Abstract

mong the several findings deriving from the application of complex network formalism to the investigation of natural phenomena, the fact that linguistic constructions follow power laws presents special interest for its potential implications for psychology and brain science. By corresponding to one of the most essentially human manifestations, such language-related properties suggest that similar dynamics may also be inherent to the brain areas related to language and associative memory, and perhaps even consciousness. The present work reports a preliminary experimental investigation aimed at characterizing and modeling the flow of sequentially induced associations between words from the English language in terms of complex networks. The data is produced through a psychophysical experiment where a word is presented to the subject, who is requested to associate another word. Complex network and graph theory formalism and measurements are applied in order to characterize the experimental data. Several interesting results are identified, including the characterization of attraction basins, association asymmetries, context biasing, as well as a possible power-law underlying word associations, which could be explained by the appearance of strange loops along the hierarchical structure underlying word categories. Comment: 5 pages, 6 figures, 3 table Document type: Preprint

Abstract

Much of our knowledge of the course of animal and plant evolution is based on shape. Recognition, description, arrangement, rearrangement, organization, reorganization, and interpretation of shape are the prime working tools of the paleontologist, the life blood of the systematist, the raw material of the evolutionist, and the dilemma of the developmental biologist. Keith Thomson's book, Morphogenesis and Evolution, deals with how shape changes both in ontogeny and in phylogeny. Morphogenesis is the study of the development of shape over an individual lifetime; evolution includes changes in shape throughout phylogeny. The development of form has been treated as a separate discipline since the German Naturphilosophie of Oken (1779-1851) and His (183 1-1904) and has been linked to phylogeny since von Baer (1792-1876). For Darwin, morphology was the soul of natural history (Darwin, 1910 p. 358), development and embryology, "one of the most important subjects in the whole round of natural history" (Darwin, 1910 p. 363). Mayr (1982 p. 468) believes that "evolutionary morphology" did not arise until the 1950's, with the distinction between function and role and the exploration of preadaptation, multiple functions, and multiple pathways. An integrated treatment of"morphogenesis and evolution" or, better, of morphogenesis as an evolutionary process therefore addresses, or should address, key questions in development, in evolution, and in the consequences of the one for the other. In developmental biology, and certainly in general treatises on animal development (of which the second edition of Scott Gilbert's [19881 Developmental Biology is the best currently available), morphogenesis is normally treated alongside differentiation (specialization of the parts of the embryo). This is not because morphogenesis and differentiation always proceed handin-hand, for even when they occur contemporaneously in space and time, each may be under separate and independent developmental control (see Maclean and Hall, 1987), but because the two, along with growth, constitute the triad of developmental processes. Morphogenesis normally occurs alongside cellular differentiation in growing tissues or organs. Differentiating cells often change shape as they grow (either by