The Illusion of Conscious Will (7 page)

Most of Bair’s experimental participants couldn’t wiggle their ears when asked, so he tried various tactics to help them along. The first was seeing whether giving a person an “idea of movement” would help. This involved sending a small electrical current through the retrahens muscle to make it contract artificially. The participant had an electrode pasted on the skin over the muscle, held another electrode in her hand (actually a big wet sponge—recall this was 1901), and then pressed a switch to complete the circuit and give the ear muscle a little shock. This created a fine wiggle, at least from Bair’s point of view, but the participants reported no sense that they were voluntarily wiggling their ears, just that they were voluntarily pushing a button that made their ears jerk involuntarily.

As it turns out, voluntary and involuntary ear wiggles are not even very similar. The involuntary movements were quick jerks, whereas voluntary movements tend to be slower and more fluid and graceful, a kind of ear ballet. Moreover, providing the “idea of movement” through involuntary ear jerks was useless for helping the participants to gain voluntary control over their ears. Bair instructed his subjects to try several things—just feeling the artificial movement sometimes, or trying to move in concert with the electric contraction, or straining against the contraction to get a sense of what it was doing—but none of this did much for their voluntary ear wiggles. Involuntary movement didn’t serve as a model for voluntary movement. If this
had
worked, we could all learn Beethoven piano sonatas by plugging our hands into hi-tech milking machines that would push our fingers in all the right directions repeatedly until we, too, had the “idea of movement” (perhaps the second movement of piano sonata, op. 13, “Pathétique”).

2
. It is also something a person can
not do
when asked not to do it. The ability to inhibit voluntary acts is so impressive that it is sometimes described as a hallmark of voluntary behavior (Kimble and Perlmuter 1970; Welch 1955). Inhibiting an involuntary act such as a hiccup is much more difficult.

The only thing that yielded eventual success for Bair’s would-be wigglers was a lengthy process of trying first to get the ears to wiggle voluntarily in
some
way—by lifting the brow violently, or by clenching the jaw. Some perhaps threw themselves to the ground. Then, over time, this movement of all the muscles in the area could be relaxed and the specific movement of the desired ear muscle could occur by itself. Although only about half the participants succeeded in the course of the experiment, those who did all followed this pattern. Bair went on to suggest that this might be how voluntary actions are developed as a rule. They seem to be winnowed from the more general movements our bodies do, selected and organized by practice.

Voluntary actions don’t just spring up from nowhere, then, but are learned, sometimes with great effort. Indeed, the notion that voluntary actions are modifiable through experiencing their consequences is a key facet of the definition of action rather than mere movement. In studies of action in animals, for instance, this is the main way in which voluntariness is identified (e.g., Passingham 1993). A nonhuman primate reaching for a banana might learn to reach differently depending on whether the banana is attained or not, and this malleability is the hallmark of apparent willfulness of action in all those creatures who can’t otherwise report on their sense of will. In human beings and other animals, actions that are not sensitive to rewards and punishments may be thought of as involuntary and normally are not believed to be subject to willful control.

What can be voluntary and what cannot is determined in part by the muscles, nerves, and brain systems underlying a particular behavior. A good example of this is facial expression. It is almost impossible to simulate voluntarily the involuntary facial expression associated with having someone pop a paper bag behind your head (Ekman, Friesen, and Simons 1985). To get the true “startle” expression, you just have to send someone behind you with a bag and then wait. Just as in the case of Bair’s electrically stimulated ear wiggles, even a voluntary eye blink differs in form and timing from an involuntary one (Kimble 1964). And, in general, the facial expressions people make in response to real emotional stimuli (a joke, a sad movie, a piano falling from above) differ from those made in the voluntary attempt to simulate the facial expressions. The nerve pathways for involuntary facial expressions don’t overlap those used for voluntary ones, and this makes the pattern and timing of facial muscle contractions for involuntary and voluntary expressions differ (Ekman and Friesen 1975; Matsumoto and Lee 1993; Rinn 1984).

The smiling muscles illustrate these effects very nicely. An involuntary smile will typically involve not only upturned corners of the mouth but also smiling eyes—the muscles in the upper face join in the action (Ekman, Davidson, and Friesen 1990). When the appropriate mouth and eye muscles are contracted together (
fig. 2.2
, left), observers judge the face to be truly smiling. People who are trying to fake a smile, on the other hand, often forget to scrunch their eyes in the corners and end up with a smile that looks painted on, like the smile (
fig. 2.2
, right) induced by electrical stimulation of just the mouth muscles.
³
Ekman (1985) re-ports that voluntarily faked smiles can also be more asymmetric than genuine ones (one eyebrow arched, for example) and are often much longer or shorter in duration than involuntary smiles as well. The sycophant who flashes you a grin in passing, for instance, or the beauty contestant who cements a smile in place for the whole pageant, is probably doing this voluntarily rather than having it simply happen.

Figure 2.2

A genuine smile (
left
) is contrasted with a smile induced by electrical stimulation of the mouth muscles (
right
). From Duchenne de Boulogne (1862). Courtesy Cambridge University Press.

Studies of people who have suffered certain kinds of nerve damage substantiate that different nerve pathways serve voluntary and involuntary facial expressions (Rinn 1984). Some patients show mimetic facial paralysis in which the facial muscles can be moved voluntarily but all spontaneous movement is lost. They don’t smile at something funny unless they do it on purpose. Other patients, in contrast, show involuntary laughing or weeping (often with only slight provocation) and cannot inhibit these responses voluntarily. Anatomical studies show that voluntary movements of the face arise in a part of the outer surface of the brain— the cortical motor area—whereas involuntary facial movements arise deeper in the brain, in the extrapyramidal motor system (Rinn 1984).

The ear wiggling and facial expression research, in sum, leads us to several preliminary observations about the nature of voluntary action. Not all actions can be performed voluntarily (witness all the poor folks who’ve tried to wiggle their ears and failed); voluntary actions may differ in form from those that are involuntary; voluntary actions appear to occur “on command” or “at will” in that they can be started or stopped by the doer; voluntary actions are malleable over time, capable of being transformed through learning; and voluntary actions occur through specific brain and nerve pathways that are sometimes anatomically distinct from pathways that serve involuntary movements. An action must be voluntary in order to be consciously willed. But, of course, we don’t know from just looking at voluntariness whether conscious will has been exerted. This still seems to be something the person needs to report.

3
. These photos are not particularly fetching representations of smiles, but they have some historical significance. Duchenne de Boulogne completed the first major studies of facial expression in 1862 using this man as a prime experimental participant. The man had a condition that left his face insensitive to pain, and so the muscles could be electrically stimulated to produce various expressions without creating discomfort.

Sensing Effort

Where does this report arise? If we look specifically at the voluntary pathways, it makes sense to try to find the will somewhere in the link between brain and muscles. Psychologists and physiologists long hoped to establish where exactly in the connection from brain to body and back again the feeling of effortful action might be found (Scheerer 1987). They presumed that the feeling of effort is the same as the sense of will, or at least that the two experiences are related (although this is certainly arguable; see Ginet 1986). Does the feeling of moving a finger, for example, arise as the brain sends an impulse along the efferent or motor nerves to the finger, or does the feeling arise when the muscle sends a return impulse along the afferent or sensory nerves back to the brain?

The basic question is, At what point in this sequence does consciousness experience the action? The premovement brain signal of action has variously been called
efference copy
(to suggest that the brain makes a copy of the instruction it sends to create the muscle effect and then delivers this to consciousness; von Holst 1954) or
corollary discharge
(to suggest that there is merely some spillover of this information; Sperry 1950), or sometimes just the
sense of effort
(Merton 1964; 1972). Studies both classic and contemporary have focused on whether we know our acts through one of these premovement brain processes, or whether we sense them through afference after they have happened by feeling our muscles move via
muscle sense
. The researchers studying this experience often seem to have believed that the sensation of effort is exactly the same thing as the experience of will, and so they examined the sensation earnestly and deeply.

Much study and thought has been devoted to the sense of effort that seems to be involved in the intriguing case of eye movement. When one moves the eyes normally, the visual world is seen as unchanged despite the fact that the image of that world on the retina is in fact moving about. However, when the eye is moved passively, the visual world seems to move. Tapping on the eyelid with your eye open, for example, makes your eye jump about a bit, and the world you see with that eye jumps about as well. This suggests that in the intentional movement of the eye, there is some sensation of the effort of eye movement that can then be used by the brain to adjust its perception of the visual world for the movement. A kind of internal feedback or cancellation of the intentional action seems to be necessary to create this phenomenon. Isolating the pathways of such feedback has preoccupied a generation of physiologists.

The issue has been sufficiently baffling, however, to inspire one researcher to have an operation performed on his own big toe to see if tension on a muscle tendon all by itself is perceptible (it is; the researcher was the senior author of McCloskey, Cross et al. 1983). Much of the research in this area is meticulously grisly because it depends on carefully ruling out a variety of sources of sensation (by the anesthetization of skin or joints, for example) before people are asked to judge their degree of effort in various tasks. This is necessary because people can get feedback about their movement not just through muscle discharges but also through nerves in the skin and bones (not to mention by looking). The issue is still not resolved, but the best guess at this time is that both kinds of sensation exist—sensation of the motor command from the brain
and
sensation of the muscle moving—and that both can contribute to the sense of effort we experience in performing muscle movement (Gandevia, 1987; Jeannerod 1997; Jones 1988; Matthews 1982; McCloskey 1978; Roland 1978).

The most striking cases relevant to muscle sense involve people with no muscle sense at all. In extremely rare instances, apparently because of unidentified viral infections, people have lost the return sensations from their muscles while at the same time retaining their ability to send commands to those muscles. Jonathan Cole (1995; Cole and Paillard 1995) re-ports on one such man, Ian Waterman, and his profound action problems. Struck by a mysterious illness at the age of nineteen that stopped his muscle sensations below the neck, Waterman first simply slumped into a heap, unable to control even moving an arm or sitting up. He had to watch all his actions to see what effect they were having, and if he didn’t pay rapt attention at all times, the act would fail. If he looked away toward one arm he was trying to move, the other arm might flail about. Even sitting still was a challenge. If he didn’t watch his hands, they could float away. And if he lost concentration as he was sitting, he could easily fall over.

Although Waterman learned to walk after prodigious effort over many months, he had to look down at his limbs all the time to guide his movements, and he remained uncomfortable walking with people or in unpredictable environments because any unanticipated bump could throw him to the ground. Without the ability to sense his movements, he also couldn’t make adjustments that people make quite automatically to catch themselves before they fall. Walking in close quarters was out of the question, as any jostling could yield a spill. Even the most minor issues had to be thought out in detail—for example, he needed to remember to shift his body backward slightly whenever he extended his arm, so that the weight of his outstretched arm would not make him fall forward. Apparently, the ability to send signals to the muscles without learning anything back from them creates havoc.