His interest in the study of human behavior in kind antiquely ___

The word "deep" best describes a profound thorough interest in human behavior fitting the sentence’s context. "Strong" "large" and "broad" are less precise for intellectual pursuits. Choosing the right adjective ensures accurate expression especially in academic or professional writing about psychology or sociology. This skill is crucial for conveying nuanced ideas. Precise vocabulary enhances credibility and clarity in essays or reports particularly when describing complex concepts or interests in fields requiring in-depth analysis or discussion.