Thansk for the clarification, but still needs more to be clear.
As one person studied several people, it could mean a few different things.
- consistency on the fundamentals. - the people studied all had the same attributes on certain fundamental things; as in, the same as each other. For example, they might have all been careful with money.
- consistency on the fundamentals. - the people studied might have been self-consistent in certain fundamental things, but not necessarily the same as each other.
That is, the ones who were careful with money, might have been always careful with money, not only sometimes. Others might have had different "fundamentals" which they also did not deviate from.
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Without more, can't tell which meaning except by guessing which is more likely. You can do that from your understanding of the topic.
Enjoy.
NTN. No thanks necessary. More questions, sure, but no thanking comment necessary.