From experience, it seems that less intelligent people are less likely to partake in discussion of anything, besides the most basic, everyday things. I can't mentally give random people IQ tests, but I can estimate what their IQ is through their expressed thoughts, behaviors, and general status in life.

It seems that people with IQs below 90 are incapable of having adult-level discussions of any kind. They may be able to discuss certain adult topics, but at the level of someone lacking logical potential, i.e., the ability to make inferences, so they can't understand anything beyond the superficial of whatever they're talking about. It also seems that people with IQs below 90 are more likely to avoid discussion in the first place, and that people with IQs below 75 avoid discussion almost entirely. You can make statements to people with IQs of 75 and below, and they can give you statements in return, but they are incapable of thinking in paragraphs, i.e., larger collections of logical statements. The only discussions people with IQs below 85 have are of things we all know about and occurrences we all experience, or are at least familiar with, like mundane types of work, common emotional experiences, and bodily pleasures. So, essentially, people with IQs below 85 are incapable of having any meaningful discussions.