Despite her promise to Lynch, she phoned Adam first.
‘Adam, when we were with Sandra Regan, did anything else unusual strike you about her?’
‘As you said, Kate, she was detached, nervous, defensive … Why?’
‘Do you remember on the flight to Paris, when we were talking about the brain’s development – the id, the ego and the super-ego, and how sustained trauma can interfere with cohesive development?’
‘Kind of.’
‘It’s because the brain goes through a massive change in the early stages. If traumatised, the temporal gyrus, which stores autobiographical memory, doesn’t develop correctly and can sometimes cause a split.’
‘What kind of split?’
‘It’s all part of a person developing a coherent sense of self.’
‘Talk English, Kate.’
‘Okay. A child is under a sustained level of emotional trauma. The brain is changing as they are growing older, not just psychologically but physically. The two are intertwined. When a child finds themselves under a pressure that they can’t cope with, other forms of coping mechanism come into play. For example, a shy, nervous child, being bullied at school, might one day find that a different side of their personality slots into place, a more aggressive side, and they are able to take on the bully. The stronger, more assertive part of their brain defends them. At least, that’s how it starts off, as a form of protection, not long-term division.’
‘I’m listening.’
‘Sometimes the temporal gyrus splits at a point in the brain’s early development. One part of the brain doesn’t like the dark, difficult memories, so it closes them off, creating two identities.’
‘Are you talking schizophrenia?’
‘No, no. Schizophrenia happens when a person hears voices which they can’t tell are not real. This is different. There are mixed views on the development of multiple personalities, or extreme dissociative identity disorder. In every individual the clinical presentation varies, and the level of functioning can change from severely impaired to adequate and manageable. Importantly, the sufferer is capable of fooling themselves as well as others. The majority of patients with DID report early sexual and physical abuse, consistent with our killer’s profile. Often, the identities are unaware of each other, as they have compartmentalised memories and knowledge to a different part of their brain, a split. Sufferers can experience time disturbance, thinking they’ve been asleep or even forgetful. The primary identity, which is often the one using the birth name, tends to show various established personality traits, being passive, dependent, suffering guilt or depression, with the other side of the personality assuming a more active, aggressive or hostile role. The latter of the two, the darker, more aggressive side, usually contains more complete memories, because they have the ability to face them, and can be aware of the perceived weaker strand’s existence, even though the weaker side might be unaware of them.’
‘Kate, I don’t know. It sounds a bit far-fetched.’
‘But it is possible. Multiple personalities or dissociative disorder is a way of coping. In extreme cases, one side of the brain is fully protected from the other.’
‘So, there’s a dominant side?’
‘That can change too. Both sides operate independently. They have to, if they’re to function, but the switching usually happens because of stress factors, again consistent with our killer’s profile. In the earlier development of the disorder, the switching might have occurred because of the abuse, and then later, when other pressure points arose. By then it would have been a learned response mechanism, recurring over and over. The darker side was developed as the protection, so if the person is put under pressure, the learned behaviour of switching to the active aggressive and hostile side of the personality will slot into place.’
‘What makes you so sure the killer could be suffering from this disorder? What did you call it? Multiple personality disorder?’