Each historical era is marked by a small number of questions that recruit intense curiosity. One such question in 2013 asks how any psychological phenomenon emerges from brain activity. This query could not have ascended to prominence until elegant machines that could measure brains were invented over the past 30 years. Most neuroscientists are confident that one day they will be able to predict and explain all mental events and actions from knowledge of a person’s brain activity milliseconds earlier. I remember an evening about 12 years ago when I asked an eminent neuroscientist whether he could, with complete knowledge of my brain at that moment, know that I was thinking of crawling under the table at which we were sitting. To my surprise he answered affirmatively.
Nature is full of examples of novel properties emerging from elements that do not possess them. A collection of iron atoms can be shaped into a wheel, knife, or frying pan. The functions of these objects—rolling, slicing, and cooking food—honor principles and are described with words that do not apply to iron atoms. The terms used to describe a tornado—width, height, and speed—do not apply to the air and water molecules that are its constituents. Similarly, perceiving a dogwood tree in bloom, remembering a dream in which the dreamer is drowned, and feeling tired after a day’s work are emergent events that, although derived from brain activity, cannot be described in sentences that contain only words for brains, neurons, molecules, and the neural patterns they generate.
Mathematicians understand that a concept used in two distinctive domains can be logically consistent within each domain, but inconsistent if used with the same meaning in both domains. The concept of infinity is one example. The concept of time in Newton’s writings is inconsistent with the meaning of time in Einstein’s theory of relativity. Analogously, many concepts that are semantically consistent within the writings of neuroscientists and psychologists are inconsistent when applied to both domains. The concepts fear, anger, consciousness, regulate, compute, evaluate, select, mature, and number sense have a consistent meaning within neuroscience and within psychology, but do not have the same meaning in both domains.
I have read many books by neuroscientists trying to make the leap from certain facts about the brain to the fuzzier phenomena of psychology. The authors of these books adopted a similar strategy. Most of the prose summarized what has been learned about the sense organs and select motor systems. The final chapters argued that these facts, when added to new ones to be discovered, would eventually account for all psychological events. But the authors failed to compose the sentences that would explain how this victory might be attained. They asked readers to accept their bold conclusion on faith. When these authors wrote that collections of neurons represent a child’s perception of a red ball rolling on a carpet they seem to think they have explained how the brain allowed the child to perceive this event. A collection of air and water molecules represents the elements of a tornado, but that sentence does not explain how a tornado emerges from the collection. Specifying the constituents of a phenomenon does not explain how the phenomenon emerges.
The natural scientist’s reflexive distrust of psychological processes that cannot be seen or measured with accuracy makes it easy for them to treat thoughts and interpretations as epiphenomena that one day will be explained and understood as due to neurons that can be seen and measured. I often have the feeling while reading the papers written by neuroscientists that they regard a person’s thoughts as politically incorrect obscenities that must never be acknowledged explicitly. A research team at the University of Denver provides an example. These investigators found that adults whose childhoods were spent in poverty showed a pattern of brain activity when regulating their emotions that differed from the pattern displayed by adults who grew up in more advantaged families. Rather than conclude that the different thoughts of those raised in poverty or affluence provided the most reasonable explanation of the evidence, these investigators declared that the adult brain profile represented the earlier state of being poor or affluent. This position is odd in light of the fact that a person’s expectation that a pill, injection, or ointment will alleviate pain or distress usually activates one or more of the brain’s neurochemical systems which, in turn, alters brain sites and mutes the distress, even when the pill, injection, or ointment is a placebo with no active ingredients. Simply anticipating a pleasant outcome generates relevant changes in the brain. Some biologists had claimed that sugar enhances a person’s self-control through the direct action of glucose on the brain. Carol Dweck and colleagues revealed the flaw in that assumption by showing that the effect of glucose on attention and control of impulsive decisions depended on the person’s belief about the nature of self -control. Adults who believed that their ability to exercise willpower was an unlimited resource showed no improved attention or control of impulsivity after drinking a liquid containing sugar. Only those who believed that willpower had a limited capacity showed better self-control when they ingested sugar . The person’s belief about the properties of willpower, not the effects of glucose on the brain, was the critical determinant of quality of performance on a cognitive task.
Several obstacles frustrate those who believe that all mental events will eventually be described in sentences whose words refer only to the activity of neurons and their circuits. The different vocabularies for the bases of brain activity and psychological events represent one of the most serious problems. The vocabulary that describes the brain cannot at present replace the terms used to describe the perception of sadness in a friend’s face, remembering a childhood misdemeanor, anticipating a future birthday, understanding a metaphor, feeling nostalgic, planning to stand up, or playing the guitar. In addition, many psychological phenomena are controlled by the immediate social context , but the neuroscientist is limited to measuring the brain in the unusual context of the laboratory. The probability that an adolescent will bully a peer, overeat, or have unprotected sex is influenced by the local conditions at the moment a decision to act occurs. These conditions cannot be recreated in the laboratory where the brain measures are gathered. Thus, the biological evidence cannot fully explain the psychological events that occur in the settings in which persons live.
The modest predictability between brain activity and a psychological outcome is due, in large measure, to the fact that a cascade of brain events follows exposure to an event. For example, adults who see the face of an unfamiliar male with the eyes and the mouth wide open ( as in fear or surprise) are in brain state E (E for event). State E is imposed on the person’s usual brain state U ( for usual), which varies across persons. Oxytocin concentrations in the brain, for example, affect state U, and the brains of males and females react differently to the same concentration of oxytocin. State E is affected by the physical features of a stimulus independent of the meaning a person imposes. A face with the eyes fully open contains more contrast between the dark pupil and the white sclera than a face with a neutral expression and, as a result, enhances activity in several sites. Moreover, the neurons at a site called the fusiform area, which is typically responsive to faces, are tuned to respond to curved contours in the upper half of the perceptual field. The eyes are circular shapes located in the upper half of the face. State E is also affected by the person’s expectations. If the individual expects to see a face the brain areas that usually respond to faces will be active, even if no face is presented. Activity in the brains of those who expected to see an animal, but were presented with a face, would differ from the activity in the brains of those who expected and saw a face. Hence, the same conscious perception in two individuals can be preceded by different brain states.
Each adult’s associations to the face generate a third brain state A ( for associations), which are often different across individuals. For example, a man who had recently seen his wife display a fearful facial expression to a mouse will have unique associations to a female face with eyes and mouth wide open. A picture of a rowboat on a lake, which would be neutral for most adults, would provoke in my brain a rush of unique associations, accompanied by unique blood flow patterns, because I had a frightening experience in a rowboat on a lake when I was five years old.
The brain state that is most often measured in humans ( called F for final) is a pattern of blood flow to various sites recorded about six seconds after the event of interest appeared. The human brain detects a human face within the first quarter of a second, which is close to five seconds before the changes in blood flow are measured. In addition, state F is a product of the combination of states U, E, and A, which, readers will recall, are not the same in all persons. This fact makes it difficult to be certain of the thoughts or feelings that transpired before state F was recorded. If state F were preceded by the activation of five sites, each associated with a different psychological outcome, scientists examining state F could not be certain of the prior brain or psychological events.
Moreover, a different index of brain activity that relies on changes in the magnetic moments of active neurons or direct measurement of neurons often yields evidence that is inconsistent with the blood flow data. Scientists at Massachusetts Institute of Technology found only a modest relation between an estimate of brain activity based on the magnitude of blood flow to a site and a more accurate estimate based on direct recordings of neuronal activity in that region ( using electrodes). The correlation was roughly equivalent to the correlation between the height and weight of 1000 adults. Most adults who are six feet tall can possess a weight that ranges from 150 to 300 pounds. The evidence implies that the profile of activation inferred from blood flow evidence gathered under the unusual conditions existing in a laboratory may not resemble the pattern of brain activity displayed to the same event in the person’s usual setting. The neuroscientist’s frustration is exacerbated by the surprising discovery of dissimilar patterns of blood flow in a single person’s brain while doing the same task in each of 10 scanners in each of 10 different laboratories. This observation raises the possibility that a result found in one laboratory might not be repeated in a different laboratory.
Neuroscientists should be troubled by the observation that the patterns of blood flow in adults watching films of 1,705 different kinds of objects and actions failed to reveal any evidence suggesting that the adults were activating representations of the concepts good and bad. The psychological data indicate that humans are continually activating these concepts, albeit subtly and outside of consciousness, when exposed to pictures of objects or events. Scientists at Northeastern University measured the blood flow to a site, called the central gray, that is active when animals are threatened or experience pain. The adults saw sets of aversive as well as neutral pictures. Although the scenes depicting serious injuries to human bodies generated greater blood flow to the central gray than neutral pictures, surprisingly the adults who showed the largest increase in blood flow reported being the least aroused or upset by the pictures.
Many scientists studying the relation between brain and mind have been too admiring of an old fashioned physics that assumed certainty was possible. Too many investigators are copying the physicist’s premises and assume that the relation between biological and psychological phenomena can be described with equations as elegant as E = mc2.. The aping of physics by some biologists and social scientists is misguided because living forms have unique features denied to inanimate matter. The properties of oxygen have not changed over the past billion years; but the shapes and physiology of living organisms have changed over the same interval.
Yes, the brain is the foundation of all psychological phenomena, as the sun is the foundation of all life on earth. Evolutionary biologists accept the sun’s significance and proceed to fill in the details that might explain how the first living cells were formed without ever mentioning the sun. Neuroscientists have to do more than declare the obvious truth that thoughts and emotions originate in the brain. They have to explain how one pattern of brain activity led some humans to believe in a spiritual force and a second pattern led others to deny all metaphysical ideas.
Lines from Shakespeare’s “Measure for Measure” invite a little more humility among those who are certain that sometime in the future measures of a person’s brain will permit accurate prediction of his or her thoughts, emotions, and actions.
Man, proud man,
Drest in a little brief authority,
Most ignorant of what he’s most assur’d,
His glassy essence, like an angry ape,
Plays such fantastic tricks before high heaven,
As makes the angels weep.
A joke contains the same message. The rabbi of Krakow suddenly interrupted his sermon to tell the congregation that he had just had a vision that the rabbi of Warsaw had died moments earlier. The congregation was duly impressed with the rabbi’s remarkable powers. Several weeks later a few Krakow residents visiting Warsaw learned that the rabbi there was alive and reported this fact to their friends when they returned home. When some Krakow Jews began to snicker about the rabbi’s inaccurate prediction, his defenders answered the criticisms by noting that perhaps his prophecy was wrong, but it was a marvelous vision.