Comment: Boosting Algorithms: Regularization, Prediction and Model Fitting

The authors are doing the readers of Statistical Science a true service with a well-written and up-to-date overview of boosting that originated with the seminal algorithms of Freund and Schapire. Equally, we are grateful for high-level software that will permit a larger readership to experiment with, or simply apply, boosting-inspired model fitting. The authors show us a world of methodology that illustrates how a fundamental innovation can penetrate every nook and cranny of statistical thinking and practice. They introduce the reader to one particular interpretation of boosting and then give a display of its potential with extensions from classification (where it all started) to least squares, exponential family models, survival analysis, to base-learners other than trees such as smoothing splines, to degrees of freedom and regularization, and to fascinating recent work in model selection. The uninitiated reader will find that the authors did a nice job of presenting a certain coherent and useful interpretation of boosting. The other reader, though, who has watched the business of boosting for a while, may have quibbles with the authors over details of the historic record and, more importantly, over their optimism about the current state of theoretical knowledge. In fact, as much as ``the statistical view'' has proven fruitful, it has also resulted in some ideas about why boosting works that may be misconceived, and in some recommendations that may be misguided. [arXiv:0804.2752]Comment: Published in at http://dx.doi.org/10.1214/07-STS242B the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Implications of single-neuron gain scaling for information transmission in networks

Summary: 

Many neural systems are equipped with mechanisms to efficiently encode sensory information. To represent natural stimuli with time-varying statistical properties, neural systems should adjust their gain to the inputs' statistical distribution. Such matching of dynamic range to input statistics has been shown to maximize the information transmitted by the output spike trains (Brenner et al., 2000, Fairhall et al., 2001). Gain scaling has not only been observed as a system response property, but also in single neurons in developing somatosensory cortex stimulated with currents of different amplitude (Mease et al., 2010). While gain scaling holds for cortical neurons at the end of the first post-natal week, at birth these neurons lack this property. The observed improvement in gain scaling coincides with the disappearance of spontaneous waves of activity in cortex (Conheim et al., 2010).

We studied how single-neuron gain scaling affects the dynamics of signal transmission in networks, using the developing cortex as a model. In a one-layer feedforward network, we showed that the absence of gain control made the network relatively insensitive to uncorrelated local input fluctuations. As a result, these neurons selectively and synchronously responded to large slowly-varying correlated input--the slow build up of synaptic noise generated in pacemaker circuits which most likely triggers waves. Neurons in gain scaling networks were more sensitive to the small-scale input fluctuations, and responded asynchronously to the slow envelope. Thus, gain scaling both increases information in individual neurons about private inputs and allows the population average to encode the slow fluctuations in the input. Paradoxically, the synchronous firing that corresponds to wave propagation is associated with low information transfer. We therefore suggest that the emergence of gain scaling may help the system to increase information transmission on multiple timescales as sensory stimuli become important later in development. 

Methods:

Networks with one and two layers consisting of hundreds of model neurons were constructed. The ability of single neurons to gain scale was controlled by changing the ratio of sodium to potassium conductances in Hodgkin-Huxley neurons (Mainen et al., 1995). The response of single layer networks was studied with ramp-like stimuli with slopes that varied over several hundreds of milliseconds. Fast fluctuations were superimposed on this slowly-varying mean. Then the response to these networks was tested with continuous stimuli. Gain scaling networks captured the slow fluctuations in the inputs, while non-scaling networks simply thresholded the input. Quantifying information transmission confirmed that gain scaling neurons transmit more information about the stimulus. With the two-layer networks we simulated a cortical network where waves could spontaneously emerge, propagate and degrade, based on the gain scaling properties of the neurons in the network

Techniques and Forces and the Communicative Constitution of Organization: A Deleuzian Approach to Organizational (In)Stability and Power

This article introduces five principles of Deleuzian ontology and the conceptual framework of techniques and forces into emerging CCO scholarship addressing (dis)organization and power. By introducing Deleuzian concepts of (1) the virtual, (2) mutual (in)stability of meaning and materiality, (3) forces (and techniques), (4) communication, and (5) power, this essay builds a relational ontology that centers communication, speaks across existing theories of CCO, and offers a more detailed emphasis on power. In doing so, it enhances the explanatory power of CCO in general, as a set of theories useful for describing how organizational constitution and power play out in an increasingly (dis)organized world where the prevalence of bounded stable organizations can no longer be taken for granted

Postmodern/Poststructural Approaches

Postmodern and poststructural approaches to organizational communication are marked by an emphasis on ruptures, disjunctions, tensions, instabilities, and other inconsistencies as a part of everyday organizational life. This emphasis is part of an attempt to question, critique, and often compromise the normalized, mundane power structures that regulate organizational life. By questioning and critiquing, these approaches reveal norms and power structures as contingently constructed with particular interests at play. This contrasts with more traditional assumptions that treat norms and power structures as natural, neutral, and stable constructions. Poststructural and postmodern approaches to organizational communication find their roots in broader philosophical movements and the “linguistic turn” among organizational communication scholars. The linguistic turn of the 1980s saw an epistemological shift toward qualitative methods for understanding the communication/organization relationship and an ontological shift from the assumption that organizations are stable entities that contain communication to the assumption that organizations are more flexibly constructed through communication (see Putnam and Pacanowsky, 1983). Postmodern and poststructural approaches are two of many perspectives that were made possible by this shift, although there are plenty of others that follow the linguistic turn that do not claim the methods and assumptions of poststructural and postmodern approaches. Although poststructuralism and postmodernism are not synonymous, the two approaches are grounded in the same (Eurocentrically defined) historical moment. Understanding the influence of these philosophical movements on organizational communication approaches requires a broad understanding of the movements themselves

Lived experiences of informal caregivers of people with chronic musculoskeletal pain: a systematic review and meta-ethnography

BACKGROUND: People with chronic pain often seek support from friends and family for everyday tasks. These individuals are termed informal caregivers. There remains uncertainty regarding the lived experiences of these people who care for individuals with chronic musculoskeletal pain. The aim of this paper is to synthase the evidence on the lived experiences of informal caregivers providing care to people with chronic musculoskeletal pain. METHODS: A systematic literature review was undertaken of published and unpublished literature databases including: EMBASE, MEDLINE, CINAHL, PubMed, the WHO International Clinical Trial Registry and ClinicalTrials.gov registry (to September 2019). Qualitative studies exploring the lived experiences of informal caregivers of people with chronic musculoskeletal pain were included. Data were synthesised using a meta-ethnography approach. Evidence was evaluated using the Critical Appraisal Skills Programme (CASP) qualitative appraisal tool. RESULTS: From 534 citations, 10 studies were eligible (360 participants: 171 informal caregivers of 189 care recipients). The evidence was moderate quality. Seven themes arose: the relationship of caregivers to healthcare professionals, role reversal with care recipients; acting the confidant to the care recipient; a constant burden in caregiving; legitimising care recipient’s condition; knowledge and skills to provide caregiving; and the perception of other family members and wider-society to the caregiver/care recipient dyad. CONCLUSIONS: The lived experiences of caregivers of people with chronic musculoskeletal pain is complex and dynamic. There is an inter-connected relationship between caregivers, care recipients and healthcare professionals. Exploring how these experiences can be modified to improve a caregiving dyad’s lived experience is now warranted

Paradox as resistance in male dominated fields and the value of (sur)facing enthymematic narratives

Women working in masculine organizational contexts face a challenge of balancing (1) access to power by co-opting masculine discourse in ways that risk reinforcing it, with (2) challenging and resisting practices that privilege masculinity. In this manuscript, we address one communication strategy for navigating that challenge: The denial/acknowledgment paradox in which women explicitly deny that gender affected their experience, but also describe the many ways it affected their experience. To do so, we examined transcripts of interviews with 11 women candidates who ran in the 2017 Virginia House of Delegates election in the United States and demonstrated this paradoxical communication strategy. Our analysis offers five different structures of the denial/acknowledgment paradox and shows how four of those structures engage what we call an “enthymematic narrative” of victimhood. Ultimately, we argue that (sur) facing the enthymematic narrative amplifies the generative potential of the denial/acknowledgment paradox and suggest that (sur)facing enthymematic narratives should be taken up more broadly as a strategy for organizational and social change

Boosted Classification Trees and Class Probability/Quantile Estimation

The standard by which binary classifiers are usually judged, misclassification error, assumes equal costs of misclassifying the two classes or, equivalently, classifying at the 1/2 quantile of the conditional class probability function P[y = 1|x]. Boosted classification trees are known to perform quite well for such problems. In this article we consider the use of standard, off-the-shelf boosting for two more general problems: 1) classification with unequal costs or, equivalently, classification at quantiles other than 1/2, and 2) estimation of the conditional class probability function P[y = 1|x]. We first examine whether the latter problem, estimation of P[y = 1|x], can be solved with Logit- Boost, and with AdaBoost when combined with a natural link function. The answer is negative: both approaches are often ineffective because they overfit P[y = 1|x] even though they perform well as classifiers. A major negative point of the present article is the disconnect between class probability estimation and classification. Next we consider the practice of over/under-sampling of the two classes. We present an algorithm that uses AdaBoost in conjunction with Over/Under-Sampling and Jittering of the data (“JOUS-Boost”). This algorithm is simple, yet successful, and it preserves the advantage of relative protection against overfitting, but for arbitrary misclassification costs and, equivalently, arbitrary quantile boundaries. We then use collections of classifiers obtained from a grid of quantiles to form estimators of class probabilities. The estimates of the class probabilities compare favorably to those obtained by a variety of methods across both simulated and real data sets

Asset, liability, possibility: Metaphors of human difference and the business case for diversity

Purpose – This analysis draws on interviews with 19 self-identified US diversity consultants and 94 diversity statements posted on corporate websites. The findings challenge existing literature that characterizes the business case for diversity as monolithic and wholly problematic for the way it constructs understandings of human difference. The authors accomplish this using metaphor analysis to demonstrate how business case arguments incorporate three metaphorical systems for thinking and speaking about human differences – as asset, as liability and as possibility. Given this diversity of metaphors, the business case does not construct human difference in a monolithic way, but in a variety of ways that both challenge and sustain problematic treatments of difference. The authors argue scholars and practitioners should attend to these nuanced difference within the discourse of the business case, and more carefully consider how these metaphorical systems both enable and constrain the design and execution of diversity work in organizations. The paper aims to discuss these issues. Design/methodology/approach – The analysis draws on two data sets: initial interviews with 19 self-identified US diversity consultants analyzed using metaphor analysis. To triangulate findings, the metaphorical framework was applied to 94 diversity statements posted on corporate websites. Findings – Business case arguments operate according to three root metaphors of human difference: human difference as asset, human difference as liability and human difference as possibility. This challenges existing literature that treats the business case as a monolithic discourse. Research limitations/implications – This analysis offers the three metaphorical system and highlights the “constrained capacity” of each. This framework offers an analytical and practical tool for scholars and practitioners, enabling them to more thoroughly understand and respond to their unique organizational and socio-historical context. It also provides a way to analyze how concepts of difference are mobilized across social and historical contexts. Practical implications – The findings offer the “constrained capacity” that is, the strategic limitations and possibilities for practitioners who use the business case in their diversity work. This enables more skilled and ethically informed diversity initiatives. Social implications – The findings offer insight into the subtle ways that hierarchies of human difference embedded in US history are subtly reinforced and made present through language. This enables social justice workers to better challenge problematic constructions of human difference and create new understandings when needed. Originality/value – This piece makes two significant original contributions to existing literature. It offers more nuance to both critical and uncritical analyses of the business case by showing the diversity of business case assumptions about human difference as demonstrated in three different metaphorical systems and highlighting the constrained capacity of three different metaphorical systems. It offers unique analysis grounded in contemporary discourses, but correlated to historical systems of thought. This enables empirical identification of how certain types of thinking about human difference move across socio-historical contexts