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The Dunning-Kruger Effect

Cognitive biases that interfere with Foundation Inspections: The Dunning-Kruger Effect

Dunning Kruger Effect-1In previous blogs I noted that for survival reasons, humans have developed heuristic mental shortcuts that often lead to erroneous conclusions with complex problems. By better understanding these cognitive biases, we make better decisions and fewer mistakes.

The Dunning-Krugar effect is in it’s simplest terms the common over confidence that comes with a lack of knowledge. In contrast, it is common to see scientists and engineers with a great deal of expertise speak cautiously in terms of probabilities being careful themselves to guard against their own cognitive biases and more importantly not to overstate their position always leaving room for alternative points of view or new data.


It is very common to see individuals, foundation sales guys, or uninformed foundation repair contractors make overconfident claims … many of which are completely unsupported! For example, one such individual has claimed that by installing rain gutters to divert water from reaching the soil below footings you can control all foundation movement. There are several problems with this line of thinking, here are just a few:

  • Installing rain gutters, if done properly, does stop much of the water from reaching the foundation. It does not stop all water, including surface drainage, or subsurface drainage. There is no way to positively stop all or even significantly all water from reaching the soil below footings.
  • This line of thinking completely ignores the fact that if there are clay soils below the footings, drying them up causes shrinkage and is likely to induce settlement. Therefore, this advice could be counterproductive.
  • Many foundation settlement problems are a result of deeper soil mechanics where surface moisture has limited or no immediate effect. These deeper soils have significant overburden soil weight on top of them and may continue to settle regardless of a discontinuance of surface moisture.

This is not untypical. Foundation repair salesmen and contractors are trained to be overconfident and are many times taught that they know just as much or more than licensed professional engineers. They fulfil this role easily since they have comparatively little knowledge making them perfect for the Dunning-Krugar Effect.

in contrast, licensed professional engineers do not speak with over confidence; they communicate more in terms of likely probabilities. I titled a series of blogs, Rules of Thumb in Foundation Inspections (to read the series, click HERE & scroll to the bottom of the page). One of the main points that I have emphasized is that any one particular rule of thumb can in fact with varying degrees of probability, point to various conclusions. In fact it takes a detailed look at all or many of the important factors to reach a solid conclusion … and even then sometimes it takes more investigation. No conclusion is ever not subject to rethinking with new data or better analysis.

Projecting in an overconfident way does not validate a claim. In fact due to the Dunning-Kruger Effect it should make us all wary of those who do.