Neuroscience and personhood

Naturalizing Personhood Defining “Person” The earliest explicit definition of personhood came from the sixth-century philosopher Boethius, who equated a person with “an individual substance of a rational nature” For Locke, there were three essential characteristics of personhood: rationality, selfawareness, and the linkage of this self-awareness by memory across time and space. For Kant: ability to distinguish between persons (rational beings) and things and treat them accordingly. Rational beings exist as ends in and of themselves and means to ends, as are things.

Defining “Person” • •

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More recent: Daniel Dennett: the ability to understand others as having intentional mental states, which requires language. Language confers a “special consciousness.” Dennett concedes that all definitions of personhood suffer from arbitrariness. That is – were are imposing dichotomous distinctions on continuous or multifaceted traits (language, memory, selfawareness, morality, etc.). Joseph Fletcher: 15 criteria for personhood (usual suspects – memory, language, self-awareness, etc), including a specific IQ scores, (at least above 20). Arbitrariness: why is a 21 a person, while a 20 is not? Authors’ conclusion: satisfactory defining criterion or criteria for personhood – illusive. “We are left setting criteria that feel, in Dennett’s words, arbitrary. In effect, personhood is a concept that everyone feels they understand but no one can satisfactorily define.” (p. 39).

Neuroscience of personhood • Neuroscience will allow us to translate the psychological criteria for personhood (language, self-awareness, memory, etc) into neurological criteria. But this will not eliminate problem of defining personhood. It will only give it a different vocabulary. • Nearly all criteria for personhood refer to neocortical brain function. Is a person someone with a functioning neocortex? • Problem: brain development is gradual not punctuate. When exactly does “brain life” begin?

Brain-created reality • We live in the world our brains create. If the brain cannot process it, we do not experience it. We can only experience the categories the brain represents. This is true both for physical categories (red vs. blue; cold vs. hot, sweet vs. salty, etc) as well as social categories (persons vs. non persons).

The brain’s “person” system • Early evidence suggesting its existence: Prosopagnosia -- a specific deficit in face recognition due to damage in the temporal lobe, equally complex pattern recognition can be preserved, only faces affected. Also, inverse disorder has also been documented – globally pattern recognition disorder with preserved face recognition. Indicating dedicated face recognition system in brain • Location of face recognition area: fusiform gyrus of temporal lobe • Fusiform face area only one part of a larger “person” system

The brain’s “person” system • Human body recognition area(s): fusiform gyrus separate from face area and temperoparietal juncture • Part of TPJ also responds to body movements with different parts responding to goal-directed movements and another when thinking about another’s mental state. “She’s biting her lip because she wants him to think that she’s apprehensive.” • Medial Prefrontal cortex: also involved in TOM, thinking about other’s mental states. For example, if people think they are playing “rock-paper-scissors” with another person MPC active. If they think they are playing with computer, MPC less active.

The brain’s “person” system

• Summary of person system • FFA: face recognition • FFG & TPJ: human body recognition, goal directed action recognition, thoughts behind actions • MPC: TOM

The brain’s “person” system • System shows evidence of being both autonomous and innate. • Autonomous: system will engage automatically with minimal evidence and even when we know consciously and rationally that no person is present. • For example: children and adults will describe geometric forms “chasing” each other as goal-directed agents compelled by emotions.

The brain’s “person” system • Innateness: present at birth with little or no learning required. • For example: infants as young as 30 mins after birth will track face-like pattern more than equally complex other patterns. Damage as early as 1 day after birth to FFA, will lead to lifelong deficit in face recognition. Other pattern recognition areas do not take over function. • Habituation studies: By 5 months, infant expect human, but not mechanical, movements to be rational. So if a human reaches around a barrier to get an object and the barrier is subsequently removed, infants are not surprised if the human reaches directly for the object. They are surprised if a mechanical arm reaches directly for object. • Autism studies show less activity in person system.

What does this tell us about personhood? • Because the person system is autonomous (separate from other brain systems) it encourages the illusion that personhood exists as a distinct entity out in the world. When it kicks in, there is a person out there, when it does not there is no person out there. • But since it is designed to react to minimal stimulation it frequently over identifies persons. It says “person” when our rational brain knows there is no person. • Over attributing personhood is adaptive, we all start life as non-persons!! • Personhood defined by a specific criterion (or criteria) may be futile. • Note: other philosophical approaches define personhood by relationships with others.