Cultural Differences in Perceptual Reorganization in US and Pirah? Adults

Visual illusions and other perceptual phenomena can be used as tools to uncover the otherwise hidden constructive processes that give rise to perception. Although many perceptual processes are assumed to be universal, variable susceptibility to certain illusions and perceptual effects across populations suggests a role for factors that vary culturally. One striking phenomenon is seen with two-tone images—photos reduced to two tones: black and white. Deficient recognition is observed in young children under conditions that trigger automatic recognition in adults. Here we show a similar lack of cue-triggered perceptual reorganization in the Pirahã, a hunter-gatherer tribe with limited exposure to modern visual media, suggesting such recognition is experience- and culture-specific.     

Spatial Associations, Size–Distance Relationships and Population Structure of Two Dominant Life Forms in a Semiarid Enclave of the Venezuelan Andes

The role of three thorny legume species as nurse plants and competitive relationships with columnar cacti were evaluated in a semiarid enclave of the Venezuelan Andes. Abundance and size of three columnar cacti species (Stenocereus griseus, Cereus repandus and Pilosocereus tillianus) under isolated shrubs of three thorny legumes species (Prosopis juliflora, Acacia farnesiana and A. macracantha) were recorded and compared with open areas. Using size–distance data we inferred the intensity of intra- and interspecific competition between both life forms in a “cardonal” (xeric zone) and “espinar” (mesic zone) of the enclave. Sixty-one columnar cacti were found beneath the three thorny legume species (92%), while only 5 cactus individuals were found in open areas (8%). Comparison of observed and expected number of cactus individuals shows that S. griseus and C. repandus are significantly associated with isolated shrubs of A. farnesiana and A. macracantha. Although P. juliflora contributed more than 40% of the total legume plant cover, the number of columnar cacti under its isolated shrubs was significantly lower than would be expected by chance. In all, 19 of 21 possible plant–plant combinations between and within columnar cacti and legume shrubs were recorded (espinar: 18, cardonal: 13, common combinations: 12). In both zones, intra- and interspecific combinations among columnar cacti species were relatively high (positive correlation between the sum of neighbour plant sizes and the distances separating them). Our results strongly suggest, at least for case of S. griseus and C. repandus, that these columnar cacti species require nurse plants for their establishment. The results on interference need still support from further research. We discuss the effects of plant–plant positive interactions on natural regeneration of these columnar cacti.     

The Influence of Between-Farm Distance and Farm Size on the Spread of Classical Swine Fever during the 1997–1998 Epidemic in The Netherlands

As the size of livestock farms in The Netherlands is on the increase for economic reasons, an important question is how disease introduction risks and risks of onward transmission scale with farm size (i.e. with the number of animals on the farm). Here we use the epidemic data of the 1997–1998 epidemic of Classical Swine Fever (CSF) Virus in The Netherlands to address this question for CSF risks. This dataset is one of the most powerful ones statistically as in this epidemic a total of 428 pig farms where infected, with the majority of farm sizes ranging between 27 and 1750 pigs, including piglets. We have extended the earlier models for the transmission risk as a function of between-farm distance, by adding two factors. These factors describe the effect of farm size on the susceptibility of a ‘receiving’ farm and on the infectivity of a ‘sending’ farm (or ‘source’ farm), respectively. Using the best-fitting model, we show that the size of a farm has a significant influence on both farm-level susceptibility and infectivity for CSF. Although larger farms are both more susceptible to CSF and, when infected, more infectious to other farms than smaller farms, the increase is less than linear. The higher the farm size, the smaller the effect of increments of farm size on the susceptibility and infectivity of a farm. Because of changes in the Dutch pig farming characteristics, a straightforward extrapolation of the observed farm size dependencies from 1997/1998 to present times would not be justified. However, based on our results one may expect that also for the current pig farming characteristics in The Netherlands, farm susceptibility and infectivity depend non-linearly on farm size, with some saturation effect for relatively large farm sizes.     

Dialysance of Molecules of Different Size in Reused Kiil,Ab-Gambro,and Rh?ne-Poulenc Dialysers

Dialysances of urea, creatinine, ethylenediamine tetraacetic acid, and ouabain were determined in three different flat-bed dialysers during three successive uses on 15 patients. There were no untoward reactions. A significant decrease in dialysing efficiency was observed only with the Ab-Gambro dialyser, in which the dialysance of the small molecules decreased more than that of the large. This is thought to result from blood deposits on the membrane surface inhibiting exchange.     

Interaction between Oligomers of Stefin B and Amyloid-�� in Vitro and in Cells

To contribute to the question of the putative role of cystatins in Alzheimer disease and in neuroprotection in general, we studied the interaction between human stefin B (cystatin B) and amyloid-β-(1–40) peptide (Aβ). Using surface plasmon resonance and electrospray mass spectrometry we were able to show a direct interaction between the two proteins. As an interesting new fact, we show that stefin B binding to Aβ is oligomer specific. The dimers and tetramers of stefin B, which bind Aβ, are domain-swapped as judged from structural studies. Consistent with the binding results, the same oligomers of stefin B inhibit Aβ fibril formation. When expressed in cultured cells, stefin B co-localizes with Aβ intracellular inclusions. It also co-immunoprecipitates with the APP fragment containing the Aβ epitope. Thus, stefin B is another APP/Aβ-binding protein in vitro and likely in cells.     

Determinants of Dwell Time in Visual Search: Similarity or Perceptual Difficulty?

The present study examined the factors that determine the dwell times in a visual search task, that is, the duration the gaze remains fixated on an object. It has been suggested that an item's similarity to the search target should be an important determiner of dwell times, because dwell times are taken to reflect the time needed to reject the item as a distractor, and such discriminations are supposed to be harder the more similar an item is to the search target. In line with this similarity view, a previous study shows that, in search for a target ring of thin line-width, dwell times on thin linewidth Landolt C's distractors were longer than dwell times on Landolt C's with thick or medium linewidth. However, dwell times may have been longer on thin Landolt C's because the thin line-width made it harder to detect whether the stimuli had a gap or not. Thus, it is an open question whether dwell times on thin line-width distractors were longer because they were similar to the target or because the perceptual decision was more difficult. The present study de-coupled similarity from perceptual difficulty, by measuring dwell times on thin, medium and thick line-width distractors when the target had thin, medium or thick line-width. The results showed that dwell times were longer on target-similar than target-dissimilar stimuli across all target conditions and regardless of the line-width. It is concluded that prior findings of longer dwell times on thin linewidth-distractors can clearly be attributed to target similarity. As will be discussed towards the end, the finding of similarity effects on dwell times has important implications for current theories of visual search and eye movement control.     

A Test of Rensch’s Rule in Greater Horseshoe Bat (Rhinolophus ferrumequinum) with Female-Biased Sexual Size Dimorphism

Sexual size dimorphism (SSD) is widespread within the animal kingdom. Rensch’s rule describes a relationship between SSD and body size: SSD increases with body size when males are the larger sex, and decreases with body size when females are the larger sex. Rensch’s rule is well supported for taxa that exhibit male-biased SSD but patterns of allometry among taxa with female-biased size dimorphism are mixed, there is evidence both for and against the rule. Furthermore, most studies have investigated Rensch’s rule across a variety of taxa; but among-population studies supporting Rensch’s rule are lacking, especially in taxa that display only slight SSD. Here, we tested whether patterns of intraspecific variation in SSD in greater horseshoe bats conform to Rensch’s rule, and evaluated the contribution of latitude to Rensch’s rule. Our results showed SSD was consistently female-biased in greater horseshoe bats, although female body size was only slightly larger than male body size. The slope of major axis regression of log₁₀ (male) on log₁₀ (female) was significantly different from 1. Forearm length for both sexes of greater horseshoe bats was significantly negatively correlated with latitude, and males displayed a slightly but nonsignificant steeper latitudinal cline in body size than females. We suggest that variation in patterns of SSD among greater horseshoe bat populations is consistent with Rensch’s rule indicating that males were the more variable sex. Males did not have a steeper body size–latitude relationship than females suggesting that sex-specific latitudinal variation in body size may not be an important contributing factor to Rensch’s rule. Future research on greater horseshoe bats might best focus on more comprehensive mechanisms driving the pattern of female-biased SSD variation.     

Does Glass Size and Shape Influence Judgements of the Volume of Wine?

Background

Judgements of volume may influence the rate of consumption of alcohol and, in turn, the amount consumed. The aim of the current study was to examine the impact of the size and shape of wine glasses on perceptions of wine volume.

Methods

Online experiment: Participants (n = 360; recruited via Mechanical Turk) were asked to match the volume of wine in two wine glasses, specifically: 1. the Reference glass holding a fixed reference volume, and 2. the Comparison glass, for which the volume could be altered until participants perceived it matched the reference volume. One of three comparison glasses was shown in each trial: ‘wider’ (20% wider but same capacity); ‘larger’ (same width but 25% greater capacity); or ‘wider-and-larger’ (20% wider and 25% greater capacity). Reference volumes were 125ml, 175ml and 250ml, in a fully factorial within-subjects design: 3 (comparison glass) x 3 (reference volume). Non-zero differences between the volumes with which participants filled comparison glasses and the corresponding reference volumes were identified using sign-rank tests.

Results

Participants under-filled the wider glass relative to the reference glass for larger reference volumes, and over-filled the larger glass relative to the reference glass for all reference volumes. Results for the wider-and-larger glass showed a mixed pattern across reference volume. For all comparison glasses, in trials with larger reference volumes participants tended to fill the comparison glass less, relative to trials with smaller reference volumes for the same comparison glass.

Conclusions

These results are broadly consistent with people using the relative fullness of glasses to judge volume, and suggest both the shape and capacity of wine glasses may influence perceived volume. Perceptions that smaller glasses contain more than larger ones (despite containing the same volume), could slow drinking speed and overall consumption by serving standard portions in smaller glasses. This hypothesis awaits testing.     

Flight Initiation Distance and Starting Distance: Biological Effect or Mathematical Artefact?

In many studies, flight initiation distance (FID, the distance at which a prey starts to flee at the approach of a walker) is positively related to starting distance (SD, the distance at which the walker begins to approach) and alert distance (AD, the distance at which the focal individual becomes alert to the threat). In spite of the fundamental differences between SD, a covariate that may not have any biological effect, and AD, a measure related to the behaviour of the animal, it is common to use SD as a proxy for AD when AD is hard to measure (e.g. in species that do not exhibit distinguishable alert postures). However, the relationship between SD and AD or FID may not have any biological reasons, but may instead simply result from a mathematical artefact because of the constraints SD ≥ AD ≥ FID. Under such constrains, the homoscedasticity assumption is violated, and thus, the classical null hypothesis of linear regression (slope = 0) is invalid. In this study, we first show that using SD as a proxy for AD can strongly affect the results on FID. Using data from FID tests on alpine marmots (Marmota marmota), a linear mixed model with AD as a covariate, suggested that the interaction between previous activity and AD had an effect on FID, while this effect was not detected when SD replaced AD as the covariate in the analysis. We then propose that the actual statistical test of the relationship between SD, AD and FID should be based on a null hypothesis that incorporates the constraint SD ≥ AD ≥ FID ≥ 0 and generate 95% CI of simulated slopes obtained from random values under this constraint. This null hypothesis can be rejected if the observed slope of the relationship between two of these variables is outside the 95% CI. We demonstrated that, for alpine marmots, the observed slope of the relationship between AD and SD was within the 95% CI of the simulated slopes. The absence of a statistically significant biological effect in the relationship between SD and AD raises important questions on the outcome of relationship between SD and FID. In Alpine marmot flight, decision should be studied separating the effect of SD on AD and the effect of AD on FID.     

Perceptual “Read-Out” of Conjoined Direction and Disparity Maps in Extrastriate Area MT

Cortical neurons are frequently tuned to several stimulus dimensions, and many cortical areas contain intercalated maps of multiple variables. Relatively little is known about how information is “read out” of these multidimensional maps. For example, how does an organism extract information relevant to the task at hand from neurons that are also tuned to other, irrelevant stimulus dimensions? We addressed this question by employing microstimulation techniques to examine the contribution of disparity-tuned neurons in the middle temporal (MT) visual area to performance on a direction discrimination task. Most MT neurons are tuned to both binocular disparity and the direction of stimulus motion, and MT contains topographic maps of both parameters. We assessed the effect of microstimulation on direction judgments after first characterizing the disparity tuning of each stimulation site. Although the disparity of the stimulus was irrelevant to the required task, we found that microstimulation effects were strongly modulated by the disparity tuning of the stimulated neurons. For two of three monkeys, microstimulation of nondisparity-selective sites produced large biases in direction judgments, whereas stimulation of disparity-selective sites had little or no effect. The binocular disparity was optimized for each stimulation site, and our result could not be explained by variations in direction tuning, response strength, or any other tuning property that we examined. When microstimulation of a disparity-tuned site did affect direction judgments, the effects tended to be stronger at the preferred disparity of a stimulation site than at the nonpreferred disparity, indicating that monkeys can selectively monitor direction columns that are best tuned to an appropriate conjunction of parameters. We conclude that the contribution of neurons to behavior can depend strongly upon tuning to stimulus dimensions that appear to be irrelevant to the current task, and we suggest that these findings are best explained in terms of the strategy used by animals to perform the task.     

Can Attention Be Confined to Just Part of a Moving Object? Revisiting Target-Distractor Merging in Multiple Object Tracking

While it was initially thought that attention was space-based, more recent work has shown that attention can also be object-based, in that observers find it easier to attend to different parts of the same object than to different parts of different objects. Such studies have shown that attention more easily spreads throughout an object than between objects. However, it is not known to what extent attention can be confined to just part of an object and to what extent attending to part of an object necessarily causes the entire object to be attended. We have investigated this question in the context of the multiple object tracking paradigm in which subjects are shown a scene containing a number of identical moving objects and asked to mentally track a subset of them, the targets, while not tracking the remainder, the distractors. Previous work has shown that joining each target to a distractor by a solid connector so that each target-distractor pair forms a single physical object, a technique known as target-distractor merging, makes it hard to track the targets, suggesting that attention cannot be restricted to just parts of objects. However, in that study the target-distractor pairs continuously changed length, which in itself would have made tracking difficult. Here we show that it remains difficult to track the targets even when the target-distractor pairs do not change length and even when the targets can be differentiated from the connectors that join them to the distractors. Our experiments suggest that it is hard to confine attention to just parts of objects, at least in the case of moving objects.     

Distance to High-Voltage Power Lines and Risk of Childhood Leukemia – an Analysis of Confounding by and Interaction with Other Potential Risk Factors

We investigated whether there is an interaction between distance from residence at birth to nearest power line and domestic radon and traffic-related air pollution, respectively, in relation to childhood leukemia risk. Further, we investigated whether adjusting for potential confounders alters the association between distance to nearest power line and childhood leukemia. We included 1024 cases aged <15, diagnosed with leukemia during 1968–1991, from the Danish Cancer Registry and 2048 controls randomly selected from the Danish childhood population and individually matched by gender and year of birth. We used geographical information systems to determine the distance between residence at birth and the nearest 132–400 kV overhead power line. Concentrations of domestic radon and traffic-related air pollution (NO_x at the front door) were estimated using validated models. We found a statistically significant interaction between distance to nearest power line and domestic radon regarding risk of childhood leukemia (p = 0.01) when using the median radon level as cut-off point but not when using the 75^th percentile (p = 0.90). We found no evidence of an interaction between distance to nearest power line and traffic-related air pollution (p = 0.73). We found almost no change in the estimated association between distance to power line and risk of childhood leukemia when adjusting for socioeconomic status of the municipality, urbanization, maternal age, birth order, domestic radon and traffic-related air pollution. The statistically significant interaction between distance to nearest power line and domestic radon was based on few exposed cases and controls and sensitive to the choice of exposure categorization and might, therefore, be due to chance.     

Socio-cultural Determinants of Human–Bat Interactions in Rural Ghana

Bats are known to be a natural reservoir for a lot of disease pathogens and can spread several diseases. All 11 genera of fruit bat found in West Africa are found in Ghana, and human–bat interactions are common. However, there is a dearth of knowledge about the socio-cultural factors that shape these interactions. This paper explores the socio-cultural factors that bring humans into contact with bats. Data were obtained through focus group discussions and in-depth interviews. The findings indicate that gender, religious affiliation, and belief systems influence the interaction between humans and bats. We conclude that the hunting and consumption patterns of bats have farreaching consequences for the transmission of bat-borne zoonotic diseases. Educational campaigns, therefore, should be intensified and, in particular, target groups that are most at risk of contracting bat-borne zoonotic diseases.     

What Are You or Who Are You? The Emergence of Social Interaction between Dog and an Unidentified Moving Object (UMO)

Robots offer new possibilities for investigating animal social behaviour. This method enhances controllability and reproducibility of experimental techniques, and it allows also the experimental separation of the effects of bodily appearance (embodiment) and behaviour. In the present study we examined dogs’ interactive behaviour in a problem solving task (in which the dog has no access to the food) with three different social partners, two of which were robots and the third a human behaving in a robot-like manner. The Mechanical UMO (Unidentified Moving Object) and the Mechanical Human differed only in their embodiment, but showed similar behaviour toward the dog. In contrast, the Social UMO was interactive, showed contingent responsiveness and goal-directed behaviour and moved along varied routes. The dogs showed shorter looking and touching duration, but increased gaze alternation toward the Mechanical Human than to the Mechanical UMO. This suggests that dogs’ interactive behaviour may have been affected by previous experience with typical humans. We found that dogs also looked longer and showed more gaze alternations between the food and the Social UMO compared to the Mechanical UMO. These results suggest that dogs form expectations about an unfamiliar moving object within a short period of time and they recognise some social aspects of UMOs’ behaviour. This is the first evidence that interactive behaviour of a robot is important for evoking dogs’ social responsiveness.     

Extreme Sexual Brain Size Dimorphism in Sticklebacks: A Consequence of the Cognitive Challenges of Sex and Parenting?

Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology and behaviour. However, apart from the controversial report that males have slightly heavier brains than females in humans, evidence for substantial sexual dimorphism in brain size is scarce. This apparent sexual uniformity is surprising given that sexually distinct selection pressures are ubiquitous and that brains are one of the most plastic vertebrate organs. Here we demonstrate the highest level of sexual brain size dimorphism ever reported in any vertebrate: male three-spined stickleback of two morphs in an Icelandic lake have 23% heavier brains than females. We suggest that this dramatic sexual size dimorphism is generated by the many cognitively demanding challenges that males are faced in this species, such as an elaborate courtship display, the construction of an ornate nest and a male-only parental care system. However, we consider also alternative explanations for smaller brains in females, such as life-history trade-offs. Our demonstration of unprecedented levels of sexual dimorphism in brain size in the three-spined stickleback implies that behavioural and life-history differences among the sexes can have strong effects also on neural development and proposes new fields of research for understanding brain evolution.     

Interaction of hydrolytic and phosphorolytic enzymes of starch metabolism in Kalanchoë daigremontiana

The degradation of starch by a protein fraction of Kalanchoë daigremontiana Hamet et Perrier, obtained by ammoniumsulfate precipitation (30–70%), was found to be catalyzed by -and -amylase (EC 3.2.1.1 and EC 3.2.1.2, respectively) and by starch phosphorylase (EC 2.4.1.1). The activity of these enzymes was determined by chromatographic analysis of the reaction products; separation and identification of -amylase was accomplished by heat-inactivation of -amylase and -glucosidase. When the interaction of amylolytic and phosphorolytic enzymes was comparatively studied, it was found that without inorganic phosphorus in the reaction mixture, ¹⁴C-starch was converted predominantly to maltose and glucose; supplementation with 1–10 mM orthophosphate (Pi) resulted in an increase in glucose-1-phosphate formation and a concomitant reduction of maltose production. Since the total volume of starch degradation remained approximately constant, Pi apparently inhibits -amylase (Ki about 3 mM Pi). Thus, free Pi in the cell participates in the regulation of starch catabolism, serving as a substrate for starch phosphorylase while simultaneously reducing the production of maltose. With respect to glucan synthesis, adenosinediphosphoglucose--1,4-glucosyltransferase (EC 2.4.1.22), maltose phosphorylase and maltoseglucosyltransferase were also found to be active. The last-named enzyme catalyzes an exchange between dextrins and is considered to provide primer carbohydrates for the synthesis of polyglucans.Abbreviations ADPG adenosinediphosphoglucose - G1P glucose-1-phosphate - PEG polyethylenglycol - PEP phosphoenolpyruvate - Pi orthophosphate     

Foveal and Peripheral Fields of Vision Influences Perceptual Skill in Anticipating Opponents’ Attacking Position in Volleyball

The importance of perceptual-cognitive expertise in sport has been repeatedly demonstrated. In this study we examined the role of different sources of visual information (i.e., foveal versus peripheral) in anticipating volleyball attack positions. Expert (n = 11), advanced (n = 13) and novice (n = 16) players completed an anticipation task that involved predicting the location of volleyball attacks. Video clips of volleyball attacks (n = 72) were spatially and temporally occluded to provide varying amounts of information to the participant. In addition, participants viewed the attacks under three visual conditions: full vision, foveal vision only, and peripheral vision only. Analysis of variance revealed significant between group differences in prediction accuracy with higher skilled players performing better than lower skilled players. Additionally, we found significant differences between temporal and spatial occlusion conditions. Both of those factors interacted separately, but not combined with expertise. Importantly, for experts the sum of both fields of vision was superior to either source in isolation. Our results suggest different sources of visual information work collectively to facilitate expert anticipation in time-constrained sports and reinforce the complexity of expert perception.     

Does Intraspecific Size Variation in a Predator Affect Its Diet Diversity and Top-Down Control of Prey?

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity.