Among all the questions the human mind has come up with, some of the more intriguing are the questions about how the human mind itself works. What is knowledge, how do we know what we know, what are the limits to our knowledge, and how can we recognize them? For some, at least a partial answer to these questions lies in the evolution of the human brain.
Wolfgang Amadeus Mozart is known the world over as a musical genius, and was recognized as such even in his own day. The English journal, Philosophical Transactions, carried an article written by Daines Barrington in 1770, after he had personally tested young Wolfgang’s musical skills in reading, memory, and musical improvisation.
What especially intrigued Barrington was the nature of genius itself. How is it, he wondered, that this child could be so exceptional in one particular arena, and so normal a child in apparently every other way? Not only did Mozart look like a child, but …whilst he was playing to me (Barrington wrote, a favorite cat came in, upon which he immediately left his harpsichord, nor could we bring him back for a considerable time. He would also sometimes run about the room with a stick between his legs (playing horse.
When asked to write a song of love, and a song of rage, Mozart astonished Barrington with passion he had trouble attributing to an eightyear-old boy, with presumably limited experience of such passions.
Barrington reasoned that the fundamental emotions in our behavioral storehouses are dissociable and that our totality must be an amalgam of separable components. Such a splintering of skills is also evident sometimes in severely handicapped people, and we are all familiar with people who can reckon the day of the week for any date over centuries in their head. This suggests that we must construct our understanding of the world from separate modules, and this principle of dissociation may be a key to the nature of the evolution of intelligence.
This was not the view of Georges Cuvier, who in 1812 argued his principle of “the correlation of parts,” the theory that all features of an organism are intricately designed and coordinated to function in a certain optimal way. No part, he argued, can change by itself and any conceivable alteration in one organ would require the redesign of every other feature, for optimal function requires complete integration: Every organized individual forms an entire system of its own, all the parts of which mutually correspond and concur to produce a certain definite purpose, by reciprocal reaction, or by combining toward the same end. Hence none of these separate parts can change their forms without a corresponding change in the other parts of the same animal, and consequently each of these parts, taken separately, indicates all the other parts to which it belonged.
Cuvier used this principle primarily to argue that he could reconstruct entire organisms from fossil fragments, because one bone implied a necessary shape for all others. But Cuvier had a Second, even grander motive — the denial of evolution. How can transmutation occur if parts cannot alter separately, or at least with some degree of independence? If each tiny modification requires a redesign of absolutely every other feature, then inertia itself must prevent evolution. Cuvier continued: Animals have certain fixed and natural characters, which resist the effects of every kind of influence, whether proceeding from natural causes or human interference; and we have not the smallest reason to suspect that time has any more effect upon them than climate.
The logic of this argument is impeccable. If parts are not dissociable, then evolution cannot occur. But although Cuvier’s logic was correct, his premise of total integrity was false. Evolution proceeds, in fact, by dissociating complex systems into parts, or modules made of a few correlated features, and by altering the various units at differing rates and times. Biologists refer to this principle as mosaic evolution, and we need look no further for an illustration than the history of our own species. Our human ancestors, we now know, evolved an upright posture of nearly modern design before any substantial enlargement of the brain had occurred.
This fundamental principle of dissociability works just as well for the mental complexities of emotions and intelligence as for designs of entire bodies. As he began to compile the notes that would lead to his evolutionary theory, Charles Darwin recognized that he could not give an evolutionary account of human emotions without the principles of modularity and dissociation.
He wished, for example, to trace facial gestures to antecedent states in ancestral animals. But if the human complement forms an integrated array, locked together by our unique consciousness, then a historical origin from simpler systems becomes impossible. Darwin recognized that two principles must underlie the possibility of evolution. First, gestures cannot be subject to fully conscious control; some, at least, must represent automatic, evolved responses. As evidence for ancestral states, Darwin cited several gestures that make no sense without modern morphology, but must have served our ancestors well. In sneering, we tighten our upper lips and raise them in the region of our canine teeth. This motion once exposed the fighting weapons of our ancestors, but human canines are no bigger than our other teeth and this inherited reaction has lost its original function.
Second, just as young Mozart could separate and abstract single emotions, Darwin realized that standard facial gestures must be modules of largely independent action and that the human emotional repertoire must be more like the separate items in a shopper’s bag than the facets of an unbreakable totality. Evolution can mix, match, and modify independently. Otherwise we face Cuvier’s dilemma: if all emotions are inextricably bound by their status as interacting, optimal expressions, then how can anything ever change?
Many experiments with animals affirm and extend the principle of modularity. Newborn gulls, for example, peck vigorously at their parents’ beak, apparently aiming for a red spot near the tip. If an infant makes proper contact, the parent brings up a parcel of food and the baby gull gets its first meal.
But what inspires the pecking behavior? The baby gull has no conscious understanding of a reward to be gained. It has never eaten before and cannot know that a knock on a parents bill will provide. The behavior must be innate and unlearned.
At what, then, does the baby bird direct its pecks? At first consideration, one might entertain that the entire form of the parent would provide an optimal target. After all, what could be more appealing than the parent’s totality — a full, three-dimensional image with the right movements and odors? But consider the issue a bit more deeply; the hatchling has never seen a bird. Can the complexities of the entire parental form be planted innately upon its untested brain? Wouldn’t the goal be more readily achieved — easier to program if you will if the hatchling responded to one or a few abstract particulars, that is, to modules extracted from the total form?
As a result of extensive research on gulls, we now know that hatchling gulls do respond to modules and abstractions. They peck preferentially at long and skinny objects, red things, and regions of markedly contrasting colors. As an effect of this simplified modularity, they hit the spot at the tip of the parental bill the only red region at the end of a long object, in an area of contrasting color with surrounding yellow. Complex totality may be beyond the cognitive capacity of a hatchling gull, but any rich object can be broken down to simpler components and then built up. Any developing complexity — whether in the cognitive growth of an individual or the evolution of a lineage — may require this principle of construction from modules.
The concept of modularity lies at the heart of much innovative research in cognitive science. The brain does a great deal of work by complex coordination among its parts, but we have also known for a long time that highly particular attitudes and behaviors map to specific portions of the brain. Barrington’s study of Mozart and the modern scientific research on the behavior of newborn gulls may seem at first sight to have little in common. However, although we may read it to learn more about the life of a man revered for his contribution to the world of art, the illustration of modularity evidenced both in Mozart’s own behavior and in his ability to separate and abstract single emotions is an important contribution to our understanding of the human mind.
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