A Comparison of Prose and Algorithms for Presenting Complex Instructions. Document Design Project, Technical Report No. 17

Complex conditional instructions ("if X, then do Y") are prevalent in public documents, where they typically appear in prose form. Results of two previous studies have shown that conditional instructions become very difficult to process as the structure becomes more complex. A study was designed to investigate whether this difficulty can be alleviated by presenting conditional instructions in formats other than prose. It was hypothesized that the major sources of difficulty--disjunction, negation, hierarchical structure, and ambiguous punctuation--would be eliminated by the use of algorithms. Subjects were presented with a sample of complex conditional instructions in three formats--prose and two forms of algorithms, lists and flow charts. Results showed that conditional instructions were easier to follow when presented as algorithms than as prose when subjects were prepared to follow algorithms by practice with feedback. In general, the algorithm helped performance when the condition in the instruction was logically complex. The overall superiority of algorithms was qualified, however, by three complications: (1) the difference between flowcharts and lists changed the speed relationships between prose and algorithms, (2) the effect of partial processing changed the speech relationships, and (3) the difficulty with the first exposure to the instruction drastically reversed the algorithm advantage in both speed and accuracy. (HOD)