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PubMed2005

The influence of intentional and incidental learning on acquiring spatial knowledge during navigation.

In order to study the influence of intentional and incidental learning conditions on route learning, young adults walked a route through a university building. Half of the participants focused their attention on the route (intentional learning condition), while the other half did not (incidental learning condition). Five tests of spatial knowledge were employed: a route-length-estimation, landmark recognition, landmark ordering, map-drawing and navigation task. The intentional group performed better than the incidental group on the map-drawing and navigation task. No difference between the intentional and incidental group was found on the landmark-recognition and landmark-ordering task. Moreover, the intentional group overestimated the walking distance, while the incidental group underestimated it. These results suggest that route knowledge (landmark recognition and landmark ordering) requires less effortful processing than survey knowledge (developing a map-like representation and actual navigation).

Adult↗
PubMed2006

Imaginal repositioning in everyday environments: effects of testing method and setting.

Two experiments examined spatial knowledge access after imagined perspective switches in everyday environments. Blindfolded volunteers had to point to target objects in a well-known surrounding while imagining being repositioned into different spatial perspectives defined as self-rotations of the observer in the horizontal plane (0 degrees , 45 degrees , and 135 degrees ). Testing was either conducted in the space the target locations had been learned in (actual room testing), or while participants were away from this room, but should imagine being situated there (remote room testing). Experiment 1, in which perspective switches were tested on a trial-to-trial basis, revealed increases in pointing latency and error as a function of the amount of angular disparity between real and imagined perspective under actual and remote room conditions. Experiment 2, in which knowledge access was tested in blocks of multiple trials per perspective, showed increases in pointing latency with angular disparity for actual space testing, and to a much lesser degree for remote space testing. Implications of both findings for theoretical accounts of knowledge access after imaginal perspective switches are discussed, and recommendations for using different testing methods and settings are given.

Adult↗
PubMed2006

Biased representations of the spatial structure of navigable environments.

Recent studies (e.g., Shelton & McNamara in Cognitive Psychology, 43(4), 274-310, 2001; Valiquette, McNamara, & Smith in Memory and Cognition, 31(3), 479-489, 2003) have demonstrated that judgments of relative direction (JRD) access a single enduring orientation-dependent allocentric representation of the layout of objects in an environment, regardless of whether the space is viewed from one or multiple vantage points. Two experiments tested the limits of this phenomenon. In both experiments participants learned the locations of objects in a large room from two views: one view was aligned with salient environmental frames of reference (edges of the mat on which objects were placed and walls of the enclosing room) and expected to be preserved in long-term memory; the other view was misaligned and not expected to be preserved in long-term memory. The first experiment demonstrated that performing JRD between studying the misaligned view and studying the aligned view did not result in the misaligned view being maintained in long-term memory. The second experiment demonstrated that after studying the layout extensively from the misaligned view, 30 s of exposure to the aligned view (with no instructions to learn the layout from that view) resulted in the aligned but not the misaligned view being preserved in long-term memory. These findings indicate that the human spatial memory and navigation system is strongly biased to represent the spatial structure of navigable environments with reference directions or axes that are aligned with salient environmental frames of reference.

Bias↗
PubMed2006

Spatial updating in virtual reality: the sufficiency of visual information.

Robust and effortless spatial orientation critically relies on "automatic and obligatory spatial updating", a largely automatized and reflex-like process that transforms our mental egocentric representation of the immediate surroundings during ego-motions. A rapid pointing paradigm was used to assess automatic/obligatory spatial updating after visually displayed upright rotations with or without concomitant physical rotations using a motion platform. Visual stimuli displaying a natural, subject-known scene proved sufficient for enabling automatic and obligatory spatial updating, irrespective of concurrent physical motions. This challenges the prevailing notion that visual cues alone are insufficient for enabling such spatial updating of rotations, and that vestibular/proprioceptive cues are both required and sufficient. Displaying optic flow devoid of landmarks during the motion and pointing phase was insufficient for enabling automatic spatial updating, but could not be entirely ignored either. Interestingly, additional physical motion cues hardly improved performance, and were insufficient for affording automatic spatial updating. The results are discussed in the context of the mental transformation hypothesis and the sensorimotor interference hypothesis, which associates difficulties in imagined perspective switches to interference between the sensorimotor and cognitive (to-be-imagined) perspective.

Adolescent↗
PubMed2006

Human non-visual discrimination of gradual turning is poor.

We report three measures of the ability of normally sighted adults to discriminate turning while walking blindfolded outdoors. Constant error in selecting line drawings of paths indicated that participants under represent the amount of turning along more curved paths and over represent the amount of turning on less curved paths. Constant error in the direction of pointing to the origin of paths indicated a bias consistent with the direction of turning along more curved paths. Participants produced more accurate drawings of paths as the amount of turning increased. The results suggest that non-visual cues that accompany self movement are not sufficient for accurate representation of large radius curves in geographic scale travel.

Adolescent↗
PubMed2006

The role of body-based sensory information in the acquisition of enduring spatial representations.

Although many previous studies have shown that body-based sensory modalities such as vestibular, kinesthetic, and efferent information are useful for acquiring spatial information about one's immediate environment, relatively little work has examined how these modalities affect the acquisition of long-term spatial memory. Three groups of participants learned locations along a 146 m indoor route, and subsequently pointed to these locations, estimated distances between them, and constructed maps of the environment. One group had access to visual, proprioceptive, and inertial information, another had access to matched visual and matched inertial information, and another had access only to matched visual information. In contrast to previous findings examining transient, online spatial representations, our results showed very few differences among groups in the accuracy of the spatial memories acquired. The only difference was the improved pointing accuracy of participants who had access to proprioceptive information relative to that of participants in the other conditions. Results are discussed in terms of differential sensory contributions to transient and enduring spatial representations.

Adult↗
PubMed2006

The role of visuo-spatial working memory in map learning: new findings from a map drawing paradigm.

Recently, increasing attention has been devoted to the study of the role of visuo-spatial working memory (VSWM) in environmental learning and spatial navigation. The present research was aimed at investigating the role of VSWM in map learning using a map drawing paradigm. In the first study, a dual task methodology was used. Results showed that map drawing was selectively impaired by a spatial tapping task that was executed during the map learning phase, hence supporting the hypothesis that VSWM plays an essential role in learning from maps. In the second study, using a correlational methodology, it was shown that performance in simultaneous VSWM tasks, but not in sequential VSWM tasks, predicted map drawing skills. These skills "in turn" correlated with map learning abilities. Finally, in the third study, we replicated the results of the second study, by using a different map. To our knowledge, the present study is the first to find evidence that the simultaneous aspects of VSWM play a fundamental role in learning from maps.

Adult↗
PubMed2003

Spatial and temporal variation in mortality of newly settled damselfish: patterns, causes and co-variation with settlement.

Local abundance and dynamics of sedentary species with a dispersing life stage reflect factors that influence input and loss rates to patches of suitable habitat. For reef fishes, more attention has focused on sources of variation in input (larval settlement) than on patterns and causes of subsequent losses. We estimated spatial and temporal variation in juvenile mortality of a tropical damselfish, yellow-tail dascyllus (Dascyllus flavicaudus; Pomacentridae), using a fixed density experiment that was repeated 5 times at the same eight mid-lagoon localities at Moorea, French Polynesia. There was little temporal variation in the overall percent of outplanted fish lost in 48 h among five time periods (range: 32-37%), whereas there was substantial variation among the sites in the average percent lost (range: 16-56%). Differences in loss rates among the sites were highly consistent among the time periods. Densities of predators of juvenile dascyllus varied substantially among the eight sites and were highly correlated with loss rate of dascyllus. We used the empirically derived relationship between predator density and damselfish loss rate to predict the loss rate of dascyllus at four additional sites, and there was excellent agreement between the predicted and observed loss rates. There was a strong positive relationship between predator densities at the 12 sites and structural attributes of the reefs that do not change on a fast time scale, suggesting why there was strong spatial and weak temporal variation in mortality rates, with no interaction between spatial and temporal variation. Natural settlement rates of yellow-tail dascyllus and of a close congener (humbug dascyllus, D. aruanus) varied among the sites, and settlement of the two species was inversely correlated (r=-0.68). Settlement of these species was not statistically correlated with variation in mortality rate, but there was a weak trend for settlement of yellow-tail dascyllus to be greater at sites with higher mortality (r=0.27), and for settlement of humbug dascyllus to be greater at sites with lower mortality (r=-0.32). We calculated that even these weak co-variances could reduce (yellow-tail dascyllus) or increase (humbug dascyllus) the spatial variance in density of 48-h-old recruits arising at settlement by 19 and 27% respectively. Taken together, the findings suggest that the interactions between and relative contributions of input and loss processes can differ substantially over a scale of a few kilometers, resulting in a mosaic of local patches characterized by different abundances and dynamics.

Analysis of Variance↗
PubMed2003

Using stable isotopes to investigate migratory connectivity of the globally threatened aquatic warbler Acrocephalus paludicola.

Understanding the links between breeding and wintering areas of migratory species has important ecological and conservation implications. Recently, stable isotope technology has been used to further our understanding. Stable isotope ratios vary geographically with a range of biogeochemical factors and isotope profiles in organisms reflect those in their food and environment. For inert tissues like feathers, isotope profiles reflect the environment in which they were formed. Following large-scale habitat destruction, the globally threatened aquatic warbler Acrocephalus paludicola has a fragmented breeding population across central Europe, largely in Belarus, Poland and Ukraine. The species' sub-Saharan African wintering grounds have not yet been discovered, and this significantly hampers conservation efforts. Aquatic warblers grow their flight feathers on their wintering grounds, and we analysed stable isotope ratios (delta(15)N, delta(13)C, delta D) in rectrices of adults from six main breeding sites (subpopulations) across Europe to determine whether different breeding subpopulations formed a single mixed population on the wintering grounds. delta(15)N varies considerably with dietary trophic level and environmental factors, and delta D with the delta D in rainfall; neither varied between aquatic warbler subpopulations. Uniform feather delta(15)N signatures suggest no major variation in dietary trophic level during feather formation. High variance and inter-annual differences in mean delta D values hinder interpretation of these data. Significant differences in mean delta(13)C ratios existed between subpopulations. We discuss possible interpretations of this result, and consider differences in moulting latitude of different subpopulations to be the most parsimonious. delta(13)C in plants and animals decreases with latitude, along a steep gradient in sub-Saharan Africa. Birds from the most northwesterly breeding subpopulation (Karsibor, Poland) had significantly lower variance in delta(13)C and delta(15)N than birds from all other sites, suggesting either that birds from Karsibor are less geographically dispersed during moult, or moult in an area with less isotopic heterogeneity. Mean delta(13)C signatures from winter-grown feathers of different subpopulations were positively correlated with the latitude and longitude of breeding sites, suggesting a strong relationship between European breeding and African winter moulting latitudes. The use of stable isotopes provides novel insights into migratory connectivity and migration patterns in this little-known threatened species.

Animals↗
PubMed2005

Using animal movement paths to measure response to spatial scale.

Animals live in an environment that is patchy and hierarchical. I present a method of detecting the scales at which animals perceive their world. The hierarchical nature of habitat causes movement path structure to vary with spatial scale, and the patchy nature of habitat causes movement path structure to vary throughout space. These responses can be measured by a combination of path tortuousity (measured with fractal dimension) versus spatial scale, the variation in tortuousity of small path segments along the movement path, and the correlation between tortuousities of adjacent path segments. These statistics were tested using simulated animal movements. When movement paths contained no spatial heterogeneity, then fractal D and variance continuously increased with scale, and correlation was zero at all scales. When movement paths contained spatial heterogeneity, then fractal D sometimes showed a discontinuity at transitions between domains of scale, variation showed peaks at transitions, and correlations showed a statistically significant positive value at scales smaller than patch size, decreasing to below zero at scales greater than patch size. I illustrated these techniques with movement paths from deer mice and red-backed voles. These new analyses should help understand how animals perceive and react to their landscape structure at various spatial scales, and to answer questions about how habitat structure affects animal movement patterns.

Animals↗
PubMed2006

Latitudinal gradients in abundance, and the causes of rarity in the tropics: a test using Australian honeyeaters (Aves: Meliphagidae).

Several studies have uncovered interspecific latitudinal gradients in abundance (population density) such that tropical species tend to be, on average, less abundant than species at higher latitudes. The causes of this relationship remain poorly studied, in contrast to the relative wealth of literature examining the relationship to latitude of other variables such as range size and body mass. We used a cross-species phylogenetic comparative approach and a spatial approach to examine three potential determining factors (distribution, reproductive output and climate) that might explain why abundance correlates with latitude, using data from 54 species of honeyeaters (Meliphagidae) in woodland environments in eastern Australia. There is a strong positive correlation between mean abundance and latitude in these birds. Reproductive output (clutch size) was positively linked to both abundance and latitude, but partial correlation analysis revealed that clutch size is not related to abundance once the effects of latitude are removed. A subsequent multiple regression model that also considered range size, clutch size and body mass showed that latitude is the only strong predictor of abundance in honeyeaters. In the separate spatial analysis, the climatic variables that we considered (temperature, rainfall and seasonality) were all strongly linked to latitude, but none served as a better predictor of abundance than latitude per se, either individually or collectively. The most intriguing result of our analyses was that the cross-species latitudinal pattern in abundance was not evident within species. This suggests an intrinsic cause of the pattern of 'rarity in the tropics' in Australian honeyeaters. We suggest that evolutionary age may provide a key to understanding patterns of abundance in these birds.

Animals↗
PubMed2006

Density-dependent regulation of population size in colonial breeders: Allee and buffer effects in the migratory Montagu's harrier.

Expanding populations offer an opportunity to uncover the processes driving spatial variation in distribution and abundance. Individual settlement decisions will be influenced by the availability and relative quality of patches, and by how these respond to changes in conspecific density. For example, conspecific presence can alter patch suitability through reductions in resource availability or territorial exclusion, leading to buffer effect patterns of disproportionate population expansion into poorer quality areas. However, conspecific presence can also enhance patch suitability through Allee effect processes, such as transmission of information about resources or improved predator detection and deterrence. Here, we explore the factors underlying the settlement pattern of a growing population of Montagu's harriers (Circus pygargus) in Spain. The population increased exponentially between 1981 and 2001, but stabilised between 2001 and 2004. This population increase occurred alongside a remarkable spatial expansion, with novel site use occurring prior to maximum densities in occupied sites being reached. However, no temporal trends in fecundity were observed and, within sites, average fecundity did not decline with increasing density. Across the population, variance in productivity did increase with population size, suggesting a complex pattern of density-dependent costs and benefits. We suggest that both Allee and buffer effects are operating in this system, with the benefits of conspecific presence counteracting density-dependent declines in resource availability or quality.

Animal Migration↗
PubMed2003

Determinants of competency judgments by experienced laparoscopic surgeons.

BACKGROUND: The definitive criteria for assessing competence remain elusive. In our study, we aimed to identify the determinants of competence assessment used by individual laparoscopic surgeons. METHODS: In a blinded fashion, five laparoscopic surgeons rated 27 subjects on three laparoscopic simulations in four skill categories: clinical judgment, dexterity, serial/simultaneous complexity, and spatial orientation. The raters then assessed overall subject competence for each procedure. Point-biserial correlational analyses and cluster analyses were performed to ascertain the relationships among the various scales. RESULTS: All of the correlations between the skills' ratings and competence judgments were statistically significant ( p <.05). No skill rating was consistently more highly correlated with the competence rating. There were no distinct patterns of correlations for each rater or each procedure. One factor emerged from each cluster analysis of the skills measures. CONCLUSIONS: The results suggest that the four skills scored in the study are highly correlated with each other and are important in determining competence. The cluster analyses revealed that the surgeon raters shared a common perception of competence.

Adult↗
PubMed2003

Training in tasks with different visual-spatial components does not improve virtual arthroscopy performance.

BACKGROUND: We earlier showed that training in the Procedicus KSA Simulator improves the performance of tasks done later in the same simulator. However, it is still unclear how performance in a specific visual-spatial simulator context may change after training in other simulators with different visual-spatial components. In particular, the aim of this study was to test whether performance in the Procedicus Virtual Arthroscopy (VA) Knee Simulator would remain unchanged after a training session in three other simulators with different visual-spatial components. METHODS: Twenty-eight medical students participated in a quasi-transfer study. They were randomly allocated to an experimental group ( n = 14) and a control group ( n = 14). RESULTS: Performance in the Procedicus VA Knee Simulator did not improve after training in other simulators with different visual-spatial components ( t-test p = NS). No significant correlation was found between the Procedicus VA Knee and the Minimally Invasive Surgical Trainer (MIST) simulators. CONCLUSION: One hour of training in different visual-spatial contexts was not enough to improve the performance in virtual arthroscopy tasks. It cannot be excluded, however, that experienced trainees could improve their performance, because perceived similarity between different situations is influenced by many psychological factors, such as the knowledge or expertise of the person performing the transfer task.

Adult↗
PubMed2004

Laparoscopic virtual reality and box trainers: is one superior to the other?

BACKGROUND: Virtual reality (VR) simulators now have the potential to replace traditional methods of laparoscopic training. The aim of this study was to compare the VR simulator with the classical box trainer and determine whether one has advantages over the other. METHODS: Twenty four novices were tested to determine their baseline laparoscopic skills and then randomized into the following three group: LapSim, box trainer, and no training (control). After 3 weekly training sessions lasting 30-min each, all subjects were reassessed. Assessment included motion analysis and error scores. Nonparametric tests were applied, and p < 0.05 was deemed significant. RESULTS: Both trained groups made significant improvements in all parameters measured ( p < 0.05). Compared to the controls, the box trainer group performed significantly better on most of the parameters, whereas the LapSim group performed significantly better on some parameters. There were no significant differences between the LapSim and box trainer groups. CONCLUSIONS: LapSim is effective in teaching skills that are transferable to a real laparoscopic task. However, there appear to be no substantial advantages of one system over the other.

Adult↗
PubMed2004

New model for skills assessment and training progress in minimally invasive surgery.

BACKGROUND: With the spread of minimally invasive surgery and training in this field, development of metrics for skills assessment and training progress has become increasingly important. Our approach was to use the tracking of motion for the definition of objectives metrics. METHODS: We have developed an inanimate model and tracked the 3D coordinates of the instrument tips with an ultrasound system. Besides already validated parameters (time, error time, and distance efficiency ratio) we examined the transit and the speed profile for their evidentiary power. Performances of experts (who have already performed >100 laparoscopic operations) and novices (<20 laparoscopic operations) were evaluated. RESULT: The standardized time, the error time as a precision indicator, and the transit profile parameter for spatial perception could significantly ( p < 0.05) distinguish between experts and novices. Furthermore, these parameters and the distance efficiency ratio improved significantly during a training course in laparoscopic surgery. CONCLUSION: Our model showed changes of the mentioned parameters with experience. According to our results, it can be used for skills assessment and as a training progress measurement system. We propose transit profile as an additional important parameter for assessment.

Adult↗
PubMed2004

Possibilities and limitations of current stereo-endoscopy.

BACKGROUND: Stereo-endoscopy has become a commonly used technology. In many comparative studies striking advantages of stereo-endoscopy over two-dimensional presentation could not be proven. To show the potential and fields for further improvement of this technology is the aim of this article. METHOD: The physiological basis of three-dimensional vision limitations of current stereo-endoscopes is discussed and fields for further research are indicated. New developments in spatial picture acquisition and spatial picture presentation are discussed. RESULTS: Current limitations of stereo-endoscopy that prevent a better ranking in comparative studies with two-dimensional presentation are mainly based on insufficient picture acquisition. CONCLUSION: Devices for three-dimensional picture presentation are at a more advanced developmental stage than devices for three-dimensional picture acquisition. Further research should emphasize the development of new devices for three-dimensional picture acquisition.

Depth Perception↗
PubMed2003

Development of interception of moving targets by chimpanzees (Pan troglodytes) in an automated task.

The experiments investigated how two adult captive chimpanzees learned to navigate in an automated interception task. They had to capture a visual target that moved predictably on a touch monitor. The aim of the study was to determine the learning stages that led to an efficient strategy of intercepting the target. The chimpanzees had prior training in moving a finger on a touch monitor and were exposed to the interception task without any explicit training. With a finger the subject could move a small "ball" at any speed on the screen toward a visual target that moved at a fixed speed either back and forth in a linear path or around the edge of the screen in a rectangular pattern. Initial ball and target locations varied from trial to trial. The subjects received a small fruit reinforcement when they hit the target with the ball. The speed of target movement was increased across training stages up to 38 cm/s. Learning progressed from merely chasing the target to intercepting the target by moving the ball to a point on the screen that coincided with arrival of the target at that point. Performance improvement consisted of reduction in redundancy of the movement path and reduction in the time to target interception. Analysis of the finger's movement path showed that the subjects anticipated the target's movement even before it began to move. Thus, the subjects learned to use the target's initial resting location at trial onset as a predictive signal for where the target would later be when it began moving. During probe trials, where the target unpredictably remained stationary throughout the trial, the subjects first moved the ball in anticipation of expected target movement and then corrected the movement to steer the ball to the resting target. Anticipatory ball movement in probe trials with novel ball and target locations (tested for one subject) showed generalized interception beyond the trained ball and target locations. The experiments illustrate in a laboratory setting the development of a highly complex and adaptive motor performance that resembles navigational skills seen in natural settings where predators intercept the path of moving prey.

Animals↗