The Echo Maker

Capgras syndrome is a rare condition in which the individual is able to recognize the faces of people closest to them but feels those people are imposters. Mark’s Capgras syndrome is triggered by a brain injury that appears to have disrupted the connection between his emotional attachments and his conscious understanding. As Gerald Weber explains it:

In Capgras, the person believes their loved ones have been swapped with lifelike robots, doubles, or aliens. They properly identify everyone else. The loved one’s face elicits memory, but no feeling. Lack of emotional ratification overrides the rational assembly of memory. Or put it this way: reason invents elaborately unreasonable explanations to explain a deficit in emotion. Logic depends upon feeling (106).

Neuroscience sometimes finds it useful to look at the brain in three evolutionary stages. The amygdala, sometimes called the reptilian brain, is the oldest evolved part of the brain, which controls movement and instinctive behavior. The next evolved part of the brain is the mammalian or limbic brain, which contains memory and emotion. The pre-frontal cortex (PFC) is the most recently evolved part of the human brain. It is thought to be the center of personality, and part of its function is to take in information from the environment and compare it to past experiences and internal states. If there is a mismatch, the PFC decides whether to correct the external perception or the internal state.

Weber hypothesizes that Mark’s injury has created a lesion between his mammalian brain and his pre-frontal cortex. This occurs in roughly 25% of cases of Capgras. Consequently, although his PFC can take in information from outside, it can’t check that information against information from the limbic and reptilian brains. The lesion acts as a wall in Mark’s brain. When Mark tries to check his memory and emotion, his effort echoes off that wall and springs back without meaning.

Because the reptilian and limbic regions of the brain are most engaged in survival, they take precedence over the more sophisticated cortex, which is why, when the modern and ancient parts of the brain disagree, as they do in Mark’s case, the older part of the brain wins. Mark has no choice but to use his pre-frontal cortex to create a story that explains why his emotional knowledge doesn’t match his external reality.

It is rare for Capgras to be caused by a brain injury, as it is in Mark’s case. Even in such a case, Capgras is virtually always associated with other delusional states such as Alzheimer’s syndrome, bipolar disorder, and schizophrenia. Mark’s manifestation of Capgras is partially explained by his family history. Several members of his family have had schizophrenia. Mark’s father and his uncle exhibited a paranoid belief in conspiracy theories. His mother also exhibited distorted thinking in her obsessive religiosity. Though it is not known if there is a special gene for schizophrenia or other psychotic disorders, they tend to run in families.