Kluge: The Haphazard Construction of the Human Mind (Houghton Mifflin; 2008)

That same mix, minus whatever inhibitory mechanisms normal people use to calm down, may exacerbate, or maybe even spawn, several other aspects of mental illness. Take, for example, the common symptom of paranoia. Once someone starts down that path — for whatever reason, legitimate or otherwise — the person may never leave it, because paranoia begets paranoia. As the old saying puts it, even the paranoid have real enemies; for an organism with confirmation bias and the will to deny counterevidence (that is, motivated reasoning), all that is necessary is one true enemy, if that. The paranoid person notices and recalls evidence that confirms his or her paranoia, discounts evidence that contradicts it, and the cycle repeats itself.

Dיpressives too often lose touch with reality, but in different ways. Dיpressives don't generally hallucinate (as, for example, many schizophrenics do), but they often distort their perception of reality by fixating on the negative aspects of their lives — losses, mistakes, missed opportunities, and so forth — leading to what I call a "ruminative cycle," one of the most common symptoms of depression. An early, well-publicized set of reports suggested that dיpressives are more realistic than happy people, but today a more considered view is that dיpressives are disordered in part because they place undue focus on negative things, often creating a downward spiral that is difficult to escape. Mark Twain once wrote, in a rare but perceptive moment of seriousness, "Nothing that grieves us can be called little; by the eternal laws of proportion a child's loss of a doll and a king's loss of a crown are events of the same size." Much, if not all, depression may begin with the magnification of loss, which in turn may stem directly from the ways in which memory is driven by context. Sad memories stoke sadder memories, and those generate more that are sadder still. To a person who is depressed, every fresh insult confirms a fundamental view that life is unfair or not worth living. Contextual memory thus stokes the memory of past injustices. (Meanwhile, motivated reasoning often leads dיpressives to discount evidence that would contradict their general view about the sadness of life.) Without some measure of self-control or a capacity to shift focus, the cycle may persist.

Such feedback cycles may even contribute a bit to bipolar disorder, not only in the "down" moments but also even in the manic ("up") phases. According to Kay Redfield Jamison, a top-notch psychologist who has herself battled manic depression, when one has bipolar disorder,

there is a particular kind of pain, elation, loneliness, and terror

involved in this kind of madness . . . When you're high it's tre

mendous. The ideas and feelings are fast and frequent like shoot

ing stars .. . But, somewhere, this changes. The fast ideas are far

too fast, and there are far too many; overwhelming confusion re

places clarity... madness carves its own reality.

Without sufficient inherent capacity for cognitive and emotional control, a bipolar person in a manic state may spiral upward so far that he or she loses touch with reality. Jamison writes that in one of her early manic episodes she found herself "in that glorious illusion of high summer days, gliding, flying, now and again lurching through cloud banks and ethers, past stars, and across fields of ice crystals .. . I remember singing 'Fly Me to the Moon' as I swept past those of Saturn, and thinking myself terribly funny. I saw and experienced that which had been only in dreams, or fitful fragments of aspiration." Manic moods beget manic thoughts, and the spiral intensifies.

Even the delusions common to schizophrenia may be exacerbated by — though probably not initially caused by — the effects of motivated reasoning and contextual memory. Many a schizophrenic, for example, has come to believe that he is Jesus and has then constructed a whole world around that notion, presumably "enabled" in part by the twin forces of confirmation bias and motivated reasoning. The psychiatrist Milton Rokeach once brought together three such patients, each of whom believed himself to be the Son of the Holy Father. Rokeach's initial hope was that the three would recognize the inconsistency in their beliefs and each in turn would be dissuaded from his own delusions. Instead, the three patients simply became agitated. Each worked harder than ever to preserve his own delusions; each developed a different set of rationalizations. In a species that combines contextually driven memory with confirmation bias and a strong need to construct coherent-seeming life narratives, losing touch with reality may well be an occupational hazard.