This is the 17543rd most frequent Korean word.
성질에
"성질에" means "to one's nature or temperament."
The word '성질에' refers to 'to one's disposition' or 'according to one's temperament'.
그는 성질에 따라 행동한다.
He acts according to his disposition.
Here, '성질에' pertains to 'the nature or characteristics of humans' under research.
인간의 성질에 대해 깊이 연구하다.
To study deeply about human nature.
In this sentence, '성질에' refers to the innate characteristics or behaviors specific to the cat.