Final answer:
The statement that temperament tendencies at birth play a substantial role in shaping adult personality is most accurate, recognizing the influence of both inborn traits and environmental factors in personality development.
Step-by-step explanation:
The question pertains to the influence of temperament on adult personality development. Among the statements provided, the one that most accurately reflects the consensus amongst contemporary psychologists is that temperament tendencies at birth play a substantial role in shaping adult personality. This is based on the understanding that temperament, which appears very early in our lives, has a biological basis and includes characteristics such as reactivity and self-regulation.
However, it is important to recognize that environmental factors, such as family interactions, and the process of maturation also significantly impact the final personality structure in adulthood. Therefore, while inborn temperament traits certainly contribute to the foundation of adult personality, experiences and interactions throughout one's life will modify and shape these initial tendencies.