The hunter-gatherer hypothesis of Silverman and Eals (1992) is the best-supported evolutionary explanation for sex differences in human spatial cognitive skills. It proposes that the sex differences in performance on a range of spatial task are a consequence of males (who hunted much more than did females) being better adapted to encode space allocentrically, and to rely on Euclidian navigational strategies employing distant landmarks, whereas females (who gathered much more than did males) are better adapted to encode space more egocentrically, navigating based more on local landmarks, and to be better able to precisely encode the position of particular objects. We tested this hypothesis by comparing the performance of male and female participants in a virtual navigation task (in which we could manipulate the landmark information available), a virtual dead-reckoning task and an object location memory task. The patterns of sex differences in the spatial tasks were strongly supportive of the hunter-gatherer hypothesis, but the sex-specific correlations between tasks thought to be underpinned by the same spatial-cognitive ability were not always supportive of the hypothesis, suggesting that the hunter-gatherer hypothesis requires some revisions or extensions.
Following the methodology established byPrice, this paper analyzes the empirical evidence of citation matrices. Using the data cleaned and tabulated by Computer Horizons, Inc. from the Science Citation Index data banks, it is shown that the non-diagonal elements of the square citation matrices can be accounted for very satisfactorily by assigning each nation a characteristic output and input coefficient in each field measured; the ratio of these coefficients provides a measure of quality. Deviations from this simple model give measures of particular linkage strengths between nations showing some evidence of preferences and avoidances that exist for reason of language, social structure, etc. It is also shown that the diagonal data can be accounted for by the measurable phenomenon that each nation seems to publish partly for the international knowledge system and party for its own domestic purposes. Thus, three parameters and a cluster map can parsimoniously describe the citation data within the limits of random error.