I regularly advise writers to use grammatical parallelism and visual formatting to influence document quality. (Use the links if you don’t know what I mean.) But I saw some evidence presented by colleagues at a recent conference that led me to refine that advice. Here’s the bottom line for those who don’t want the details:

  1. Use both parallelism and format to improve readability reading efficiency and accurate identification and recall of information.
  2. Use format alone to improve readability reading efficiency and accurate identification and recall of information.
  3. Don’t use parallelism alone to improve readability accurate identification and recall of information.

It pains me to offer you #3. It runs counter to what I’ve long held to be true. I suspect that’s true for many of you as well. But I can’t ignore the evidence. Ugh. Details below.

July 22, 2014 Update: I’ve tweaked the wording of my guidance based on more investigation of related research. See this post for details.

Some Background on the Research

The researchers did two studies where they asked people to read documents and then tested their recall by asking multiple-choice content questions without allowing them to look back at the documents.

Study 1. To test the effect of grammatical parallelism and visual formatting on readability, 100 people read a version of a passage from Ordnance Instructions for the United States Navy from 1866. (This limited the possibility of influence based on previous knowledge.)  There were 4 document versions: (a) parallel [P+] and formatted [V+], (b) parallel and unformatted, (c) nonparallel and formatted, and (d) nonparallel and unformatted.

ParallelABC.005 cropped

They found that accuracy was most affected by visual formatting and not much at all by grammatical parallelism. These results are the basis for my first two pieces of advice at the beginning of this post.

Study 2. To test the effect of grammatical parallelism and visual formatting on emotional response, 87 people read one of the four versions of the same passage from Study 1 followed by a question measuring their emotional response and then received either (a) parallel [Q+] or (b) nonparallel multiple-choice content questions again followed by a question measuring their emotional response.

ParallelABC.008 cropped

They found the greatest inconsistency of emotional response in document versions without visual formatting and with grammatical parallelism of both the reading text and the multiple-choice questions. These results are the basis for my third piece of advice at the beginning of this post.

So What’s Wrong with Inconsistent Emotional Response?

If you’ve read this far, I’m pretty sure this is the question you’re asking. Here goes.

clashing visual elements

Unity is a fundamental quality of human perception. Humans actively seek and prefer experiences that we can interpret as unified. This idea from Gestalt psychology is one I wrote about extensively in a 1995 book on document design. The lack of unity or consistency in color is the reason Smashing Magazine used the website shown at right in its Ugly Showcase.

My colleagues, Nicole Amare and Alan Manning, argue that unity or consistency is especially important for types of textual elements they call “decoratives.” That includes grammatical parallelism (and color). Decoratives are aesthetic. Parallelism does not convey information itself. Rather, it evokes a feeling about that information. Many people describe parallel text with terms related to organization: tidy, orderly, tight, neat, uncluttered, etc. As Manning said,

Parallel but visually unformatted text evidently disrupts that unified feeling and is therefore less desirable.

Visually formatted but nonparallel text was not a problem, confirming visual format is far more salient to readers than parallelism. I suspect inconsistent feelings slow down cognitive processing and distract us from our quest for comprehension. I’ve long believed parallelism affects efficiency more than effectiveness in documents with a primarily informative function. But that research hasn’t been done — yet.


Amare, N. & Manning, A. (October, 2013). Grammatical and visual parallelism in business communication pedagogy. Association for Business Communication Convention, New Orleans, LA.

Amare, N. & Manning, A. (2013). A Unified Theory of Information Design: Visuals, Text & Ethics. Amityville, NY: Baywood.

Campbell, K.S. (1995). Coherence, Continuity & Cohesion: Theoretical Foundations for Document Design. Hillsdale, NJ: Lawrence Erlbaum.