Final answer:
The observer's belief in their own ability, or self-efficacy, is affected by a vicarious experience, wherein observing another's performance influences one's own belief in their ability to succeed.
Step-by-step explanation:
The observer's self-efficacy belief has been affected by vicarious experience. This happens when people see others perform tasks and outcomes from those tasks influence observers' beliefs in their own abilities to succeed in similar activities. According to Albert Bandura, self-efficacy is developed through social experiences and affects how we approach challenges and reach goals. Vicarious experiences, along with mastery experiences, social persuasion, and physiological states, are ways in which self-efficacy can be influenced. In the given scenario, by observing a peer's distress and perceived incompetence, the person doubts their own capability, which demonstrates the impact of vicarious experiences.