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Judgment is paramount in engineering practice as it results from the use of intuition and reasoning, as well as from a fragment of codes, practical rules, applied science and evaluation and management processes. In various decisions concerning, for example, the option to stabilize a slope with a nailed shotcrete lining instead of an anchored structure, or the option for a rockfill dam solution on a rocky foundation, as an alternative to a concrete dam, the geotechnical engineer needs judgment to take his decisions and guide his actions. As pointed out by Parkin (2000)Parkin, J. (2000). Engineering judgment and risk (224 p.). Thomas Telford., these judgments are informed by experience, expertise, reasoning or analysis. They are carried out during the development of the process, or after silent deliberation, and may be the result of solitary work on the computer or the result of extensive consultation, conflict and persuasion. From immediate to strategic, judgments define the structure of engineering.
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The art of geotechnical engineering has been described as the ability to make sound decisions face up to imperfect knowledge. The resulting decisions and forecasts always incorporate uncertainty to a lesser or greater degree, so the engineer has to apply judgment, that is, the very real interpretive process that results from the sum of experience, discernment and intuition. Sometimes judgements under uncertainty are quantified as numerical probabilities (subjective probabilities), using the same laws of statistic probabilities (Vick, 2002Vick, S.G. (2002). Degrees of belief: subjective probability and engineering judgment (455 p.). ASCE.).
Five decades ago, right in the introduction to the Soil Mechanics and Foundations class of Instituto Superior Técnico, in Lisbon (Mineiro, 1971Mineiro, A.J.C. (1971). Soil mechanics and foundations course. Instituto Superior Técnico (in Portuguese).), when geotechnicians of a new generation were taking their first steps in geotechnics, it was taught that the resolution of a soil engineering problem was a combination of various factors and knowledge, almost always differently from case to case, and that the ability to judge became indispensable to achieve the best solution, and also that the satisfactory solution of soil engineering problems always involved the combination of soil mechanics and one or more components, including geology, experience and economics as shown in Figure 1 (Lambe & Whitman, 1969Lambe, T.W., & Whitman, R.V. (1969). Soil mechanics (576 p.). John Wiley & Sons, Inc.). This was one of the quotes that immediately alerted and sensitized to the importance of the practice of engineering judgement and that now accompanies the professional life of so many geotechnicians. It is also the inspirational quote of the theme of this paper. The motivation for this reflection resulted from practising the professional activity of geotechnical engineering and from the raised questions of whether the judgements that were being made in the projects, taken as engineering decisions and actions, would be the most appropriate ones.
These combined factors turn any problem involving soils unique and, for all practical purposes, impossible to obtain an exact solution. Hence the importance of robust engineering judgement. Lambe & Whitman (1969)Lambe, T.W., & Whitman, R.V. (1969). Soil mechanics (576 p.). John Wiley & Sons, Inc. appropriately state that while a sound knowledge of soil mechanics is essential to a successful soil engineer, engineering judgement is usually the distinguishing feature of the exceptional soil engineer. This was, however, a seldom explored aspect of the judgement as before it was restricted to the final decision-making phase of the geotechnical process, after gathering all the knowledge about the process in question. However, it was neither defined nor known what the engineering judgement really was, and what kind of knowledge and preparation was required to make judgments, what were the heuristics and bias and associated uncertainties, as well as which risks were involved. Nevertheless, it had the advantage of combining judgement together with other components of geotechnics, which, to a certain extent, was a precursor of the progressive relevance that the judgement has acquired over the last 50 years.
Judgment is a cognitive ability of our brain leading us or not to make decisions and develop actions. In institutional settings, where major objectives shape our behaviour, we use reasoning and, maybe, analysis to help judgment (Parkin, 2000Parkin, J. (2000). Engineering judgment and risk (224 p.). Thomas Telford.). Marr (2006)Marr, W.A. (2006). Geotechnical Engineering and Judgment in the Information Age. In Proc. Geo-Congress 2006 (Vol. 1, pp. 52-68). Reston: ASCE. seeks to be more objective, defining judgment as the exercise of thinking clearly, logically and calmly about a problem, weighing the known facts, suppositions, missing information and consequences and then taking a decision. It is the ability to arrive at sensible decisions about a problem in the presence of incomplete and contradicting information. To demonstrate the importance of the judgement, Table 1 is presented, highlighting the central role that the judgement plays in the four phases where the geotechnical engineering process is developed: defining, investigating and characterizing, analysing, designing (prediction), and observing and evaluating (Marr, 2006Marr, W.A. (2006). Geotechnical Engineering and Judgment in the Information Age. In Proc. Geo-Congress 2006 (Vol. 1, pp. 52-68). Reston: ASCE., 2020Marr, W.L. (2020). Geotechnical judgment. Risk in geotechnical practice. ASCE Geo-institute. Geostrata.). In each one of these phases, critical thinking skills are required, and therefore judgment plays a central role in all phases of the geotechnical engineering process.
Bandura (1986)Bandura, A. (1986). Social foundations of thought & action, a social cognitive theory. Prentice Hall., considered the father of social cognitive theory, showed that human functioning is determined by the interaction of personal characteristics, behaviour and environmental factors. Each influences the others in time and all influence all stages of the judgment function for action. People do not perceive the same attributes (or clues) or do not reach the same conclusions. How do this ability to make sound judgments develop? Margolis (1987)Margolis, H. (1987). Patterns, thinking, and cognition: a theory of judgment (332 p.). University of Chicago Press. in his treatise on cognition and judgement indicates that it is a natural step in contemporary brain evolution. The steps of cognitive development appear to be seven: simple feedback, pattern recognition, learning, choice, intuitive judgment, reasoning, and calculation.
In recent times intuitive judgement has been supplemented and helped by reasoning and calculation. The relationship between these three functions in modern judgement can be explained by the extension of Brunswick's (Brunswik, 1952Brunswik, E. (1952). The conceptual framework of psychology. International encyclopedia of unified science (Vol. 1, No. 10). Chicago: The University of Chicago Press.) perception research, which provided the basis for the study of intuitive judgement called cognitive continuum theory (Hammond, 1996Hammond, K.R. (1996). Human judgment and social policy: irreducible uncertainty, inevitable error, unavoidable injustice (448 p.). Oxford University Press.). How do people use their reasoning skills and intuitive judgment to track modern technical and social problems? According to Hammond (1996)Hammond, K.R. (1996). Human judgment and social policy: irreducible uncertainty, inevitable error, unavoidable injustice (448 p.). Oxford University Press. the answer lies in the ability to go back and forth between the intuitive mode and the more analytical mode, during the period of time necessary to reflect on the problem and arrive at a judgment, as outlined in Figure 2, adapted from Parkin (2000)Parkin, J. (2000). Engineering judgment and risk (224 p.). Thomas Telford.. This figure shows the fluctuation of the intensity of professional specialisation along the cognitive continuum from intuition to analysis with the nature of the task. In some situations, errors related to rules or knowledge resulting from false specialisation may manifest. It turns out that no matter how analytical the engineers may be, in the end the intuitive judgement is always present. It is evident that what we can calculate, allows us to make better judgements and result in better engineering solutions.
When making judgments to fill data gaps in information and knowledge, engineers intrinsically make subjective assessments of the importance of the various uncertainties, that is, they make a subconscious risk assessment weighing the uncertainties and assessing the potential consequences of possible outcomes of decisions and recommendations. But they take shortcuts with consequent biases that might lead to faulty results. Most engineers deal with uncertainty using heuristics that ignore many of the most basic rules of probability. A surprising number of engineers take subjective probabilities for granted, considering them coherent and calibrated while in fact they are not (Baecher & Christian, 2003Baecher, G.B., & Christian, J.T. (2003). Reliability and statistics in geotechnical engineering (618 p. ). Wiley.). This is why probabilistic thinking needs to be taught and practiced. 2ff7e9595c
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