Hacking an Individual's Personality Through Their Gut Contents

A few years ago, a controversial surgeon announced his decision to perform the first human head transplant. His decision caused a storm in the media. The head transplant raised several philosophical and ethical concerns. However, it seems that the most philosophical issue that arose was who is the owner of the new hybrid: the donor of the head or the body—in other words, whether the self and identity are related to the brain or other parts of the body.

Where does the sense of self come from?

The concept of "self" is an old unresolved issue in history. Most old philosophers and scholars held that the self belongs to an immaterial entity that is called the soul. The soul was considered immortal and remained after the death and destruction of the body. In some cultures, it is believed that souls can transfer from one body to another after death. Most followers of major religions believe that the soul ascends to the afterlife world after death and lives eternally.

The belief that the self is a mobile entity and can transfer between bodies and worlds has taken root even in contemporary people's minds. However, the concept of the soul has been modernized for today's individuals. The concept of mind uploading into a supercomputer to recreate oneself in cyberspace, or transferring one's mind to another person through a chipset, as depicted in movies and media, reflects ancient beliefs. New findings further reveal the mind and body are integrated entities and are influenced by the social environment to form the personality of each person.

The foreign guests of the body secretly control the host’s emotions.

Due to the expansion of media and the internet, most people are now aware of the impact of microbes residing in our body, known as the microbiome, on brain functions and cognition. In addition to its effects on physiological and pathological body functions such as inflammation and immunity, the microbiome has a profound impact on brain functions. Most studies have explored the effects of these microbes on psychological disorders such as depression and anxiety. The studies using the transfer of gut microbiota from one animal to another, from humans to animals, and from humans to humans have revealed that psychological distress and stress-related behaviors can be transferred to other subjects.

However, it has been shown that the microbiome may also influence desires, decisions, and beliefs. Although the brain is the main tool for producing these functions, several factors influence them, such as microbes, particularly gut-residing microbes, through the gut-brain axis. We are unsure to what extent the microbiome affects the brain's functions; however, their effect cannot be neglected.

The composition of the microbiome is unique to each individual and is influenced by environmental factors such as nutrition, proximity to other individuals or pets, psychological status, and the use of medications like antibiotics. The ultimate mental effects of these diverse compositions of microbes are complex and depend on numerous known and unknown factors. At least in this case, Robert M. Sapolsky is right, as he stated in his book, Determined: A Science of Life Without Free Will. He believes that our decisions and behaviors are influenced by various factors, such as those related to prenatal conditions, childhood experiences, and socio-economic status, even though we tend to attribute them to our free will.

A transplantation that transfers a part of the donor's cognitional traits to the recipients

There is some limited evidence that organ transplantation may alter personality. Almost half of heart transplant recipients have claimed to experience changes in their cognition. Other organ transplant recipients, such as those who have received kidney and liver transplants, have also reported similar experiences.¹ However, these reports are based on self-declaration and are scientifically questionable.

As mentioned above, the extent of the microbiome's effect on cognitive functions and personality is unclear. However, based on new findings, it should be accepted that the microbiome plays a critical role in shaping personality and identity. When Josiah Zayner, a former NASA scientist, decided to perform an unapproved experiment on himself to improve his gut issues, he did not anticipate that the outcomes would extend beyond gastrointestinal functions. After fecal implantation (FMT), he experienced some new cognitive characteristics, including an intent to eat sugary food, which was a personality trait of the fecal donor.

The psychological changes during FMT have been studied in both animals and humans. These studies indicate that FMT could serve as a novel therapeutic intervention for psychiatric conditions such as depression, anxiety disorders, schizophrenia, substance use disorders, and childhood disorders.² Recently, it has been explored that patients with schizophrenia exhibit a significant difference in the microbes responsible for metabolizing tryptophan compared to those in normal individuals. This study indicates the mutual interplay between the microbiome and cognitive disorders.³ Also, studies demonstrate that there are differences among microbes responsible for synthesizing glutamate, butyrate, serotonin, and gamma-aminobutyric acid (GABA) in individuals with and without depression.⁴

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In addition to the interesting philosophical aspects of FMT and the factors that contribute to shaping the self and personality, it offers a new opportunity for manipulating psychological disorders by altering the microbiome composition. However, the risks of infectious diseases that may be transmitted through feces necessitate further research to develop improved methods as a supplementary intervention in managing psychiatric conditions.