Dr. Joe Vukov, a neuroscience researcher, introduced an article on Personhood and Neuroscience, displaying the challenges that philosophers have faced while trying to specify the criteria of what makes up personhood (Farah et al. 2007). Philosophers have explored cognitive capacities such as rationality to be one of the most prominent features of personhood, which can be connected to the ability of humans to predict what others are thinking along with their own thoughts. For instance, humans use their cognitive capacity of rationality to predict people’s actions through their perceptions, beliefs, and desires, also known as the theory of mind (Ho et al. 2022). Using Farah et al. 2007 representation of the brain structures involved in perception and Ho et al. 2022 studies on the theory of mind and rationality, we can better understand the criteria of personhood in humans.
Through the organization of brain structures for visual perception in humans, we can see how the face recognition system is specialized in representing personhood. For example, studies on people with prosopagnosia, a disorder in which visual recognition of the human face is impaired, reveal the significance of perception in humans. Farah et al. 2007 article discusses that prosopagnosia can be a relatively isolated impairment, meaning that some patients with this disorder may be able to recognize human faces but not objects and animals, while some patients may be able to recognize objects and animals but not human faces. The isolation in impairment in prosopagnosia is specialized to individuals as other objects and animals do not experience the same visual recognition impairments as humans. The fusiform gyrus is located on the ventral surface of the brain and is activated by the site of a human face (Farah et al 2007). However, not only can humans perceive and recognize faces and objects, but they can perceive facial expressions of emotion activated by the amygdala. The amygdala is shown to play a major role in humans' ability to perceive people’s emotional states by studies on patients with bilateral amygdala damage, resulting in an impaired perception of people’s emotional states (Farah et al. 2007). Also, humans are able to perceive the goal-directed actions of others resulting in the activation of the temporoparietal junction (Farah et al. 2007). Most importantly, humans are able to think about others' mental states without any visual input which activates the medial prefrontal cortex (Farah et al. 2007). The brain structures including the fusiform gyrus, amygdala, temporoparietal junction, and medial prefrontal cortex reveal that visual perception in humans is specialized and plays a role in what makes up personhood since non-humans do not have the same complex system of perception as humans.
In addition to the parts of the human brain that reveal our ability to recognize faces, emotions, actions, and mental states of others, prediction through the theory of mind may also play a significant role in what makes up personhood. For example, the medial prefrontal cortex can be activated without any visual input, revealing that individuals have some sort of ability to predict others' mental states. Humans contain the capacity to theorize the minds of others, which non-human forms of life such as plants and objects cannot do (Farah et al. 2007; Ho et al. 2022). For example, the theory of mind is defined as ‘The ability to make inferences about what other people believe to be the case in a given situation allows one to predict what they will do’ (Ho et al. 2022). Interestingly, humans can think about another person and predict what they will say or do without even seeing their faces or actions or receiving any visual input. Human’s ability to receive visual input and recognize others’ faces, emotions, actions, and behaviors can therefore be used as an advantage when predicting what another person is thinking, feeling, and what they are going to do. Some researchers may question this theory and believe that it is biased due to the fact that an individual may already know what the other individual is like because they have had previous experiences with them and/or a relationship with them. However, even if individuals are put into encounters with random individuals, they can predict the perceptions, beliefs, and desires of other individuals without it being in front of their faces due to the theory of mind (Ho et al. 2022).
Furthermore, not only can individuals use theories to predict the future, but they can also actively plan to change what happens in the future by using rationality (Ho et al. 2022). This is very interesting because not only do nonhumans lack the complexity of visual perception that humans obtain, but they also do not necessarily implement rationality into their decisions (Farah et al. 2007). For example, I might be hungry and understand that another individual is hungry too because I heard their stomach growl, and we are sitting in front of an apple. I know that the other individual also has the desire to eat, so I could actively plan to bring and eat my own snack from my backpack so that we could both eat. I use rationality in my decision because I know that the other individual might reach for the apple. However, if an animal, such as a dog was put in a similar situation, he or she may not understand that the other dog present also has the desire to eat and will just take the treat without giving the decision a thought. The dog does this because it does not use rationality in his or her decision and does not understand that the other dog might want that treat too. Rationality can be used to actively change what happens in the future in individuals, but not for most nonhumans, contributing to the criteria of what makes personhood (Ho et al. 2022).
Although we cannot define what makes up personhood for certain, using cognitive neuroscience including different roles of the human brain in visual perception and the theory of mind can potentially take us a step closer to understanding what makes up personhood. Humans have a very complex brain and obtain individuality through being able to recognize and perceive differently and use rationality in their decisions. Most importantly, humans can predict the mental states, perceptions, desires, and beliefs of others individually, filling the criteria of personhood, whereas nonhumans do not fill this criterion.
References:
Farah, Martha J., Heberlein, Andrea S. (2007). Personhood and Neuroscience: Naturalizing or Nihilating? The American Journal of Bioethics, 7:1, 37-48, DOI: 10.1080/15265160601064199, https://www.tandfonline.com/doi/abs/10.1080/15265160601064199
Ho, Mark K., Saxe, Rebecca, Cushman, Fiery. (2022). Planning with Theory of Mind. Trends in Cognitive Sciences, Elsevier Current Trends, 8 Sept. 2022, https://www.sciencedirect.com/science/article/pii/S1364661322001851?casa_token=A0yXmWSF9NAAAAAA%3A048O6gepK4VrRUJ7AT4hRaMhOaH7aJ_Y7ddy3KOM8tEYRSYvBlSIFtERuF9KllG2yTpMFGYiOw.
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