Bias in perception of ambiguous movement in discrete stimulus presentations

Successive presentations of two different stimulus configurations were used to generate a compelling but ambiguous apparent-motion sequence, such that the likelihood of the perceived motion being resolved as clockwise or anticlockwise was equal. In the first stimulus configuration, four small squares were arranged in a square formation (5 deg × 5 deg) about a central fixation mark; in the second, they were arranged in a diamond formation. Twelve naïve observers reported perceived direction of motion in discrete presentations (< 1 s), comprising three stimulus configurations (square - diamond - square; stimulus configuration duration 100 ms; ISI 200 ms). We were surprised to find that ten of the observers exhibited a strong bias for motion in one or other direction. This bias to report a particular direction persisted even when observers were informed of the inherent ambiguity of the stimulus. Next, in extended presentations (2 min) five observers indicated each occurrence of a perceived switch in direction. Despite individual variation, all observers reported switches in direction; an analysis of the interswitch durations conformed to a gamma distribution. These observations support the notion that uninterrupted presentations are required for perceptual switching to occur in ambiguous displays (Leopold et al, 2002 Nature Neuroscience 5 605 - 609)

Accounting for Differences in Labour Market Outcomes in Great Britain : A Regional Analysis Using the Labour Force Survey

Regional unemployment rates in Great Britain have narrowed dramatically in recent years. However, significant differences still remain in terms of both employment and economic inactivity rates, which may now better reflect relative labour market performance. This paper examines these differences in labour market outcomes using a unified empirical framework that decomposes regional differences in employment, economic inactivity and unemployment into components due to either structural or composition effects. The analysis highlights the important role that ill health and structural deficits currently play in accounting for regional differences in both employment and economic inactivity rates

How far and for how much? Evidence on wages and potential travel-to-work distances from a survey of the economically inactive

The U.K. government has recently committed itself to an ambitious 80 per cent employment rate target. Recognising that achieving this aspiration will require significant numbers of the economically inactive to (re-)engage with the labour market, the government has enacted various policy reforms seeking to encourage those on the fringes of the labour market to do so. The present paper uses unique survey data to examine three factors relevant to these issues, namely the desire to work, minimum acceptable wages and the distance the inactive are prepared to travel to work for a given minimum acceptable wage offer

Novel octaketide macrolides related to 6-deoxyerythronolide B provide evidence for iterative operation of the erythromycin polyketide synthase

AbstractBackground: The macrolide antibiotic erythromycin A, like other complex aliphatic polyketides, is synthesised by a bacterial modular polyketide synthase (PKS). Such PKSs, in contrast to other fatty acid and polyketide synthases which work iteratively, contain a separate set or module of enzyme activities for each successive cycle of polyketide chain extension, and the number and type of modules together determine the structure of the polyketide product. Thus, the six extension modules of the erythromycin PKS (DEBS) together catalyse the production of the specific heptaketide 6-deoxyerythronolide B.Results: A mutant strain of the erythromycin producer Saccharopolyspora erythraea, which accumulates the aglycone intermediate erythronolide B, was found unexpectedly to produce two novel octaketides, both 16-membered macrolides. These compounds were detectable in fermentation broths of wild-type S. erythraea, but not in a strain from which the DEBS genes had been specifically deleted. From their structures, both of these octaketides appear to be aberrant products of DEBS in which module 4 has ‘stuttered’, that is, has catalysed two successive cycles of chain extension.Conclusions: The isolation of novel DEBS-derived octaketides provides the first evidence that an extension module in a modular PKS has the potential to catalyse iterative rounds of chain elongation like other type I FAS and PKS systems. The factors governing the extent of such ‘stuttering’ remain to be determined

The Ups and Downs in Women's Employment: Shifting Composition or Behavior from 1970 to 2010?

This paper tracks factors contributing to the ups and downs in women’s employment from 1970 to 2010 using regression decompositions focusing on whether changes are due to shifts in the means (composition of women) or due to shifts in coefficients (inclinations of women to work for pay). Compositional shifts in education exerted a positive effect on women’s employment across all decades, while shifts in the composition of other family income, particularly at the highest deciles, depressed married women’s employment over the 1990s contributing to the slowdown in this decade. A positive coefficient effect of education was found in all decades, except the 1990s, when the effect was negative, depressing women’s employment. Further, positive coefficient results for other family income at the highest deciles bolstered married women’s employment over the 1990s. Models are run separately for married and single women demonstrating the varying results of other family income by marital status. This research was supported in part by an Upjohn Institute Early Career Research Award