How to make better forensic decisions

Much of forensic practice today involves human decisions about the origins of patterned sensory evidence, such as tool marks and fingerprints discovered at a crime scene. These decisions are made by trained observers who compare the evidential pattern to an exemplar pattern produced by the suspected source of the evidence. The decision consists of a determination as to whether the two patterns are similar enough to have come from the same source. Although forensic pattern comparison disciplines have for decades played a valued role in criminal investigation and prosecution, the extremely high personal and societal costs of failure—the conviction of innocent people—has elicited calls for caution and for the development of better practices. These calls have been heard by the scientific community involved in the study of human information processing, which has begun to offer much-needed perspectives on sensory measurement, discrimination, and classification in a forensic context. Here I draw from a well-established theoretical and empirical approach in sensory science to illustrate the vulnerabilities of contemporary pattern comparison disciplines and to suggest specific strategies for improvement.     

Comparison of vibration perception thresholds obtained with the Neurothesiometer and the CASE IV and relationship to nerve conduction studies.

AIMS: Vibration perception thresholds (VPTs) are used frequently to assess somatosensory pathways in clinical trials. Different equipment, testing paradigms, and stimulation sites produce varying results which make comparisons between trials and patient populations challenging. Information comparing the VPT obtained with the Neurothesiometer with that with the Vibratron is available, but not for a similar comparison with the CASE IV (computer-assisted sensory examination device). METHODS: Subjects (n = 478) including reference, non-neuropathic subjects with diabetes mellitus (DM), and diabetic patients with mild, moderate and severe diabetic sensorimotor polyneuropathy (DSP) had VPTs measured with the CASE IV and Neurothesiometer, as well as standard sural nerve conduction studies (NCS), all performed during the same half-day. The dorsum of the foot was used as the site of stimulation for the CASE IV VPT determination and the distal phalanx of the first toe for the Neurothesiometer. RESULTS: VPTs by the CASE IV and the Neurothesiometer compared moderately by linear regression analyses (R2 = 0.547, P < 0.0001), and by 95% confidence intervals. Sensitivity for the diagnosis of mild DSP was 70% with the Neurothesiometer and 49% with the CASE IV. VPTs determined by either the Neurothesiometer or the CASE IV correlated with similar agreement to the sural nerve action potential amplitude as determined by nerve conduction studies (NCS) (R2 = 0.456 and 0.461, respectively, P < 0.0001). CONCLUSIONS: The results demonstrated a significant correlation of VPT values in different stages of DSP obtained by the two methods. The Neurothesiometer was more sensitive for the diagnosis of DSP, particularly in those with mild neuropathy. Similar correlations between VPTs and electrophysiological parameters were observed, indicating that both methods are valid, and thus the Neurothesiometer may be preferable due to the ease and rapidity of testing by this method.     

The role of sensory perception in the development and targeting of tobacco products

AIMS: To examine tobacco industry research on smoking-related sensory effects, including differences in sensory perception across smoker groups, and to determine whether this research informed targeted product development and impacted the development of commercial tobacco products. DESIGN: We searched previously secret internal tobacco industry documents available online through document databases housed at Tobacco Documents Online, the British American Tobacco Document Archive and the Legacy Tobacco Documents Library. We identified relevant documents using a snowball sampling method to first search the databases using an initial set of key words and to then establish further search terms. FINDINGS: Sensory research is a priority within the tobacco industry directly impacting commercial markets both in the United States and internationally. Sensory factors contribute to smoker satisfaction and product acceptance, and play an important role in controlling puffing behavior. Cigarette manufacturers have capitalized on distinct sensory preferences across gender, age and ethnic groups by tailoring products for specific populations. CONCLUSIONS: Regulation of tobacco products is needed to address product changes that are used to reinforce or contribute to tobacco dependence; for instance, the incorporation of additives that target attributes such as smoothness, harshness and aftertaste. Greater understanding of the role of sensory effects on smoking behavior may also help to inform the development of tobacco treatment options that support long-term tobacco abstinence.     

网球运动对老年人视运动知觉能力的影响

目的探讨网球运动对老年人身体健康的影响和老年人视运动知觉能力可因为网球训练而得到改善。方法采用分组实验对比分析进行测试,使用经典随机点阵范式与经典表征动量范式测验进行数据采集,将前后实验结果进行比较。结果经过10 w活动干预后,网球活动组在左右运动、上下运动和径向运动3个方向上的阈限上与对照组存在显著差异(P<0.05);网球活动组被试前后测阈限数据比较在所有运动类型中的阈值都有所降低,其中左右运动、径向运动和旋转运动3个方向较为显著。从网球活动组和对照组在不同的测试刺激上判断相同的百分率上的结果来看,网球活动组判断水平有所提高,普通对照组无明显变化。结论参加网球活动可以提高老年人的身体健康和视觉反应能力,网球活动能有效改善老年人视运动知觉能力。     

Unifying account of visual motion and position perception

Despite growing evidence for perceptual interactions between motion and position, no unifying framework exists to account for these two key features of our visual experience. We show that percepts of both object position and motion derive from a common object-tracking system—a system that optimally integrates sensory signals with a realistic model of motion dynamics, effectively inferring their generative causes. The object-tracking model provides an excellent fit to both position and motion judgments in simple stimuli. With no changes in model parameters, the same model also accounts for subjects’ novel illusory percepts in more complex moving stimuli. The resulting framework is characterized by a strong bidirectional coupling between position and motion estimates and provides a rational, unifying account of a number of motion and position phenomena that are currently thought to arise from independent mechanisms. This includes motion-induced shifts in perceived position, perceptual slow-speed biases, slowing of motions shown in visual periphery, and the well-known curveball illusion. These results reveal that motion perception cannot be isolated from position signals. Even in the simplest displays with no changes in object position, our perception is driven by the output of an object-tracking system that rationally infers different generative causes of motion signals. Taken together, we show that object tracking plays a fundamental role in perception of visual motion and position.Research into the basic mechanisms of visual motion processing has largely focused on simple cases in which motion signals are fixed in space and constant over time (e.g., moving patterns presented in static windows) (1). Although this approach has resulted in considerable advances in our understanding of low-level motion mechanisms, it leaves open the question of how the brain integrates changing motion and position signals; when objects move in the world, motion generally co-occurs with changes in object position. The process of generating coherent estimates of object motion and position is known in the engineering and computer vision literature as “tracking” (e.g., as used by the Global Positioning System) (2). Conceptualizing motion and position perception in the broader context of object tracking suggests an alternative conceptual framework—one that we show provides a unifying account for a number of perceptual phenomena.An optimal tracking system would integrate incoming position and motion signals with predictive information from the recent past to continuously update perceptual estimates of both an object’s position and its motion. Were such a system to underlie perception, position and motion should be perceptually coupled in predictable ways. Signatures of such a coupling appear in a number of known phenomena. On one hand, local motion signals can predictively bias position percepts (3–8). On the other hand, we can perceive motion solely from changes in object position (9–12). For example, motion can be perceived in stimuli with no directional motion signal by tracking position changes along a specific direction (10). These phenomena, however, are currently regarded as arising from independent mechanisms (11–14).Given the interdependency of motion and position and the inherent noisiness of sensory signals, it is advantageous for vision to exploit the redundancy between motion and position signals and integrate them into coupled perceptual estimates. This is complicated by the fact that local motion signals can result from a combination of motions (of which object translations are only one) (15, 16). A flying, rotating soccer ball provides a prototypical example of this problem (Fig. 1A). Because the ball rotates as it flies through the air, the local retinal motion signals created by ball texture are sums of two world motions: translation and rotation of the ball. Relating local motion signals to object motion requires the solution of the “source attribution” problem (17, 18)—determining what part of a local retinal motion pattern is due to object translation and what part is due to object-relative motion of the texture pattern. To solve this attribution problem, the brain can exploit the redundant information provided by the changing stimulus position. Moreover, integrating motion and position information over time with an internal model of motion dynamics can mitigate both the uncertainty created by ubiquitous sensory noise (19) and that created by the motion source attribution problem. Although object-relative pattern motion is not a property of all moving objects, understanding how pattern motion interacts with object motion and position can help elucidate how the brain integrates motion and position signals into coherent perceptual estimates—a problem associated with all moving objects.Open in a separate windowFig. 1.Schematic illustration of the object-tracking model and its behavior. (A) An example of an object with both object boundary motion and pattern motion. (B) A generative model of the Bayesian observer. White nodes indicate hidden variables and gray nodes indicate observable variables that are noisy measurements of the connected hidden variables. Arrows indicate causal links. (C) Model behavior for a typical MIPS stimulus containing a moving pattern within a static envelope. The steady-state estimates of the three object states (position, object velocity, and pattern velocity) are plotted for different positional uncertainties. At low positional uncertainty, most of the retinal texture motion is correctly attributed to the pattern motion. Consequently, illusory object motion and MIPS are negligible. At high positional uncertainty, much of the texture motion is attributed to object motion (reflecting a prior that object motion is more likely than pattern motion). This results in relatively low estimated pattern velocity and large MIPS.Here, we propose and test a computational framework in which motion and position perception derive from a common mechanism that integrates sensory signals over time to track objects and infer their generative causes. The consequence of this process is a strong, bidirectional coupling between motion and position perception that provides a unifying account for a range of perceptual phenomena. These include motion-induced shifts in perceived position (3–6), perceptual speed biases (20), slowing of motions shown in visual periphery (21, 22), and the curveball illusion (16). The presented model also makes novel predictions about interactions between position and motion perception—predictions confirmed here. Importantly, we do not fit the model to each experiment, but fit the parameters to data from experiment 1 and show that the resulting model accurately predicts subjects’ performance in qualitatively different and more complex tasks (experiments 2 and 3).     

The visual analogue scale: Its use in pain measurement

Summary Use of pain rating scales, especially the visual analogue scale (VAS), has increased dramatically in the last decade. Consideration of the VAS in terms of its physical structure and the patient's behaviour when confronted with the scale, casts doubt on its validity. It is nonlinear and prone to bias which limits its use as a serial measure of pain severity. Measuring pain intensity alone imposes further limitations. The McGill Pain Questionnaire measuring several dimensions of pain appears to be a better alternative.     

The role of the superior colliculus in facilitating visual attention and form perception.

When interhemispheric transfer in cats is studied from an intact hemisphere to a hemisphere with a suprasylvian cortical lesion, excellent transfer of grating discriminations, but no transfer of forms, is present. Stimuli with global, repetitive features covering a large visual field (gratings), which can be discriminated by preattentive vision, are transferred; perception of stimuli with local features (forms), which require serial exploration using focal vision, is defective in the hemisphere with cortical lesion and transfer is lacking. Influence of the midbrain in facilitating focal vision is shown by the restoration of form discriminations after section of the superior collicular commissure. It is hypothesized that the perceptual defect after lesion in the suprasylvian cortex is due to poor spatial attention and its restoration after midbrain lesion is due to improved function of those collicular cells that mediate orienting of attention.     

Fusion of visual cues is not mandatory in children

Human adults can go beyond the limits of individual sensory systems’ resolutions by integrating multiple estimates (e.g., vision and touch) to reduce uncertainty. Little is known about how this ability develops. Although some multisensory abilities are present from early infancy, it is not until age ≥8 y that children use multiple modalities to reduce sensory uncertainty. Here we show that uncertainty reduction by sensory integration does not emerge until 12 y even within the single modality of vision, in judgments of surface slant based on stereoscopic and texture information. However, adults’ integration of sensory information comes at a cost of losing access to the individual estimates that feed into the integrated percept (“sensory fusion”). By contrast, 6-y-olds do not experience fusion, but are able to keep stereo and texture information separate. This ability enables them to outperform adults when discriminating stimuli in which these information sources conflict. Further, unlike adults, 6-y-olds show speed gains consistent with following the fastest-available single cue. Therefore, whereas the mature visual system is optimized for reducing sensory uncertainty, the developing visual system may be optimized for speed and for detecting sensory conflicts. Such conflicts could provide the error signals needed to learn the relationships between sensory information sources and to recalibrate them while the body is growing.     

Gustatory and metabolic perception of nutrient stress in Drosophila

Sleep loss is an adaptive response to nutrient deprivation that alters behavior to maximize the chances of feeding before imminent death. Organisms must maintain systems for detecting the quality of the food source to resume healthy levels of sleep when the stress is alleviated. We determined that gustatory perception of sweetness is both necessary and sufficient to suppress starvation-induced sleep loss when animals encounter nutrient-poor food sources. We further find that blocking specific dopaminergic neurons phenocopies the absence of gustatory stimulation, suggesting a specific role for these neurons in transducing taste information to sleep centers in the brain. Finally, we show that gustatory perception is required for survival, specifically in a low nutrient environment. Overall, these results demonstrate an important role for gustatory perception when environmental food availability approaches zero and illustrate the interplay between sensory and metabolic perception of nutrient availability in regulating behavioral state.Starvation is a condition of extreme nutrient stress that leads to rapid death. On detecting the absence of environmental nutrient sources, organisms use multiple strategies to adjust resource allocation to maximize the chances of finding a food source, including inducing longer foraging searches (1) and limiting sleep behavior (2, 3). Sleep loss in Drosophila melanogaster is a characteristic response to nutrient deprivation that appears ∼12 h after the removal of a food source; in males, it is followed by death in another 12 h (2). Sleep loss is thought to represent a cost to the organism (4–6), and mechanisms for evaluating the environment and terminating this behavioral response when food is available would likely confer an adaptive benefit. A deeper understanding of how organisms perceive and respond to environmental stress could offer substantial benefit to humans attempting to maintain maximal health in the face of food shortages and unstable environmental conditions. The strategies used by organisms to evaluate the sufficiency of a food source and to initiate or suppress sleep loss under very low nutrient conditions remain largely unknown and represent one path toward understanding global stress response.     

Assessing the homogenization of urban land management with an application to US residential lawn care

Changes in land use, land cover, and land management present some of the greatest potential global environmental challenges of the 21st century. Urbanization, one of the principal drivers of these transformations, is commonly thought to be generating land changes that are increasingly similar. An implication of this multiscale homogenization hypothesis is that the ecosystem structure and function and human behaviors associated with urbanization should be more similar in certain kinds of urbanized locations across biogeophysical gradients than across urbanization gradients in places with similar biogeophysical characteristics. This paper introduces an analytical framework for testing this hypothesis, and applies the framework to the case of residential lawn care. This set of land management behaviors are often assumed—not demonstrated—to exhibit homogeneity. Multivariate analyses are conducted on telephone survey responses from a geographically stratified random sample of homeowners (n = 9,480), equally distributed across six US metropolitan areas. Two behaviors are examined: lawn fertilizing and irrigating. Limited support for strong homogenization is found at two scales (i.e., multi- and single-city; 2 of 36 cases), but significant support is found for homogenization at only one scale (22 cases) or at neither scale (12 cases). These results suggest that US lawn care behaviors are more differentiated in practice than in theory. Thus, even if the biophysical outcomes of urbanization are homogenizing, managing the associated sustainability implications may require a multiscale, differentiated approach because the underlying social practices appear relatively varied. The analytical approach introduced here should also be productive for other facets of urban-ecological homogenization.Changes in land use and cover have transformed the biosphere (1, 2). Land changes should remain a key influence on the global environment, although the dominant source of these transformations will likely shift from agricultural expansion to urbanization (1, 3–7). Global-scale urbanization may be homogenizing ecological structure and function (cf. refs. 8–10). The composition of plant species, soil nutrient profiles, and presence or extent of surface water bodies appears to be increasingly similar across cities, even in dissimilar biophysical settings (10–14). Such trends are potentially worrisome in sustainability terms because they suggest large-scale and possibly irreversible transformations in biogeochemical cycling and trace gas fluxes are underway. Sustainability science therefore needs an improved understanding of the causes and consequences of urban land management (15). This knowledge should be grounded in the geographic patterning—that is, homogeneous versus differentiated—of human land management practices at household, neighborhood, metropolitan, and even continental scales (16, 17).     

Cortical response tracking the conscious experience of threshold duration visual stimuli indicates visual perception is all or none

At perceptual threshold, some stimuli are available for conscious access whereas others are not. Such threshold inputs are useful tools for investigating the events that separate conscious awareness from unconscious stimulus processing. Here, viewing unmasked, threshold-duration images was combined with recording magnetoencephalography to quantify differences among perceptual states, ranging from no awareness to ambiguity to robust perception. A four-choice scale was used to assess awareness: “didn’t see” (no awareness), “couldn’t identify” (awareness without identification), “unsure” (awareness with low certainty identification), and “sure” (awareness with high certainty identification). Stimulus-evoked neuromagnetic signals were grouped according to behavioral response choices. Three main cortical responses were elicited. The earliest response, peaking at ∼100 ms after stimulus presentation, showed no significant correlation with stimulus perception. A late response (∼290 ms) showed moderate correlation with stimulus awareness but could not adequately differentiate conscious access from its absence. By contrast, an intermediate response peaking at ∼240 ms was observed only for trials in which stimuli were consciously detected. That this signal was similar for all conditions in which awareness was reported is consistent with the hypothesis that conscious visual access is relatively sharply demarcated.     

The relationship between visual perception and postural control in falls of the elderly living in local communities

We have examined the relationship between visual sense information, such as perception data and postural control, and falls among elderly people aged 65 years or over living in Nishibiwajima-cho, Aichi Prefecture. Of 286 participants, 204 were enrolled and analyzed, after excluding those with a visual acuity of less than 0.3, or the activities of daily living (ADL) index of less than 11. In the analysis group, 52 people (25.2%) had already had experience of falls. Two-way analysis of variance showed that intensity of dynamic visual stimulation and the presence or absence of falls had a significant effect on body sway, although no interaction was observed. These results indicate that body sway is increased in those who have experience of falls, and that strong visual stimulation is associated with body sway. This suggests that greater dynamic visual stimulation is likely to increase the risk of falls.     

Object grouping based on real-world regularities facilitates perception by reducing competitive interactions in visual cortex

In virtually every real-life situation humans are confronted with complex and cluttered visual environments that contain a multitude of objects. Because of the limited capacity of the visual system, objects compete for neural representation and cognitive processing resources. Previous work has shown that such attentional competition is partly object based, such that competition among elements is reduced when these elements perceptually group into an object based on low-level cues. Here, using functional MRI (fMRI) and behavioral measures, we show that the attentional benefit of grouping extends to higher-level grouping based on the relative position of objects as experienced in the real world. An fMRI study designed to measure competitive interactions among objects in human visual cortex revealed reduced neural competition between objects when these were presented in commonly experienced configurations, such as a lamp above a table, relative to the same objects presented in other configurations. In behavioral visual search studies, we then related this reduced neural competition to improved target detection when distracter objects were shown in regular configurations. Control studies showed that low-level grouping could not account for these results. We interpret these findings as reflecting the grouping of objects based on higher-level spatial-relational knowledge acquired through a lifetime of seeing objects in specific configurations. This interobject grouping effectively reduces the number of objects that compete for representation and thereby contributes to the efficiency of real-world perception.In daily life, humans are confronted with complex and cluttered visual environments that contain a large amount of visual information. Because of the limited capacity of the visual system, not all of this information can be processed concurrently. Consequently, elements within a visual scene are competing for neural representation and cognitive processing resources (1, 2). Such competitive interactions can be observed in neural responses when multiple stimuli are presented at the same time. Single-cell recordings in monkey visual cortex revealed that activity evoked by a neuron''s preferred stimulus is suppressed when a nonpreferred stimulus is simultaneously present in the neuron''s receptive field (3–5). Corresponding evidence for mutually suppressive interactions among competing stimuli has been obtained from human visual cortex using functional magnetic resonance imaging (fMRI) (6).According to biased competition theory, these competitive interactions occur between objects rather than between the parts of a single object (1). This idea of object-based competition is supported by behavioral studies showing that judgments on two properties of one object are more accurate than judgments on the same properties distributed over two objects (7). However, the degree of competition among objects is strongly influenced by contextual factors, such as stimulus similarity (8–10), geometric relationships between stimuli (11), and perceptual grouping (12, 13). For example, competitive interactions in human visual cortex are greatly reduced when multiple single stimuli form an illusory contour and hence can be perceptually grouped into a single gestalt (12).Whereas the attentional benefit of grouping based on low-level cues is well established, much less is known about object grouping at more conceptual levels. Many objects in real-world scenes occupy regular and predictable locations relative to other objects. For example, a bathroom sink is typically seen together with a mirror in a highly regular spatial arrangement. When considering highly regular object pairs like these it becomes clear that the world can be carved up at different levels: based on low-level cues such as those specified by gestalt laws, but also based on conceptual knowledge and long-term visual experience; a plate flanked by a fork and a knife is both a dinner plate set and three separate objects.In the present fMRI and behavioral studies, we asked whether grouping based on real-world regularities modulates attentional competition. We hypothesized that objects that appear in frequently experienced configurations are, to some extent, grouped, resulting in reduced competition between these objects. To test this prediction, we presented pairs of common everyday objects either in their typical, regular configuration (e.g., a lamp above a table) or in an irregular configuration (e.g., a lamp below a table). Our findings indicate that grouping of objects based on real-world regularities effectively reduces the number of competing objects, leading to reduced neural competition and more efficient visual perception.     

An image-computable model of how endogenous and exogenous attention differentially alter visual perception

Attention alters perception across the visual field. Typically, endogenous (voluntary) and exogenous (involuntary) attention similarly improve performance in many visual tasks, but they have differential effects in some tasks. Extant models of visual attention assume that the effects of these two types of attention are identical and consequently do not explain differences between them. Here, we develop a model of spatial resolution and attention that distinguishes between endogenous and exogenous attention. We focus on texture-based segmentation as a model system because it has revealed a clear dissociation between both attention types. For a texture for which performance peaks at parafoveal locations, endogenous attention improves performance across eccentricity, whereas exogenous attention improves performance where the resolution is low (peripheral locations) but impairs it where the resolution is high (foveal locations) for the scale of the texture. Our model emulates sensory encoding to segment figures from their background and predict behavioral performance. To explain attentional effects, endogenous and exogenous attention require separate operating regimes across visual detail (spatial frequency). Our model reproduces behavioral performance across several experiments and simultaneously resolves three unexplained phenomena: 1) the parafoveal advantage in segmentation, 2) the uniform improvements across eccentricity by endogenous attention, and 3) the peripheral improvements and foveal impairments by exogenous attention. Overall, we unveil a computational dissociation between each attention type and provide a generalizable framework for predicting their effects on perception across the visual field.

Endogenous and exogenous spatial attention prioritize subsets of visual information and facilitate their processing without concurrent eye movements (1–3). Selection by endogenous attention is goal-driven and adapts to task demands, whereas exogenous attention transiently and automatically orients to salient stimuli (1–3). In most visual tasks, both types of attention typically improve visual perception similarly [e.g., acuity (4–6), visual search (7, 8), perceived contrast (9–11)]. Consequently, models of visual attention do not distinguish between endogenous and exogenous attention (e.g., refs. 12–19). However, stark differences also exist. Each attention type differentially modulates neural responses (20, 21) and fundamental properties of visual processing, including temporal resolution (22, 23), texture sensitivity (24), sensory tuning (25), contrast sensitivity (26), and spatial resolution (27–34).The effects of endogenous and exogenous attention are dissociable during texture segmentation, a visual task constrained by spatial resolution [reviews (1–3)]. Whereas endogenous attention optimizes spatial resolution to improve the detection of an attended texture (32–34), exogenous attention reflexively enhances resolution even when detrimental to perception (27–31, 34). Extant models of attention do not explain these well-established effects.Two main hypotheses have been proposed to explain how attention alters spatial resolution. Psychophysical studies ascribe attentional effects to modulations of spatial frequency (SF) sensitivity (30, 33). Neurophysiological (13, 35, 36) and neuroimaging (37, 38) studies bolster the idea that attention modifies spatial profiles of neural receptive fields (RFs) (2). Both hypotheses provide qualitative predictions of attentional effects but do not specify their underlying neural computations.Differences between endogenous and exogenous attention are well established in segmentation tasks and thus provide an ideal model system to uncover their separate roles in altering perception. Texture-based segmentation is a fundamental process of midlevel vision that isolates regions of local structure to extract figures from their background (39–41). Successful segmentation hinges on the overlap between the visual system’s spatial resolution and the levels of detail (i.e., SF) encompassed by the texture (39, 41, 42). Consequently, the ability to distinguish between adjacent textures varies as resolution declines toward the periphery (43–46). Each attention type differentially alters texture segmentation, demonstrating that their effects shape spatial resolution [reviews (1–3)].Current models of texture segmentation do not explain performance across eccentricity and the distinct modulations by attention. Conventional models treat segmentation as a feedforward process that encodes the elementary features of an image (e.g., SF and orientation), transforms them to reflect the local structure (e.g., regions of similarly oriented bars), and then pools across space to emphasize texture-defined contours (39, 41, 47). Few of these models account for variations in resolution across eccentricity (46, 48, 49) or endogenous (but not exogenous) attentional modulations (18, 50). All others postulate that segmentation is a “preattentive” (42) operation whose underlying neural processing is impervious to attention (39, 41, 46–49).Here, we develop a computational model in which feedforward processing and attentional gain contribute to segmentation performance. We augment a conventional model of texture processing (39, 41, 47). Our model varies with eccentricity and includes contextual modulation within local regions in the stimulus via normalization (51), a canonical neural computation (52). The defining characteristic of normalization is that an individual neuron is (divisively) suppressed by the summed activity of neighboring neurons responsive to different aspects of a stimulus. We model attention as multiplicative gains [attentional gain factors (15)] that vary with eccentricity and SF. Attention shifts sensitivity toward fine or coarse spatial scales depending on the range of SFs enhanced.Our model is image-computable, which allowed us to reproduce behavior directly from grayscale images used in psychophysical experiments (6, 26, 27, 29–33). The model explains three signatures of texture segmentation hitherto unexplained within a single computational framework (Fig. 1): 1) the central performance drop (CPD) (27–34, 43–46) (Fig. 1A), that is, the parafoveal advantage of segmentation over the fovea; 2) the improvements in the periphery and impairments at foveal locations induced by exogenous attention (27–32, 34) (Fig. 1B); and 3) the equivalent improvements across eccentricity by endogenous attention (32–34) (Fig. 1C).Open in a separate windowFig. 1.Signatures of texture segmentation. (A) CPD. Shaded region depicts the magnitude of the CPD. Identical axis labels are omitted in B and C. (B) Exogenous attention modulation. Exogenous attention improves segmentation performance in the periphery and impairs it near the fovea. (C) Endogenous attention modulation. Endogenous attention improves segmentation performance across eccentricity.Whereas our analyses focused on texture segmentation, our model is general and can be applied to other visual phenomena. We show that the model predicts the effects of attention on contrast sensitivity and acuity, i.e., in tasks in which both endogenous and exogenous attention have similar or differential effects on performance. To preview our results, model comparisons revealed that normalization is necessary to elicit the CPD and that separate profiles of gain enhancement across SF (26) generate the effects of exogenous and endogenous attention on texture segmentation. A preferential high-SF enhancement reproduces the impairments by exogenous attention due to a shift in visual sensitivity toward details too fine to distinguish the target at foveal locations. The transition from impairments to improvements in the periphery results from exogenous attentional gain gradually shifting to lower SFs that are more amenable for target detection. Improvements by endogenous attention result from a uniform enhancement of SFs that encompass the target, optimizing visual sensitivity for the attended stimulus across eccentricity.     

Contributions of the US state park system to nature recreation

Nature recreation in the United States concentrates in publicly provided natural areas. They are costly to establish and maintain, but their societal contributions are difficult to measure. Here, a unique approach is developed to quantifying nature recreation services generated by the US state park system. The assessment first uses data from five national surveys conducted between 1975 and 2007 to consistently measure the amount of time used for nature recreation. The surveys comprise two official federal surveys and their predecessors. Each survey was designed to elicit nationally representative, detailed data on how people divide their time into different activities. State-level data on time use for nature recreation were then matched with information on the availability of state parks and other potentially important drivers of recreation, so that statistical estimation methods for nonexperimental panel data (difference-in-differences) could be used to examine the net contribution of state parks to nature recreation. The results show that state parks have a robust positive effect on nature recreation. For example, the approximately 2 million acres of state parks established between 1975 and 2007 are estimated to contribute annually 600 million hours of nature recreation (2.7 h per capita, approximately 9% of all nature recreation). All state parks generate annually an estimated 2.2 billion hours of nature recreation (9.7 h per capita; approximately 33% of all nature recreation). Using conventional approaches to valuing time, the estimated time value of nature recreation services generated by the US state park system is approximately $14 billion annually.     

Effects of visual adaptation on perception of and satisfaction with own body size: two randomised studies

BackgroundBody dissatisfaction is prevalent among women and predicts eating disorders and obesity. Visual adaptation to pictures of underweight or overweight bodies changes body size perceived as normal in others. We aimed to test the hypothesis that exposure to images of underweight or overweight bodies would change perception of and satisfaction with own body size.MethodsWe recruited female students and staff aged 18–25 years from the University of Bristol via posters and emails. In study 1, participants had normal body-mass index (BMI) (19–25 kg/m²). In study 2, they had normal BMI and also high body dissatisfaction (defined as a score of >35 on the Body Dissatisfaction subscale of the Eating Disorder Inventory). Both studies had 80% power to detect an effect size of 0·36 (p=0·05). A computer-generated random sequence randomised participants into three groups, according to which category of images they would see. Participants and experimenters were masked to randomisation; and participants were unaware of the study purpose. Participants completed a 15 min adaptation task consisting of their looking at photographs of women of the same age group altered by the authors to appear slightly underweight, normal weight (control group), or slightly overweight Participants then looked at themselves in a mirror. Visual analogue scale (VAS) scores were taken before adaptation and again after adaptation and looking in the mirror. The analysis compared post-adaptation scores adjusted for pre-adaptation scores. We measured perceived size (primary outcome) and satisfaction with size (secondary outcome) and analysed data by intention to treat using linear regression, adjusting for baseline. Ethics approval for both studies was given by the Faculty of Science Research Ethics Committee, University of Bristol. Participants gave consent after being informed about the task they would complete.FindingsWe recruited 90 women between Nov 11, 2012, and Dec 16, 2013 in study 1; and 93 women (July 29, 2014, to Aug 8, 2015) in study 2. After adaptation, for every VAS point increase in group (underweight 0, normal 1, overweight 2), perceived own size post adaptation decreased by 2·2% (95% CI −4·1 to −0·3, p=0·02) in study 1, and 2·8% (–5·1 to −0·4, p=0·02) in study 2. Satisfaction with size increased by 1·5% (95% CI −0·9 to 3·9, p=0·21) in study 1 and 5·7% (2·3 to 9·0, p=0·001) in study 2. Participants shown underweight images subsequently perceived themselves as larger and were less satisfied.InterpretationThese findings suggest that, in young women, exposure to underweight images (frequently depicted in the media) changes perception of own body size and increases body dissatisfaction. This automatic mechanism could be targeted at a public health level by advocating replacement of underweight images with normal weight images. Such an intervention could reduce body dissatisfaction in normal weight women and possibly rates of eating disorders and obesity.FundingStudy 1 was unfunded. For study 2, HB was funded by an Elizabeth Blackwell Clinical Primer (Wellcome Trust Strategic Support Fund) from April to September, 2014, and subsequently as a Wellcome Trust Doctoral Training Fellow (October, 2014, to the present).     

Embedding and Sustaining a Focus on Function in Specialty Research and Care

Function and the independent performance of daily activities are of critical importance to older adults. Although function was once a domain of interest primarily limited to geriatricians, transdisciplinary research has demonstrated its value across the spectrum of medical and surgical care. Nonetheless, integrating a functional perspective into medical and surgical therapeutics has yet to be implemented consistently into clinical practice. This article summarizes the presentations and discussions from a workshop, “Embedding/Sustaining a Focus on Function in Specialty Research and Care,” held on January 31 to February 1, 2019. The third in a series supported by the National Institute on Aging and the John A. Hartford Foundation, the workshop aimed to identify scientific gaps and recommend research strategies to advance the implementation of function in care of older adults. Transdisciplinary leaders discussed implementation of mobility programs and functional assessments, including comprehensive geriatric assessment; integrating cognitive and sensory functional assessments; the role of culture, environment, and community in incorporating function into research; innovative methods to better identify functional limitations, techniques, and interventions to facilitate functional gains; and the role of the health system in fostering integration of function. Workshop participants emphasized the importance of aligning goals and assessments and adopting a team science approach that includes clinicians and frontline staff in the planning, development, testing, and implementation of tools and initiatives. This article summarizes those discussions.