Let’s say you read a big book about recycling because you want to make an informed decision about whether it really makes sense to recycle.  The book is loaded with facts: some pro, some con.  You read it all, weigh the pluses and minuses and come away strongly convinced that recycling is a good thing.

But you are human and you can only remember so many facts.  You are also a good manager so you optimally allow yourself to forget all of the facts and just remember the bottom line that you were quite convinced that you should recycle.

This is a stylized version of how we set personal policies.  We have experiences, collect data, engage in debate and then come to conclusions.  We remember the conclusions but not always the reasons.  In most cases this is perfectly rational.  The details matter only insofar as they lead us to the conclusions so as long as we remember the conclusions, we can forget about the reasons.

It has consequences however.  How do you incorporate new arguments?  When your spouse presents arguments against recycling, the only response you have available is “yes, that’s true but still I know recycling is the right thing to do.”  And you are not just being stubborn.  You are optimally responding to your limited memory of the reasons you considered carefully in the past.

In fact, we are probably built with a heuristic that hard-wires this optimal memory management.  Call it cognitive-dissonance, confirmatory-bias, whatever.  It is an optimal response to memory constraints to set policies and then stubbornly stick to them.