The Development of Non-Symbolic Probability Judgments

Uncertainty plays a role in a variety of early learning processes such as numerical reasoning, language learning, and causal reasoning. Furthermore, adults experience probabilistic data in the course of numerous tasks every day. Thus, the ability to make accurate predictions about future events is a foundational skill which serves both child and adult. Researchers have studied the development of probabilistic reasoning for decades, providing data to suggest that , until early adolescence, children are incapable of accurately predicting future outcomes based on proportion. An equally long scholarly lineage has also provided evidence that adults rely on inaccurate heuristics and biases when reasoning about probability. If prediction is so vitally important to human judgment and decision making, why does the empirical literature suggest humans have impoverished decision making skills when reasoning about uncertainty? What mental representations do humans really on to calculate probability? How do these mental representations change with age and experience? The current dissertation seeks to answer these questions by studying simple probability judgments made by children and adults. The empirical evidence provided here suggests that children and adults draw on analog magnitude representations of number in order to enumerate sets of outcomes. Furthermore, although both children and adults sometimes use inaccurate heuristics, children rely on these heuristics less with age and adults seem to use them when they perceive two outcomes to be equally likely. In chapter 2, I present findings from a series of experiments employing a non-symbolic ratio magnitude comparison task to investigate the relationship between number approximation, ratio processing, and probability estimation in adults. Empirical results reveal that performance on a probability discrimination task improves as the ratio of the two proportions increases and psychophysical modeling revealed that both numerical and non-numerical stimulus features such as field area, size, and sparsity influence probability estimation. Additionally, these findings reveal that probability estimation is influenced by formally incorrect heuristic decision rules or strategies. Furthermore, findings from two follow-up experiments indicate that these strategies are not influenced by the amount of time participants are given to compute probability and that they persist even when participants are informed that the use of this strategy is not always accurate. While previous research has investigated the influence of ratio processing and heuristic bias on probabilistic decision making, this series of experiments marks the first attempt to systematically investigate both the psychophysical properties of probability estimation and the factors which influence adults' use of heuristic decision rules in a non-symbolic probability discrimination task. Chapter 3 presents the findings from two experiments designed to investigate the developmental trajectory of children’s probability approximation abilities. These results indicate that probability judgments improve with age, become more accurate as the distance between two ratios increases, and that children’s perceived probability is influenced by the same psychophysical properties reported for adults (i.e. the size of the objects and the perceived numerosity of target objects). Older children’s performance suggested the correct use of proportions for estimating probability; but in some cases, children relied on heuristic shortcuts. Together, these results suggest that children’s non-symbolic probability judgments show a clear distance effect, and that the acuity of probability estimations increases with age. In chapter 4, I push this research further by investigating the influence of feedback on children’s use of heuristic decision rules. Results from two experiments reveal that children's use of heuristics can be overridden with the proper amount and type of feedback. Together, our findings indicate that children use heuristic decision rules to reason about the outcome of future events but that children can override the use of heuristics if they are provided with enough feedback on trials which conflict with their strategy. These results help shed light on the development of probabilistic reasoning and may lead to improved assessments of children's quantitative reasoning. Together, the results reported in this dissertation suggest that human probabilistic reasoning is not as impoverished as previous research might suggest. Although children and adults sometimes use inaccurate heuristic decision rules to aid their decision-making, they are also capable of accurately calculating probability based on proportion. Furthermore, children can learn to reformulate their calculations of probability based on feedback and reach a more sophisticated understanding of the proportional nature of probability. These findings have broad implications for a variety of domains such as cognitive development, numerical reasoning, decision-making, strategy selection, and mathematics education

Changes in cognitive flexibility and hypothesis search across human life history from childhood to adolescence to adulthood

How was the evolution of our unique biological life history related to distinctive human developments in cognition and culture? We suggest that the extended human childhood and adolescence allows a balance between exploration and exploitation, between wider and narrower hypothesis search, and between innovation and imitation in cultural learning. In particular, different developmental periods may be associated with different learning strategies. This relation between biology and culture was probably coevolutionary and bidirectional: life-history changes allowed changes in learning, which in turn both allowed and rewarded extended life histories. In two studies, we test how easily people learn an unusual physical or social causal relation from a pattern of evidence. We track the development of this ability from early childhood through adolescence and adulthood. In the physical domain, preschoolers, counterintuitively, perform better than school-aged children, who in turn perform better than adolescents and adults. As they grow older learners are less flexible: they are less likely to adopt an initially unfamiliar hypothesis that is consistent with new evidence. Instead, learners prefer a familiar hypothesis that is less consistent with the evidence. In the social domain, both preschoolers and adolescents are actually the most flexible learners, adopting an unusual hypothesis more easily than either 6-y-olds or adults. There may be important developmental transitions in flexibility at the entry into middle childhood and in adolescence, which differ across domains

International Society of Sports Nutrition Position Stand: Nutritional recommendations for single-stage ultra-marathon; training and racing

Background. In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by following an individualized and periodized strategy, comprising a varied, food-first approach; ii) Athletes should plan and implement their nutrition strategy with sufficient time to permit adaptations that enhance fat oxidative capacity; iii) The evidence overwhelmingly supports the inclusion of a moderate-to-high carbohydrate diet (i.e., ~60% of energy intake, 5 – 8 g⸱kg−1·d−1) to mitigate the negative effects of chronic, training-induced glycogen depletion; iv) Limiting carbohydrate intake before selected low-intensity sessions, and/or moderating daily carbohydrate intake, may enhance mitochondrial function and fat oxidative capacity. Nevertheless, this approach may compromise performance during high-intensity efforts; v) Protein intakes of ~1.6 g·kg−1·d−1 are necessary to maintain lean mass and support recovery from training, but amounts up to 2.5 g⸱kg−1·d−1 may be warranted during demanding training when calorie requirements are greater; Recommendations for Racing. vi) To attenuate caloric deficits, runners should aim to consume 150 - 400 kcal⸱h−1 (carbohydrate, 30 – 50 g⸱h−1; protein, 5 – 10 g⸱h−1) from a variety of calorie-dense foods. Consideration must be given to food palatability, individual tolerance, and the increased preference for savory foods in longer races; vii) Fluid volumes of 450 – 750 mL⸱h−1 (~150 – 250 mL every 20 min) are recommended during racing. To minimize the likelihood of hyponatraemia, electrolytes (mainly sodium) may be needed in concentrations greater than that provided by most commercial products (i.e., >575 mg·L−1 sodium). Fluid and electrolyte requirements will be elevated when running in hot and/or humid conditions; viii) Evidence supports progressive gut-training and/or low-FODMAP diets (fermentable oligosaccharide, disaccharide, monosaccharide and polyol) to alleviate symptoms of gastrointestinal distress during racing; ix) The evidence in support of ketogenic diets and/or ketone esters to improve ultra-marathon performance is lacking, with further research warranted; x) Evidence supports the strategic use of caffeine to sustain performance in the latter stages of racing, particularly when sleep deprivation may compromise athlete safety

Hospital admission and emergency care attendance risk for SARS-CoV-2 delta (B.1.617.2) compared with alpha (B.1.1.7) variants of concern: a cohort study

Background: The SARS-CoV-2 delta (B.1.617.2) variant was first detected in England in March, 2021. It has since rapidly become the predominant lineage, owing to high transmissibility. It is suspected that the delta variant is associated with more severe disease than the previously dominant alpha (B.1.1.7) variant. We aimed to characterise the severity of the delta variant compared with the alpha variant by determining the relative risk of hospital attendance outcomes. Methods: This cohort study was done among all patients with COVID-19 in England between March 29 and May 23, 2021, who were identified as being infected with either the alpha or delta SARS-CoV-2 variant through whole-genome sequencing. Individual-level data on these patients were linked to routine health-care datasets on vaccination, emergency care attendance, hospital admission, and mortality (data from Public Health England's Second Generation Surveillance System and COVID-19-associated deaths dataset; the National Immunisation Management System; and NHS Digital Secondary Uses Services and Emergency Care Data Set). The risk for hospital admission and emergency care attendance were compared between patients with sequencing-confirmed delta and alpha variants for the whole cohort and by vaccination status subgroups. Stratified Cox regression was used to adjust for age, sex, ethnicity, deprivation, recent international travel, area of residence, calendar week, and vaccination status. Findings: Individual-level data on 43 338 COVID-19-positive patients (8682 with the delta variant, 34 656 with the alpha variant; median age 31 years [IQR 17–43]) were included in our analysis. 196 (2·3%) patients with the delta variant versus 764 (2·2%) patients with the alpha variant were admitted to hospital within 14 days after the specimen was taken (adjusted hazard ratio [HR] 2·26 [95% CI 1·32–3·89]). 498 (5·7%) patients with the delta variant versus 1448 (4·2%) patients with the alpha variant were admitted to hospital or attended emergency care within 14 days (adjusted HR 1·45 [1·08–1·95]). Most patients were unvaccinated (32 078 [74·0%] across both groups). The HRs for vaccinated patients with the delta variant versus the alpha variant (adjusted HR for hospital admission 1·94 [95% CI 0·47–8·05] and for hospital admission or emergency care attendance 1·58 [0·69–3·61]) were similar to the HRs for unvaccinated patients (2·32 [1·29–4·16] and 1·43 [1·04–1·97]; p=0·82 for both) but the precision for the vaccinated subgroup was low. Interpretation: This large national study found a higher hospital admission or emergency care attendance risk for patients with COVID-19 infected with the delta variant compared with the alpha variant. Results suggest that outbreaks of the delta variant in unvaccinated populations might lead to a greater burden on health-care services than the alpha variant. Funding: Medical Research Council; UK Research and Innovation; Department of Health and Social Care; and National Institute for Health Research

Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes

Background The first epidemic wave of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over one-third of care homes reported an outbreak, while there was limited testing of hospital patients discharged to care homes. Aim To investigate patients discharged from hospitals as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave. Methods A clinical review was performed for all patients discharges from hospitals to care homes from 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease 2019 (COVID-19) test history, clinical assessment at discharge, whole-genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis using Cluster Investigation and Virus Epidemiological Tool software. Patient timelines were obtained using electronic hospital records. Findings In total, 787 patients discharged from hospitals to care homes were identified. Of these, 776 (99%) were ruled out for subsequent introduction of SARS-CoV-2 into care homes. However, for 10 episodes, the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data were available. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission, leading to 10 positive cases in their care home. Conclusion The majority of patients discharged from hospitals were ruled out for introduction of SARS-CoV-2 into care homes, highlighting the importance of screening all new admissions when faced with a novel emerging virus and no available vaccine