The cited paper is freely downloadable: The weighing of evidence and the determinants of confidence. Here is the rest of the quoted paragraph:
It is noteworthy that there are situations in which people exhibit overconfidence even in predicting their own behavior (Vallone, Griffm, Lin, & Ross, 1990). The key variable, therefore, is not the target of prediction (self versus other) but rather the relation between the strength and the weight of the available evidence.
This cuts against the conclusion drawn by Yudkowsky 2007. The Vallone citation is to this freely downloadable paper:
Vallone, R. P., Griffin, D. W., Lin, S., & Ross, L. (1990). Overconfident Prediction of Future Actions and Outcomes by Self and Others. Journal of Personality and Social Psychology, 58, 582-592.
To your specific question of "how often people change their mind", if you download the paper you'll see that there were a variety of self-prediction topics. Accuracy varied but I'd gloss it as "about 70%", meaning that the subjects changed their mind about 30% of the time. For questions where the subjects predicted their future actions with 90-100% confidence, they changed their mind about 25% of the time.
So, we change our minds more often than we think.
In "We Change Our Minds Less Often Than We Think", Eliezer quotes a study:
Eliezer then notes that this radically changed the way he thought:
But a) this seems like it's pre-replication crisis, b) regardless, a sample size of 24 is not nearly high enough for me to be very confident in this.
"How often people change their mind" seems like a fairly important question. Anyone know of further work in similar space here? Ideally asking the question from a few different angles.