Popper's Theory of the Searchlight: A Historical Assessment of Its Significance

On the basis of a correspondence between Karl Popper and the Dutch psychologist Adriaan de Groot, it is argued that the former's epistemology of the searchlight is historically rooted in early cognitive psychology of Otto Selz. It is furthermore argued that Popper's later critique of information processing psychology is the fruit of his assimilation of Selz's evolutionarily inspired program. In light of the current interest in evolutionary approaches to the mind, it is argued that this Popper—Selz program is as actual as ever.

In my recent book Popper, Otto Selz and the Rise of Evolutionary Epistemology (ter Hark 2004), I have attempted both to trace the origins of Popper's epistem-ology of the searchlight back to early German psychology, in particular the work of Otto Selz, and to point out the way the work of the latter diverges from the mainstream psychology at the time including the programme of the closely related Würzburger School of psychology. As I also pointed out in my book, and as has been mentioned by others as well, Otto Selz played a formative role in the rise of cognitive science in the early 1950s of the last century in the USA, notably the work of later Nobel laureates Allen Newell and Herbert A. Simon. A mediating role here has been played by the Dutch psychologist and methodologist Adriaan de Groot, who was the first to apply Selz's ideas to the thinking processes of chess masters, and whose book Het Denken van den Schaker (de Groot 1946) was studied by Newell and Simon, in the original language, in 1954, a year before the revolution started. In 1965, an English translation of de Groot's book, On Thought and Chess appeared. As some of the new footnotes make clear, de Groot in his turn has been influenced by the American reception of Selz's ideas. For now, in the computational era, he claims that thought processes, as analyzed by Selz in the pre- computational era, might be simulated by a machine-program. As the further development of cognitive science has shown, the idea of so-called strong artificial intelligence, vigorously defended by Simon by means of his notion of a physical symbol system having the necessary and sufficient means for general intelligent action, has come increasingly under attack (Simon 1996). More and more, the idea of physical symbol systems has made place for an evolutionary or biological approach to the study of intelligence.

As was pointed out in the final chapter of my book, the evolutionary approach to intelligence has been a pervasive feature of Selz's work, even neglected by de Groot. But not by young Popper. In his work on epistemology and the mind—body problem from the 1960s onwards, the evolutionary approach is again a dominating feature. From this perspective Popper's correspondence with de Groot is particularly interesting. My point of departure in this chapter is a particular letter in which they discuss the significance of Selz both for methodology and psychology, as well as the approach taken by Newell and Simon. What is illustrated by this letter is not only that there has been a typical European approach to the study of cognition, different from the American approach, but also that young Popper showed precocious awareness of the lasting significance of one of the most important contributors to this European tradition.