Dr. Bowman has developed a coding system for aggressive behaviors displayed in comic books. She has her assistants read comic books published between 1980 and 1984 and record the number of aggressive acts displayed in each comic. She also has her assistants read comic books published between 1985 and 1989 and record the number of aggressive acts displayed. This approach to studying aggressive behavior may best be categorized as .

content-analysis research.

Explanation:

Content-analysis research -

It refers to as the research method involved in order to find the presence or absence of some specific words , sentences , concepts on a given qualitative data , is referred to as the content - analysis research .

The method is used for studying various documents in the form of text , pictures , audio or video .

Hence , from the given scenario of the question ,

The correct answer is content analysis research .