Final answer:
The psychologically healthy research training environment is characterized by supportive mentorship and collaboration, facilitating personal involvement and creativity. The correct answer is option A).
Step-by-step explanation:
The defining characteristic of a psychologically healthy research training environment is supportive mentorship and collaboration. Environments that foster a sense of personal involvement, purpose, belonging, responsibility, challenge, comradeship, and love are key for well-being and creativity. Steitz's research highlights the importance of good mentorship and constant interactions with colleagues at all stages of research to promote outstanding discoveries and well-being. Similar principles apply in various contexts where social interaction and creative behavior are incentivized, contributing to both psychological health and productivity.