No Switchbacks: Rethinking Aspiration-Based Dynamics in the Ultimatum Game

Aspiration-based evolutionary dynamics have recently been used to model the evolution of fair play in the ultimatum game showing that incredible threats to reject low offers persist in equilibrium. We focus on two extensions of this analysis: we experimentally test whether assumptions about agent motivations (aspiration levels) and the structure of the game (binary strategy space) reflect actual play, and we examine the problematic assumption embedded in the standard replicator dynamic that unhappy agents who switch strategies may return to a rejected strategy without exploring other options. We find that the resulting “no switchback” dynamic predicts the evolution of play better than the standard dynamic and that aspirations are a significant motivator for our participants. In the process, we also construct and analyze a variant of the ultimatum game in which players can adopt conditional (on their induced aspirations) strategies.     

Joint modeling of multivariate hearing thresholds measured longitudinally at multiple frequencies

Pure-tone thresholds are used to estimate hearing acuity and, when measured longitudinally, can characterize age-related changes in hearing. Measured at multiple-frequencies, multiple-irregular time points, for right and left ears, these longitudinal studies of age-related hearing loss produce data of inherent complexity due to: 1) multivariate outcomes at different frequencies; 2) longitudinal measurements taken at subject-specific time intervals; and 3) inter-ear correlations due to clustering and nesting. To address limitations in existing methods, we propose a multivariate generalized linear mixed model (mGLMM) and assess its performance. We demonstrate its application using a unique dataset from a cohort study of age-related hearing loss.     

Ensemble preconditioning for Markov chain Monte Carlo simulation

We describe parallel Markov chain Monte Carlo methods that propagate a collective ensemble of paths, with local covariance information calculated from neighbouring replicas. The use of collective dynamics eliminates multiplicative noise and stabilizes the dynamics, thus providing a practical approach to difficult anisotropic sampling problems in high dimensions. Numerical experiments with model problems demonstrate that dramatic potential speedups, compared to various alternative schemes, are attainable.     

The stress of driving: A diary study

A study of daily behaviours and feelings while driving was carried out with a sample of drivers to ascertain driving stress levels and changes in these as a function of time of day and day of the week. The analysis of responses to a specially designed diary/checklist showed that drivers experience more stress in the evening than in the morning, and in mid-week than either at the beginning or end of the week. Daily driving stress varies with age and experience as well as with health condition and sleep quality. It is also related to driving conditions and depends upon people's overall perception of driving as a stressful activity.     

A stakeholder perspective on process improvement behaviours: delivering the triple bottom line in SMEs

Abstract

The primary focus of operations management is to add value through operational processes. Considerable attention has been given to using process improvement (PI) techniques to reduce costs and time, in order to develop a competitive advantage for the wider organization. However, this narrow definition of value at times overlooks the triple bottom line (TBL) which can result in a number of unintended consequences, specifically issues related to environmental and social measures of performance. To address this, a stakeholder theory lens will be used to analyze PI activities within the context of small and medium-sized enterprises. The TBL will be used to complement the stakeholder perspective, to interpret the benefits that are realized from PI activities. This article highlights both the direct benefits from PI as well as more indirect benefits realized by involving a selection of salient stakeholders in PI. It will show how a developed view of PI can provide an important mechanism for delivering improvements to a firm’s TBL. The work concludes by highlighting the contributions made to both PI practice and stakeholder theory, while acknowledging the need for more research on PI, both from a stakeholder perspective and how it impacts a firm’s TBL.     

Gender differences in life expectancy free of impairment at older ages

This article uses data from the United Kingdom Medical Research Council Cognitive Function and Ageing study (MRC CFAS) to analyze morbidity associated with three areas of impairment. We use cognitive status, functional status, and physical illness to examine differences in the proportion of time that older women and men will spend with co-morbidity. We also analyze differences among various impairments, and investigate the relationship between missing data and sex. Women have a larger burden of impairment than men, and, by including cognitive impairment together with functional impairment, a very large impairment burden is highlighted at all ages. Policy implications of the findings from the perspective of older women in the United Kingdom are discussed.     

PROCEDURES FOR DETERMINING RELATIVE FREQUENCIES OF PRODUCTION/ORDER IN MULTISTAGE ASSEMBLY SYSTEMS*

We show that the problems of determination lot sizes in a multistage assembly system for the case of instantaneous production and constant demand for the end item can be reduced to the problems of determining relative frequenceis of production/order for items at each production stage. We further show that such frequencies are independent of the demand levels. Optimal and near-optimal solution procedures for this reduced problem are provided. The near-optimal procedure successively treats each stage of production as a final production stage while simulatenously incorporating decisions made at lower stages into decisions made at higher stages. Experimental results show that the near-optimal procedure results in optimal solutions 75 percent of the time and performs considerably better than representative heuristics available in the literature. Further, its performance is relatively less susceptible to product/structural characteristics of the system.