In my last 3 blogs (1, 2, 3) I've been discussing the Lens Model which was proposed by the psychologist Egon Brunswick (1903-1955) as a way to simultaneously understand how a person relates to world and how we might go about researching and designing experiments to understand that relationship. Today I want to add a few more details.

If you do a google image search using the term "lens model" you will see lots of variations of Egon's original lens model. Here is a variation from Kenneth R. Hammond's book Human Judgment and Social Policy: Irreducible Uncertainty, Inevitable Error, Unavoidable Injustice (1996).

Kenneth Hammond was very influential in promoting Egon's ideas and also expanded upon his ideas in several books. For example, instead of using the term "cues", Kenneth prefers to use the term "indicators". In the lens model above the indicators could be economic indicators such as jobless rate, GDP growth, business sentiment, etc.... and we might be trying to figure out if the economy will grow in the next quarter or not.

One aspect of the lens model that I have not discussed so far is the arc at the top of the diagram labelled "Accuracy". Egon preferred the term "Achievement". The arc is sometimes referred to as the "functional arc". The idea is In my version of the diagram, I might use the term "Adaptation" because the utilization of indicators to make judgements is in the service of adapting to the environment. We do that if our judgements are "accurate" or if the result leads to an "achievement" of some sort. When we speak of judgements being accurate or not, Kenneth argues that Brunswick was putting forth a correspondence theory of truth in contrast to a coherence theory of truth. Most theories of decision making look at how well decisions cohere with some logical or normative ideal and in so doing portray reasoning as fallacious, biased, and error prone and we are left to wonder how we get along in the world. Egon didn't see coherence as being necessary to achieving success in the world and put forth the lens model as a way to explain how our cognitive system can adapts to the world. Note that most popular books on human reasoning dwell on errors in reasoning (using a coherence framework) and as such don't really tell us much about how we get along in the world. Egon offers a different worldview, which he called Probabilistic Functionalism, that is more focused on explaining how we achieve perceptual and cognitive competence in light of the multiple fallible indicators that we must rely upon to make judgements.