Perceptual Range Research Articles

L\xe9vy like patterns in the small-scale movements of marsupials in an unfamiliar and risky environment

We investigate the movement patterns of three different Neotropical marsupials in an unfamiliar and risky environment. Animals are released in a matrix from which they try to reach a patch of forest. Their movements, performed on a small spacial scale, are best approximated by Lévy flights. Patterns of oriented and non-oriented individuals - with forest patches within or beyond their perceptual range - differ only slightly in the value of their exponents. These facts suggest that, for these species, the appearance of Lévy flights is the product of animals innate behaviour that emerges spontaneously, as a neutral characteristic proper of a default movement mode for alerted animals.

Mosquito-inspired distributed swarming and pursuit for cooperative defense against fast intruders

Inspired by the swarming behavior of male mosquitoes that aggregate to attract and subsequently pursue a female mosquito, we study how random swarming motion in autonomous vehicles affects the success of target capture. We consider the scenario in which multiple guardians with limited perceptual range and bounded acceleration are deployed to protect an area from an intruder. The main challenge for the guardian (male mosquito) is to quickly respond to a fast intruder (female) by matching its velocity. We focus on the motion strategy for the guardians before they perceive the intruder, which we call the swarming phase. In the parameter space consisting of the intruder’s speed and guardians’ ability (i.e., maximum acceleration and perceptual range) we identify necessary and sufficient conditions for target capture. We propose a swarming algorithm inspired by the behavior of male mosquitoes to improve the target-capture capability. The theoretical results are illustrated by experiments with an indoor quadrotor swarm.

Keep your enemies closer: enhancing biological control through individual movement rules to retain natural enemies inside the field

Abstract. Biological control of pests aims at lowering population levels of pest species by favouring natural enemies, in order to reduce the use of pesticides. The movement behaviour of natural enemies is decisive in the success of biological control: when low habitat quality hinders the diffusion of natural enemies from the border, the density of natural enemies may frequently be heterogeneous inside agricultural plots. We hypothesise that the specific relationship between habitat quality and movement behaviour may allow the improvement of biological control by means of a careful allocation of habitat qualities inside and around the plot. We used three tested individual-based movement models, with different levels of complexity ranging from simple cell-to-cell movements to complex strategies including the sinuosity of the path, boundary crossings, perceptual range, and directional persistence. We used the models to explore how the manipulation of habitat quality may allow significant improvements to the residence time of natural enemies inside the field. We suggest that existing field designs are generally inadequate to retain natural enemies. Mechanistic explanations leading to the highest and lowest residence times are used to draw specific management recommendations.

Effects of mis-alignment between dispersal traits and landscape structure on dispersal success in fragmented landscapes.

Dispersal is fundamental to population dynamics and hence extinction risk. The dispersal success of animals depends on the biophysical structure of their environments and their biological traits; however, comparatively little is known about how evolutionary trade-offs among suites of biological traits affect dispersal potential. We developed a spatially explicit agent-based simulation model to evaluate the influence of trade-offs among a suite of biological traits on the dispersal success of vagile animals in fragmented landscapes. We specifically chose traits known to influence dispersal success: speed of movement, perceptual range, risk of predation, need to forage during dispersal, and amount of suitable habitat required for successful settlement in a patch. Using the metric of relative dispersal success rate, we assessed how the costs and benefits of evolutionary investment in these biological traits varied with landscape structure. In heterogeneous environments with low habitat availability and scattered habitat patches, individuals with more equal allocation across the trait spectrum dispersed most successfully. Our analyses suggest that the dispersal success of animals in heterogeneous environments is highly dependent on hierarchical interactions between trait trade-offs and the geometric configurations of the habitat patches in the landscapes through which they disperse. In an applied sense, our results indicate potential for ecological mis-alignment between species' evolved suites of dispersal-related traits and altered environmental conditions as a result of rapid global change. In many cases identifying the processes that shape patterns of animal dispersal, and the consequences of abiotic changes for these processes, will require consideration of complex relationships among a range of organism-specific and environmental factors.

Differential Evolution Based Regional Coverage-Enhancing Algorithm for Directional 3D Wireless Sensor Networks

Wireless sensor networks (WSNs) are adopted in a variety of fields where coverage enhancing is a critical challenge because of the requirements of service quality, cost, and energy consumption. Coverage-enhancing approaches have currently attracted a lot of interest owing to their superior abilities in the deployment of the WSNs, e.g., maximum coverage, minimum sensors, and minimum energy. In this paper, a differential evolution-based regional coverage-enhancing algorithm is proposed for directional 3D WSNs, which is able to maximizing coverage while minimize the number of sensors. First, a directional cone perception model is designed to better display the actual sensing performance of sensor nodes. Subsequently, the coverage region is established to describe the perceptual range of nodes. Thereafter, a three-stage coverage-enhancing method is derived, which includes the pitch angle optimization, the deflection angle optimization and the redundant node sleeping. These strategies are designed to maximize the perception range of a single sensor node, maximize the coverage rate, and minimize the number of nodes, respectively. Finally, simulation results show that our method is able to ensure better performance compared to the state-of-the-art frameworks.

Efficacy of voice therapy in patients with puberphonia- a 15-year experience

Background Puberphonia is the perseverance of high pitched voice after the pubertal age in males which causes a huge psychosocial impact. Voice therapy is one modality of management of Puberphonia. Aim The Objective of our study was to evaluate the efficacy of voice therapy in patients as the sole treatment to improve the pitch and quality of voice, the psychosocial impact and patient's satisfaction. Methods A retrospective study was carried out on 71 patients who were presented to ENT unit at the National hospital of Sri Lanka for fifteen years from 2002. Pre and post voice therapy subjective assessment was done by the speech therapist for pitch and quality and patient’s perceptual assessment using an analog scale (0-extremely poor to 10-normal voice) and a psychosocial impact assessment was also done. Results The time duration of voice therapy ranged from 1 to 10 months (average-3.6 months). Pitch and quality of the voice became normal in 78.9% and 35.2% of patients respectively. Pre-therapy perceptual score range(PSR) was 0 to 6 (mean-3.0). Post-therapy PSR was 5 to 10 (mean-7.7). 95.8% patients had improved psychosocial impact and patient satisfaction after voice therapy. Remaining opted for surgical management. Conclusion Voice therapy significantly improves the pitch, patient's satisfaction and psychosocial impact and can be used as an effective modality of treatment for Puberphonia.

Influence of Perceptual Range on Human Perceived Restoration

In daily living environments, an individual’s different state of mind influences their spatial perception. The current study, based on Attention Restoration Theory, aimed to explore differences in the health utility of nature according to individual differences in spatial perception. It focused on Cheonggyecheon stream in Seoul, South Korea. Cognitive mapping and the Perceived Restorativeness Scale (PRS) were used to assess two groups’ different perceived spatial ranges and the restorative effect of the environment. After gathering data, two groups were defined: one describing only the internal area of the research site (composed of green materials), and the other illustrating the external area of the site, including buildings and roads. The former had higher overall PRS, Being Away, Fascination, and Compatibility scores. The latter had higher scores only on the Coherence subscale. These results illustrate that the frequency of nature visits and time spent traveling influence the two groups’ attentional restoration, which has great implications for highly stressful urban environments.

Predicting monarch butterfly (Danaus plexippus) movement and egg-laying with a spatially-explicit agent-based model: The role of monarch perceptual range and spatial memory

An ∼80% decline in the eastern population of the monarch butterfly (Danaus plexippus) has prompted conservation efforts to increase summer reproductive success in the Midwest United States. Implementation of conservation practices will create a patchwork of milkweed (mainly Asclepias spp.) habitat within agricultural landscapes dominated by corn and soybean production. Since the monarch butterfly is a vagile species, reproductive success is, in part, a function of both the amount and spatial arrangement of habitat patches in a fragmented landscape. To inform conservation planning we developed a spatially-explicit, agent-based model for summer breeding, non-migratory female monarch butterfly movement and egg-laying on an Iowa, USA landscape. Our model employs a unique movement algorithm when monarch agents encounter habitat edges that incorporates monarch perceptual range to their host plant and spatial memory of previously visited habitat. These behavioral factors are rarely incorporated into animal movement algorithms; however, they can influence estimates of resource utilization. Model exploration assessed the distribution and density of eggs laid on a spatially-explicit 148,665 ha landscape comprised of 17 land cover classes with varying milkweed densities. Uncertainty analysis was undertaken by sampling 25 combinations of perceptual range, spatial memory, flight step length and flight directionality parameters from a total of 256 (44) possible combinations. Movement paths simulated with our new movement algorithm show preferential use of high density milkweed areas that would not be simulated using a correlated random walk. Increasing perceptual range caused a decrease in the area used by monarch agents and caused a skewed egg distribution where most eggs were laid in relatively few habitat patches. Increasing spatial memory caused an increase in the area used but decreased the median number of eggs laid in roadside habitat. Current national and regional monarch conservation goals assume a uniform distribution of milkweed in different land cover classes. Translating these goals into spatially-explicit, heterogeneous habitat patches is essential for predicting realized fecundity in the landscape. Our model provides the foundation to link national and regional monarch conservation goals to fine scale spatial configurations of habitat patches in defined landscapes.

Sensory influence on navigation in the weakly electric fish Gnathonemus petersii

Most animals possess multiple sensory systems, which can be used during navigation. Different senses obtain environmental information on different spatial scales and thus provide a different basis for efficient navigation. Here we used the weakly electric fish Gnathonemus petersii to investigate how different sensory inputs influence the navigational strategy and whether landmark information can be transferred flexibly between two sensory systems. Fish were trained to swim through a maze using a certain route indicated by either visual landmarks, electrical landmarks or without any landmarks. In subsequent tests, egocentric (internal cues, such as motion patterns) and allocentric cues (external cues like landmarks) were put in conflict by relocating the local landmarks. We found that all fish, independent of the available sensory input, chose the egocentric over the allocentric route. However, visual landmarks significantly improved the training duration compared to the other groups, suggesting an involvement of allocentric visual cues during route acquisition. In a second experimental series, fish were trained to use either visual or electrical landmarks for navigation and were subsequently tested in sensory transfer tests. Fish trained with visual landmarks were able to learn this allocentric navigation task and were capable of cross-modal landmark recognition, although navigation based on electrical landmarks was less efficient. The fish trained with electrical landmarks did not learn the task at all, suggesting that the short perceptual range of the electric sense prevented learning of allocentric navigation. Together our results show that the type of sensory input influences the efficiency of allocentric navigation in G. petersii and that these fish can use egocentric and allocentric strategies flexibly to navigate successfully under varying environmental conditions.

Functional connectivity of the white-footed mouse in Southern Quebec, Canada

The white-footed mouse (Peromyscus leucopus) is an important reservoir host for the pathogen responsible for Lyme disease in eastern North-America. Indigenous cases of Lyme disease in southern Quebec have increased from two cases in 2004 to 160 cases in 2015. Because of the strong relationship between the white-footed mouse occurrence and the Lyme disease pathogen prevalence, we can estimate the risk of Lyme disease by finding areas of high contact between mice. In this study, we inferred the movement patterns and contact rate of the white-footed mouse in southern Quebec. We used pattern-orientated modelling to estimate a directional measure of functional connectivity from an Individual-Based Model. We replicated the spatial pattern observed in previously published molecular analysis of a white-footed mouse population. A perceptual range of 80 m best explained the genetic structure of the white-footed mouse in the region. The paths of individuals generally overlapped the edges of urban centers and the boundary of linear obstacles such as highways and water bodies. We show that the contact probability of mice was a good predictor of the number of mice caught in the field. Our findings highlight the usefulness of individual-based models to potentially predict high contact areas and disease hotspots across landscapes.

Mobile Mixed-Reality Interfaces That Enhance Human–Robot Interaction in Shared Spaces

Although user interfaces with gesture-based input and augmented graphics have promoted intuitive human-robot interactions (HRI), they are often implemented in remote applications on research-grade platforms requiring significant training and limiting operator mobility. This paper proposes a mobile mixed-reality interface approach to enhance HRI in shared spaces. As a user points a mobile device at the robot's workspace, a mixed-reality environment is rendered providing a common frame of reference for the user and robot to effectively communicate spatial information for performing object manipulation tasks, improving the user's situational awareness while interacting with augmented graphics to intuitively command the robot. An evaluation with participants is conducted to examine task performance and user experience associated with the proposed interface strategy in comparison to conventional approaches that utilize egocentric or exocentric views from cameras mounted on the robot or in the environment, respectively. Results indicate that, despite the suitability of the conventional approaches in remote applications, the proposed interface approach provides comparable task performance and user experiences in shared spaces without the need to install operator stations or vision systems on or around the robot. Moreover, the proposed interface approach provides users the flexibility to direct robots from their own visual perspective (at the expense of some physical workload) and leverages the sensing capabilities of the tablet to expand the robot's perceptual range.

A biologically inspired controller to solve the coverage problem in robotics

The coverage problem consists on computing a path or trajectory for a robot to pass over all the points in some free area and has applications ranging from floor cleaning to demining. Coverage is solved as a planning problem—providing theoretical validation of the solution—or through heuristic techniques which rely on experimental validation. Through a combination of theoretical results and simulations, this paper presents a novel solution to the coverage problem that exploits the chaotic behaviour of a simple biologically inspired motion controller, the Braitenberg vehicle 2b. Although chaos has been used for coverage, our approach has much less restrictive assumptions about the environment and can be implemented using on-board sensors. First, we prove theoretically that this vehicle—a well known model of animal tropotaxis—behaves as a charge in an electro-magnetic field. The motion equations can be reduced to a Hamiltonian system, and, therefore the vehicle follows quasi-periodic or chaotic trajectories, which pass arbitrarily close to any point in the work-space, i.e. it solves the coverage problem. Secondly, through a set of extensive simulations, we show that the trajectories cover regions of bounded workspaces, and full coverage is achieved when the perceptual range of the vehicle is short. We compare the performance of this new approach with different types of random motion controllers in the same bounded environments.

Perceptual Ranges, Information Gathering, and Foraging Success in Dynamic Landscapes.

How organisms gather and utilize information about their landscapes is central to understanding land-use patterns and population distributions. When such information originates beyond an individual's immediate vicinity, movement decisions require integrating information out to some perceptual range. Such nonlocal information, whether obtained visually, acoustically, or via chemosensation, provides a field of stimuli that guides movement. Classically, however, models have assumed movement based on purely local information (e.g., chemotaxis, step-selection functions). Here we explore how foragers can exploit nonlocal information to improve their success in dynamic landscapes. Using a continuous time/continuous space model in which we vary both random (diffusive) movement and resource-following (advective) movement, we characterize the optimal perceptual ranges for foragers in dynamic landscapes. Nonlocal information can be highly beneficial, increasing the spatiotemporal concentration of foragers on their resources up to twofold compared with movement based on purely local information. However, nonlocal information is most useful when foragers possess both high advective movement (allowing them to react to transient resources) and low diffusive movement (preventing them from drifting away from resource peaks). Nonlocal information is particularly beneficial in landscapes with sharp (rather than gradual) patch edges and in landscapes with highly transient resources.

High Emigration Propensity and Low Mortality on Transfer Drives Female-Biased Dispersal of Pyriglena leucoptera in Fragmented Landscapes.

Dispersal is a biological process performed in three stages: emigration, transfer and immigration. Intra-specific variation on dispersal behavior, such as sex-bias, is very common in nature, particularly in birds and mammals. However, dispersal is difficult to measure in the field and many hypotheses concerning the causes of sex-biased dispersal remain without empirical confirmation. An important limitation of most empirical studies is that inferences about sex-biased dispersal are based only on emigration proneness or immigration success data. Thus, we still do not know whether sex-biased immigration in fragmented landscapes occurs during emigration, transfer or in both stages. We conducted translocation and radiotracking experiments to assess i) whether inter-patch dispersal movements of a rainforest bird (Pyriglena leucoptera) is sex-biased and ii) how dispersal stages and the perceptual range of the individuals are integrated to generate dispersal patterns. Our results showed that inter-patch dispersal is sex-biased at all stages for P. leucoptera, as females not only exhibit a higher emigration propensity but are subjected to a lower risk of predation when moving through the matrix. Moreover, our data support a perceptual range of 80 m and our results showed that dispersal success decreases considerably when inter-patch distances exceeds this perceptual range. In this case, birds have a higher probability of travelling over longer routes and, as a consequence, the risk of predation increases, specially for males. Overall, results supported that assuming dispersal as a single-stage process to describe dispersal behavior may be misleading. In this way, our study advanced our understanding of processes and patterns related to inter-patch dispersal of neotropical forest birds, shedding light on potential implications for population dynamics and for the management of fragmented landscapes.

Perceptual simultaneity range as a function of frequency separation for two pure tones

Perceptual simultaneity range as a function of frequency separation for two pure tones

가중 최소자승 필터링과 색 표현 모델을 결합한 넓은 동적 영역 이미지 표현

최근 넓은 동적 영역 이미지 기술은 컴퓨터 그래픽 분야에서 화제다. 본 논문에서는 가중 최소자승(가중회귀분석) 최적화 체계에 기반하여 넓은 동적 영역 이미지를 처리하는 톤매핑 알고리듬을 제안한다. 제안하는 방법은 시각적 후광 현상을 피하는 동시에 기존의 디스플레이에서 더 지각적인 넓은 동적 영역 이미지들을 보여주기 위해 가중 최소자승 필터링과 iCAM06모델을 결합한다. 제안된 알고리듬은 먼저 넓은 동적 영역 이미지를 base layer와 detail layer로 나눈다. Base layer는 큰 규모의 변화량을 가지고 있으며 가중 최소자승 필터링을 사용하여 얻어지고 iCAM06 모델을 포함한다. 다음으로, 인간의 시각 체계에 따라 base layer는 적응적으로 압축된다. 압축 시에는 base layer만 대비를 줄이고 detail layer을 보존한다. 본 논문에서는 객관적 화질 평가와 주관적 화질 평가를 통하여 제안하는 알고리듬을 적용한 이미지가 기존의 알고리듬을 적용한 이미지들에 비해 원본 넓은 동적 영역 이미지에 더 유사하다는 것을 보여준다. Recently high dynamic range imaging technique is hot issue in computer graphic area. We present a progressive tone mapping algorithm, which is based on weighted least squares optimization framework. Our approach combines weighted least squares filtering with iCAM06 model. To show more perceptual high dynamic range images in conventional display, we decompose high dynamic range image into base layers and detail layers. The base layers are obtained by using weighted least squares filter. Then, we adopt chromatic adaption function and non-linear compression function to deal with base layers. Only the base layers reduce contrast, and preserving detail. The image quality assessment shows that our tone mapped image is more similar to original high dynamic range image. Moreover, the subjective result shows our algorithm produces more reliable and pleasing image.

Pasture height and crop direction influence reptile movement in an agricultural matrix

Tackling the global threat of habitat fragmentation on biodiversity requires knowledge of how species move within agricultural landscapes. However, the specific mechanisms influencing dispersal within such landscapes remain poorly understood. The objective of our study was to assess how matrix type (improved pasture, native pasture or crop) and structure (grass height) influence fine-scale reptile movement, as well as influences of crop sowing direction and setting-sun position. In an agricultural region of south-eastern Australia, we first released 20 individuals of an arboreal gecko (Christinus marmoratus) at set distances from trees to determine the distance at which they could perceive their tree habitat (perceptual range). We then translocated 36 individuals into six matrix environments within their perceptual range of isolated trees to examine how gecko movement was modified by the type and structure of the matrix. We also recorded crop sowing direction and setting-sun position and examined all recorded tracks using angular statistics. We found that geckos exhibited a perceptual range of 40–80m. Short matrix environments promoted direct movements towards trees, irrespective of matrix type. Furthermore, movements were significantly affected by crop sowing direction with individuals following the planted lines. Our study has three significant implications: (i) restoring mature tree spacing to 80m apart will assist gecko movements, (ii) targeted management for low pasture height, such as by maintaining directional narrow strips of low vegetation among taller pastures, might assist movement and facilitate increased connectivity, (iii) directional sowing of crops between habitat patches presents a simple but potentially effective tool for reconnecting fragmented landscapes.

Effects of frequency separation and fundamental frequency on perception of simultaneity of the tones

Present study investigated the range of perceptual simultaneity, within which listeners perceive two asynchronous tones as simultaneous, as a function of frequency separation and fundamental frequency of the tones. This function was obtained with frequency separations ranging from 0.03 to 5.00 octaves, and fundamental frequencies ranging from 100 to 800 Hz. Listener’s task was to judge whether the two asynchronous pure tones were perceptually simultaneous or not. Results showed a V-shaped function for the perceptual simultaneity range against the frequency separation regardless of fundamental frequency. The perceptual simultaneity range steeply decreased and then gradually increased with the increment of frequency separation. The breakpoint of the V-shaped function was appeared at around the critical bandwidth. This breakpoint was best predicted by CB (Critical Bandwidth) scale, rather than by ERB (Equivalent Rectangular Bandwidth) or octave scales. These findings supported the notion (Okazaki & Ichikawa,...

Dispersal-related traits of the snail Cornu aspersum along an urbanisation gradient: maintenance of mobility across life stages despite high costs

The extreme fragmentation of natural habitats due to urbanisation can influence the evolution of dispersal strategies in species persisting in cities. The brown garden snail Cornu aspersum is an anthropophilic species, capable of maintaining its populations in highly fragmented habitats despite a high cost of movement. In this species, we studied the variation of dispersal-related behaviours and traits along an urbanisation gradient characterised at two biologically relevant spatial scales (10 and 50 m), in order to identify the effects of habitat fragmentation on movement. The olfactory perceptual range was low, between 1 and 2.5 m, meaning that snails should perceive a large range of landscapes as fragmented. In line with previous results, subadults were more prone to explore than adults in the least urbanised populations. The boundary-crossing behaviour of subadults was not affected by urbanisation, while exploration propensity of adult snails increased with urbanisation at the 50 m (long-distance dispersal) scale, to reach subadult levels in more urban sites. Foot mass (a correlate of movement speed) and perceptual range were not affected by urbanisation. These results are interpreted in relation to the different levels of competition snails are likely to experience in different environments, the high risk of local extinction in urban fragmented landscapes, and the available opportunities for reproduction. They indicate that benefits of dispersal still need to be considered even in situations where movement costs are extremely important. The maintenance of relatively high mobility and its extension to the adult stage in response to anthropogenic changes may thus play a major role in the success of Cornu aspersum in urban habitats.

Sensitivity to binaural cues beyond threshold as revealed by eye movements

Binaural cues are paramount for sound localization along the azimuth. Studies on the perception of the critical binaural cues, interaural time and level differences (ITDs and ILDs, respectively), typically measure sensitivity at threshold using N-interval, forced choice paradigms. This approach gives little or no information regarding perceptual abilities beyond threshold. In this study, an anticipatory eye movement (AEM) paradigm (cf. McMurray, 2004) was used as a novel measure to study binaural cue sensitivity throughout a wide perceptual range. This paradigm is sensitive to gradient (rather than all-or-none) perception of auditory cues. Adults with normal hearing visually tracked the location of a ball that becomes hidden on a computer screen, and anticipated its motion and reappearance via eye movements guided by binaural cues. The auditory stimuli were 4.8-s 1/3-octave narrowband noises centered at different frequencies, and contained an ILD or ITD change, indicating the impending motion of the ball. Greater cue levels elicited systematically quicker and more accurate saccades. ILD-driven AEMs were elicited for all noise center frequencies, with greater sensitivity for higher frequency noises, consistent with ecological significance. Eye movements in this study suggest variation in binaural cue perception beyond threshold that is gradient in terms of latency and accuracy.