Final answer:
A psychologist is required to report a fellow practitioner in cases of ethical misconduct or unprofessional conduct that could harm clients or the profession's integrity.
Step-by-step explanation:
When might a psychologist be required to make a mandatory report regarding a fellow practitioner? The circumstances in which a psychologist must make a report include: suspecting ethical misconduct, such as witnessing unprofessional conduct or harm inflicted on a participant. It is an ethical duty to report when a fellow practitioner violates professional standards, potentially causing harm to clients or to the integrity of the profession. This does not typically extend to personal conflicts or professional disagreements, unless those issues directly relate to unethical behavior or malpractice.