Pop quiz: what's the difference between the fields shown in Figure 1 and Figure 2?
Answer: in Figure 2, the field has character separators.
You've probably seen a paper form where the fields are divided into individual characters, as in the second figure above. Or perhaps the separators were only partial, like this:
Another term for partial separators is "combs".
Separators can also be dotted rather than solid:
Which approach is best?
We frequently get asked which of the approaches above is the best. Here's what we say:
- Do not use characters separators.
- There are only two exceptions to this rule, and they are:
- when you are scanning completed forms and using Optical Character Recognition (OCR); or
- when you are asking for an identifier with a known, stable and and large number of characters (e.g. an Australian Medicare number).
We make these recommendations because character separators:
- don't do what you might imagine they do;
- make fields less flexible;
- make design more difficult; and
- make errors harder to correct.
Keep reading for more on each of these points, and the exceptions.
Problems with character separators
They don't do what you might imagine they do
There's a certain intuitive appeal to using character separators. So the theory goes, character separators will help make form-fillers' writing easier to read (i.e. more legible). However, the research does not support this hypothesis.
In fact, way back in the late 1970s, research found that character separators do not improve legibility . Worse still, the research showed that character separators slow down both the writer and the reader, by up to 16%.
So character separators make for a poorer user experience, for the people filling out the form and the people processing completed forms. This means there has to be a damn good reason to use them.
“Because I've seen it on forms before” does not count as a good reason! Indeed, the issue of character separators shows just how foolish it can be to blindly copy the design of another form.
They make fields less flexible
Another problem with character separators is that they limit the way fields can be used. Suppose you live in Sutton in Ashfield in the UK. By writing compactly, you could fit the city name in a text field without separators (Figure 5), but not when separators are present (Figure 6).
They make design more difficult
You could avoid the space issue described above by making the city field longer — i.e. have more characters — but it takes considerable work to identify what the length needs to be. Moreover, you may not have enough space available, given the absolute minimum width for a character space is 4mm .
They make errors harder to correct
When a field has character separators and the form-filler makes a mistake, it's not at all clear how that mistake can be corrected. Specifically: should the new answer be written above the error or after it? Such confusion lowers form-filler satisfaction, increases time to complete and can negatively impact on data quality.
Separators are needed for OCR
OCR is where a computer translates scanned hand-writing into digital characters. In order to be able to do this, the computer needs to know where each character begins and ends. To date, character separators are the best way to encourage the necessary spacing in form-fillers' writing, so the computer can do this.
Separators can help entry of identifiers
When form-fillers have to provide an identifier — an abstract string of hard-to-remember characters — the separators can be a cue, indicating whether or not the necessary characters have been transcribed. Of course, this only works if the number of characters is known and stable.
If the number of characters is small, there is not much benefit from having such a cue. But if the number of characters is large — as in Figure 7 above — the advantages of the cue from the separators outweighs the disadvantages of reduced writing and reading speed.
How to separate, when you need to
If you do need to separate characters, the best approach is to use a full, solid — or nearly solid — separator, as per Figure 2. This is because:
- when separators are partial, form-fillers sometimes avoid them by writing in the unseparated space above or below;
- dotted separators can be hard to see; and
- dotted separtors confuse some form-fillers (a solid line more closely resembles the division between actual fields, and thus provides a degree of intuitiveness).
In summary, don't use character separators unless you have a good reason
Character separators — whether full or partial, solid or dotted — should only be used when the form will be OCR'ed, or the field is collecting an identifier with a known, stable and large number of characters.
 Barnard, P. and Wright, P. (1976) "The effects of spaced character formats on the production and legibility of handwritten names", Ergonomics, 19, 81–92 and Barnard, P., Wright, P. and Wilcox, P. (1978) "The effects of spatial constraints on the legibility of handwritten alphanumeric codes", Ergonomics, 21, 73–78.
 Unpublished research by David Sless showed that handwriting widths follow a normal distribution, with a quarter of form-fillers needing more than 4mm per character.