Final answer:
Dr. Heidegger does not wish to become young because he values the wisdom of age over the follies of youth, having learned from his own life experiences.
Step-by-step explanation:
The doctor in Nathaniel Hawthorne's short story "The Dr. Heidegger's Experiment" does not partake in his own experiment to become young again because he understands the value and lessons learned from age and experience.
He witness his friends revert to their younger, more reckless selves, which only solidifies his belief that wisdom should not be forsaken for youth. The doctor prefers to learn from life rather than reset it.