Fyra teorier om varför man blir mindre benägen att ändra uppfattning ju äldre man blir:

1. Hjärnan rostar med åldern: ”[P]eople’s minds just start to get crusty and hard to move as time passes, like rusty machines in need of oil. They resist change because friction in the gears impedes free thinking and hence the acceptance of new ideas. Perceived this way, resistance to change is a form of irrationality that derives from inefficient mental processes.”
2. Gamla har redan tagit hänsyn till det mesta: ”Resistance to change is the outcome of rational information processing. …. A young person has a small data set, because he has had few experiences and less time to observe the world. Consequently, the marginal impact of any new observation is larger. An older person, on the other hand, has a large data set, and therefore the marginal impact of one additional data point is likely very small.”
3. Det kostar mer att lära sig nytt med åldern, och intäkterna blir lägre: ”[O]ften skills are specific to a certain task or way of doing things, and each new skill is costly to acquire. Most people have made a substantial investment learning to do things one way. If a better way comes along, it may be optimal to stick with the old not-quite-as-good way and not pay the cost of learning something new. A young person faces the same cost (learning to do it) either way, and so might as well pick the new way. Magnifying this effect is that the benefits of learning something new are lower the older you get.”
4. Gamla vet att de inte får höra något nytt: ”This one relies on the desire of rational people to conserve their limited mental space and time. If one has only a finite amount of mental resources to spend in thinking about stuff, it’s rational to allocate less time to those subjects on which new information or discussion is unlikely to generate change.”

Jag ser teori nr. 1 och teori nr. 3 som snarlika, och teori nr. 2 och teori nr. 4 som snarlika. Nå, vilken teori ser du som mest plausibel? Det ligger nog något i samtliga teorier, även om jag själv tror att teori nr. 1 förklarar mycket. Rigiditet i tänkandet utgör en av orsakerna till att jag i regel inte tilltalas av äldre personer på ett intellektuellt plan (heller).