attached to them; a codelet may form new associations, break down old ones, or generate more codelets. A "temperature" is associated to the present state of the cytoplasm; it determines how probable it is that a destructive codelet is executed. There is a "freezing" temperature at which no destruction can occur anymore: a solution has been found. Chapter 3: Numbo: A Study in Cognition and Recognition Numbo is a program by Daniel Defays that tries to solve numerical problems similar to those used in the French game "Le compte est bon". The game consists in combining some numbers called "bricks", using the operations of multiplication, addition, and subtraction, to obtain a given result. The program is modeled on Jumbo and Copycat and uses a permanent network of known mathematical facts, a working memory in the form of a cytoplasm, and a coderack containing codelets to produce free associations of bricks in order to arrive at the result. Chapter 4: Highlevel Perception, Representation, and Analogy The chapter subtitle A Critique of Artificial-intelligence Methodology indicates that this is a polemical article, in which David Chalmers, Robert French, and Hofstadter criticize most of the research going on at that time (the early '80s) as exaggerating results and missing the central features of human intelligence. Some of these AI projects, like the structure mapping engine (SME), claimed to model high faculties of the human mind and to be able to understand literary analogies and to rediscover important scientific breakthroughs. In the introduction, Hofstadter warns about the Eliza effect that leads people to attribute understanding to a computer program that only uses a few stock phrases. The authors claim that the input data for such impressive results are already heavily structured in the direction of the intended discovery and only a simple matching task is left to the computer. Their main claim is that it is impossible to model high-level cognition without at the same time modeling low-level perception. While cognition is necessarily based on perception, they argue that it in turn influences perception itself. Therefore, a sound AI project should try to model the two together. In a slogan repeated several times throughout the book: cognition is recognition. Since human perception is too complex to be modelled by available technology, they favor the restriction of AI projects to limited domains like the one used for the Copycat project. Chapter 5: The Copycat Project This