Spatial representation for navigation in animats

This article considers the problem of spatial representation for animat navigation systems. It is proposed that the global navigation task, or "wayfinding, " is best supported by multiple interacting subsystems, each of which builds its own partial representation of relevant world knowledge. Evidence from the study of animal navigation is reviewed to demonstrate that similar principles underlie the wayfinding behavior of animals, including humans. A simulated wayfinding system is described that embodies and illustrates several of the themes identified with animat navigation. This system constructs a network of partial models of the quantitative spatial relations between groups of salient landmarks. Navigation tasks are solved by propagating egocentric view information through this network, using a simple but effective heuristic to arbitrate between multiple solutions

Household composition choices of older unmarried women

This article extends previous research on the household composition of older unmarried women, using a statistical model that treats each of a woman’s surviving children as a distinct potential provider of a shared household. Additional possibilities— living alone, living with other nuclear-family relatives, and living with others— are also recognized, providing a varied range of household-structure opportunities for older women. The approach allows us to identify individual child attributes associated with the propensity to coreside with the older unmarried mother. The results confirm earlier findings regarding the importance of income, age, and disability status as determinants of the household composition of older women. We find, however, that unmarried children, especially sons, are more likely to share a household with an elderly mother than are married children. Working reduces the likelihood that a married daughter will live with her older mother. Overall, the findings suggest that the attributes, more so than the sheer numbers, of living children influence the household structure of their mothers

VULNERABILITY AND ENVIRONMENTAL STRESS OF OLDER ADULTS IN DEPRIVED NEIGHBOURHOODS IN THE NETHERLANDS

Recent policy rests on the assumption that it is better for older people to live independently within the community for as long as possible. A related assumption is that the local community forms a supportive context for vulnerable older people; the environment can compensate the limitations resulting from growing old. However, Lawton's 'environmental docility hypothesis', in which the interaction between characteristics of the environment and a person's competence is described, forms a reason to be more careful with this assumption. In a survey of 1,939 Dutch older adults carried out in 2002-2003 this hypothesis is explored for older people living in deprived and non-deprived neighbourhoods. The results of the analysis seem to be in line with Lawton's hypothesis. In non-deprived neighbourhoods, no differences in environmental stress are found between vulnerable and non-vulnerable older adults, while in deprived neighbourhoods vulnerable older adults experience significantly higher levels of environmental stress than non-vulnerable older adults. Copyright (c) 2008 by the Royal Dutch Geographical Society KNAG.