A couple of months ago I wrote about a set of credibility factors for computational models [see ‘Credible predictions for regulatory decision-making‘ on December 9th, 2020] that we designed to inform interactions between researchers, model builders and decision-makers that will establish trust in the predictions from computational models [1]. This is important because computational modelling is becoming ubiquitous in the development of everything from automobiles and power stations to drugs and vaccines which inevitably leads to its use in supporting regulatory applications. However, there is another motivation underpinning our work which is that the systems being modelled are becoming increasingly complex with the likelihood that they will exhibit emergent behaviour [see ‘Emergent properties‘ on September 16th, 2015] and this makes it increasingly unlikely that a reductionist approach to establishing model credibility will be successful [2]. The reductionist approach to science, which was pioneered by Descartes and Newton, has served science well for hundreds of years and is based on the concept that everything about a complex system can be understood by reducing it to the smallest constituent part. It is the method of analysis that underpins almost everything you learn as an undergraduate engineer or physicist. However, reductionism loses its power when a system is more than the sum of its parts, i.e., when it exhibits emergent behaviour. Our approach to establishing model credibility is more holistic than traditional methods. This seems appropriate when modelling complex systems for which a complete knowledge of the relationships and patterns of behaviour may not be attainable, e.g., when unexpected or unexplainable emergent behaviour occurs [3]. The hegemony of reductionism in science made us nervous about writing about its short-comings four years ago when we first published our ideas about model credibility [2]. So, I was pleased to see a paper published last year [4] that identified five fundamental properties of biology that weaken the power of reductionism, namely (1) biological variation is widespread and persistent, (2) biological systems are relentlessly nonlinear, (3) biological systems contain redundancy, (4) biology consists of multiple systems interacting across different time and spatial scales, and (5) biological properties are emergent. Many engineered systems possess all five of these fundamental properties – you just to need to look at them from the appropriate perspective, for example, through a microscope to see the variation in microstructure of a mass-produced part. Hence, in the future, there will need to be an increasing emphasis on holistic approaches and systems thinking in both the education and practices of engineers as well as biologists.
For more on emergence in computational modelling see Manuel Delanda Philosophy and Simulation: The Emergence of Synthetic Reason, Continuum, London, 2011. And, for more systems thinking see Fritjof Capra and Luigi Luisi, The Systems View of Life: A Unifying Vision, Cambridge University Press, 2014.
References:
[1] Patterson EA, Whelan MP & Worth A, The role of validation in establishing the scientific credibility of predictive toxicology approaches intended for regulatory application, Computational Toxicology, 17: 100144, 2021.
[2] Patterson EA &Whelan MP, A framework to establish credibility of computational models in biology. Progress in biophysics and molecular biology, 129: 13-19, 2017.
[3] Patterson EA & Whelan MP, On the validation of variable fidelity multi-physics simulations, J. Sound & Vibration, 448:247-258, 2019.
[4] Pruett WA, Clemmer JS & Hester RL, Physiological Modeling and Simulation—Validation, Credibility, and Application. Annual Review of Biomedical Engineering, 22:185-206, 2020.
Many people take a week’s holiday at this time in the UK because Monday was the Spring Bank Holiday. We went walking in the Clwydian hills which we can see from our house to the south-west across the rivers Mersey and Dee. However, despite the walking on the wild side [see ‘Take a walk on the wild side‘ on August 26th, 2015], I did not feel particularly creative when I sat down to write this week’s blog post. Together with most of my academic colleagues, I am in the midst of reviewing student dissertations and marking end of year assessments. I have written in the past about the process of marking examinations and the tens of thousands of decisions involved in marking a large pile of scripts [see ‘Depressed by exams‘ on January 31st, 2018]. However, the constraints imposed by the pandemic have changed this process for students and examiners because the whole exercise is conducted on-line. I have set an open-book examination in thermodynamics which the students completed online in a specified time period and submitted electronically. Their scripts were checked automatically for plagiarism during the submission process and now I have to mark about 250 scripts online. At the moment, marking online is a slower process than for hardcopy scripts but perhaps that’s a lack of skill and experience on my part. However, it seems to have same impact on my creativity by using up my mental bandwidth and impeding my ability to write an interesting blog post [see ‘Depressed by exams‘ on January 31st, 2018]!
Realize Engineering 