I think that the reasons for motivated reasoning to emerge are more complex. Your proposed mechanism is that motivated reasoning is like having the internal CoT, and not just external speech, optimized[1] for being persuasive to others.
I also see a different mechanism. The infamous Buridan’s ass is the problem in decision theory where the difference between proposed benefits of two alternatives is far less than the cost of pinpointing the better one. In this case it’s likely rational to choose randomly according to probabilities based on imprecise estimates, then to stick to the chosen solution; said probabilities are likely close to 1⁄2and are prone to shift if new evidence appear. However, multiple such shifts require people to reassess many decisions or even waste resources trying to fix the mistakes. Motivated reasoning in a case of genuine uncertainty caused those who exhibit such behavior to arrive to a solution faster and to stick to the chosen opinion tighter, reducing waste.
A similar mechanism is the master-slave model where the slave is to demonstrate alignment and benefits from having terminal values similar to what the society prescribes. The slave believing in a false fact related to an agenda would also make more compelling cases for the agenda than the slave who is just tasked with defending it.
I think that the reasons for motivated reasoning to emerge are more complex. Your proposed mechanism is that motivated reasoning is like having the internal CoT, and not just external speech, optimized[1] for being persuasive to others.
I also see a different mechanism. The infamous Buridan’s ass is the problem in decision theory where the difference between proposed benefits of two alternatives is far less than the cost of pinpointing the better one. In this case it’s likely rational to choose randomly according to probabilities based on imprecise estimates, then to stick to the chosen solution; said probabilities are likely close to 1⁄2 and are prone to shift if new evidence appear. However, multiple such shifts require people to reassess many decisions or even waste resources trying to fix the mistakes. Motivated reasoning in a case of genuine uncertainty caused those who exhibit such behavior to arrive to a solution faster and to stick to the chosen opinion tighter, reducing waste.
A similar mechanism is the master-slave model where the slave is to demonstrate alignment and benefits from having terminal values similar to what the society prescribes. The slave believing in a false fact related to an agenda would also make more compelling cases for the agenda than the slave who is just tasked with defending it.