4,350 research outputs found

    The Ecology and Evolution of Patience in Two New World Monkeys

    Get PDF
    Decision making often involves choosing between small, short-term rewards and large, long-term rewards. All animals, humans included, discount future rewards-the present value of delayed rewards is viewed as less than the value of immediate rewards. Despite its ubiquity, there exists considerable but unexplained variation between species in their capacity to wait for rewards-that is, to exert patience or self-control. Using two closely related primates-common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus)-we uncover a variable that may explain differences in how species discount future rewards. Both species faced a self-control paradigm in which individuals chose between taking an immediate small reward and waiting a variable amount of time for a large reward. Under these conditions, marmosets waited significantly longer for food than tamarins. This difference cannot be explained by life history, social behaviour or brain size. It can, however, be explained by feeding ecology: marmosets rely on gum, a food product acquired by waiting for exudate to flow from trees, whereas tamarins feed on insects, a food product requiring impulsive action. Foraging ecology, therefore, may provide a selective pressure for the evolution of self-control.Psycholog

    Global Climate Change, Food Security and the U.S. Food System

    Get PDF
    Climate change influences on the major pillars of food security. Each of the four elements of food security (availability,access,utilization,andstability) is vulnerable to changes in climate. For example,reductions in production related to regional drought influence food availability at multiple scales. Changes in price influences the ability of certain populations to purchase food (access). Utilization maybe affected when production zones shift, reducing the availability of preferred or culturally appropriate types of food within a region. Stability of the food supply may be highly uncertain given an increased incidence of extreme climatic events and their influence on production patterns

    A Novel Approach to Constrain the Escape Fraction and Dust Content at High Redshift Using the Cosmic Infrared Background Fractional Anisotropy

    Full text link
    The Cosmic Infrared Background (CIB) provides an opportunity to constrain many properties of the high redshift (z>6) stellar population as a whole. This background, specifically, from 1 to 200 microns, will contain any information about the era of reionization and the stars responsible for producing these ionizing photons. In this paper, we look at the fractional anisotropy delta I/I of this high redshift population, which is the ratio of the magnitude of the fluctuations (delta I) and the mean intensity (I). We show that this can be used to constrain the escape fraction of the population as a whole. The magnitude of the fluctuations of the CIB depend on the escape fraction, while the mean intensity does not. This results in lower values of the escape fraction producing higher values of the fractional anisotropy. This difference is predicted to be larger at the longer wavelengths bands (above 10 microns), albeit it is also much harder to observe in that range. We show that the fractional anisotropy can also be used to separate a dusty from a dust-free population. Finally, we discuss the constraints provided by current observations on the CIB fractional anisotropy.Comment: 8 pages, 4 figures, accepted to ApJ, some clarifications added, matches accepted versio

    The Child Guidance Center

    Get PDF
    The child guidance center is the most recent manifesta­tion of the interest in child welfare that has distinguished social thought in recent years. The close relationship of behavior and personality maladjustments to delinquency, crime, and insanity has made the guidance clinic a valuable agency for general social welfare. It is the purpose of this study to indicate to some degree the need for scientific child guidance, to show how child guidance centers have developed, how they are operating, and what they are trying to accomplish. This account is primarily descriptive of the typical workings of the more important clinics in the field, because these serve as models for most of the smaller centers. Sources of material have been for the most part the re­ ports and descriptions of those who are actively engaged in child guidance work. Additional information was obtained by investigation of available Milwaukee resources in child guid­ance
    corecore