Computer models of the acquisition of cognitive skills build on a long and progressive tradition of research. Since 1979, a wide range of psychologically plausible mechanisms for learning during skill practice have been implemented in computational models. This repertoire of mechanisms goes a long way towards answering the questions implied by Fitts’ (1964) division of practice into three phases: How does skill practice get started? How is a partially learned skill improved during practice? How does a skill change as practice is extended beyond mastery? Nine distinct modes of learning are identified. Each can be implemented in several different ways. The majority of models explain the speed-up of task completion that occurs during practice. There are fewer attempts to model the origin, consequences, and ultimate elimination of errors.

Life is change. Natural forces continuously knead our material environment as if it were so much dough in the cosmic bakery, and few features of our social environment remain constant for even one generation. How do human beings live in ubiquitous change? How do we cope with, and adapt to changes in our environment? How do we initiate change and create novelty? Due to late 20th-century advances in the natural sciences, these questions are more difficult to answer than they once seemed.

Few changes are so beguiling to children, poets and whomever else has the good sense to stop and look as a change of season. In four-season climes, the visual transformation of the landscape as the dominant color moves from green to red and on to white is stunning. The spectacle of an early autumn snowstorm must have overwhelmed the first band of hunter-gatherers to push north into a temperate climate zone and convinced them that their world was coming to an end.

Yet, children, poets and hunter-gatherers are wrong; striking as it is, seasonal change is no change. Winter displaces summer, true enough; but after winter, summer returns, and all is as it was. The change is cyclic, hence stable; hence not a change.

Western culture recognizes three fields of activity as particularly devoted to the exercise of originality. Artists aim to create original works, scientists seek to discover previously unknown phenomena and technologists strive to invent new devices and techniques. The three verbs create, discover and invent jointly triangulate the application of mind to the production of novelty.

Novelties are diverse in character and consequence. In 1935, when war in Europe seemed unavoidable, Arnold F. Wilkins, a junior scientific officer of the British National Physical Laboratory, was asked by his superior, superintendent Robert Watson Watt, to calculate whether radio waves could be emitted with enough force and precision to boil the blood of the pilot of an approaching enemy aircraft. Watson Watt had in turn been asked this question by a member of the Committee for the Scientific Study of Air Defence. When Wilkins's calculations showed that this death ray concept was not workable, his superior asked how radio technology could be used to defend Britain instead. In a momentous act of inspiration, Wilkins proposed that perhaps we can detect enemy air planes at a distance by bouncing radio waves off them. Calculations showed that a detection device, unlike the death ray, could work. Five years later, when the bombers of the German Luftwaffe attacked, a string of radar stations along Britain's east coast gave the British Royal Air Force (RAF) advance warning of their approach.

On March 18, 1965, the Soviet astronaut Alexei Leonov exited from the airlock on the Voskhod 2 space shuttle and floated in orbit above the Earth for 20 minutes. This was the first space walk and the endpoint of a process that started approximately 200,000 years ago, when members of Homo sapiens migrated out of Africa and into what we now call the Fertile Crescent. The move out of Africa was the beginning of the colonization of Earth by humans. By the middle of the 20th century, the ocean depths and outer space were the only habitats as yet uninhabited.

In the course of this giant dispersal, human beings colonized environments so different from one another that they might as well have been on different planets. South of the Fertile Crescent lies what we now call the Arabian Peninsula, sand dune upon sand dune promising nothing but dehydration and heat stroke between here and the horizon. Yet the ancestors of the Arabs lived successfully there, figuring out how to tame the bad-tempered camel, protect themselves against the sun with layers of cloth and locate what little water there was.

The founders of cognitive science found it useful to remind everybody that no benevolent deity has issued psychologists an insurance against complexity. They implied that if the mind is complex, then we should expect theories of mind to reflect that complexity. H. A. Simon and A. Newell wrote that their “… theory posits internal mechanisms of great extent and complexity.… That is all there is to it.” The three micro-theories of creativity, adaptation and conversion proposed in this book conform to this expectation. In each case, the behavioral phenomenon that the theory was designed to explain can be described in one or two paragraphs, but its explanation requires a chapter-length exposition. If the ultimate theory of cognition is a conjunction of many such micro-theories, then that theory is complex indeed.

But the founders might have taken their realism a shade too naively. Scientific theories are human constructions and they are shaped as much by our ambitions, desires and needs as by the reality they explain. Scientists strive for concise principles because they cannot think effectively with complex ones, due to the very limits on cognitive processing that the founders themselves did so much to reveal.

If the deep learning thesis is at least approximately correct, our cognitive processes not only endow us with cognitive mechanisms for learning new knowledge and skills but also allow us to override what we have learned. The three micro-theories of creativity, adaptation and conversion describe cognitive mechanisms that accomplish this. It would be foolish to claim that the micro-theories are exactly accurate. Further research will no doubt force revisions. However, there is no reason to expect the fundamental principle that knowledge is, and must be, defeasible to be contradicted by future research. This feature of cognition is grounded in the ceaseless turbulence of the material and social worlds and in our evolutionary strategy of relying more on acquired skills than on innate behaviors.

The consequence is that we sometimes succeed by projecting the past onto the current situation, but at other times we do better if we override prior experience and generate a novel response to the situation at hand.

An inventor, scientist or artist might work on one and the same project for a day, a week, a month, a year or many years. The thought processes associated with such extended activities are not equally creative throughout. Even when the work results in a creative product, much of what occurs along the way is analytical thinking or even habitual or routine behavior. What distinguishes creative from analytical processes is that the former are punctuated by insights, mental events in which new ideas come to mind. An extended project is likely to require more than one insight before completion. Projects vary with respect to the density of insight events, but each such event is of short duration compared to the duration of the project as a whole. I call this the Raisins in the Dough Principle.

To explain creativity is therefore to carry out three theoretical tasks: Describe analytical thinking, explain what happens in moments of insight and clarify how insight expands the power of analytical thinking.

To someone standing on the African savannah, walking across a field in the Fertile Crescent or riding across the North American prairie, the evidence of the senses is unequivocal: The Earth is flat. There are local perturbations – valleys and mountains – but they cancel each other over long distances, so the Earth extends in all directions in the horizontal plane. Although it is difficult to prove anything about the beliefs of pre-historic peoples, it would be surprising if they conceived of the Earth in any other way. But the flat Earth generates puzzles: How far does it extend? Does it have an edge? If so, what is beyond the edge? If the ocean extends all the way to the edge, what happens with the water? If it pours over the edge, must not the ocean empty out eventually? Where does the water go? To anyone with the disposition and the opportunity to consider such questions, the lack of intelligible answers must have generated doubt. People living by the sea could make two observations that point to a different conception: Looking out from a high observation point, an observer sees the horizon curve ever so slightly. When a ship approaches, the mast appears over the horizon before the hull.

The theme of this book is that human beings possess cognitive processes that enable them to override the imperatives of past experience and to act and think in novel ways, and that these processes differ from the types of cognitive processes usually envisioned in psychological theories of learning. The capability for what I call deep learning – or, more precisely, non-monotonic cognitive change – constitutes a distinct aspect of mind that follows its own laws and hence requires its own theory. The book develops this theme by summarizing and extending prior research by me and others with respect to three specific types of non-monotonic change: the creation of novelty; the adaptation of cognitive skills to changing circumstance; and the conversion from one belief to another, incompatible belief. The book offers novel theories of the mental processes operating in each of these three types of cognitive change, as well as a unified theory that captures the abstract principles that they share.

My interest in creativity, adaptation and conversion preceded my awareness that these topics are variations on a theme. As a graduate student at the University of Stockholm in the late 1970s, I tried to relate the Gestalt view of insight to the information-processing theory of problem solving proposed by A. Newell and H. A. Simon. My first attempt at such a synthesis was published in 1984, and over the years it morphed into the theory of insight in Chapter 4. I thank my Ph.D. advisor, Yvonne Waern, for her constant encouragement and strong support for this as well as other oddball activities, and for managing a weekly cognitive seminar where her students could argue about cognition.

A theory of change must be rooted in some initial conception of the thing that is changing, some working assumption, however incomplete and preliminary. This has been so in other sciences. Chemists had to describe material substances in terms of atoms and molecules before they could explain chemical reactions in terms of the rearrangement of atoms. The description of the double helix structure of DNA paved the way for a deeper understanding of genetic mutations and biological evolution, and the discovery that the crust of the Earth consists of continental plates floating on a molten core was a prerequisite for the plate tectonics theory of geological change. Likewise, the principles about the nature of mind set forth in this chapter serve as a backdrop for the study of cognitive change. They are not new, and they are not mine but represent a collective achievement of the cognitive sciences. Although the principles are unlikely to be entirely accurate, they constitute the best available framework for the study of deep learning. In a mature science, a chapter like this would be unnecessary, but as things stand, disagreements go deep, so a theorist needs to declare his intellectual commitments.

Beliefs can be expressed in discourse (I believe that …; In my opinion …), but they are consequential primarily because they guide action. Only someone who believes that the Earth is round would set sail for China by sailing west from Europe, and only someone who believes that a nuclear chain reaction is physically possible would try to build a nuclear power plant. In everyday life, mundane actions are guided by myriads of beliefs of smaller scope: If you believe that the movie starts at four o'clock, you will try to be at the theater shortly before that time. Beliefs can inhibit action as well as guide it. In the late 19th century, some argued that rockets could not work outside the Earth's atmosphere because the rocket exhaust would have nothing to push against. If this belief had persisted, people would presumably not have built rockets for space travel and there would have been no moon walks.

The outcomes of actions reflect back on the belief or belief system that guided those actions. There can be no better way to become convinced that the Earth is round than by circumnavigating it. The success of the action, the triumphant homecoming, increases confidence in the relevant belief.