Glossary · 3 · Understanding
Comprehensibility
Also known as: Understandability, Text comprehensibility
German: Verständlichkeit
In technical communication, comprehensibility is the degree to which the intended readers understand a text correctly, in its context of use and for the purpose it serves; it is a property of the relation between text, reader and task and is established by testing readers, not by counting words or sentence lengths.
- Applied cognitive psychology
- Understanding
In one sentence
Comprehensibility is how well intended readers understand a text in its context of use, established by testing readers rather than counting words.
Example
A maintenance instruction scores well on a readability formula, yet in a test four of six technicians misunderstand which of two valves “the upstream valve” is; the team adds a figure with labeled valves and the instruction becomes comprehensible.
Rests on
- Situation model and Construction-integration model: understanding means building a correct model of the situation the text describes, not only decoding sentences.
- Inference (reading comprehension): readers fill gaps with their own knowledge; a text is comprehensible when the inferences it requires are ones its readers can make correctly.
- Working memory: long dependencies and dense noun phrases tax it.
How it applies
- Test with readers: Ask representative readers to perform the task, to explain the text in their own words or to answer questions on it; observe where they misunderstand. See usability testing and think-aloud protocols.
- Hamburg comprehensibility model: Langer, Schulz von Thun and Tausch described four dimensions rated by trained judges: simplicity (Einfachheit), structure and order (Gliederung–Ordnung), brevity and conciseness (Kürze–Prägnanz) and stimulating additions (anregende Zusätze). The model is widely used in German-speaking training and administration; it is an expert rating, not a test with readers.
- Machinery and software documentation: Terms used consistently and matched to what is on the machine or screen, one action per step, the result stated, references ("it", "this valve") that cannot be misread.
Comprehensibility vs. readability
Safety information readability and readability in general concern whether text can be read and decoded easily: legibility, wording, sentence length. Readability formulas estimate this from surface features. Comprehensibility asks whether readers understand the content correctly for their task, which depends on their knowledge and the context. A readable text can still be misunderstood.
Limits
- Comprehensibility is always relative to readers and tasks; a text cannot be comprehensible in general.
- Comprehension tests show whether readers understood what is written; they do not show whether the right information is there. What safety information is needed follows from the risk assessment.