Models of verbal working memory capacity: What does it take to make them work?

Theories of working memory (WM) capacity limits will be more useful when we know what aspects of performance are governed by the limits and what aspects are governed by other memory mechanisms. Whereas considerable progress has been made on models of WM capacity limits for visual arrays of separate objects, less progress has been made in understanding verbal materials, especially when words are mentally combined to form multiword units or chunks. Toward a more comprehensive theory of capacity limits, we examined models of forced-choice recognition of words within printed lists, using materials designed to produce multiword chunks in memory (e.g., leather brief case). Several simple models were tested against data from a variety of list lengths and potential chunk sizes, with test conditions that only imperfectly elicited the interword associations. According to the most successful model, participants retained about 3 chunks on average in a capacity-limited region of WM, with some chunks being only subsets of the presented associative information (e.g., leather brief case retained with leather as one chunk and brief case as another). The addition to the model of an activated long-term memory component unlimited in capacity was needed. A fixed-capacity limit appears critical to account for immediate verbal recognition and other forms of WM. We advance a model-based approach that allows capacity to be assessed despite other important processing contributions. Starting with a psychological-process model of WM capacity developed to understand visual arrays, we arrive at a more unified and complete model

Second-generation p-values: improved rigor, reproducibility, & transparency in statistical analyses

Verifying that a statistically significant result is scientifically meaningful is not only good scientific practice, it is a natural way to control the Type I error rate. Here we introduce a novel extension of the p-value - a second-generation p-value - that formally accounts for scientific relevance and leverages this natural Type I Error control. The approach relies on a pre-specified interval null hypothesis that represents the collection of effect sizes that are scientifically uninteresting or are practically null. The second-generation p-value is the proportion of data-supported hypotheses that are also null hypotheses. As such, second-generation p-values indicate when the data are compatible with null hypotheses, or with alternative hypotheses, or when the data are inconclusive. Moreover, second-generation p-values provide a proper scientific adjustment for multiple comparisons and reduce false discovery rates. This is an advance for environments rich in data, where traditional p-value adjustments are needlessly punitive. Second-generation p-values promote transparency, rigor and reproducibility of scientific results by a priori specifying which candidate hypotheses are practically meaningful and by providing a more reliable statistical summary of when the data are compatible with alternative or null hypotheses.Comment: 29 pages, 29 page Supplemen

Women at risk for sexually transmitted diseases: correlates of intercourse without barrier contraception

Objective: The purpose of this study was to evaluate the correlates of vaginal intercourse without barrier contraception (unprotected intercourse). Study Design: Baseline data from a randomized trial were analyzed to evaluate factors that are associated with intercourse without barrier method use among women \u3c35 years old. Logistic regression models provided estimates of the association of demographic, reproductive, and sexual history variables with unprotected intercourse. Results: Intercourse without barrier contraception was common; 65% of participants had ≥2 episodes of intercourse without barrier contraception use in the past month. Factors that were associated with increased odds of unprotected intercourse included the number of coital episodes, a male partner’s unwillingness to use condoms (adjusted odds ratio, 4.1; 95% CI, 2.3-6.9), and, among women \u3c20 years old, low condom use self-efficacy score (adjusted odds ratio, 1.6; 95% CI, 1.0-2.9). Conclusion: Risk factors for unprotected intercourse included coital frequency and the male partner’s unwillingness to use condoms. Self-efficacy for condom use was especially important for women \u3c20 years old

Tailored intervention to increase dual-contraceptive method use: a randomized trial to reduce unintended pregnancies and sexually transmitted infections

Objective: The objective of the study was to determine whether a transtheoretical model–tailored expert system intervention increases dual-method contraceptive use, compared with a nontailored educational intervention. Study Design: We performed a randomized clinical trial of 542 women at high risk for sexually transmitted infections (STIs) and unintended pregnancy. The intervention group received computer-based tailored feedback using a multimedia program. The control group received general contraceptive information and nontailored advice. Results: Participants in the intervention group were more likely to report use of dual contraceptive methods during follow-up (adjusted hazard rate ratio 1.70, 95% confidence interval 1.09, 2.66), compared with controls. However, there were no differences in the rates of incident STI or unintended pregnancy between the 2 groups. Conclusions: The computer-based transtheoretical model–tailored intervention resulted in a 70% increase in reported dual-method contraceptive use in a group of women at high risk for STIs and unintended pregnancy. Inconsistent use of dual methods may explain the lack of effect on unintended pregnancy rates and incident STIs

Is a previous unplanned pregnancy a risk factor for a subsequent unplanned pregnancy?

Objective: The objective of the study was to determine whether a history of unplanned pregnancy was a risk factor for a subsequent unplanned pregnancy. Study Design: We analyzed 542 women aged 14-35 years, enrolled in Project PROTECT, a randomized clinical trial to promote dual-method contraception use to prevent sexually transmitted diseases and unplanned pregnancy. Predictors of unplanned pregnancy were assessed by comparing women with and without a history of unplanned pregnancy. Results: More than 1 in 5 women (22.5%) experienced an unintended pregnancy. History of an unintended pregnancy was a predictor of unintended pregnancy (adjusted odds ratio, 1.91; 95% confidence interval, 1.09-3.34). Other factors that were significantly associated with unplanned pregnancy included young age and low educational status. Conclusions: Future efforts should focus on bridging the gap between identifying risk factors for unplanned pregnancy and interventions aimed at reducing the incidence in high-risk groups

Coastal acidification impacts on shell mineral structure of bivalve mollusks

Ocean acidification is occurring globally through increasing CO2 absorption into the oceans creating particular concern for calcifying species. In addition to ocean acidification, near shore marine habitats are exposed to the deleterious effects of runoff from acid sulfate soils which also decreases environmental pH. This coastal acidification is being exacerbated by climate change- driven sea- level rise and catchment- driven flooding. In response to reduction in habitat pH by ocean and coastal acidification, mollusks are predicted to produce thinner shells of lower structural integrity and reduced mechanical properties threatening mollusk aquaculture. Here, we present the first study to examine oyster biomineralization under acid sulfate soil acidification in a region where growth of commercial bivalve species has declined in recent decades. Examination of the crystallography of the shells of the Sydney rock oyster, Saccostrea glomerata, by electron back scatter diffraction analyses revealed that the signal of environmental acidification is evident in the structure of the biomineral. Saccostrea glomerata, shows phenotypic plasticity, as evident in the disruption of crystallographic control over biomineralization in populations living in coastal acidification sites. Our results indicate that reduced sizes of these oysters for commercial sale may be due to the limited capacity of oysters to biomineralize under acidification conditions. As the impact of this catchment source acidification will continue to be exacerbated by climate change with likely effects on coastal aquaculture in many places across the globe, management strategies will be required to maintain the sustainable culture of these key resources