Phineas Gage suffered damage to his ______ that resulted in an inability to plan for the future and to conduct himself according to social rules.

A) temporal lobe
B) prefrontal cortex
C) parietal lobe
D) corpus callosum

Phineas Gage suffered damage to his prefrontal cortex, which is known to be involved in planning, decision-making, and moderating social behavior. This injury led to significant changes in his personality and behavior, illustrating the role of the prefrontal cortex in these functions.