I think your question is unclear because the question says How can people answer a question consistently? But it appears instead of learning how to answer messy questions yourself you want to know why others do not give consistent answers. Given diverse input information and different backgrounds I am not surprised that the answers vary. This page is a good example of the variability of answers.
A better plan is to understand the methods and reasoning used by the best experts in thinking have solved problems and answered questions. With this research you can develop criteria and methodology that lead to accurate solutions and consistent answers.
In terms of countries near equator are you seeing cause or effect. Equator regions should have been able to live off the land (eat and use plants that they did not have to grow) In northern countries people either hunted to survive or became agriculture based society. Either way they would have put in more planning and effort. Repeat this for a few hundred years might result in more creativity and reasoning ability.