Final answer:
Phineas Gage experienced a behavioral change after an iron rod pierced his frontal lobe. The damage to his frontal lobe affected his personality and behavior, causing him to become irritable, temperamental, and lazy.
Step-by-step explanation:
Phineas Gage, a 19th-century railroad worker, experienced a significant behavioral change after an iron rod pierced his brain, specifically his frontal lobe. Before the accident, Gage was described as well-mannered and soft-spoken, but after the accident, he became irritable, temperamental, and lazy. The frontal lobe is responsible for impulse control, and damage to this area can lead to changes in personality and behavior.