed the effects of alignment(left-aligned or justified) and line spacing (1, 1.5 or 2 lines)on outcome measures; where appropriate, post hoc analy-ses were conducted to test for specific differences betweenline spacings.

3.1. Accuracy

3.1.1. Hits

The percentage of hits as a proportion of all responsesmade was calculated as a measure of accuracy. A hit wasdefined as a correct response to a target word that was pres-ent in the content frame of a subsequently presented webpage. The effects of spacing, F(2,124) = 38.83, e2 = .19,p < .001, alignment, F(1, 62) = 8.74, e2 = .05, p < .01, andthe interaction effect, F(2,124) = 5.40, e2 = .03, p < .01, weresignificant (see also Table 1, row 1). Simple effect tests withBonferroni correction showed that the effect of spacingwas significant with left alignment, F(2,48) = 6.04,e2 = .30, p < .001, and also with justified alignment,F(2, 76) = 52.09, e2 = .73, p < .001. Multiple comparisonswith Sidak correction demonstrated that with left alignmentthe differences between 1 and 1.5 line spacings (p < .05) andbetween 1 and 2 (p < .001) were significant, but the differencebetween 1.5 and 2 line spacings was not (p > .05). Furthermultiple comparisons with Sidak correction showed that

Table 1Descriptives by line spacing and alignment

1 Line

M (SD)

Hits Left 84.36 (7.66Justified 74.36 (12.1

Correct rejections Left 96.44 (6.19Justified 79.49 (30.1

RT (hits) Left 1637 (417)Justified 1504 (292)

RT (correct rejections) Left 2056 (679)Justified 2530 (939)Overall 2339 (870)

Aesthetic value Leftb 3.45 (1.17Justifiedc 3.65 (1.20

Preferencea Left 8.00 (17.4Justified 10.26 (20.4

a Percentages add up to close to 100% because of missing data.b Left presented line as alignment for rating of aesthetic value.c Justified presented as alignment for rating of aesthetic value.

with justified alignment the difference within each pair of linespacings was significant (all p < .001).

3.1.2. Correct rejections

The percentage of correct rejections was calculated. Acorrect rejection was defined as a correct response to a tar-get word that was absent in the navigation or contentframe of a subsequently presented web page. The effect ofalignment was significant, F(1,62) = 7.08, e2 = .08, p < .01(see Table 1, row 2). However, the effect of spacing,F(2,124) = 1.60, e2 < .01, p > .05, and the interaction effect,F(2,124) = 1.23, e2 < .01, p > .05, were not.

3.2. Speed

3.2.1. Reaction times for hits

The effect of spacing was significant, F(2, 124) = 16.90,e2 = .04, p < .001 (see Table 1, row 3). However, the effectof alignment, F(1,62) = 1.63, e2 < .01, p > .05, and theinteraction effect, F < 1, were not. Multiple comparisonswith Sidak correction showed that the differences between1 and 2 and between 1.5 and 2 line spacings were significant(both p < .001), but the difference between 1 and 1.5 wasnot (p > .05).

3.2.2. Reaction times for correct rejections

The effect of alignment was significant, F(1, 60) = 4.22,e2 = .05, p < .05 (see Table 1, row 4). However, the effectof spacing, F(2,124) = 2.06, e2 < .01, p > .05, and the inter-action effect, F(2,124) = 1.66, e2 < .01, p > .05, were not.

3.3. Aesthetic value

The aesthetics scale was checked for reliability. Theinstrument was found to be reliable for each of the sixalignment-spacing combinations (Cronbach’s alpha > .70).

1.5 Lines 2 Lines

M (SD) M (SD)

) 91.60 (11.43) 92.44 (10.00)4) 83.85 (8.15) 92.31 (11.44)

) 94.40 (10.03) 91.27 (13.25)1) 78.46 (26.71) 79.02 (28.53)

1671 (404) 1765 (441)1557 (311) 1689 (299)

2072 (674) 2102 (640)2447 (877) 2627 (951)2300 (819) 2422 (876)

) 4.92 (0.89) 5.31 (1.08)) 5.20 (1.02) 5.57 (1.08)

3) 36.00 (13.33) 53.33 (21.52)5) 36.75 (12.78) 50.43 (25.21)

J. Ling, P. van Schaik / Displays 28 (2007) 60–67 65

Therefore, average aesthetics scores were calculated foreach combination and these were used in subsequent anal-yses. The effects of spacing, F(2, 124) = 75.26, e2 = .36,p < .001, and alignment, F(1, 57) = 9.84, e2 < .01, p < .01,were significant (see Table 1, row 5). There were no othersignificant effects. Multiple comparisons with Sidak correc-tion showed that the difference within each pair of linespacings was significant (p < .001 between 1 and 1.5 andbetween 1.5 and 2 line spacings, p < .01 between 1.5 and 2).

3.4. Preference

3.4.1. Line spacing

The percentage of times participants chose particularline spacing over the others was calculated as a measureof preference. The effect of spacing was significant,F(2, 124) = 52.65, e2 = .45, p < .001, but the effects of align-ment and the interaction effect were not, both F < 1 (seeTable 1, row 6). Multiple comparisons with Sidak correc-tion showed that the difference within each pair of linespacings was significant (all p < .001).

3.4.2. AlignmentThe number of times participants who chose left-aligned

and justified when presented with these two types of align-ment was recorded. Of those using left-aligned in the visualsearch task, 67% chose justified. Participants using justifiedin the visual search task chose justified in 74% of cases. Achi square test of independence of alignment type used dur-ing visual search and preference for alignment demon-strated independence, v2(1) < 1. Over both types ofalignment during visual search, justified was preferred overleft-aligned, v2(1) = 10.90, p < .001.

3.5. Correlations between performance and preference

measures

The positive correlation between percentage preferencefor a line spacing of 1 and aesthetic value for a line spacingof 1 was significant, r = .32, p < .05 when presented withleft alignment and r = .26, p < .05 when presented with jus-tified alignment. The negative correlation between percent-age preference for a line spacing of 2 and aesthetic value fora line spacing of 1 was significant, r = �.41, p < .01 whenpresented with left alignment and r = �.35, p < .01 whenpresented with justified alignment.

Accuracy was positively correlated with speed for hitswith a line spacing of 1, r = .36, p < .01, but not with otherline spacings (p > .05). Accuracy was negative correlatedwith speed for correct rejections with all lines spacings,r = �.67, p < .001 for 1 line spacing, r = �.61, p < .001 for1.5 line spacings and r = �.66, p < .001 for 2 line spacings.

4. Discussion

The present research examined the influence of two vari-ables, line spacing and text alignment, on objective and

subjective measures in the visual search of web pages.Overall, the findings were consistent. Where a differenceexisted between the types of presentation for the accuracyand speed measures, the order of performance was thesame for both spacing and alignment: participants per-formed better with double line spacing than with 1.5 spac-ing, and better with 1.5 than single spacing. Similarly,where a difference existed, performance was always betterwith left-aligned than justified text. The results related toboth hits and correct rejections indicated that justified textwas more difficult to search accurately although increasingthe line spacing to 2 lines can compensate for this. The onlyexception to this pattern was in participants’ subjectiveviews: although in all measures where performance dif-fered, left-aligned text was superior to justified, partici-pants still preferred justified text.

The finding that measures of performance and prefer-ence were sensitive to experimental manipulations givesvalidity to the use of both types of data in future research.The recommendation of speed measures in particular isfurther supported by the impact of user interface designparameters on users’ interaction strategies: ‘Although mil-liseconds may seem too small to matter, milliseconds addedto each low-level step of interactive behaviour quickly addup’ ([11]: 334). In other words, investigation of the fullrange of factors involved in interaction with web pages islikely to lead to clear cumulative benefits.

The observed divergence between performance and pref-erence data has been found in other studies exploring webuse (e.g., [2,18]) and can cause problems for designers ofweb pages [29]. The decisions that are made will likely bedependent on the type of web site concerned. For commer-cial sites, aesthetic decisions should perhaps be prioritisedover more objective ones. However, for other sites wheresite traffic is of less relevance, designers may be betterserved by the performance data. The Internet is movingtowards standardisation with the emphasis given on sitesthat conform to widely publicised design guidelines (e.g.,[39]). Designers may too readily focus on performance datain the construction of web pages; however, our results showthat preference data should also be taken into consider-ation (particularly if there are no differences in perfor-mance) as this is likely to have a positive impact onusers’ acceptance of sites.

This study used objective and subjective measures toexplore the effects of varying text presentation on userbehaviour. As the summary of the results indicates, therewas an effect of line spacing and text alignment, with dou-ble spaced text and left-aligned text leading to faster andmore accurate visual search. These results have practicalimplications for the design of web pages. First, when textis presented to be read or scanned quickly, it should bedouble spaced. This supports earlier research using printedmatter that has indicated that there may be an advantageof increased character density on number of fixations andhence reading speed [16]. Research regarding the influenceof line spacing on the search of visual displays is scarce; this

66 J. Ling, P. van Schaik / Displays 28 (2007) 60–67

study makes an important contribution to our understand-ing of the impact of this variable on reading text presentedon screen.

Previous work examining the influence of text alignmenton use of printed material found no advantage of left align-ment (e.g., [9]); this research has not been supported by thepresent study in the context of presentation of on screenmaterial. Our findings suggest that text should be left-aligned rather than justified. Although prior research hasnot explored the influence of text alignment on user behav-iour in this way there is evidence that longer line lengthsmay help reading speed (though not necessarily visualsearch times; [8]). In other words, all text should be left-aligned when information is presented that needs to bescanned quickly.

Although there is a substantial corpus of work inves-tigating the influence of typographical variables onprinted material, research on these parameters on userinterfaces is much sparser [6]. Earlier work indicates thatthere are significant differences between the way in whichtext is read from the page and when it is read from thescreen [3]. Although savings made in accuracy or timemay be small, they do accumulate. The current researchfound clear effects of text alignment and line spacing forvisual search, and these now need to be examined in thecontext of reading for comprehension. It is a likelythough untested proposition that these variables will alsoimpact on text that is being read rather than scanned.Empirical investigation of this conjecture is required.Further research in this field will have clear benefits tousers of graphical user interfaces generally, and theWeb in particular. Research needs to establish not onlyhow individual factors influence interaction with on-screen text, but also how these variables interact witheach other. In addition, the relationship between objec-tive and subjective measures needs to be established, par-ticularly in relation to online commerce.

Finally, there are more high-level issues that also requireconsideration relating to the influence of typographic vari-ables as only one of a range of parameters that will influ-ence users’ interactions with online text. These issuesinclude organisation of pages, relationship between pages(both in terms of style and logical relationship) and theimpact of graphics.

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