Psychologically sound means mentally sound or sane. This refers to the idea that one is rational and able to understand actions and consequences. The correlation between how one is taught and whether one is mentally sound enough to be taught does not exist. Some people who suffer from different mental disorders may need to be taught differently based upon their learning style (but this does not differ from the general public).
For example, a teacher may choose to teach a person who has a visual learning style differently than one who has a "hands-on" tactile style and one who has dyslexia differently from one who has a visual style, but none of these choices reflects psychological soundness, stability or saneness. Similarly, choices between different methods of teaching a person with ADHD, given limits to attention spans, also dose not reflect psychological factors of stability, etc.
A good teacher will figure out what kind of learner a student is and adapt his or her teaching style to this particular type of learner. Sometimes the teacher will begin with one style and move through other styles to insure the majority learns.
There are three major learning styles (visual, auditory, and kinetic). Just because one learns best kinetically (through physical manipulation) does not mean that he or she is psychologically unsound. It simply refers to the fact that he or she needs learns through manipulation. In the same way, some learners need to see how something is worked out in order to learn. If the student cannot physically see how something works, he or she will have more work to do in grasping the concept.
Essentially, how one learns has absolutely nothing to do with one's psychological and mental stability. We are unique individuals with unique qualities. Our learning strategies work the same way.