Search

We investigate how the rewards of individual tasks dictate a priori how easy it is to interleave two discrete tasks efficiently, and whether people then interleave efficiently. Previous research found that people vary in their ability to interleave efficiently. Less attention has been given to whether it was realistic to expect efficient interleaving, given the reward rate of each of the involved tasks. Using a simulation model, we demonstrate how the rewards of individual tasks lead to different dual-task interleaving scenarios. We identify three unique dual-task scenarios. In easy scenarios, many strategies for time division between tasks can achieve optimal performance. This gives great opportunity to optimize performance, but also leads to variation in the applied strategies due to a lack of pressure to settle on a small set of optimal strategies. In difficult scenarios, the optimal strategy is hard to identify, therefore giving little opportunity to optimize. Finally, constrained scenarios have a well-defined prediction of the optimal strategy. It gives a narrow prediction, which limits the options to achieve optimal scores, yet given the structure people are able to optimize their strategies. These scenarios are therefore best to test people's general capability of optimizing interleaving. We report three empirical studies that test these hypotheses. In each study, participants interleave between two identical discrete tasks, that differ only in the underlying reward functions and the combined result (easy, difficult, or constrained scenario). Empirical results match the theoretical pattern as predicted by simulation models. Implications for theory and practice are discussed.

Purpose: A social gradient in adolescent mental health exists: adolescents with higher socioeconomic status (SES) have fewer mental health problems than their peers with lower SES. Little is known about whether adolescents' societal beliefs play a role in this social gradient. Belief in a just world (BJW) may be a mediator or moderator of the social gradient in adolescent mental health., Methods: Using data from 848 adolescents (M age  = 17) in the Netherlands, path analyses examined whether two indicators of BJW (general and personal) mediated or moderated the associations between two indicators of SES (family affluence and perceived family wealth), and four indicators of adolescent mental health problems (emotional symptoms, conduct problems, hyperactivity, and peer problems)., Results: Adolescents with lower family affluence and lower perceived family wealth reported more emotional symptoms, and the association between perceived family wealth and emotional symptoms was mediated by lower personal and general BJW. Furthermore, higher personal BJW amplified the negative association between SES and peer problems., Conclusion: This study suggests BJW may both mediate and amplify the social gradient in adolescent mental health. Adolescents' beliefs about society may be important to include in research aimed at understanding this social gradient., (© 2021. The Author(s).)

By their paternal transmission, Y-chromosomal haplotypes are sensitive markers of population history and male-mediated introgression. Previous studies identified biallelic single-nucleotide variants in the SRY, ZFY and DDX3Y genes, which in domestic goats identified four major Y-chromosomal haplotypes, Y1A, Y1B, Y2A and Y2B, with a marked geographical partitioning. Here, we extracted goat Y-chromosomal variants from whole-genome sequences of 386 domestic goats (75 breeds) and seven wild goat species, which were generated by the VarGoats goat genome project. Phylogenetic analyses indicated domestic haplogroups corresponding to Y1B, Y2A and Y2B, respectively, whereas Y1A is split into Y1AA and Y1AB. All five haplogroups were detected in 26 ancient DNA samples from southeast Europe or Asia. Haplotypes from present-day bezoars are not shared with domestic goats and are attached to deep nodes of the trees and networks. Haplogroup distributions for 186 domestic breeds indicate ancient paternal population bottlenecks and expansions during migrations into northern Europe, eastern and southern Asia, and Africa south of the Sahara. In addition, sharing of haplogroups indicates male-mediated introgressions, most notably an early gene flow from Asian goats into Madagascar and the crossbreeding that in the 19th century resulted in the popular Boer and Anglo-Nubian breeds. More recent introgressions are those from European goats into the native Korean goat population and from Boer goat into Uganda, Kenya, Tanzania, Malawi and Zimbabwe. This study illustrates the power of the Y-chromosomal variants for reconstructing the history of domestic species with a wide geographical range., (© 2022 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

In the last decades, several endangered breeds of livestock species have been re-established effectively. However, the successful revival of the Dutch and Danish Landrace goats involved crossing with exotic breeds and the ancestry of the current populations is therefore not clear. We have generated genotypes for 27 FAO-recommended microsatellites of these landraces and three phenotypically similar Nordic-type landraces and compared these breeds with central European, Mediterranean and south-west Asian goats. We found decreasing levels of genetic diversity with increasing distance from the south-west Asian domestication site with a south-east-to-north-west cline that is clearly steeper than the Mediterranean east-to-west cline. In terms of genetic diversity, the Dutch Landrace comes next to the isolated Icelandic breed, which has an extremely low diversity. The Norwegian coastal goat and the Finnish and Icelandic landraces are clearly related. It appears that by a combination of mixed origin and a population bottleneck, the Dutch and Danish Land-races are separated from the other breeds. However, the current Dutch and Danish populations with the multicoloured and long-horned appearance effectively substitute for the original breed, illustrating that for conservation of cultural heritage, the phenotype of a breed is more relevant than pure ancestry and the genetic diversity of the original breed. More in general, we propose that for conservation, the retention of genetic diversity of an original breed and of the visual phenotype by which the breed is recognized and defined needs to be considered separately., (© 2016 The Authors. Journal of Animal Breeding and Genetics Published by Blackwell Verlag GmbH.)

Objective: This report describes the outcomes of a social networking approach (SNA) in a heterosexually transmitted syphilis epidemic by street nurses in British Columbia, Canada., Methods: Street nurses used SNA interviewing cues, environmental observation, peer outreach, serial interviewing, conducted blood tests, and offered treatment on the street. Rates of cases of syphilis identified by outreach nurses and cases linked to another case were compared before and after adoption of an SNA., Results: SNA resulted in a significantly increased proportion of cases identified by the street nurses (p = 0.01) and increased the percentage of cases linked to a previous case (p = 0.03)., Conclusion: This preliminary study confirms that SNA can increase the number of cases and contacts identified in an epidemic of a sexually transmitted disease in a vulnerable, hard to reach population.

To determine the prevalence of udder infections in fresh calved heifers all quarters of 98 heifers on eleven commercial farms were sampled weekly during the first eight weeks of lactation. The samples during the first four weeks of this period were used for bacteriological examination and in all samples a somatic cell count was made. The prevalence of S. aureus after calving in these heifers was 12.5%. Coagulase-negative staphylococci (CNS) were isolated from half of the heifers. The predominant coagulase-negative staphylococcus species were S. xylosis and S. hyicus. The CNS, with exception of S. hyicus, had a very small effect on the cell count.