limitations of our cognitive system? Or are errors indispensable parts of every intelligent system? From the first perspective, all errors are at best unnecessary and at worst harmful. Consider an error commonly made by children. When asked to find the sum of 1/2 and 1/3. the answer is often 2/5. This is called the freshman error of adding numerators and adding denominators {Silver. 1986). But ...

and Vagners (1971, 1972) expressed this phenomenon elegantly by introducing the concept of "terminal mode" for the optimum grain size to which a mineral can be reduced, given the force and energy typically available in the glacial environment. Thus, hard, uncleaved or poorly cleaved minerals such as quartz, fcldspar, garnet, pyrite and magnetite dominate either the medium or the fine sand fract...

A symbol is a pattern (of physical marks, electromagnetic energy, etc.) which denotes, designates, or otherwise has meaning. The notion that intelligence requires the use and manipulation of symbols, and that humans are therefore symbol systems, has been extremely in uential in arti cial intelligence. keywords: symbol, reasoning, intelligence, representation, logic This article has two parts. W...

Introduction No other European gull has shown such a dramatic and rapid change of distribution in the last decades as the Mediterranean Gull Larus melanocephalus. Whereas in the 1940s breeding locations were restricted to coastal areas of the Black Sea in the Ukraine, Mediterranean Gulls can now be found nesting in many places scattered over Europe, in locations as near to Scotland as the Nethe...