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Hampson, P. J. & Morris, P. E. (1996) Chapter 8: Planning and actions: Successes and failures. In Understanding Cognition, Blackwell, Cambridge MA.

Author of the summary: Debajyoti Pati, 2000, gte811q@prism.gatech.edu

The chapter focuses on how the plans and goals of humans shape their behavior. The discussions include how human behavior is organized towards attainment/fulfillment of plans, and how plans sometimes fail to be carried out.

The notion that the behavior of organisms depend on the events occurring around it is accepted by all. There are however two conflicting viewpoints. The behaviorists hold the optimist"s view which argues that the relation between the environment and action is simple and straightforward. In contrast, the pessimists maintain that the way an event effect behavior depends on the way that event is represented in the organism"s picture of itself and its universe. Miller et al. (1960), a pessimist, emphasized the role of structures in life, and argued that humans constantly construct plans to achieve certain targets in the future. In order to handle the analysis of action, they organized behavior at several levels of complexity, revolving around two general concepts of "plan" and "image". The plan controls the order in which sequence of operations are performed. The image is the knowledge an organism has about itself and the world. They further assumed that adult humans have access to a large number of plans ready for execution. They introduced the TOTE unit for a more detailed annuluses of the plans. The TOTE unit is a flow chart incorporating a series of tests for incongruity with the plan. It also employs operations to rectify problems , and involves a constant circuit of tests and operations until congruity is achieved and the next stage of the program could be implemented. Through some examples of TOTE units, they also demonstrate the possibility of embedding lower-level instructions within higher-level parts, thus making hierarchical TOTE units, which is very similar to the concept of schema. The TOTEs, however, have certain weak points. One of its main weakness is its emphasis on feedbacks, where the continuous use of feedback at every stage during action does not seem practical. Further, the over emphasis on feedback seem to distract attention from the more important operate stage. Finally, TOTEs are susceptible to continuous looping in case of unsatisfactory accomplishment.

In schemas past experience is used for the interpretation and control of new stories and action, and several models make use of schematas rather than TOTEs and plans. Norman (1981) provides an example of the schema theory of action, called the ATS (activation-trigger-schema). His theory assumes the presence of a large number of schema as well as procedural knowledge (to control motor activity). The schemas are organized hierarchically with the highest-level schema called as "parent" schema, and those initiated by that called as "child" scheme. Child schemas could be the parent schema to other child schema. Intentions are related to the highest level schema, and there could be several intentions active at any time. Several schemas could be active at the same time. For practiced skills only the highest level schema is specified, and the lower level schemas complete the action without further intervention most of the time. Before a schema could be used, it has to be activated and appropriately triggered.

The idea of different levels of control in action planning seem to be common to many models. More specifically, it is assumed that the system for control of behavior is organized in such a way that common tasks are handled by specially developed subsystems, thus relieving the planning of actions from dealing with common details. Craik and Barlett proposed the idea that the control of complex systems could be best organized by the separation of components into modules, and having a sutra system of overall control over the modules. While the lower level modules handle the common, mundane tasks, the higher level systems get free to plan actions depending on the complexity of the task. Human beings are aware of the higher level actions, unless they are learning a new skill. Morris and Hampson"s (1983) BOSS-Consciousness model accounts for the association of higher level action with awareness and consciousness. The overall control remains with the BOSS system which supervises the EMPLOYEE systems (to which actios are delegated). Perceptual EMPLOYEEs provide information about the state of the world and the state of the person to the BOSS, and the movement is controlled by Motor EMPLOYEEs.

A major factor influencing action is emotion. There is a growing consciousness in cognitive science about the relation between cognition and emotion. Emotion is defined, in part, as the evaluation of the implications of the cognitive procession. Scherer"s (1984) SECs (Stimulus-Evaluation-Checks) theory is an example of this approach. According to this theory several checks are involved in the processing of new events, including the checks for novelty, pleasantness, goal/need significance, potential, and norm/self compatibility. Scherer associates particular patterns of outcomes of the series of checks with different emotions.

Another important area of human action deals with human error. Slips and lapses are among the more mundane ones. Reason (1977,1979) collected examples of failure to carry out intentions, and Norman (1981) and Reason & Mycielska (1982) have developed models of action planning and control to interpret these errors. Some of the common errors categorized by Reason include absentmindedness and data-driven. Errors. Norman ascribes errors to either faulty activation or triggering of a schema. The GEMS (Genetic Error Modelling System) developed by Rasnussen (1986) is one example of a model incorporating human errors in action planning. In this model there are three levels of action control; the skill based level, the rule based level, and the knowledge based level. The model associates various human errors with a particular level of action control. While slips and lapses are more of a skill based error, mistakes take place at the knowledge based or rule based level.

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