Speech errors across the lifespan

Dell, Burger, and Svec (1997) proposed that the proportion of speech errors classified as anticipations (e.g., " moot and mouth ") can be predicted solely from the overall error rate, such that the greater the error rate, the lower the anticipatory proportion (AP) of errors. We report a study examining whether this effect applies to changes in error rates that occur developmentally and as a result of ageing. Speech errors were elicited from 8- and 11-year-old children, young adults, and older adults. The error rate decreased and the AP increased from children to young adults, but neither error rate nor AP differed significantly between young and older adults. In cases where fast speech resulted in a higher error rate than slow speech, the AP was lower. Thus, there was overall support for Dell et al.'s prediction from speech error data across the lifespan

Dynamic temperature selection for parallel-tempering in Markov chain Monte Carlo simulations

Modern problems in astronomical Bayesian inference require efficient methods for sampling from complex, high-dimensional, often multi-modal probability distributions. Most popular methods, such as Markov chain Monte Carlo sampling, perform poorly on strongly multi-modal probability distributions, rarely jumping between modes or settling on just one mode without finding others. Parallel tempering addresses this problem by sampling simultaneously with separate Markov chains from tempered versions of the target distribution with reduced contrast levels. Gaps between modes can be traversed at higher temperatures, while individual modes can be efficiently explored at lower temperatures. In this paper, we investigate how one might choose the ladder of temperatures to achieve more efficient sampling, as measured by the autocorrelation time of the sampler. In particular, we present a simple, easily-implemented algorithm for dynamically adapting the temperature configuration of a sampler while sampling. This algorithm dynamically adjusts the temperature spacing to achieve a uniform rate of exchanges between chains at neighbouring temperatures. We compare the algorithm to conventional geometric temperature configurations on a number of test distributions and on an astrophysical inference problem, reporting efficiency gains by a factor of 1.2-2.5 over a well-chosen geometric temperature configuration and by a factor of 1.5-5 over a poorly chosen configuration. On all of these problems a sampler using the dynamical adaptations to achieve uniform acceptance ratios between neighbouring chains outperforms one that does not.Comment: 21 pages, 21 figure

Incentives and Static and Dynamic Gains from Market Reform in an Emerging Profits Models.

This paper develops a dynamic model to account for the enhanced incentive effects that result from market reform in the form of a move toward private property rights and competitive market.INCENTIVES ; ECONOMIC REFORM ; PROPERTY RIGHTS

Incentives and static and dynamic gains from market reform: rice production in Vietnam

This article develops a dynamic model to account for the enhanced incentive effects that result from market reform through a move toward private property rights and competitive markets. Reform is captured through an emerging profits function which depends on effective prices and incentives to work harder. Static and dynamic output gains from reform are derived through increases in total factor productivity and induced capital accumulation. The model is applied to rice production in Vietnam over the period 1976–94. The more extensive is market reform, the larger the effects found on rice output, the capital stock and transitional growth rates, suggesting that incentives and more competitive markets matter greatly.Crop Production/Industries, Marketing,

Early Medieval Ecclesiastical Sites in the Landscape of South-West Wales

This study integrates archaeological, documentary and place-name evidence for early medieval ecclesiastical sites in the counties of Ceredigion and Pembrokeshire (here defined as south-west Wales), and contextualises it through a spatial framework based on the landscape. Rather than focusing in detail on individual sites, it studies patterns and variations across the whole region, which are examined with reference to existing models of ecclesiastical and secular land organisation. A high overall density of sites and proliferation of high status early medieval ecclesiastical sites is seen as reflecting control by a local elite who held their land by hereditary right and managed ecclesiastical lands as part of their holdings, integrating them into existing patterns of land use and communication. The reuse of antecedent sites is interpreted as a mechanism to reinforce social identity and territorial claims by referencing a real or imagined ancestral past. Sites in apparently isolated locations are seen as a conscious attempt to create a ‘stylised wilderness’ as part of a wider Christian phenomenon seen across Britain and Ireland. Curvilinear ecclesiastical enclosures, in use from at least the seventh century onwards, are comparative in size and form to Irish examples and may have been modelled according to similar principles. Their incorporation of springs and watercourses may also have been integral to Christian ideals. The locations of early medieval ecclesiastical sites are understood as the product of a world centred on the agricultural landscape, but outward-looking to the Irish Sea with cultural connections to the Mediterranean world, and later to Wessex. In addition to perpetuating existing social relationships, they could help define rights to land and resources at a time when new identities and allegiances were being forged. Christianity provided a framework which incorporated land proprietorship into a belief system which could reinforce these rights into the future.Arts and Humanities Research Council (AHRC

Unionisation, unemployment and economic growth

This paper employs a simple overlapping generations endogenous growth model with an R&D sector to establish a link between union bargaining power, long-run unemployment and long-run growth. The model consists of a competitive final goods sector, two intermediate goods sectors, one competitive and the other a monopoly and a competitive R&D sector. Increased union bargaining power in the monopolized intermediate-goods sector is shown to increase wages and unemployment in the sector and reduce the economy’s long-run growth rate. This result is shown to hold for both closed- and open-shop unions

Serial control of phonology in speech production

The aim of this thesis is to further our understanding of the processes which control the sequencing of phonemes as we speak: this is an example of what is commonly known as the serial order problem. Such a process is apparent in normal speech and also from the existence of a class of speech errors known as sound movement errors, where sounds are anticipated (spoken too soon), perseverated (repeated again later), or exchanged (the sounds are transposed). I argue that this process is temporally governed, that is, the serial ordering mechanism is restricted to processing sounds that are close together in time. This is in conflict with frame-based accounts (e.g. Dell, 1986; Lapointe & Dell, 1979), serial buffer accounts (Shattuck-Hufnagel, 1979) and associative chaining theories (Wickelgren, 1969). An analysis of sound movement errors from Harley and MacAndrew's (1995) corpus shows how temporal processing bears on the production of speech sounds by the temporal constraint observed in the pattern of errors, and I suggest an appropriate computational model of this process. Specifically, I show how parallel temporal processing in an oscillator-based model can account for the movement of sounds in speech. Similar predictions were made by the model to the pattern of movement errors actually observed in speech error corpora. This has been demonstrated without recourse to an assumption of frame and slot structures. The OSCillator-based Associative REcall (OSCAR) model, on the other hand, is able to account for these effects and other positional effects, providing support for a temporal based theory of serial control