Knowledge acquisition is a constructive modeling process, not simply a matter of "expertise transfer." Consistent with this perspective, we advocate knowledge acquisition practices and tools that facilitate active collaboration between expert and knowledge engineer, that exploit a serviceable theory in their application, and that support knowledge-based system development from a life-cycle perspective. A constructivist theory of knowledge is offered as a plausible theoretical foundation for knowledge acquisition and as an effective practical approach to the dynamics of modeling. In this view, human experts construct knowledge from their own personal experiences while interacting with their social constituencies (e.g., supervisors, colleagues, clients, patients) in their niche of expertise. Knowledge acquisition is presented as a cooperative enterprise in which the knowledge engineer and expert collaborate in constructing an explicit model of problem solving in a specific domain. From this perspective, the agenda for the knowledge acquisition research community includes developing tools and methods to aid experts in their efforts to express, elaborate, and improve their models of the domain. This functional view of expertise helps account for several problems that typically arise in practical knowledge acquisition projects, many of which stem directly from the inadequacies of representations used at various stages of system development.To counter these problems, we emphasize the use of mediating representations as a means of communication between expert and knowledge engineer, and intermediate representations to help bridge the gap between the mediating representations themselves, as well as between the mediating representations and a particular implementation formalism.

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Patients with cardiorespiratory disease have an increased risk of perioperative complications. Several prediction tools have been developed in an attempt to quantify this risk. Goldman, Detsky, and Lee each produced scoring systems to predict the likelihood of cardiac complications and Arozullah provides us with a risk prediction equation for postoperative respiratory failure. These focus on only a single organ and make little assessment of the severity of each contributing risk factor.Overall risk also depends on the type of surgery with thoracic and intra-abdominal procedures associated with the highest complication rates. Direct complications of surgery or anaesthesia account for only 1% of overall mortality. The majority of adverse events are therefore linked to the severity of pre-existing cardiorespiratory disease and the functional ability of patients to meet the extra metabolic demands required when undertaking significant surgery.

Easterbrook (1959) has predicted that (a) performance on tasks involving the use of a wide,range of cues will be impaired under high-drive conditions and that (b) performance on tasks requiring the use of only a narrow range of cues will be facilitated under such conditions.Using the Porteus Maze Test, relatively clear evidence was obtained to support the first prediction. Using the Stroop Colour Word Interference Test some evidence was obtained in support of the second prediction.In a recent review of the literature, Easterbrook (1959) has proposed that high drive leads to reduction in the range of cue utilization, or in other words to a narrowing of attention. Whether performance is facilitated or disrupted by high drive depends upon the range of cues demanded by a given task. For example, a reduction in the range of cue use, as a result of high drive, will impair performance on a complex multi-cue task on the assumption that some task-relevant cues will be omitted from attention. Conversely, such a reduction of cue use will lead to improved Performance on a simple task, one requiring a few selected cues, on the assumption that task irrelevant cues and distractions are omitted from attention.Using a multi-cue task, Bahrick, Fitts and Rankin (1952) reported that increasing rewards for total task proficiency led to gains in central task tracking but a t the cost of proficiency in responding to peripheral task lights. Callaway and his co-workers (1958a, 1958b) having subjects respond rapidly to colour tints, while attempting to ignore the inappropriate colour names on which they were superimposed, reported superior performance for high drive (stimulant drug) subjects.It is the purpose of this study to test Easterbrook's proposal that increases in drive level adversely affect performance on tasks involving the simultaneous use of a large number of relevant cues, such as Porteus Maze Test (1~5g), but lead to improved performance on tasks requiring the selection of relatively few cues, such as the Stroop Colour Word Interference Test (1935). METHOD Subjects.The subjects were 50 male undergraduate students, ranging in age from 17 to 32 years, who were assigned a t random to one of three groups which did not differ in terms of age distribution.Measures. All subjects received the Ishihara Test for colour blindness, in addition to repeat testing on the Stroop and Porteus Tests.The Stroop Test consists of three cards. On the first card, the names of four colours (red, blue, yellow, green) are printed IOO times in random order while on the second card dots are painted in the same four colours and arranged roo times in random order. The third card contains IOO examples of the four colours superimposed on the printed names of the colours, the actual colour being superimposed on the name of a different colour. For example, the printed word "red" may be tinted yellow or blue. For Card I, the subject is required to read the names of the colours as quickly as possible. On Card I1 he is required to report the colour of each o...