Conjoined Twins Share a Mind

What’s the Latest Development?

When, at the age of 20, Felicia Simms found out she was pregnant with twins conjoined at the head, her doctor offered her the option of terminating the pregnancy. Simms declined immediately and the babies were brought to term. Now, at the ages of four, her daughters Krista and Tatiana Hogan are wowing the scientific community with their unique brain structure—in many ways they share a mind—and giving sociologists an insight into how families cope with such diverse and challenging circumstances.

What’s the Big Idea?

Krista and Tatiana’s brains are connected at the thalamus, the part of the brain that regulates sensory experience, by a neural pathway that allows the twins to share experiences. “Because the thalamus functions as a relay station, the girls’ doctors believe it is entirely possible that the sensory input that one girl receives could somehow cross that bridge into the brain of the other. One girl drinks, another girl feels it. …Tatiana and Krista are also a study in the more expansive neural system of sociology: the feedback loop of how their family responds to difference, how the world outside the walls of their home responds to the family’s response and how the girls respond in turn.”