Three experiments are reported which examine the action plans readers create for written instructions containing conditionals (if, if not, unless). Experiment 1 shows, from the pattern of errors and latencies with True/False items, that if not is represented as a positive action and negative condition, whereas unless is represented as a negative action and positive condition ('Do not if.. .'), even when the materials permit other recoding options. Experiment 2 focuses on unless and suggests that errors arise mainly from recoding operations, whereas speed of response is determined by the clause order used for the instruction. Experiment 3 introduces prohibitions ('Do not do X'). These impair performance with if and if not but facilitate performance with unless. This is consistent with readers representing unless in action plans as 'Do not if', the reader-generated representation of the negative action being cancelled by the explicit prohibition in the instruction. The practical implications of these findings are pointed out.Relatively few studies have explored how readers transform their understanding of a text into a plan for action. Much of the focus of reading research has been on educational settings, either the acquisition of the reading skill itself or of other information through reading. Nevertheless, Sticht (1 985) has shown that, whereas most of the reading tasks in school involve 'reading to learn', most of the reading done at work is 'reading to do'. Here people not only have to understand what they read but have to be able to apply the knowledge gained from reading. In order to know how to write instructions that can be easily followed, there is a practical need for understanding more about how people create action plans on the basis of what they read. The studies reported here seek to open up such investigations and are particularly concerned with instructions involving negative conditionals.
Action plansNorman (1 981) argued that action sequences are generally represented as hierarchies of schemas, where the superordinate schema corresponds to intention and the subordinate schemas are triggered by appropriate conditions. Although helpful, this notion of hierarchical schemas leaves unspecified the way positive and negative actions (prohibitions) may be represented. The tacit implication is that similar hierarchies will be created for both kinds of instructions. However, Dixon (1982Dixon ( , 1985 has shown that readers' representation of action plans, at the level of 188 P . Wright and A . J. Hull subordinate schemas, can vary both with the surface structure characteristics of the verbal instruction and the details of the task to be carried out. Experiment 1 examined whether readers exploit the recoding options available within written instructions in order to avoid explicitly representing negative elements in the action plans they create.
ExceptionalipNegative conditionals (except, unless, if not) are an interesting case for several reasons.Sentences containing various kinds of negation have been ass...