Final answer:
The exact reason for the Kaplans' study is not specified in the provided information, but psychological research often explores the relationship between mental processes, environmental factors, and depression, as seen in the work of Seligman and others on learned helplessness and attribution styles.
Step-by-step explanation:
The Kaplans' study reason is not provided in the given context, so it is not possible to determine the exact motivation behind their research. However, studies related to the psychological field often explore various aspects of human behavior and mental processes, including issues related to depression. For instance, psychologist Martin Seligman's research on learned helplessness, which posits that experiencing uncontrollable negative events can lead to feelings of helplessness similar to depression, is a key study in understanding the impact of one's environment and cognition on their mental health.
Further, the provided texts mention how people's attitudes toward money and the pursuit of financial gain, often linked to perceived happiness, have been the subject of psychological studies, such as those by David Myers. These studies could investigate whether the desire for monetary success adversely impacts one's sense of well-being and potentially leads to depression. The study by Peterson and Seligman (1984) also highlights the role of attribution styles in the development of depressive symptoms when faced with negative life experiences.