A common image for popular accounts of the "The Mind" is a brain in a bell jar. The message is that inside that disembodied lump of neural tissue is everything that is you.
It's a scary image but misleading. A far more dangerous idea is that brains cannot become minds without bodies, that two-way interactions between mind and body are crucial to thought and health, and the brain may partly think in terms of the motor actions it encodes for the body's muscles to carry out.
We've probable fallen for disembodied brains because of the academic tendency to worship abstract thought. If we take a more democratic view of the whole brain we'd find far more of it being used for planning and controlling movement than for cogitation. Sports writers get it right when they describe stars of football or baseball as "geniuses"! Their genius requires massive brain power and a superb body, which is perhaps one better than Einstein.
The "brain-body" view is dangerous because it requires many scientists to change the way they think: it allows back common sense interactions between brain and body that medical science feels uncomfortable with, makes more sense of feelings like falling in love and requires a different approach for people who are trying to create machines with human-like intelligence. And if this all sounds like mere assertion, there's plenty of interesting research out there to back it up.
Interactions between mind and body come out strongly in the surprising links between status and health. Michael Marmot's celebrated studies show that the lower you are in the pecking order, the worse your health is likely to be. You can explain away only a small part of the trend from poorer access to healthcare, or poorer food or living conditions. For Marmot, the answer lies in "the impact over how much control you have over life circumstances". The important message is that state of mind — perceived status — translates into state of body.
The effect of placebos on health delivers a similar message. Trust and belief are often seen as negative in science and the placebo effect is dismissed as a kind of "fraud" because it relies on the belief of the patient. But the real wonder is that faith can work. Placebos can stimulate the release of pain-relieving endorphins and affect neuronal firing rates in people with Parkinson's disease.
Body and mind interact too in the most intimate feelings of love and bonding. Those interactions have been best explored in voles where two hormones, oxytocin and vasopressin, are critical. The hormones are released as a result of the "the extended tactile pleasures of mating", as researchers describe it, and hit pleasure centres in the brain which essentially "addict" sexual partners to one another.
Humans are surely more cerebral. But brain scans of people in love show heightened activity where there are lots of oxytocin and vasopressin receptors. Oxytocin levels rise during orgasm and sexual arousal, as they do from touching and massage. There are defects in oxytocin receptors associated with autism. And the hormone boosts the feeling that you can trust others, which is key part of intimate relations. In a recent laboratory "investment game" many investors would trust all their money to a stranger after a puff of an oxytocin spray.
These few stories show the importance of the interplay of minds and hormonal signals, of brains and bodies. This idea has been taken to a profound level in the well-known studies of Anthony Damasio, who finds that emotional or "gut feelings" are essential to making decisions. "We don't separate emotion from cognition like layers in a cake," says Damasio, "Emotion is in the loop of reason all the time."
Indeed, the way in which reasoning is tied to body actions may be quite counter-intuitive. Giacomo Rizzolatti discovered "mirror neurones" in a part of the monkey brain responsible for planning movement. These nerve cells fire both when a monkey performs an action (like picking up a peanut) and when the monkey sees someone else do the same thing. Before long, similar systems were found in human brains too.
The surprising conclusion may be that when we see someone do something, the same parts of our brain are activated "as if" we were doing it ourselves. We may know what other people intend and feel by simulating what they are doing within the same motor areas of our own brains.
As Rizzolatti puts it, "the fundamental mechanism that allows us a direct grasp of the mind of others is not conceptual reasoning but direct simulation of the observed events through the mirror mechanism." Direct grasp of others' minds is a special ability that paves the way for our unique powers of imitation which in turn have allowed culture to develop.
If bodies and their interaction with brain and planning for action in the world are so central to human kinds of mind, where does that leave the chances of creating an intelligent "disembodied mind" inside a computer? Perhaps the Turing test will be harder than we think. We may build computers that understand language but which cannot say anything meaningful, at least until we can give them "extended tactile experiences". To put it another way, computers may not be able to make sense until they can have sex.