Royal Society Open Science最新文献

Processing task-relevant visual information is important for many everyday tasks. Prior work demonstrated that older adults are more susceptible to distraction by salient task-irrelevant stimuli, leading to less efficient visual search. However, these studies often used simple stimuli, and less is known about how ageing influences visual attention in environments more representative of real-world complexity. Here, we test the hypothesis that ageing impacts how the visual complexity of the environment influences visual search. Young and older adults completed a virtual reality-based visual search task in environments with increasing visual complexity. As visual complexity increased, all participants exhibited longer times to complete the task, which resulted from increased time transferring gaze from one correct target to the next and increased delay between when correct targets were fixated and selected. The increase in time to completion can also be attributed to longer times spent re-fixating task-relevant objects and fixating task-irrelevant objects. These changes in visual search and target selection with increasing visual complexity were greater in older adults, and working memory capacity was associated with multiple performance measures in the visual search task. These findings suggest that visual search performance could be integrated into assessments of working memory in dynamic environments.

Familiarity plays a pivotal role in within-person face recognition. However, previous research in this field mostly used only one task: Identity Card Sorting. This study aims to explore the links between within-person recognition and other standardized face processing tests, and to extend the sample beyond the WEIRD (western, educated, industrialized, rich and democratic) population. We recruited Taiwanese, Pakistanis and another group of international adults who were neither Taiwanese nor Pakistanis. Each participant completed Face Identity Sorting, Face Discrimination, the Cambridge Face Memory Test (CFMT) and the Prosopagnosia Index (PI-20). Results showed a significant familiarity effect in Face Identity Sorting, with Taiwanese and Pakistani groups, but not the International group, sorting fewer piles for familiar faces (i.e. Pakistani or Taiwanese celebrities). Correlational analyses combining all participants further revealed that Card Sorting performance positively correlated with CFMT and Face Discrimination scores, and showed a marginally negative correlation with PI-20. This suggests that individuals with better face memory and detail-oriented discriminability tend to make fewer errors in the unfamiliar within-person recognition task. This study is the first to examine within-person face recognition in Pakistani and Taiwanese adults, demonstrating a robust effect of familiarity and strong associations with objective assessments of face processing abilities.

Musculoskeletal modelling opens windows into how muscle properties interact with neural control to govern movement. Although musculoskeletal models produce vast computational data, they lack a visual language that compactly communicates how joint dynamics relate to time-varying muscle activation, force and length change. We developed a novel representation of joint-level force-velocity (joint-FV) properties, which shows how agonist and antagonist muscles contribute to the overall joint state and its trajectory throughout a movement. Using a model of human goal-directed reaching, we used joint-FV visualizations to discern the salient joint dynamic features across joints and between different reach targets. Regardless of target, we found that the shoulder, elbow and wrist joints traversed a near circular trajectory through joint-FV space when muscle forces were dominant, but trajectories were more complex when joint-interaction forces dominated (i.e. cross-joint forces due to Coriolis, Euler and centrifugal effects). Additionally, we found that co-contraction steepens the slope of the instantaneous joint-FV curve, causing damping, which helps stabilize against small perturbations. We therefore propose that our joint-FV visualization can be used to explain the intricate features seen in musculoskeletal simulation data to reveal how intrinsic muscle properties govern the behaviour of dynamical systems.

Identifying linked cases of an infectious disease can improve our understanding of its epidemiology by distinguishing sustained local transmission from frequent introductions with little onward transmission. This evidence can, in turn, inform decisions on interventions. Knowledge of epidemiological distributions and reporting probabilities is key in identifying linked cases. However, with multi-host pathogens quantitative differences between hosts may need consideration. In this study, an existing graph-based approach to detecting outbreak clusters was extended to allow for group-specific reporting probabilities and epidemiological distributions and to assess the level and importance of assortative mixing. This method was applied to data on animal rabies cases in Tanzania. Group-specific differences in reporting probabilities and epidemiological distributions and the level of assortative mixing had a marked impact on the size and composition of clusters. Results of the rabies cases analysis supported higher reporting probabilities in domestic animals than wildlife, no difference in mean transmission distance between groups, and frequent inter-species transmission. The method described here could be applied to other multi-host or multi-group systems in which heterogeneities in reporting probabilities, distributional parameters and/or levels of mixing exist between groups. This would allow more accurate characterization of transmission dynamics and thus facilitate implementation of more effective interventions.

Food insecurity is associated with higher body weight in humans and other species, but the causal effect of unpredictable food availability on weight gain is unknown. We measured food intake and weight in starlings (Sturnus vulgaris) exposed to repeated irregular periods of food deprivation. We manipulated the predictability of deprivation between subjects with a 1 h visual cue that either reliably preceded deprivation (Predictable group) or was uncorrelated with deprivation (Unpredictable group). During the cue, Predictable birds reduced their food intake and spent less time inactive, indicating that they had learnt the contingency. Despite these responses, they lost less weight during subsequent deprivation. They also ate less and gained less weight when food was returned. Birds with the largest behavioural response to the cue had the lowest overall variance in body weight. Consistent with the insurance hypothesis, food intake and body weight increased over time in both groups and body weight was higher in the Unpredictable group. Our results suggest that when food deprivation was predictable, birds were less reliant on stored fat and instead used conditioned hypometabolism to mitigate the effects of food deprivation. We discuss the implications of our findings for the differential health impacts of food insecurity and intermittent fasting.

This study used a rigorous actuarial approach to estimate excess mortality across German federal states during the first three years of the COVID-19 pandemic. Regional trends were analysed alongside associations with state-level indicators: reported COVID-19 deaths and infections, policy stringency, vaccination rates, demographic and socioeconomic factors. Average excess mortality was moderate in the first year, with substantial regional variation. It increased slightly in the second year, with stable regional patterns. In the third year, excess mortality rose sharply, regional differences diminished, and the most affected states shifted, indicating the emergence of a new excess mortality driver. In the first two years, excess mortality strongly correlated with COVID-19 deaths, although reported COVID-19 deaths substantially exceeded excess deaths. Despite rising excess mortality, COVID-19 deaths declined over time. In the third year, only vaccination rate and trust in institutions showed notable associations, with the latter fully mediated by vaccination rate. Higher vaccination rates correlated with larger increases in excess mortality and with smaller declines in COVID-19 deaths and case fatality rates, even after adjusting for prior mortality levels and time-invariant confounders. This robust finding underscores the need for urgent investigation into potential unintended effects of vaccination or other previously neglected mortality drivers.

People sometimes perceive causal relationships between non-contingent events. When having to assess the contingency between a putative cause and an outcome, it is vital to ensure that all other causal forces are held constant whether the studied cause is present or not. Nevertheless, a recent work suggested that, in conventional contingency learning scenarios, people do not necessarily assume that it is the case. A possible contributing factor to this asset is that instructions in contingency learning tasks do not typically clarify this point. In two experiments, we manipulated the task instructions so that only half of the participants were explicitly informed that the introduction of the putative cause was randomly decided for each trial. The second experiment further instructed participants in the implications of random assignment regarding the control of alternative causes. Results of both experiments indicated that the manipulation of the instructions had no impact on the strength of causal illusions (minimum BF ₀₁ = 5.853). Nevertheless, the susceptibility to develop causal illusions was related to a lack of an appropriate consideration of alternative causal forces and a tendency to overweight the importance of the probability of the outcome in the presence, rather than in the absence, of the putative cause.

The visual system has been suggested to extrapolate an object's position by integrating proximal motion signals to compensate for inevitable neural delays. This anticipatory extrapolation hypothesis is consistent with visual illusions such as the flash-lag effect, where a moving object appears ahead of a physically aligned flash, and the flash-drag effect, where the perceived position of a flash is shifted in the direction of its surrounding motion. In contrast to such motion-induced position shifts, we demonstrate an illusion in which a moving object appears to be standing still at a shifted position when surrounded by motion in the same direction. For this dissociation between perceived motion and position, we propose a computational model that incorporates the biphasic centre-surround antagonistic responses of motion detectors. In our model, positional signals derive from the temporal integration of motion-detector responses but remain unperceived during early suppression, reaching conscious perception only afterwards. The illusion was strongest when the object and surrounding motion began simultaneously, and weakened with increasing asynchrony or longer duration. The model predicts these results and accounts for several motion- and saccade-induced mislocalization phenomena, offering a unified account of dynamic position perception shaped by local and global motion signals and perceptual lag.

Eagle rays, cownose rays and manta rays are the only batoid families exhibiting oscillatory locomotion, and are characterized by long, slender tails. This study investigates whether tail length influences body stability when the pectoral fins are held in an extended, static position. We measured relative tail lengths across the four families (Rhinopteridae, Myliobatidae, Aetobatidae and Mobulidae), finding that spotted eagle rays have the longest tails (greater than 4× body length (BL)), while giant manta rays have the shortest (approx. 0.9× BL). To test the effects of tail length on posture and stability, we used three-dimensional-printed models based on a myliobatid body and a NACA 0012 foil in a flow tank across increasing speeds. Pitch, roll and overall dynamic body acceleration (ODBA) were recorded using embedded accelerometers. Models without tails showed increased roll and ODBA, while models with tails greater than or equal to 0.9× BL, which was the minimum length found in measured animals, maintained a steadier position. This result indicates that tails enhance passive stability by providing drag-based damping and a restoring torque that helps the ray models resist and recover from disturbances. As longer tails did not further improve stability, tails exceeding 0.9× BL may serve additional roles, such as communication, mating or sensing.

In this article, we research the material, mechanical, geometrical and chemical characteristics of the Turkana Abarait, a wrist blade used ubiquitously by Turkana people (both male and female) in north-western Kenya. To characterize the blades, we used a combination of three-dimensional scanning, scanning electron microscopy coupled with Image Analysis techniques, X-ray diffraction, X-ray fluorescence and Vickers hardness testing at HV30. We find that the blades are made from low-carbon bloomery iron, containing particulates of slag inclusions, or soot-based remnants, as well as trace elements of magnesium, sodium, aluminium, sulfur, phosphorus, chlorine, cobalt and potassium. While the soot particulates are likely derived from the incomplete refinement and non-uniform heating typical of pre-industrial forging methods, we deduce that the other trace elements originate from irons smelted from riverbed ore. We find that while blade edge angle does not differ between the blades (p $>$ 0.05, 95% confidence), the blade edge widths are significantly different (p $<$ 0.001, 99.9% confidence), indicating inconsistencies in the manufacturing processes. We find that there are mechanically significant differences in both inter- and intra-blade hardness values (p $<$ 0.001, 99.9% confidence), adding to our proposition that Abarait blades are manufactured inconsistently. The blades are nevertheless fit for purpose, achieving a balance of hardness and ductility suited to their dual role as cutting tools and close-combat weapons.