Ironic that you like statistical plots (most of us do), which are designed to help make generalizations. But if the generalization doesn't work in your favor, it is bad.
But you didn't provide any statistical plot, or any other experimental data for that matter, to support your reasoning. It was entirely personal opinion based on your experience. A lot of people are of the same opinion. However, the problem with even requesting experimental data on this sort of thing is....with maturity as the independent variable, what would be the measure of medical student success (the dependent variable)? Graduation rates, grades, or USMLE scores, no? Well then, we've already unfortunately got sampling bias involved, since we're talking about people here who are highly academically skilled to begin with. Per conventional wisdom, this whole medical application process is a mertiocracy, so if that 19 year old gets in, he's going to be well-qualified. One would hypothesize the dependent variables we could use to measure how successful these people are in school would be largely identical, as we are only measuring them in terms of academic success. The ability to be "reassuring," as you've put it, is not easily measurable in an accurate way because it is too subject to a number of biases in the event of, for example, a study being done on patients rating their emotional satisfaction with the doctor on a scale of 1-10. Nevertheless, I do concede that any adept data masseuse can make otherwise ill-sounding data sing beautifully.
maturity correlating with age is quite common in all aspects of life.
We'd need to better define maturity and its characteristic composition. Then run statistically significant studies measuring those characteristics and how they correlate with age, if at all. Of course I'm misinformed, so I don't know if this has been done or not.
As you get older, you learn to roll with the punches and adapt when things don't work perfectly in your favor. Medicine is going to require that skill.
That's another point, separate from the example of the ability to provide reassurance that you gave. Nearly all people pursuing medicine will require the skill of adaptation. However, I don't see how one could definitively argue for the theoretical exclusivity of age in determining one's ability to adapt. In fact, number, quality, and intensity of experiences may be a better theoretical determinant. It is possible many younger individuals have had intense experiences throughout their childhood and into adulthood that have required them to consistently adapt to various difficulties, more so than many others who are much older than them. And even putting that aside, we've also got to consider that the application process for getting into medical school in the first place can be quite strenuous in an of itself, particularly the process of studying for the MCAT, and as such those who aren't able to adapt to fairly significant mental stresses may get weeded out right then and there. A younger person who is able to pass through all of that without losing his/her motivation may prove quite capable when put in a medical setting. The whole process may have been instituted, in part, as a test of the applicant's ability to adapt.
The adcoms have been doing this a long time and they pick great classes for the most part. I tend to think they know their stuff.
I sort of addressed that. I've seen no data indicating that certain decisions an adcom makes on the basis of age have affected the relative graduation rates, mean USMLE scores or mean clinical grades of the class as a whole. Therefore, I can't know that deferring to an adcom's expertise is the correct decision for this particular matter - that is, making predictions about the individual's performance solely on the basis of age. And barring any intellectual/moral/whatever dicussion on this matter, if we only look at DO schools, to deny an individual admission on the basis of age would be in direct contradiction with accreditation standards.
That doesn't matter, though, for the simple reason that accreditation standards don't determine what an adcom can and will do in a practical setting. The simple fact is this: They are the deciders. They will decide. I'm fine with that. This is just an innocent theoretical discussion.
No matter what though, you'll be fine when you apply, because there is a place for everyone in terms of personality.
Unless you're a sadist, of course.