Assertion:Creating an atmosphere of unconditional positive regard is crucial for fostering the improvement of individuals' self-concept.

Reasoning: In client-centered therapy, which was developed by Erik Erikson, the primary goal is to establish this condition. 

Assertion is true, but Reasoning is false.

Creating an atmosphere of unconditional positive regard is crucial for fostering the improvement of individuals' self-concept. In client-centered therapy, which was developed by Rogers, the primary goal is to establish this condition. Unconditional positive regard refers to an accepting and nonjudgmental attitude towards the client, where they are valued and respected regardless of their thoughts, feelings, or behaviors. By providing this supportive and accepting environment, client-centered therapy aims to facilitate personal growth, self-exploration, and the development of a positive self-concept in individuals seeking therapy.