Science | November 15, 2017 10:00 am

How Conjoined Twins Make Scientists Question the Concept of Self

The new documentary "Inseperable" explores what it means to share your consciousness.

Krista and Tatiana Hogan are 11-years-old, and they are conjoined at the skull, making them craniopagus twins. Craniopagus twins are the rarest sort, reports The Walruswith only about six percent of conjoined people falling into that category.

When they were about a year-and-a-half old, the doctor told Felicia Hogan, the twin’s mother, that it was impossible to separate them without harming or killing on. The girls’ skulls are not merely fused, but instead, they form a single continuous cranium which houses four cerebral hemispheres.

A new CBC documentary titled Inseparable looks at the lives the sisters lead. Director Judith Pyke is able to show an intimate bond that has ramifications on the nature of self.

Doctors did not expect the twins to survive their first 24-hours. About half of conjoined twins are born stillborn, reports The Walrus. When they survived their first day, doctors then said the girls would be stuck in bed, unable to dress, eat, or bathe themselves. But when a pacifier was put in one girl’s mouth, the other would stop crying. An MRI revealed that each girl’s thalamus is connected to the other’s via a “thalamic bridge,” which means the twins can “tune in” to each other’s experiences, reports The Walrus. 

The documentary shows the girls leading a lovely life, despite many limitations. It also discusses the idea that the twins, without trying, have confounded the most basic rule about having a self: “your experiences are your own,” writes The Walrus. The girls seem to suggest that they can talk inside their heads, but at the same time, they are utterly distinct, and have different thoughts and desires.

Watch the video above for more.