Which Are More Legible: Serif or Sans Serif Typefaces?

Introduction

An argument has been raging for decades within the scientific and typographic communities on what seems a very insignificant issue: Do serifs contribute to the legibility of typefaces, and by definition, are sans serif typefaces less legible? To date, no one has managed to provide a conclusive answer to this issue.

Part 1 provides typographical definitions.

Part 2 reviews the evidence for and against the legibility of serif and sans serif typefaces.

1. Definitions

Legibility vs. readability

Legibility is concerned with the very fine details of typeface design, and in an operational context this usually means the ability to recognise individual letters or words. Readability however concerns the optimum arrangement and layout of whole bodies of text:

"An illegible type, set it how you will, cannot be made readable. But the most legible of types can be made unreadable if it is set to too wide a measure, or in too large or too small a size for a particular purpose". ( Dowding 1957, p.5; in Lund, 1999 )

Typographical features

There are many elements in the design of a typeface which can contribute to its legibility.

Serif / Sans Serif

"Serifs" are the small finishing strokes on the end of a character. "Sans serif" fonts do not have these small finishing strokes.

Figure 1
Examples of serif and sans serif letters

Examples of serif and sans serif letters

Point size

Point size is perhaps the element most used to describe the legibility of a type face, but it can also be the most deceptive. Point size is a legacy from the letterpress system, where each letter is held on a small metal block. The point size actually refers to the size of this metal block, and not the actual size of the letter. The letter does not have to take up the full area of the block face, so two fonts with the same nominal point size can quite easily have different actual sizes. ( Bix, 2002)

Figure 2
The difference between point size and actual letter size (Image © Bix, 2002 )

'Point size' refers to the block of metal that letters were mounted on in letterpress system, and can be bigger than the letter itself

X-height

X-height refers to the height of the lower case "x" in a typeface. It is often a better indicator of the apparent size of a typeface than point size ( Poulton, 1972 ; Bix, 2002 ).

Figure 3
X-height

X-height for Arial is higher than that for Times New Roman at the same point size

Counters

Counters are the "negative spaces" inside a character. They are also good indicators of the actual size of the type.

Figure 4
Counters

Arial Black has a smaller counter size than that of Arial

Ascenders and descenders

Ascenders and are the vertical strokes which rise above the body of a character or x-height. Descenders are strokes which fall below the baseline of the x-height.

Figure 5
Ascenders and descenders

'y' has a descender, 'h' has an ascender

2. Evidence

Overview of legibility research: serif vs. sans serif

There are plenty of studies that show no difference between the legibility of serif and sans serif typefaces ( Tinker, 1932 ; Zachrisson, 1965 ; Bernard et al., 2001 ; Tullis et al., 1995 ; De Lange et al., 1993 ; Moriarty & Scheiner, 1984 ; Poulton, 1965 ; Coghill, 1980) ).

There are some high profile studies which claim to show the superiority of serif typefaces ( Robinson et al., 1983 ; Burt, 1959 ; Weildon, 1995 ) but these have been soundly criticised on points of methodology. ( Lund, 1997, 1998, 1999 ).

Particularly interesting is the case of Sir Cyril Burt, well known in psychology circles for being accused of fabricating his results. It turns out that he is likely to have continued this deceptive behaviour in his typographical work ( Hartley & Rooum, 1983).

Unfortunately, many researchers, typographers and graphic designers continue to cite Burt and Weildon uncritically, meaning that many of the informal resources on typography found on the web today continues to propagate unsubstantiated claims on the utility of serifs.

Most disappointing however, is that in more than one hundred years of legibility research, researchers have failed to form a concrete body of theoretical knowledge on the part that serifs may play in legibility ( Lund, 1999 ). Nor have they managed to make their work sufficiently known in the typographic community ( Spencer, 1968, p.6 ).

Arguments in favour of serif typefaces

Serifs are used to guide the horizontal "flow" of the eyes; The lack of serifs is said to contribute to a vertical stress in sans serifs, which is supposed to compete with the horizontal flow of reading ( De Lange et al., 1993 )

These are the most common claims when trying to make a case for the utility of serifs. However, serifs cannot in any way be said to "guide the eye". In 1878 Professor Emile Javal of the University of Paris established that the eyes did not move along a line of text in one smooth sweep but in a series of quick jerks which he called saccadic movements ( Spencer, 1968, p. 13 ; Rayner & Pollatsek, 1989, pp. 113-123 ). Unfortunately many graphic designers and typographers continue to use this rationale for the existence of serifs, due to a lack of communication and cooperation with the research community.

Serifs are used to increase spacing between letters and words to aid legibility

Serifs are not required to control letter and word spacing – in fact, serifs would be woefully inadequate for this purpose. In traditional letterpress systems, spacing is achieved with small pieces of metal inserted between the letters, and by the spacing between the letter form and the edge of the print block. Spacing is even easier to manipulate with modern computerised typesetting equipment. ( Sassoon, 1993 ; Rubinstein, 1988 )

Serifs are used to increase contrast (and irregularity) between different letters to improve identification

Well established research has shown that whole words can be recognised just as quickly as letters during an eye fixation and that single letters can be identified quicker when embedded in a word. Such a ‘Word superiority effect’ would indicate that serifs are not needed for distinguishing between single letters ( Reynolds, 1979 ).

Serifs are used to bind characters into cohesive ‘word wholes’

The simple Gestalt created by spaces between words would be enough to bind letters into ‘wholes’. Furthermore, other features such as character ascenders and descenders should have a much greater effect on word recognition than serifs ( Poulton, 1965).

Readers prefer body text set in serif typefaces, so they must be more legible

Many studies conducted in the past did indeed find a preference for serif typefaces ( Tinker, 1963 ; Zachrisson, 1965 ). However, Tinker commented that perceived legibility was due to a great extent to familiarity with the typeface. 40 years ago sans serif typefaces were not as common as they are now, and if these studies were repeated, it would not be surprising to find completely different results. Indeed, more recent studies have shown that computer users prefer sans serif typefaces for body text online ( Boyarski et al., 1998 , Bernard et al., 2000-2001 , Tullis et al., 1995 , Reynolds, 1979 ).

What is important to bear in mind is that in almost all legibility studies, reader preference or perceived legibility tends to be inconsistent with user performance ( Lund, 1999 ).

Serifs are used for body text because sans serif causes fatigue

It is often claimed that reading large amounts of body text set in sans serif causes fatigue, but there is no evidence to support this, as measuring fatigue has not been a concern in the vast majority of legibility research comparing serif and sans serif typefaces.

Furthermore, "no satisfactory objective method of measurement has been devised. Subjective assessments of fatigue are subject to modification by a great many factors which may be totally unrelated to the experimental situation". (Reynolds 1979, p313)

Arguments in favour of sans serif typefaces

Serifs are just an historical artefact

This could be true to a great extent, especially since claims attempting to justify serifs in retrospect have been less than convincing.

Many researchers attribute the origin of serifs to the Romans, some claiming that "Roman masons … terminated each stroke in a slab of stone with a serif to correct the uneven appearance made by their tools". ( Craig, 1980; in Bix, 2002 ). Others state that "design by brush before execution in stone gave rise to … tapering serifs at the terminals of many strokes". (Bigelow, 1981; in Rubinstein, 1988, p10).

What ever their origin, serifs have been around for so long that perceived legibility is very likely to have been affected by familiarity – readers tend to rate as more legible the typefaces they are most used to ( Tinker, 1963 ; Zachrisson, 1965 ).

Sans serif are better on the web

Although studies of screen reading show no difference between reading from screen and from paper ( Dillon, 1992 ; Bernard, 2001 ), there could be some validity to this argument.

When typefaces are digitised for use on computers, the letter forms have to fit within a relatively small pixel grid, often leading to what are called the "jaggies" ( Rubinstein, 1988 ). Many web professionals such as graphic designers claim that this relatively low resolution cannot render effectively enough the fine finishing strokes of serif typefaces, and that sans serif typefaces lend themselves more naturally to being digitised, and come out cleaner and thus more legible.

Figure 6
Digitised typefaces have to fit into a relatively small pixel grid (image © Gillespie )

The jagged curves of a digitised typeface can be seen close-up

However, this has not been borne out by recent evidence ( Bernard, 2001 , Boyarski et al., 1998 , Tullis et al., 1995 , De Lange ), that shows no difference in legibility between serif and sans serif font on the web.

Sans serif is better at small sizes. Sans serif fonts survive reproduction and smearing because of their simple forms

Some research has shown that serifs may actually become visual noise at very small sizes, detracting from the main body shape of the letter form ( Morris, et al., 2001 ). However, this has not been confirmed in tests of continuous reading ( Poulton, 1972 ). Other factors such as stroke thickness, counter size and x-height are likely to have a far greater effect in preserving the overall identity of a letter form whether it be through smearing or size reduction ( Poulton, 1972 ; Reynolds, 1979 ).

Sans serif is better for children learning to read

Books produced for children are often printed with sans serif text as teachers claim that the simplicity of the letter shapes makes them more recognisable ( Coghill, 1980) , Walker, 2001 ). But studies with child participants have found no difference in their ability to read either style of typeface. ( Coghill, 1980) ; Zachrisson, 1965 , Walker, 2001 )

3. Conclusion

What initially seemed a neat dichotomous question of serif versus sans serif has resulted in a body of research consisting of weak claims and counter-claims, and study after study with findings of "no difference". Is it the case that more than one hundred years of research has been marred by repeated methodological flaws, or are serifs simply a typographical "red herring"?

It is of course possible that serifs or the lack of them have an effect on legibility, but it is very likely that they are so peripheral to the reading process that this effect is not even worth measuring ( Lund, 1999 ).

Indeed, a greater difference in legibility can easily be found within members of the same type family than between a serif and a sans serif typeface. ( Tinker, 1963 , Zachrisson, 1965 ). There are also other factors such as x-height, counter size, letter spacing and stroke width which are more significant for legibility than the presence or absence of serifs. Poulton, 1972 ; Reynolds, 1979 )

Finally, we should accept that most reasonably designed typefaces in mainstream use will be equally legible, and that it makes much more sense to argue in favour of serif or sans serif typefaces on aesthetic grounds than on the question of legibility. (Bernard, 2001 ; Tinker, 1963)


Publetariat Editor’s Note: What do you think? Use the ‘add new comment’ link (below the following references) to weigh in.


4. References

Bell R.C., Sullivan J.L.F. (1981). Student preferences in typography. Programmed Learning and Educational Technology18(2), 57-61.

Comment about this source:

A typical study on the aesthetic quality of fonts – these types of studies are only useful for a short time before fashion or technology changes the whims of readers. That said, they do need to be done from time to time if what I say in the conclusion is true.

Bernard, M., Mills, M. (2000). So, what size and type of font should I use on my website? Usability News 2.2[Online]. http://psychology.wichita.edu/surl/usabilitynews/2S/font.htm

Bernard, M., Mills, M., Frank, T., McKown, J. (2001). Which font do children prefer to read online? Usability News 3.1[Online]. http://psychology.wichita.edu/surl/usabilitynews/3W/fontJR.htm

Bernard, M., Liao, C., Mills, M. (2001). Determining the best online font for older adults. Usability News 3.1[Online]. http://psychology.wichita.edu/surl/usabilitynews/3W/fontSR.htm

Bernard, M., Mills, M., Peterson, M., Storrer, K. (2001). A Comparison of Popular Online Fonts: Which is Best and When? Usability News 3.2[Online]. http://psychology.wichita.edu/surl/usabilitynews/3S/font.htm

Comment about this source:

A collection of well thought out, up to date studies from Bernard et al concentrating on fonts for the web, though it is not clear if they have been published in a peer-reviewed periodical.

Bix, L. (2002). The Elements of Text and Message Design and Their Impact on Message Legibility: A Literature Review. Journal of Design Communication, No. 4. Available at: http://scholar.lib.vt.edu/ejournals/JDC/Spring-2002/bix.html

Comment about this source:

A nice balanced review of the elements of legibility and readability of typefaces, although does not explicitly mention readability, choosing to talk about how text is set and laid out under the "umbrella" term of legibility.

Acknowledges that the serif/sans serif debate is divided and inconclusive but refers to Burt uncritically and wheels out the old argument about serifs reinforcing horizontal eye flow.

Still, implies correctly that x-height, colour contrast, counter size and other factors are more significant for legibility than the presence or absence of serifs, and that the combination of all factors is the most important thing.

Boyarski, D., Neuwirth, C., Forlizzi, J., Regli, S.H. (1998). A Study of Fonts Designed for Screen Display. Proceedings of ACM CHI 98 Conference on Human Factors in Computing Systems.1, 87-94.

Comment about this source:

Pits Times Roman against Georgia and Georgia against Verdana.

Burt, C. (1959). A psychological study of typography. Cambridge: Cambridge University Press.

Coghill, V. (1980). Can children read familiar words in unfamiliar type? Information Design Journal 1(4), 254-260

Comment about this source:

Very interesting study which implies that because young children have not had the time or the ability to become accustomed to certain fonts, this confounding factor can be eliminated from the experiment. Coghill finds that there is no significant difference between serif and sans serif fonts although some methodological issues are worrying. For example, being a teacher she states that sometimes she couldn’t stop herself from helping the children if they couldn’t read a word, although she claims that this does not affect the validity of her study.

Dillon, A. (1992). Reading from paper versus screens: a critical review of the empirical literature. Ergonomics, 35(10), 1297-1326.

Gaultney, V. (2000). Balancing typeface legibility and economy: practical techniques for the type designer. [Online] http://www.sil.org/~gaultney/research.html

Gillespie, J. (n.d.) Web page design for designers. [Online]http://www.wpdfd.com/wpdtypo.htm

Hartley, J. (1987). Designing electronic text: the role of print-based research.Educational Communication and Technology, 35(1), 3-17.

Hartley J. and Rooum D. (1983). Sir Cyril Burt and typography: A re-evaluation, British Journal of Psychology 74(2), 203-212.

Comment about this source:

A remarkable study showing that Burt’s habit of deception also extended into his typographical research. Lund comments that:

Donald Rooum and James Hartley have convincingly shown that Burt’s well-known dubious practices also extended into his work on legibility and typography. They point out that of 123 statements about typography in Burt’s book, only three – 3 – were either supported by data or by reference to named sources (Rooum, 1981; Hartley and Rooum, 1983; in Lund, 1995 ).

Scary! Even more scary is the fact that so many researchers cite Burt uncritically …

Humphreys, Glyn W. (1989). Visual cognition: computational, experimental, and neuropsychological perspectives. Hove : Lawrence Erlbaum. pp. 273-286.

Julie A. Jacko & Andrew Sears. 2002. The Human-Computer Interaction Handbook: Fundamentals, Evolving Technologies and Emerging Applications. Lawrence Erlbaum Associates.

Kahn, P., Lenk, K. (1995). Screen Typography: Applying Lessons of Print to Computer Displays. Seybold Report on Desktop Publishing, 7(3).

De Lange, R. W., Esterhuizen, H. L., Beatty, D. (1993). Performance differences between Times and Helvetica in a reading task.Electronic Publishing, 6(3), 241-248.

Comment about this source:

Very good section going through the arguments for and against serifs.

Lansdale, M.W., Ormerod, T.C. (1994). Understanding interfaces: A Handbook of human-computer interaction. London: Academic Press. pp. 53-59.

Comment about this source:

Some good basic information on spatial frequency.

Lund, O. (1995). In black and white: an r&d report on typography and legibility. Review article. Information design journal, 8(1), 91-95.

Lund, O. (1997). Why serifs are (still) important.Typography Papers, 2, 91-104.

Lund, O. (1998). Type and layout: how typography and design can get your message across – or get in the way. Review article. Information design journal, 9(1), 74-77.

Lund, O. (1999). Knowledge Construction in Typography: The case of legibility research and the legibility of sans serif typefaces. Thesis submitted for the degree of Doctor of Philosophy. Reading: The University of Reading, Department of Typography & Graphic Communication.

Comment about this source:

The masterwork of the whole serif / sans serif debate. Reviews a selection of 28 legibility studies (from a total of 72) since the first one in 1896 to the late 90’s, inspecting each one for holes in its internal validity. Other issues are explored such as the lack of real theory after a century of empirical research and the philosophical and historical movements affecting this strand of research.

Considering that aesthetic preference is supposed to have a significant effect upon the results of legibility studies, it would have been an ideal space to compare the results of the many preference studies conducted at the same time as the empirical studies. An analysis could have been made to see if there was a correlation with the more positive results for sans serif typefaces and the growing existence and acceptance of these same typefaces.

Includes a fascinating look behind the scenes in the history of legibility research, with Pyke’s disappointment in 1926, The scandal of Burt’s deceptions and bitter arguments over traffic signs in the 70’s.

States explicitly, however, that the thesis does not attempt to be just another legibility study, but uses serif / sans serif debate as a "lense" through which to examine the process and philosophy of scientific enquiry. A great shame that he stops there, since he is probably the most able researcher to be able to resolve the debate once and for all.

Marcus, A. (1992). Graphic design for electronic documents and user interfaces. ACM Press.

Mills, C.B., Weldon, L. J. (1987). Reading text from computer screens, ACM Computing Surveys (CSUR), 19(4), 329-357.

Moriarty, S., Scheiner, E. (1984). A study of close-set type. Journal of Applied Psychology,69, 700-702.

Morris, R. A., Berry, K., Hargreaves, K. A., Liarokapis, D. (1991). How typeface variation and typographic variation affect readability at small sizes.IS&T’s Seventh International Congress on Advances in Non-impact Printing Technologies, volume 2, edited by Ken Pietrowski, Portland, OR, USA.

Morris, R. A., Aquilante, K., et al. (2001). Serifs slow RSVP reading at very small sizes, but don"t matter at larger sizes. Submitted

Oborne, D., Holton, D. (1998). Reading from screen versus paper: there is no difference. International Journal of Man-Machine Studies, 28, 1-9.

Poulton, E.C. (1965). Letter differentiation and rate of comprehension in reading. Journal of Applied Psychology, 49(5), 358-362.

Poulton, E.C. (1972). Size, style, and vertical spacing in the legibility of small typefaces. Journal of Applied Psychology, 56(2), 156-161.

Pyke, R.L. (1926). Report on the Legibility of Print. Medical Research Council: Special Report. Series No. 10. UK.

Comment about this source:

Pyke give a clue to the nature of the the serif debate when he lamented: "the problem of legibility seemed simple at the outset; it is in fact complex and elusive".

Rayner, K. & Pollatsek, A.. (1989). The Psychology of Reading. Englewood Cliffs: Prentice-Hall Inc. pp. 113-187.

Comment about this source:

Excellent general resource on many issues on reading, including eye movements

Reynolds, L. (1979). Legibility studies: Their relevance to present-day documentation methods. Journal of Documentation, 35(4), 307-340.

Robinson, D.O, Abbamonte, M., Evans, S.H. (1971). Why serifs are important: the perception of small print.Visible Language, 4, 353-359.

Rubinstein, R. (1988). Digital Typography. Addison Wesley Longman.

Sassoon, R. (1993). Computers and Typography.Oxford: Intellect Books.

Spencer, H. (1968). The Visible Word. London: Lund Humphries.

Tinker, M.A. (1963). Legibility of Print, 3rd edition. Iowa: Iowa State University Press.

Comment about this source:

The most prolific and respected researcher in legibility. The study cited below is the only one that deals specifically with serifs and is reprinted in this book.

Tinker, M. A., Paterson, D.G. (1932). Studies of typographical factors influencing speed of reading: X. Style of typeface. Journal of Applied Psychology, 16(6), 605-613.

Comment about this source:

A landmark study in many ways, although often misinterpreted. Tinker described his results as showing more or less equal legibility for most of the typefaces, although a slightly longer reading time for Kabel Light, the only sans serif typeface in the study, has been claimed by others to show the superiority of serif typefaces. There are problems however, as in having only one sans serif typeface, you cannot be claiming to be comparing serifs and sans serifs, but only that specific typeface – Kabel Light. Furthermore, no one is saying that Kabel Light is a particularly good example of a sans serif typeface. Thirdly, chances are that if you performed the study today, the results could easily go in the favour of Kabel Light, since people are simply more used to sans serif typefaces.

Tullis, T. S., Boynton, J. L., Hersh, H. (1995). Readability of Fonts in the Windows Environment (Interactive Poster). Proceedings of ACM CHI’95 Conference on Human Factors in Computing Systems, 2, 127-128.

Walker, S. (2001). Typography for children: serif or sans?. Department of Typography & Graphic Communication, The University of Reading [Online] http://www.textmatters.com/kidstype/serif_or_sans_.html

White, J.V. (1988). Graphic Design for the Electronic Age. New York: Watson-Guptill Publishers.

Weildon, C. (1995). Type and layout: How typography and design can get your message across–or get in your way. Berkeley: Strathmoor.

Zachrisson, B. (1965). Studies in the Legibility of Printed Text. Stockholm: Almqvist & Wiksell.

Comment about this source:

A contemporary of Tinker, disagreed often on methods but found largely similar results in terms of legibility differences between serif and sans serif typefaces.

This article was written by Alex Poole and published on Alex Poole’s Literature Review: 7 April, 2005

 
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