Take a theory of consciousness that calculates how aware any information-processing network is – be it a computer or a brain. Trouble is， it takes a supercomputer billions of years to verify its predictions. Add a maverick cosmologist， and what do you get? A way to make the theory useful within our lifetime.
采用一种意识理论，以此来计算人类是如何意识无所不在的信息处理网络的，这是一件非常麻烦的事情。不论是用一台计算机还是一个大脑来计算，这样的计算需要一台超级计算机用几十亿年来验证它的预言。还得要加上一位与众不同的宇宙学家，你能得到什么？解决的方式是找到一种我们在有生之年可以使用的理论。
Integrated information theory (IIT) is one of our best descriptions of consciousness. Developed by neuroscientist Giulio Tononi of the University of Wisconsin at Madison， it’s based on the observation that each moment of awareness is unified. When you contemplate a bunch of flowers， say， it’s impossible to be conscious of the flower’s colour independently of its fragrance because the brain has integrated the sensory data. Tononi argues that for a system to be conscious， it must integrate information in such a way that the whole contains more information than the sum of its parts.
整合信息理论(Integrated information theory ，IIT)是我们描述意识的最佳方法之一。该方法由麦迪逊威斯康辛大学神经科学家朱利奥·托诺尼（Giulio Tononi）发展而成，这一理论基于这样的观察，每一刻的知晓都是统整的。当你凝视一束花的时候，不可能独立于花的芳香而单独意识到花的颜色，因为大脑已经对这些感觉数据进行了集成。托诺尼认为，信息整合必须以这样的方式完成：系统的整体的信息必须大于各部分之和。
The measure of how a system integrates information is called phi. One way of calculating phi involves dividing a system into two and calculating how dependent each part is on the other. One cut would be the “cruellest”， creating two parts that are the least dependent on each other. If the parts of the cruellest cut are completely independent， then phi is zero， and the system is not conscious. The greater their dependency， the greater the value of phi and the greater the degree of consciousness of the system.
衡量系统整合信息方式的方法称为φ（phi）。计算φ（phi）值的一种方式是将一个系统分成两个部分，并且分别计算每个部分依赖另一个部分的程度。一种“最残酷的”切割创造了彼此最少依赖的两个部分。如果这个最残酷切割的两个部分是彻底的独立的，那么φ（phi）为零，并且该系统是非意识的。两个部分之间的依赖性越大，φ（phi）的值就越大，并且这个系统的意识程度就越大。
The cruellest cut 最残酷的切割
Finding the cruellest cut， however， is almost impossible for any large network. For the human brain， with its 100 billion neurons， calculating phi like this would take “longer than the age of our universe”， says Max Tegmark， a cosmologist at the Massachusetts Institute of Technology.
然而，任何的大网络系统要发现这个最残酷的切割几乎都是不可能的。麻省理工学院的一位宇宙学家特德马克（Tegmark）说，人类大脑有1000亿个神经元，计算如此之大的φ（phi）值所耗费的时间将会“超过我们宇宙的年龄”。
Tegmark has come up with a fast way of approximating phi. He treats each neuron in the network as a node and their interconnections as links. He assigns a thickness to each link， proportional to the strength of the interconnection. Now， imagine turning a knob so that the thinnest links fade out. The picture will look somewhat different. Try again， fading out the next-thinnest links. Continue until the single interconnected web breaks into two. Tegmark has shown that this configuration approximates the cruellest cut.
特德马克已经找到了一条计算φ（phi）近似值的捷径。他把网络中的每个神经元看作是一个节点，并把它们之间相互联系看作为一种链接。他为每个链接分配的厚薄程度与连接的强度成正比。现在，想象转动一个旋钮，以便最薄的链接逐渐消失。这样的画面看起来就会有些不一样了。再试一次，下一个最薄的链接消失掉。继续进行，直到单一链接的互联网断裂两个部分为止。特德马克已经向我们呈现了这种接近最残酷切割的格局。
Just a second 刚好一秒
Crucially， this dramatically cuts down the time it takes to find phi. “It goes from being above the age of the universe to something quite manageable，” says Tegmark – he estimates it would take less than a second for a human brain.
最关键的是，这大大减少了发现φ（phi）值的时间。“它从超过宇宙的年龄走到了相当容易管理的地步。”特德马克说。他估计，计算人类大脑φ值用不了一秒的时间。
“It’s cool stuff，” says Christof Koch of the Allen Institute for Brain Science in Seattle. “It’s essential if we are ever to measure phi for real systems and not just toy models with 10 or 20 binary neurons.”
“这是很酷的发现，”西雅图亚伦大脑科学学院的克里斯多佛·考齐(Christof Koch)说，“如果我们要测量真实系统的φ值，而不是仅仅有着10个或20个二进制神经元的玩具模型，这是非常必要的”。
The reduced computation time means we should be able to test the theory. This can be done using things like fMRI scans to map the neural interconnections of people in varying states of consciousness – people in a coma， in dreamless sleep or looking at a bunch of flowers， for example. Applying Tegmark’s model to approximate phi in each case， we should find that it scales with the person’s level of awareness.
运算时间的减少意味着我们能够检验这个理论。例如，可通过使用诸如fMRI来绘制人们在各种意识状态下——昏迷中的、无梦睡眠中的或看一束花时的——神经元相互链接的地图。用特德马克的模型估计每种情况中的φ（phi）值，我们应该发现它可以衡量人的意识水平。
Two halves of the whole 一个整体的两瓣儿
The theory could also be tested in people whose brain hemispheres have been surgically separated as a treatment for epilepsy. Michael Gazzaniga of the University of California， Santa Barbara， has discussed with Tononi the idea of measuring the phi of each half of the brain. His work shows that each hemisphere retains its own consciousness and is unaware of the other half. IIT predicts that the phi for each individual hemisphere should be less than the phi for the unseparated brain. “The idea of making the measurement easier is very appealing，” says Gazzaniga.
这个理论也能在大脑两个半球被切开的癫痫病人哪儿进行检验。圣芭芭拉加州大学的迈克尔·加扎尼加（Michael Gazzaniga）已经与托诺尼讨论了测量这种大脑每个一半球φ（phi）值的想法。他的研究表明，每个半球都保留着它自己的意识，而且另一半对此一无所知。IIT预言，每个单独半脑φ（phi）值应该比未分开的大脑的φ（phi）值更少。加扎尼加说：“让这个测量更加容易的想法是非常吸引人的”。
Once IIT is verified， phi could be used to identify people with consciousness disorders who have been misdiagnosed. For example， someone who is conscious but completely paralysed may be diagnosed as being in a minimally conscious state. Their high phi value would alert doctors to the mistake. Steven Laureys， a neurologist at the University of Liege in Belgium has worked with Tononi to find ways of calculating phi for his patients. He is excited that Tegmark is on board to share a physicist’s perspective on the project. “This is wonderful， this is what we need，” he says. “This is the problem for science—the origin of the universe and matter and how we are conscious in that universe.”
一旦IIT得到验证，φ（phi）的值就可以用来识别出那些被误诊的意识障碍患者。例如，也许会将一些有意识但完全麻痹之人的意识状诊断为最小值。他们的高φ（phi）值会警告医生的错误。比利时列日大学的一位神经学家史蒂文·劳雷(Steven Laureys)已经与托诺尼(Tononi)一起找到了计算他病人φ（phi）值的方法。令他激动的是，特德马克为这个项目共享一个物理学的观点。“非常美妙，这是我们需要的。”他说，“宇宙和物质的起源，以及我们在那个宇宙中的意识是怎样的。这是科学的问题所在”。
But Laureys cautions that IIT is a long way from solving the so-called hard problem of consciousness: explaining how the neural activity of a material brain gives rise to seemingly immaterial mental life. “Truly， nobody at present understands how we go from matter to mind，” he says.
但劳雷警告说，IIT离解决意识之难题还有很长一段的路：需要解释一个物质大脑的神经元活动如何产生了貌似非物质的心智生活。他说：“事实上，目前没有人能理解我们如何从物质走向了思维”。
Journal reference: pre-print，arxiv.org/abs/1601.02626
A shorter version of this article was published inNew Scientist magazineon 20 February 2016
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