自由意志是虛幻還是真實？
在你察覺自己做出決定之前，腦中的神經細胞就先幫你出主意了？
在受試者察覺到自己的意圖之前，大腦就已經做出決定。從本質上來說，無意識的大腦活動才是真正的決策者。
【重點提要】
■神經科學、哲學以及更廣泛的公共議題，有一個主要的問題：大家對於「人們擁有自由意志」的這個假設，是否在本質上有所誤解？若真如此，社會所依循的許多法律以及道德規範，都將面臨挑戰。
■關於自由意志是否存在的疑慮，來自於近幾十年來一些設計巧妙的實驗所得到的結果：在我們察覺到自己的某些決定之前，大腦已產生相關運作活動。若此為真，自由意志的角色何在？
■人們所擁有的自由意志可能低於自己的認知，但這並不表示完全沒有自由意志。最近有一些社會心理學實驗顯示，有意識的推理和意圖會對我們的行為產生明顯影響。
2014年秋天的某個夜晚，我躺著思索該如何寫這篇文章。我設想了各種可行的開場白與接下來的句子，接著又推敲如何串連這些句子與後續的段落。各種選項的優缺點在我腦中縈繞，令我無法入眠。在這些思索的過程中，我腦中的神經細胞也強烈活化著。的確，神經活動可解釋為什麼我想到了這些選項、為什麼我正寫下這些文字，同時也可解釋為什麼我有自由意志。
越來越多神經科學家、心理學家以及一些學者專家認為我是錯的。在許多廣為引用的論文支持下，他們主張無意識的訊息處理過程決定了我最後選擇的文字。他們認為，無意識的神經活動已經先決定了我們的行為，然後我們的意識思維與決策才跟著出現；由於「大腦已經幫我們決定了」（幫我們選擇了某個選項），所以自由意志只是幻象。
最常引用的實驗是已故的神經生理學家利貝特（Benjamin Libet）在1980年代於美國加州大學聖地牙哥分校所做的一連串研究，他要求頭上戴有電極的受試者在任何他們想要的時刻移動手腕。結果發現，大約在受試者動手之前的1/2秒，就可以偵測到名為「準備電位」（readiness potential）的電訊號活動；而受試者察覺到自己想要動手，其時間點大約是在動手前的1/4秒。因此，在受試者察覺到自己的意圖之前，大腦就已經做出決定。從本質上來說，無意識的大腦活動才是真正的決策者。
最近的功能性磁共振造影（fMRI）顯示，無意識決定的時間點似乎發生得更早。德國柏林柏恩斯坦計算神經科學中心的海恩斯（John-Dylan Haynes）與同事在2013年發表了一項研究，他們要求受試者自行決定要把兩個數字相加或相減，fMRI的研究結果發現，在受試者察覺到自己做出決定的四秒前，透過神經活動的反應模式就可預測他們即將選擇加法或減法（四秒的時間差距算是相當久）。
的確，這些研究（以及其他相關發現）導致許多人一面倒地宣稱：自由意志已死！海恩斯在《新科學家》雜誌評論道：「在意識介入之前，我們的選擇早就已經在無意識中被決定了。大腦似乎比人們更早做出決定。」其他人也有類似的看法，例如，演化生物學家柯尼（Jerry Coyne）認為：「我們所有的選擇都不是出自於自身有意識的自由決定。我們無法自主決策，也沒有自由意志。」根據這些發現，神經科學家哈里斯（Sam Harris）也做出結論，認為我們只是「生化傀儡」：「如果我們可以透過腦部掃描，在人們察覺到自己的決定前就先偵測到他們的選擇，那麼人們宣稱可以用意識控制自己的內在心智，將會直接受到挑戰。」
Sam Harris on "Free Will"：從frre will無法在宇宙取得一致性的論證，嘗試說服frre will is an illusion(比幻象更糟的是：frre will是an incoherent idea)，促使大家重新思考對於道德、宗教等議題。
SAM HARRIS IS THE AUTHOR of the New Work Times bestsellers, The Moral Landscape, The End of Faith and Letter to a Christian Nation. His new book is short (96) pages, to the point, and will change the way we all view free will, as Oliver Sacks wrote: "Brilliant and witty — and never less than incisive — Free Will shows that Sam Harris can say more in 13,000 words than most people do in 100,000." UCSD neuroscientist V.S, Ramachandran notes: "In this elegant and provocative book, Sam Harris demonstrates — with great intellectual ferocity and panache — that free will is an inherently flawed and incoherent concept, even in subjective terms. If he is right, the book will radically change the way we view ourselves as human beings."
但是，這些研究真的顯示出我們的意識思維和計畫只是無意識大腦活動的副產物，而且完全無法影響我們的行為嗎？
不，絕非如此。基於許多理由，我( Eddy Nahmias )和弗羅里達州立大學的哲學家梅勒（Alfred R. Mele）等人則認為：堅稱自由意志只是幻象的說法是誤導了大家。
Does Contemporary Neuroscience Support or Challenge the Reality of Free Will?
“All the world’s a stage, and all the men and women merely players.” — Shakespeare
Humans love stories. We tell each other the stories of our lives, in which we are not merely players reading a script but also the authors. As authors we make choices that influence the plot and the other players on the stage. Free will can be understood as our capacities both to make choices—to write our own stories—and to carry them out on the world’s stage—to control our actions in light of our choices.
What would it mean to lack free will? It might mean we are merely puppets, our strings pulled by forces beyond our awareness and beyond our control. It might mean we are players who merely act out a script we do not author. Or perhaps we think we make up our stories, but in fact we do so only after we’ve already acted them out. The central image in each case is that we merely observe what happens, rather than making a difference to what happens.
人，不過是個生化魁儡。
How might neuroscience fit into the story I am telling? Most scientists who discuss free will say the story has an unhappy ending—that neuroscience shows free will to be an illusion. I call these scientists “willusionists.” (意志幻象學者Willusionists include Sam Harris, Jerry Coyne, Jonathan Bargh, Daniel Wegner, John Dylan Haynes, and as suggested briefly in some of their work, Stephen Hawking and Richard Dawkins.) Willusionists say that neuroscience demonstrates that we are not the authors of our own stories but more like puppets whose actions are determined by brain events beyond our control. In his new book Free Will, Sam Harris says, “This [neuroscientific] understanding reveals you to be a biochemical puppet.” Jerry Coyne asserts in a USAToday column: “The ineluctable scientific conclusion is that although we feel that we’re characters in the play of our lives, rewriting our parts as we go along, in reality we’re puppets performing scripted parts written by the laws of physics.”
There are several ways willusionists reach their conclusion that we lack free will. The first begins by defining free will in a dubious way. Most willusionists’ assume that,
by definition, free will requires a supernatural power of non-physical minds or souls: it’s only possible if we are somehow offstage, beyond the causal interactions of the natural world, yet also somehow able to pull the strings of our bodies nonetheless.(For example,Read Montague.)
意志幻象學者的定義上：自由意志要來自非物性的心靈超神經傳導的力量。然後，基於此定義而做出討站自由意志的結論
It’s a mysterious picture, and one that willusionists simply assert is the ordinary understanding of free will. Based on this definition of free will, they then conclude that neuroscience challenges free will, since it replaces a non-physical mind or soul with a physical brain.
But there is no reason to define free will as requiring this dualist picture (然而，並無理由需將自由意志定義在物性與靈性兼備的基礎上). Among philosophers, very few develop theories of free will that conflict with a naturalistic understanding of the mind—free will requires choice and control, and for some philosophers, indeterminism, but it does not require dualism. Furthermore, studies on ordinary people’s understanding of free will show that, while many people believe we have souls, most do not believe that free will requires a non-physical soul. And when presented scenarios about persons whose decisions are fully caused by earlier events, or even fully predictable by brain events, most people respond that they still have free will and are morally responsible. These studies strongly suggest that what people primarily associate with free will and moral responsibility is the capacity to make conscious decisions and to control one’s actions in light of such decisions.
But willusionists also argue that neuroscience challenges free will by challenging this role for consciousness in decision-making and action. Research by Benjamin Libet, and more recently by neuroscientists such as John Dylan Haynes, suggests that activity in the brain regularly precedes behavior—no surprise there!—but also precedes our conscious awareness of making a decision to move. For instance, in one study neural activity measured by fMRI provided information about which of two buttons people would push up to 7-10 seconds before they were aware of deciding which to push.
If such early brain activity always completely determines what we do before our conscious thinking ever comes into the picture, then this would suggest we lack free will, because our conscious thinking would happen too late to influence what we did—an audience rather than author. But the data does not show that brain activity occurringprior to awareness completely causes all of our decisions. In the study just described, the early brain activity correlates with behavior at only 10% above chance. It is not surprising that our brains prepare for action ahead of time and that this provides some information about what people will do.
Of course, improved brain imaging technology will likely provide increasingly precise predictions of future behavior. But here’s my prediction: the more complex the decisions and behavior, the more likely such predictions will be based on information about the very neural processes that are the basis of conscious deliberation and decision-making.
Once we assume that all mental processes have neural correlates, then whether consciousness plays a role in our complex behavior turns on whether the neural correlates of conscious processes occur at the right time and place to influence behavior. It’s unlikely that the neural processes involved in complex deliberations, planning, and self-control play no role in behavior. Instead, there is evidence that conscious and rational thinking can play an important causal role in complex behavior. If we give up the mysterious picture of our conscious selves being offstage, then we can give up the threatening image of our brains pulling the strings while we helplessly watch.
One reason it is easy to move from the assumption that neural processes cause behavior to the presumption that consciousness does nothing is that neuroscience still lacks a theory to explain how certain types of brain processes are the basis of conscious or rational mental processes. Without such a story in place, it is easy to assume that neuroscientific explanations supersede and bypass explanations in terms of conscious and rational processes. But that conclusion is unwarranted. Explanations in organic chemistry do not explain away life; they explain life. A more complete scientific theory of the mind will have to explain how consciousness and rationality work, rather than explaining them away. As it does, we will come to understand how and when we have the capacities for conscious and rational choice, and for self-control, that people ordinarily associate with free will. These are the capacities to reflect on our desires and reasons, to consider which of them we want to motivate us, and to make efforts to act accordingly—or as Roy Baumeister explained in his recent post, to habituate ourselves to make choices that accord with our reflectively endorsed goals.
By understanding how the most complex thing in the universe—the human brain—works, we can better understand our capacities to make choices and to control our actions accordingly. On this telling of the tale, neuroscience can help to explain how free will works rather than explaining it away.
Now, if one insists that free will requires that we have an impossible ability to make choices beyond the influence of anything, including our own brains—or to make choices for no reason at all—then you will be disappointed by the story I am telling. Here, willusionists like Sam Harris and I agree that we cannot have what is impossible. Our choices do not arise from nothing any more than an author’s stories arise from nothing, but our choices do influence the way our stories unfold.
Nonetheless, fascinating research suggests that our conscious reasoning and planning isnot pulling the strings as much as we tend to believe. We are subject to biases and influences beyond our awareness, and we sometimes confabulate or rationalize our behavior. But our stories are not always fiction. Other research suggests that our deliberations and decisions can have significant causal influences on what we decide and do, especially when we have difficult decisions to make and when we make complex plans for future action.
Free will is not all-or-nothing. It involves capacities that we develop as we mature, but that have limitations. Recognizing that people have differing degrees of free will can help us better determine when, and to what extent, people are responsible for their actions, and are deserving of praise or blame. Indeed, where it really matters—legal responsibility—it is most useful to understand free will as a set of capacities for reasoning and self-control which people possess to varying degrees and have varying opportunities to exercise.
In this respect, neuroscience and other sciences of the mind can play an important role by providing new insights into our capacities for rationality and self-control, as well as their limitations. We do not write our stories from scratch, but within the context of a complicated world of influences and interactions, our tales are not “full of sound and fury, signifying nothing.”
Questions for the discussion:
【出處】http://sa.ylib.com/MagCont.aspx?Unit=featurearticles&id=2657
