support techniques representing the six general kinds of cognitive support that human decision makers need. The six classes are: process models which assist in projecting the future course of complex processes; choice models, which support integration of decision criteria across and/or alternatives; information control techniques which help in storage, retrieval, organization and integration of data and knowledge; analysis and reasoning techniques which support application of problem-specific expert reasoning procedures; representation aids which assist in expression and manipulation of a specific representation of a decision problem; and judgement amplification/refinement techniques, which help in quantification and de-biasing of heuristic judgements. Additional distinctioms are provided to distinguish the individual techniques in each of these primary categories. The taxonomy also has practical use as a design aid for decision support systems. The kinds of decision support needs represented by the taxonomy are general and can be used to guide the analysis and decomposition of a given decision prior to decision aid design. Specific needs for assistance can then be tied to specific computational techniques in the taxonomy. Methodological suggestions for using the taxonomy as a design aid are given. and The Influence of Color-Enhanced in Graphical Information Presentation Decision Making Isak Benbasat, Albert S. Dexter, and Peter Todd A laboratory experiment was conducted to assess the influence of graphical and color-enhanced information presentation on information use and decision quality in a simulation setting. This is the third in a series of studies examining the effects of colors and graphics in a managerial decision making task. The findings reported in this paper indicate that graphical presentations are more useful when evaluating information in order to determine promising directions in the search for an optimal solution bit when the task requires the determination of exact data values for computational purposes, graphical reports are less useful than tabular ones. Benefits of color include taking fewer iterations to complete the task. However, these benefits are associated more strongly with the graphical report as indicated by the significantly higher use of color enhanced graphical reports over monochromatic ones. The benefits of color are also restricted to the early stages in the decision task with color graphic report usage dropping sharply over time. Volume 2, Number 2, 1986 Task-Action Grammars: A Model o f the Mental Representation of Task L a n g u a g e s Stephen J. Payne and T. R. G. Green We present a formal model of the mental representation of task languages. The model is a metalanguage for defining task-action grammars: generative grammars which rewrite simple tasks into action specification. Important features of the model are: (1) Identification of the "simple tasks" that users can perform routinely and which require no control structure; (2) Representation of simple tasks by collections of semantic components reflecting a categorisation of the task world; (3) Marking of tokens in rewrite rules with the semantic features of the task world to supply selection restrictions on the rewriting of simple tasks into action specifications. This device allows the representation of family resemblances between individual task-action mappings. Simple complexity metrics over task-action grammars make predictions about the relative learnability of different task language designs. Some empirical support for these predictions is derived from the existing empirical literature on command language learning and from two unreported experiments. Task-action grammars also provide designers with an analytic tool for exposing the configural properties of task languages. Learning F l o w o f Control: Recursive lterative P r o c e d u r e s Claudius M. Kessler and J o h n R. Anderson and Two experiments were performed to study students' ability to write recursive and iterative programs and transfer between these two skills. They wrote functions to accumulate instances into a list. Problems varied in terms of whether they were recursive or iterative, whether they operated on lists or numbers, whether they accumulated results in forward or backward manner, whether they accumulated on success or failure, and whether they simply skipped or ejected on failure to accumulate. Subjects had real difficulty only with the dimensions concerned with flow of control--namely, recursive versus iterative, and skip versus eject. We found positive transfer from writing iterative functions to writing recursive functions, but not vice versa. A subsequent protocol study revealed subjects had such a poor mental model of recursion that they developed poor learning strategies which hindered their understanding of iteration. It is SIGCHI Bulletin July 1987 Volume19 Number 1

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