Neither.
Psychopathy’s characteristic neural deficits (reduced activity and gray-matter volume in the vetromedial prefrontal cortex, anterior cingulate, amygdala, and circuits connecting them) sit squarely in the “paleomammalian” (limbic) and “neomammalian” (prefrontal cortex) layers described by the old triune-brain model—not in the reptilian brainstem or basal ganglia.
What’s missing or muted is the mammalian socio-emotional circuitry that normally regulates impulse control, empathy, and moral learning.
So these are failures of development in higher mammalian systems, not a reversion to reptile-level architecture.
‘Lack of impulse control’ is not a trait of psychopaths in and of itself, but rather an end of the ‘I want everything I see’ throughline. The other end is deferred gratification capability and hypocritical perfection. https://pathwhisperer.info/2009/04/15/sociopathic-through-lines/
The Path Whisperer 