"Okay, this is a question I've been wanting to ask for a while. Even given Ozarque's clarification... I still want to ask it, and I hope it won't be taken amiss. Is the assumption here that all people are dominant in one sense? "
It's a reasonable and appropriate question -- no reason it would be taken amiss.
First, I need to specify that I find the existing scientific research on this matter inadequate. If there are strong solid research studies available, I'm not familiar with them and I would be extremely pleased to know about them. The standard (nonmedical) techniques and tests for identifying sensory dominance in children, for example, are in my opinion unreliable; the studies I've seen fail to rule out various wild variables; much of the alleged evidence is anecdotal. I don't know a source that I would feel comfortable citing here. I think rigorous research isn't done because scientists see no reason why it should be done. That said, here's my answer, based on the information that does seem to me to be reliable.
By the time children are about five or six years old they've discovered that one of their sensory systems -- ordinarily sight or hearing or touch -- works better for them than the others for processing information. That is, they find it easier to learn and remember and analyze and understand with one of their sensory systems than with the others. Kindergarten teachers are usually aware of this on a common-sense basis; if asked, they can tell you which children in their class need to be told things, which ones need something to look at, and which ones have trouble learning unless they have a way to "get into it with both hands." We don't know whether this sensory preference/dominance is genetic or learned; the fact that it's on a timetable would indicate some genetic input, but -- in my opinion -- there's no solid evidence either way. There seem to be more touch dominant individuals in cultures where touch is more highly valued than it is in the American mainstream, but whether that's an inherited characteristic or a learned one I can't say. My opinion ... only an opinion ... is that both nature and nurture are involved.
So far, so uniform. What happens as the children grow older isn't uniform, however. We see individuals in whom the preference for a given sense is so strong that "dominance" is the only possible term; they seem to find it almost impossible to cope with information that isn't tailored to their dominant sensory system. We see other individuals who develop excellent coping strategies -- they may strongly prefer data from one sense, but they learn ways to use information from the other sensory systems efficiently and effectively. And we see everything in between. My hypothesis -- based only on experience, not on a double-blind controlled study -- is that the more multisensory the environment provided to children and teenagers is, the more likely they are to become comfortable using multiple sensory systems. (And I include the language environment, which is typically neglected in this regard.) I believe that almost anything kids need to learn can be presented to them in a format tailored for all three of the major senses, and the "learning styles" movement in education does make an effort to do that; if they had really good research evidence, they could do a better job. For the touch dominant children in mainstream American culture, the "don't touch" message they constantly encounter interferes with their ability to process information just because of the rejection and negativity -- that's a separate issue.
The only time sensory dominance becomes something to be concerned about in language interactions is when someone is trying to communicate under stress -- during arguments, in job interviews and loan interviews, in hostage negotiations, in doctor/patient conversations, at accident scenes, during testimony in court -- in situations where people are tense and anxious. In those situations, people tend to become locked in to their dominant sensory mode [the vocabulary and associated body language of their preferred/dominant sensory system]; when that happens, communication will be better if the sensory modes being used match. When the level of tension and stress decreases, the sensory mode lock goes away. It's unfortunate that so much communication in the mainstream American culture today is communication under stress.