On the spread of semantic excitation

Summary Access to word-representations in memory was studied in two experiments. A lexical decision paradigm was used in both: Ss had to decide whether a string of letters shown to them was a word or a nonword. Decision time was the main dependent variable. Independent variables were context-similarity and context-intensity. The former is defined in terms of the categorical relationship that holds between a set of context-words and a subsequently presented test-word. The latter is defined by the number of highly related context-words, all sampled from a small semantic subcategory, that preceded the test-stimulus. In theory, the presentation of the context-words generates semantic excitation that spreads over memory and activates other memory representations. Differences in mean decision time, as a function of experimental conditions, are attributed to differences in the activation of test-words. Two hypotheses about the course or gradient of excitation-spread in lexical memory were studied. The results indicate that a simple spread-of-excitation hypothesis as proposed by Meyer, Schvaneveldt and Ruddy (1972, 1974) is sufficient to account for the data. For the conditions studied in the experiments, there was no reliable evidence of inhibitory processes that confine spread of excitation to a small region of lexical memory.This paper reports work that was conceived and begun at Stanford University, Calif., USA, where the author spent a year as a postdoctoral fellow. The fellowship was made possible by the Deutsche Forschungsgemeinschaft, Bad Godesberg, West Germany, Grant Schm 350/1. I thank Prof. Richard G. Atkinson and Dr. Stephan Monsell for discussing aspects of this work with me. I further thank Paul Matthews for introducing me to the art of running computerized experiments.