Final answer:
Lawrence Kohlberg focused his research on moral reasoning, developing a theory with three levels of moral development. He suggested that men often progress beyond stage four in this development more than women, a point later challenged by Carol Gilligan who argued that men and women may exhibit different patterns of moral reasoning.
Step-by-step explanation:
The focus of Lawrence Kohlberg's research was moral reasoning. Kohlberg developed a theory of moral development comprising three levels: preconventional, conventional, and postconventional. Boys and girls were proposed to exhibit different approaches to moral reasoning according to Carol Gilligan's critique of Kohlberg's theory, suggesting that while boys tend to use a justice perspective, girls are more inclined towards a care and responsibility perspective.
Kohlberg's work has had a lasting impact on our understanding of how individuals arrive at a sense of morality, which includes considering the collective good and societal norms. Meanwhile, Gilligan challenged the alleged gender bias in his theory, arguing that females might display different patterns in moral development, because they focus more on interpersonal relationships and the ramifications of actions.
Thus, in the question posed, the correct answer is Option 3: Moral reasoning is the primary focus of Lawrence Kohlberg's research.