人类可以仅凭思想沟通吗?一个多世纪以来，心灵感应问题一直使科学界意见不一，直至今天依然在学界精英中引发着激烈的争论。

Can human beings communicate by thought alone? For more than a century the issue of telepathy has divided the scientific community, and even today is still sparks bitter controversy among top academics.

上世纪70年代以来，世界各地顶尖高校和科研院所的超心理学家冒着遭受那些持怀疑态度的同事们嘲笑的危险，将关于心灵感应的各种断言假说放入几十个严谨的科学研究中进行试验。试验的结果及其启示甚至将发现该结果的研究者们也分成了几派。

一些研究者认为试验结果构成令人信服的证据，表明心灵感应是真实存在的。其他超心理学家则认为该学科曾试图提出明确的科学论证，但却失败了，因此正处于瓦解的边缘。不过，怀疑者和倡导者却在一个问题上达成共识：即迄今为止令人印象最为深刻的证据出自所谓的“ganzfeld”(超感官知觉全域测试)实验中，这一德文术语的意思是“整个领域”。人类在冥想状态下的心灵感应体验报告使超心理学家怀疑心灵感应可能包含人与人之间传递的“信号”。这种信号十分微弱，以至于往往被正常的大脑活动所淹没。如此说来，这种信号可能更容易被那些沉浸于冥想般宁静中的人检测到。他们所处的“整个领域”有着令人放松的灯光，怡人的声音和温暖的环境。

Since the 1970s, parapsychologists at leading universities and research institutes around the world have risk the derision of sceptical colleagues by putting the various claims for telepathy to the test in dozens of rigorous scientific studies. The results and their implications are dividing even the researchers who uncovered them.

超感官知觉全域测试试图重新营造这些条件，让参与者坐在一个封闭房间里的柔软躺椅上，听着令人放松的声音，用特殊滤光器将参与者的眼睛蒙住，使他们只能看见柔和的粉红色光线。在早期的超感官知觉全域测试实验中，心灵感应测试包括识别从大型图片库中随机选择的四张图片中的其中一张。试验的想法是有一个人作为“发送者”，尝试把图像发送给在封闭房间中休息的“接收者”。传递过程结束时，接收者需要回答四张图片中的哪一张是刚刚使用过的。随机猜测的命中率是25％，但如果心灵感应是真实存在的，命中率应该更高。1982年，此项研究的先驱者之一，英国超心理学家Charles Honorton对第一批超感官知觉全域测试研究结果进行了分析。研究结果显示了高于30％的典型命中率。虽然效果不甚明显，但统计测试显示不能将它归因于偶然。

其言下之意是超感官知觉全域测试方法揭示了心灵感应的真实证据。但这种说法有一个关键的漏洞——一个在较传统的科学领域经常被忽视的问题。仅仅由于这种解释排除了偶然因素并不能证明心灵感应一定存在；通过很多其他的方法也能获得积极结果。这些可能性既包括“感官泄漏”，即与图片有关的线索意外地传给了接收者，也包括彻底的欺诈。作为回应，研究者们发表了一份综述，总结了1985年以前进行的所有超感官知觉全域测试研究，以表明80％的研究都发现了有统计意义的证据。但他们也同意目前实验中尚有太多的问题可能导致积极的结果，他们还草拟了一份清单，要求为今后的研究设立新的标准。

Some researchers say the results constitute compelling evidence that telepathy is genuine. Other parapsychologists believe the field is on the brink of collapse, having tried to produce definitive scientific proof and failed. Sceptics and advocates alike do concur on one issue, however: that the most impressive evidence so far has come from the so-called 'ganzfeld' experiments, a German term that means 'whole field'. Reports of telepathic experiences had by people during meditation led parapsychologists to suspect that telepathy might involve 'signals' passing between people that were so faint that they were usually swamped by normal brain activity. In this case, such signals might be more easily detected by those experiencing meditation-like tranquility in a relaxing 'whole field' of light, sound and warmth.

此后，许多研究人员转向了自动超感官知觉全域测试，这是一种技术的自动化变体，也就是使用电脑完成许多关键任务，如随机选择图像。通过最大限度地减少人为参与，这一想法是要将有缺陷的结果最小化。1987年，Honorton使用“荟萃分析”，即从一系列研究中寻找整体结果的统计技术，对上百次的自动超感官知觉全域测试结果进行了研究。结果虽然没有以往引人注目，却仍然令人印象深刻。

然而，一些超心理学家仍然为单个超感官知觉全域测试研究之间缺乏一致性感到烦恼。心灵感应捍卫者指出，要求每一项研究都提供令人印象深刻的证据忽略了一个基本的统计事实：检测这些微小影响需要大量的样本支持。如果像目前研究结果表明的那样，心灵感应的命中率仅仅略高于概率预测的25％，涉及40人左右的典型超感官知觉全域测试也不太可能检测得到：试验群体根本不够大。只有当大量研究结合在一个荟萃分析之中，心灵感应的微弱信号才会真正明显起来。而这似乎正是研究者们所发现的。

The ganzfeld experiment tries to recreate these conditions with participants sitting in soft reclining chairs in a sealed room, listening to relaxing sounds while their eyes are covered with special filters letting in only pink light. In early ganzfeld experiments, the telepathy test involved identification of a picture chosen from a random selection of four taken from a large image bank. The idea was that a person acting as a 'sender' would attempt to beam the image over to the 'receiver' relaxing in the sealed room. Once the session was over, this person was asked to identify which of the four images had been used. Random guessing would give a hit-rate of 25 per cent; if telepathy is real, however, the hit-rate would be higher. In 1982, the results from the first ganzfeld studies were analysed by one of its pioneers, the American parapsychologist Charles Honorton. They pointed to typical hit-rates of better than 30 per cent – a small effect, but one which statistical tests suggested could not be put down to chance.

然而，他们肯定当然不会发现主流科学家们的态度有任何变化：大部分人仍然完全排斥心灵感应的观点。至少一部分问题在于心灵感应缺乏合理的机制。

各种理论都被提了出来，很多以理论物理学的深奥思想为重点。其中包括“量子纠缠”：无论两组原子间距离多么遥远，影响一组原子的事件都会立即影响另一组原子。虽然物理学家们用专门准备的原子演示了“纠缠”，但这一现象是否同样存在于构成人类头脑的原子中却无人知晓。对于这些问题的回答将改变超心理学。这使得一些研究人员认为该学科的未来不在于收集更多心灵感应的证据，而在与探索其可能的机制。一些工作已经开始进行，研究人员试图识别在自动超感官知觉全域测试中特别成功的被试者。早期的结果表明有创造力和艺术性的人们的表现要远远高于平均水平：在爱丁堡大学的一次研究中，音乐家的测试命中率高达56％。或许更多诸如此类的测试最终将为研究人员提供他们正在寻求的证据，巩固加强心灵感应存在的依据。

The implication was that the ganzfeld method had revealed real evidence for telepathy. But there was a crucial flaw in this argument- one routinely overlooked in more conventional areas of science. Just because chance had been ruled out as an explanation did not prove telepathy must exist; there were many other ways of getting positive results. These ranged from 'sensory leakage'—where clues about the pictures accidentally reach the receiver – to outright fraud. In response, the researchers issued a review of all the ganzfeld studies done up to 1985 to show that 80 per cent had found statistically significant evidence. However, they also agreed that there were still too many problems in the experiments which could lead to positive results, and that drew up a list demanding new standards for future research.

After this, many researchers switched to autoganzfeld tests – an automated variant of the technique which used computers to perform many of the key tasks such as the random selection of images. By minimising human involvement, the idea was to minimise the risk of flawed results. In 1987, results from hundreds of autoganzfeld tests were studied by Honorton in a 'meta-analysis', a statistical technique for finding the overall results from a set of studies. Though less compelling than before, the outcome was still impressive.

Yet some parapsychologists remain disturbed by the lack of consistency between individual ganzfeld studies. Defenders of telepathy point out that demanding impressive evidence from every study ignores one basic statistical fact: it takes large samples to detect small effects. If, as current results suggest, telepathy produces hit-rates only marginally above the 25 per cent expected by chance, it's unlikely to be detected by a typical ganzfeld study involving around 40 people: the group is just not big enough. Only when many studies are combined in a meta-analysis will the faint signal of telepathy really become apparent. And that is what researchers do seem to be finding.

What they are certainly not finding, however, is any change in attitude of mainstream scientists: most still totally reject the very idea of telepathy. The problem stems at least in part from the lack of any plausible mechanism for telepathy.

Various theories have been put forward, many focusing on esoteric ideas from theoretical physics. They include 'quantum entanglement', in which events affecting one group of atoms instantly affect another group, no matter how far apart they may be. While physicists have demonstrated entanglement with specially prepared atoms, no-one knows if it also exists between atoms making up human minds. Answering such questions would transform parapsychology. This has promoted some researchers to argue that the future lies not in collecting more evidence for telepathy, but in probing possible mechanisms. Some work has begun already, with researchers trying to identify people who are particularly successful in autoganzfeld trials. Early results show that creative and artistic people do much better than average: in one study at the University of Edinburgh, musicians achieved a hit-rate of 56 per cent. Perhaps more tests like these will eventually give the researchers the evidence they are seeking and strengthen the case for the existence of telepathy.