According to Altshuller methods of problem solving cannot be discovered by studying how humans solve problems because they do it by random trials and errors. Instead of studying human thinking Altshuller proposed to, conversely, teach them how to think. The rules of thinking have to be found beyond it, e.g. by studying trends and patterns of technological systems evolution. Humans should be taught thinking in line with these trends.
Controversial as it may appear but Altshuller's idea was in line with the pattern of all previously successful attempts to design a system that performs a function of animals or humans. They indeed did not imitate how animals/humans do it. Cars do not have legs and planes do not have flapping wings. Why would powerful artificial methods of thinking deviate from this pattern and imitate human thinking ? It appears that Altshuller was right in his vision.
Nevertheless, studying of how humans think can also be beneficial for methodology of problem solving. It is not so much observation of how other people think as introspection of how one solves problems himself.
I was trying to develop the faculty of introspecting since long time ago. As time passed I became a good introspector (self-analyst) and was able to provide good introspective accounts of how I solved problems. Last month I presented one such account. This month I present another one. In both cases the introspection allowed finding something new to TRIZ.
Of course, introspective analysis cannot be taken as a proof unlike independently verifiable facts. Moreover, most people do not have faculty to simultaneously solve problem and observe themselves and memorize how they think. "Introspection" of most people is just a retroactive recollection, which cannot be accurate and trustworthy.
One may even think that a plausible introspection is not at all possible due to uncertainty principle. However, the latter does not apply here and interference of introspection with thinking can indeed be minimized by a skilled introspector (if not eliminated at all by making it part of his thinking).
The faculty of thinking and introspecting the process of thinking at the same time can definitely be developed by practicing. Developing the ability of expressing one's thoughts is a good starting point.
I will try to provide more introspective accounts of how I solve problems as and when the opportunity presents itself.