= I I I I I • • , In: Cognitive Penetrability of Perception Editor: Athanassios Raftopoulos, pp. 31-47 ISBN 1-59033-991-6 © 2005 Nova Science Publishers, Inc. Chapter 3 TOP-DoWN AND BOTTOM-UP INFLUENCES ON OBSERVATION: EVIDENCE FROM COGNITIVE PSYCHOLOGY AND THE HISTORY OF SCIENCE William F. Brewer and Lester Loschky Department of Psychology, University of Illinois at Urbana-Champaign The hypothesis that theories might influence observation was proposed in the important early work of Hanson (1958) and Kuhn (1962). It has been brought to a new focus by the interchanges between Fodor (1984, 1988) and Churchland (1979, 1988). Fodor has argued that perception is not cognitively penetrable, while Churchland has argued for a strong form of theory-Iadenness. This issue has led to very heated debate in the philosophy of science because many scholars have felt that if observation is theory-laden there can be no neutral observation data, and this leads to epistemological relativism. We wish to criticize two assumptions that have been made in this debate. OVEREMPHASIS OF THE ROLE OF VISUAL PERCEPTION First, we think that the emphasis on visual perception and scientific observation reflects a narrowing of focus that began in philosophy with the British Empiricists, became very strong with the work of the Logical Positivists, continued undiminished with the anti-Positivist work of Kuhn and Hanson, and remains strong today in the debate between Fodor and Churchland. Several scholars have recently pointed out that data in modem science are typically not based on the perceptual experience of the scientist. Bogen and Woodward (1992) provide a very powerful analysis of the types of information used in scientific practice and conclude that, "It is data rather than perceptual beliefs that playa central evidential role in science and data are typically not descriptions of perceptual appearances or reports of perceptual belief at all" (p. 599). And Fodor (1991), with typical flair, has dramatically undercut the relevance of