The Abative Effect: A New Term to Describe the Action of Antecedents that Reduce Operant Responding

The Analysis of Verbal Behavior - Behavior-analytic terminology concerning the so-called inhibitory effect of operant antecedents lacks precision. The present paper describes the problem with...     

Woody vegetation and canopy fragmentation along a forest-to-urban gradient

To identify patterns that can be used to predict vegetation and landscape characteristics in urban environments, we surveyed the species composition and size of woody plants, as well as the landscape structure of forest canopies, along a forest-to-urban gradient near Oxford, Ohio, USA. The gradient included six sites of increasingly urban land-use: a preserve, a recreational area, a golf course, a residential subdivision, apartment complexes, and a business district. We recorded species identity and stem diameter for all woody plants greater than 3 cm diameter at breast height (DBH) to examine the distribution of individual species as well as overall community composition. We used digitized aerial photographs to compare the spatial characteristics of the forest canopy at each site. We found predictable patterns in species diversity (Shannon index), spatial heterogeneity in species composition (mean percent dissimilarity), and all measures of patch fragmentation (canopy cover and patch number and size). There were clear differences in tree density and total basal area between forested sites and developed sites, but there was little resolution among developed sites. Species richness and average DBH showed no clear pattern, suggesting that landscaping preference largely determined these values. We present a modified version of an intermediate heterogeneity model that can be used to predict diversity patterns in urban areas. We discuss probable mechanisms that led to these patterns and the potential implications for animal communities in urban environments.     

The dangers posed by saddle points, and other problems, when using central composite designs

This paper discusses two problems, which can occur when using central composite designs (CCDs), that are not generally covered in the literature but can lead to wrong decisions-and therefore incorrect models-if they are ignored. Most industrialbased experimental designs are sequential. This usually involves running as few initial tests as possible, while getting enough information as is needed to provide a reasonable approximation to reality (the screening stage). The CCD design strategy generally requires the running of a full or fractional factorial design (the cube or hypercube) with one or more additional centre points. The cube is augmented, if deemed necessary, by additional experiments known as star-points. The major problems highlighted here concern the decision to run the star points or not. If the difference between the average response at the centre of the design and the average of the cube results is significant, there is probably a need for one or more quadratic terms in the predictive model. If not, then a simpler model that includes only main effects and interactions is usually considered sufficient. This test for 'curvature' in a main effect will often fail if the design space contains or surrounds a saddle-point. Such a point may disguise the need for a quadratic term. This paper describes the occurrence of a real saddle-point from an industrial project and how this was overcome. The second problem occurs because the cube and star point portions of a CCD are sometimes run as orthogonal blocks. Indeed, theory would suggest that this is the correct procedure. However in the industrial context, where minimizing the total number of tests is at a premium, this can lead to designs with star points a long way from the cube. In such a situation, were the curvature test to be found non-significant, we could end with a model that predicted well within the cube portion of the design space but that would be unreliable in the balance of the total area of investigation. The paper discusses just such a design, one that disguised the real need for a quadratic term.     

Estimating Increment-Decrement Life Tables with Multiple Covariates from Panel Data: The Case of Active Life Expectancy*

A fundamental limitation of current multistate life table methodology-evident in recent estimates of active life expectancy for the elderly-is the inability to estimate tables from data on small longitudinal panels in the presence of multiple covariates (such as sex, race, and socioeconomic status). This paper presents an approach to such an estimation based on an isomorphism between the structure of the stochastic model underlying a conventional specification of the increment-decrement life table and that of Markov panel regression models for simple state spaces. We argue that Markov panel regression procedures can be used to provide smoothed or graduated group-specific estimates of transition probabilities that are more stable across short age intervals than those computed directly from sample data. We then join these estimates with increment-decrement life table methods to compute group-specific total, active, and dependent life expectancy estimates. To illustrate the methods, we describe an empirical application to the estimation of such life expectancies specific to sex, race, and education (years of school completed) for a longitudinal panel of elderly persons. We find that education extends both total life expectancy and active life expectancy. Education thus may serve as a powerful social protective mechanism delaying the onset of health problems at older ages.     

Population control and politics

At all times and places population and resources must be kept in balance with each other if a high, or at least acceptable, quality of life is to be maintained. Evidence is presented that thinkers and men and women of affairs have been aware of these necessities from time immemorial and that the ancients invented most of the basic concepts of modern population ecology, at leastin embryo. This task is a problem of social control, the central process in all societies. If society's controllers and their institutions are aware, intelligent, flexible, and suitably motivated, there is no reason why most problems of population, development, and pollution should not be solved and then kept permanently in check. This must involve politics, there is no way out. As Aristotle pointed out, "Man is a political animal," and it is only through politicking that we can set up, maintain, change, and generally operate our social control systems. Deeply dysfunctional attitudes towards freedom and control—especially population control—are described and analysedvia a ten-stage argument, and helpful proposals put forward. The function which scientists in general and social scientists in particular can perform in helping human-kind to solve its complex and manifold problems is heavily stressed. Scientists in general should not become politicians, but politicians in general should become numerate and "ecolate"—to quote Garrett Hardin, and start to think more deeply and longer-term. To focus practical thinking the concepts "survival-theory" and the "principle of minimum innovation" are set forth and a final plea made for the necessity and therefore moral legitimacy of controlling numbers as well as resources. If population control seems slow in returning—it used to be the norm—recent events in Eastern Europe give good grounds for optimism about the fluidity of both human values and political institutions.     

Auditory status and experiences of abuse among college students

Studies that explore experiences of abuse among deaf or hard of hearing college students are sparse and usually focus on lifetime experiences rather than the college years. A random sample of more than 1,000 college students at a campus in Upstate New York provided the data for this study. An institute for the deaf or hard of hearing was one of the colleges at the university and provided a unique opportunity to explore experiences among this demographic. Victimization rates and experiences by auditory status--deaf and hard of hearing or hearing--were examined. Binomial regression analyses were employed and findings indicated a significant association with being deaf or hard of hearing and physical and psychological abuse at the hands of a partner. Implications for policy and future research are discussed.     

Relative Risk Aversion: What Do We Know?

The relative risk aversion measure that represents the risk preferences of a decision maker depends on the outcome variable that is used as the argument of the utility function, and on the way that outcome variable is defined or measured. In addition, the relationship between any two such relative risk aversion measures is determined by the relationship between the corresponding outcome variables. These well-known facts are used to adjust several reported estimates of relative risk aversion so that those estimates can be directly compared with one another. After adjustment, the significant variation in the reported relative risk aversion measures for representative decision makers is substantially reduced. JEL Classification: D81