Declining extra-pair paternity with laying order associated with initial incubation behavior, but independent of final clutch size in the blue tit

Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species

Impact of a brief intervention on physical activity and social cognitive determinants among working mothers: A randomized trial.

Working mothers exhibit high levels of inactivity, and theory-based interventions to bolster physical activity within this population are needed. This study examined the effectiveness of a brief social cognitive theory-based intervention designed to increase physical activity among working mothers. Participants (N = 141) were randomly assigned to an intervention only, intervention plus follow-up support, or waitlist control condition. The intervention consisted of two group-based workshop sessions designed to teach behavior modification strategies using social cognitive theory. Data were collected at baseline, immediately post-intervention, and 6-month follow-up. Results showed intervention participants exhibited short-term increases in physical activity, which were partially maintained 6 months later. Improvements in physical activity were mediated by increases in self-regulation and self-efficacy. This study provides some support for the effectiveness of a brief intervention to increase physical activity among working mothers. Future programs should explore alternative support mechanisms which may lead to more effective maintenance of initial behavior changes

Measuring disability in multiple sclerosis: Is the Community Dependency Index an improvement on the Barthel Index?

The Community Dependency Index (CDI) was developed due to concerns that the Barthel Index (BI) was limited as a measure of physical function in community settings. However no studies have compared the two rating scales within multiple sclerosis (MS). The aim of this study was to determine whether in a community-based sample of people with MS, the CDI is a better measure than the BI. BI and CDI data were collected from 90 people with MS. Four measurement properties were compared: scaling assumptions (item mean scores, corrected item-total correlations), acceptability (score distributions, floor/ceiling effects), reliability (Cronbach's alpha) and validity (concurrent, discriminant, group differences, relative validity). Both scales satisfied recommended criteria for scaling assumptions (indicating it was legitimate to report a summed score) and internal consistency reliability (alpha>0.85). The scales were highly correlated (r=0.96), indicating they measured the same construct. Both scales demonstrated good group differences validity, but the BI was marginally superior. Notable ceiling effects (BI > CDI) were demonstrated for both scales, particularly in those less disabled. This study sample had relatively minor levels of disability, with over 70% still being independently mobile. In this sample of people with MS, the measurement properties of the BI and CDI examined were very similar, suggesting the CDI does not appear to have achieved its goal of better measurement. © Arnold 2004

Measuring quality of life in multiple sclerosis: Not as simple as it sounds

Data from a clinical study presented an opportunity to examine the psychometric properties of the Leeds Multiple Sclerosis Quality of Life scale (LMSQoL), which has undergone limited psychometric evaluation. LMSQoL and Multiple Sclerosis Quality of Life-54 (MSQoL-54) data were collected from 90 people with multiple sclerosis (MS) living in the community. Standard psychometric methods to examine data quality, scaling assumptions, scale to sample targeting, reliability, validity, and responsiveness were employed. The LMSQoL satisfied criteria for data quality (no missing data), scaling assumptions (item-total correlations: 0.24-0.56), reliability (Cronbach's alpha: 0.71), and demonstrated responsiveness (effect size: 0.34). Correlations between the LMSQoL and MSQoL-54 physical (range: -0.02 to -0.50) and emotional subscales (range: -0.38 to -0.65) were similar; the magnitude and pattern was not consistent with predictions based on the construct purported to be measured by the LMSQoL. The LMSQoL satisfied many psychometric criteria in this small study, however, it was difficult to interpret the validity data. From this, two fundamental measurement issues are highlighted. Firstly, current methods of examining rating scales provide only circumstantial evidence of validity; secondly, health-rating scales should be developed on the basis of clear conceptual definitions. © 2005 Edward Arnold (Publishers) Ltd