John Holland

American computer scientist and psychologist at the University of Michigan, the founder of genetic algorithmsgenetic algorithm, n.: A problem-solving method that copies natural evolution: many candidate solutions compete, the best are 'bred' by mixing and randomly tweaking them, and over many generations the solutions improve.. After working on the logical design of IBM's first commercial computer, he earned one of the earliest US doctorates in computer science (Michigan, 1959). In the 1960s he and his students developed methods that evolve populations of candidate solutions, encoded as strings, through selection, crossover and mutation, and his 'Adaptation in Natural and Artificial Systems' (1975) gave them a theory, including the schema theorem, and analyzed adaptation as a balance between exploration and exploitationexploration–exploitation trade-off, n.: The choice between trying something new that might turn out better and sticking with what already works — like picking a familiar restaurant versus testing a new one.. He also invented learning classifier systems, rule-based agents whose bucket-brigade algorithm passes credit back along chains of rules, a precursor of temporal difference learningtemporal difference learning, n.: A way of learning predictions by adjusting each guess toward the next, slightly better-informed guess instead of waiting for the final outcome — like revising a weather forecast every day as the date approaches. for the credit assignment problemcredit assignment problem, n.: The puzzle of figuring out which of many earlier decisions, or which parts of a system, deserve the credit or blame for a final outcome — like working out which moves won a chess game.. A founding figure of complexity science at the Santa Fe Institute, he wrote 'Hidden Order' (1995) and 'Emergence' (1998). He received a MacArthur Fellowship (1992).