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The problems of model specification in one- and two-dimensional stationary random fields are considered, with particular reference to the class of spatial autoregressions. The role of the autocorrelation function is discussed and it is shown to have a valuable exploratory use, especially in identifying directional bias in random fields. It is recommended that this analysis be supplemented by a likelihood-ratio test, which permits more precise tests of hypotheses about the form of the underlying model.

The directional orientation of pre- and post-reproductive migration was studied in the Brazilian red-bellied toad Melanophryniscus cambaraensis, a species that forms explosive-breeding aggregations at irregular intervals throughout the entire year. Migrating toads were captured by enclosing the breeding site in dual drift fences with inward- and outward-facing funnel traps. Data were collected over 5 mo and totalled 333 captures. The observed directional orientation was significantly different from expected under a uniform distribution for both pre- and post-reproductive migration, regardless of gender. Males and females did not differ significantly from each other in the orientation of entry or exit, and the directional orientation of pre-reproductive migration was not significantly different from post-reproductive migration. It is suggested that the observed directional bias may be due to a dirt road next to the breeding site that could restrict juvenile dispersal to the adjacent forest.

We report the results of a numerical study of nonequilibrium steady states for a class of Hamiltonian models. In these models of coupled matter-energy transport, particles exchange energy through collisions with pinned-down rotating disks. In Commun. Math. Phys. 262, 237-267, 2006, Eckmann and Young studied 1D chains and showed that certain simple formulas give excellent approximations of energy and particle density profiles. Keeping the basic mode of interaction in Commun. Math. Phys. 262, 237-267, 2006, we extend their prediction scheme to a number of new settings: 2D systems on different lattices, driven by a variety of boundary (heat bath) conditions including the use of thermostats. Particle-conserving models of the same type are shown to behave similarly. The second half of this paper examines memory and finite-size effects, which appear to impact only minimally the profiles of the models tested in Commun. Math. Phys. 262, 237-267, 2006. We demonstrate that these effects can be significant or insignificant depending on the local geometry. Dynamical mechanisms are proposed, and in the case of directional bias in particle trajectories due to memory, correction schemes are derived and shown to give accurate predictions.

Nearly all organisms show directional bias in sensitivity to environmental signals. In this study, the behavioral sensitivity of a common estuarine copepod, Acartia tonsa, varies significantly with respect to their orientation to a well-characterized fluid mechanical signal. Maximum sensitivity occurs at an angle of 25°–30° and lowest sensitivity occurs at angles of 60°–90° relative to the source. These results support the hypothesis that copepods are not uniformly sensitive to fluid signals and show directional bias in mechanosensitivity. The data also show that large copepods initiate their escape reaction further from the source than small copepods. There is, however, an uncharacteristically large increase in sensitivity at the transition between the nauplii and C1 stage despite being similar in size. This suggests that the mechanosensory system of the naupliar stages is less sensitive to fluid signals and helps to explain the higher predation rates experienced by nauplii.

Hatching failure is inversely correlated with population bottleneck size among exotic birds introduced to New Zealand, but the mechanism for this is unclear. We assess whether the bottlenecks these species experienced during their introduction have affected hatching failure through deleterious changes in egg morphology. We measured egg size and shape of 13 species that passed through bottlenecks of 11-800 individuals during their establishment in the 19th century. Eggs were also measured in the source populations ('pre-bottleneck') of each species to compare pre- and post-bottleneck egg morphology directly. Significant changes in egg volume were found in six of 13 species, with most laying smaller eggs in New Zealand. Egg shape changed in four of 13 species but there was no directional bias; two species developed more elongated eggs and two species broader eggs. There was no relationship between bottleneck size and change in egg volume, but species passing through severe bottlenecks had greater variability in egg volume and were more likely to have eggs that deviated in shape from their source populations. There was no relationship between changes in either egg volume or shape and rates of hatching failure. Further work is needed to assess whether changes in egg morphology have negative consequences on offspring fitness and whether the observed changes are the result of differing environmental conditions in the introduced range.

Planaria (Dugesia tigrina) are freshwater flatworms that are frequently studied because of their simple well-defined nervous system. Previous studies concluded that planaria can be trained to favor a direction in a Y- or T-maze using shock or other negative stimuli, but many of these experiments performed few overall runs and/or tested few individuals. The current study examines whether planaria have a directional bias and the ability to learn by using Y-mazes. The pre-conditioning period determined initial directional bias and was used to assign training directions. The conditioning period used electrical shock as a negative stimulus to condition planaria to select a specific turning direction in the Y-maze. Post-conditioning tested whether planaria maintained their learned behavior. Control planaria were not shocked during the conditioning period. Each period consisted of 3 trials with 10 runs in each trial. When examining the results of a single trial, many planaria demonstrated a directional ...

One of the first questions that paleontologists ask when they identify a large-scale trend in the fossil record (e.g., size increase, complexity increase) is whether it is passive or driven. In this article, I explore two questions about driven trends: (1) what is the underlying cause or source of the directional bias? and (2) has the strength of the directional bias changed over time? I identify two underdetermination problems that prevent scientists from giving complete answers to these two questions.

Certain widely used wind rose programs and air dispersion models use an overly simple data-transfer algorithm that induces a directional bias in their output products. The purpose of this paper is to provide a revised algorithm that corrects the directional bias that occurs from the aliasing that occurs when the sector widths used to report wind direction data are on the same order of magnitude, but not equal, to the sector widths used in the wind direction summaries. The directional bias issue arises when output products in 16 direction sectors (22.5 degrees each) are produced from wind direction data reported in terms of 36 sectors (10 degrees each). The result directional bias affects the results of simulations of air and surface concentrations using widely applied air dispersion models. Datasets or models with the directional bias discussed here give consistent positive biases (approximately 30%) for cardinal direction sectors (north, south, east, and west) and consistent negative biases for all of the other sectors (around -10%). Data summary and air dispersion programs providing outputs in direction sectors that do not match the observational sectors need to be checked for this bias. A revised data-transfer algorithm is provided that corrects the directional bias that can occur in transferring wind direction data between different sector widths.

The DARPA Urban Challenge is providing an opportunity for interested scientists to compete in designing and proving an unmanned vehicle.The autonomous vehicle must avoid collisions, operate in compromised conditions and be robust and independent of human operators. Navigation may be achieved by a varied number of methods. Most will rely on Global Positioning System (GPS) for waypoints, checkpoints and general travel. A route file will be provided for the test site that contains information related to GPS coordinates throughout the course. Vehicles must safely navigate to checkpoints while maintaining road ruleswithsafety.IntheeventthatGPSislostorcompromised,thevehiclesmuststillnavigate to the checkpoints while determining traversable pathways. Optional techniques have been developed in order to navigate without GPS. We build a map of all of the waypoints along with other route information. Whenever we need to navigate to a checkpoint or gate in the absence of GPS, we identify the location we want to head to and use that as a directional bias compared to our current location. We then follow road rules to get through correct gates to the checkpoint using modified orienteering techniques.

A three-dimensional (3D) constitutive model based on a statically constrained microplane theory with volumetric–deviatoric split is proposed for polycrystalline shape memory alloys (SMAs) under multiaxial loading paths. Microplane governing equations are 1D stress–strain relations for normal and shear stresses on each microplane, in which suitable relationships between the microscopic and macroscopic quantities are considered so that switching between elastic and inelastic local responses automatically occurs according to the macroscopic response of SMA without additional constraint. Shear stress on each microplane is expressed by the resultant shear component within the plane to overcome directional bias and to prevent the appearance of shear strain in a pure axial loading or axial strain in a pure shear loading while microplane formulations based on two shear directions may predict such impractical results. The behaviour of SMA under simple and complicated loadings has been studied. In nonproportional loading paths, the model shows interaction between stress components, as well as deviation from normality. Predicted results from the model are in good agreement with those of the existing theoretical and experimental investigations.

Recently, researchers reported a bias for placing agents predominantly on the left side of pictures. Both hemispheric specialization and cultural preferences have been hypothesized to be the origin of this bias. To evaluate these hypotheses, we conducted a study with participants exposed to different reading and writing systems: Germans, who use a left-to-right system, and Israelis, who use a right-to-left system. In addition, we manipulated the degree of exposure to the writing systems by testing preschoolers and adults. Participants heard agent-first or recipient-first sentences and were asked to draw the content of the sentences or to arrange transparencies of protagonists and objects such that their arrangement depicted the sentences. Although preschool-age children in both countries showed no directional bias, adults manifested a bias that was consistent with the writing system of their language. These results support the cultural hypothesis regarding the origin of spatial-representational biases.

BCR-723 is the only environmental certified reference material for platinum-group elements (PGEs) Pt, Pd and Rh. It has been an integral component of quality control/quality assurance procedures in environmental laboratories measuring PGEs, since 2001. Here, we present an extensive quantitative review of the published PGEs measured in BCR-723, since its introduction. A statistical examination of concentrations, measurement precision and accuracy for 25 studies is presented. Measurement typically starts with an aqua regia digestion, followed by some form of pre-concentration or separation procedure, and quantitation by ICP-MS. Use of a sample mass below the recommended value of 100 mg has been shown to produce biased results for acid-based digestions or with laser ablation. Platinum is the most precisely and accurately measured PGE in BCR-723, followed by Rh, and finally by Pd. Literature precision data for all autocatalyst PGEs did not differ significantly ( α = 0.05) from those obtained by the original laboratories used to certify BCR-723. Measurement accuracies for the literature tabulated PGE data did not differ significantly from zero, indicating an overall lack of directional bias. These results should be encouraging to the analytical community, but further advancements, especially for Pd quantification are required.

Objective: To elicit the magnitude, directional bias, and frequency of bracket positioning errors caused by the transfer of brackets from a dental cast to the patient’s dentition in a clinical setting. Materials and Methods: A total of 136 brackets were evaluated. The brackets were placed on dental casts and scanned using cone beam computed tomography (CBCT) to capture 3-D positioning data. The brackets were then transferred to the patient’s dentition with an indirect bonding method using vinyl polysiloxane (VPS) trays and later scanned using CBCT to capture the final bracket positioning on the teeth. Virtual models were constructed from the two sets of scan data and digitally superimposed utilizing best-fit, surface-based registration. Individual bracket positioning differences were quantified using customized software. One-tailed t tests were used to determine whether bracket positioning was within limits of 0.5 mm in the mesiodistal, buccolingual, and vertical dimensions, and 2° for torque, tip, and rotation. Results: Individual bracket positioning differences were not statistically significant, indicating, in general, final bracket positions within the selected limits. Transfer accuracy was lowest for torque (80.15%) and highest for mesiodistal and buccolingual bracket placement (both 98.53%). There was a modest directional bias toward the buccal and gingival. Conclusion: Indirect bonding using VPS trays transfers the planned bracket position from the dental cast to the patient’s dentition with generally high positional accuracy.

Approximately 90% of the human population is right-handed. The emergence of this hand preference in humans is thought to be linked to the ability to execute complex tasks and habitual bipedalism. In order to test these hypotheses, the present study explored, for the first time, hand preference in relation to both body posture (seated and bipedal) and task complexity (bimanual coordination and two tool use tasks of different complexity) in bonobos (Pan paniscus). Few studies have explored the effects of both posture and task complexity on handedness, and investigations with bonobos are scarce, particularly studies on tool use. Our study aims to overcome such a gap by addressing two main questions: 1) Does a bipedal posture increase the strength of hand preference and/or create a directional bias to the use of the right hand? 2) Independent of body posture, does task complexity increase the strength of the hand preference and/or create a directional bias to the use of the right hand? Our results show that independent of body posture, the more complex the task, the more lateralization occurred. Moreover, subjects tended to be right-handed for tasks involving tool use. However, posture had no significant effect on hand preference in the tasks tested here. Therefore, for a given task, bonobos were not more lateralized in a bipedal posture than in a seated one. Task complexity might thus have contributed more than bipedal posture to the emergence of human lateralization and the preponderance of right-handedness, although a larger sample size and more data are needed to be conclusive.

We studied the direction of the three-dimensional fingertip force vector in young and old adults during a simple pressing task with the index finger. Ten young and ten old subjects pressed against a force plate with their index finger and maintained target forces that ranged from 2.5 to 15 N. Subjects viewed a display of the force normal to the force plate; forces tangential to the force plate were not displayed. Young adults produced fingertip forces that were nearly perpendicular to the plate at all target forces while old adults produced fingertip forces that deviated in the proximal direction of the horizontal plane, and ulnar direction of the vertical plane. The fingertip force deviated from the onset of pressing in both groups, but in young subjects the force aligned to perpendicular within 200 ms. Additional study is required to determine if these biased force vector directions contribute to clumsiness and slowing that are characteristic of fine manipulation in old age.

Psychophysical evidence in humans indicates that localization is different for stationary flashed and coherently moving objects. To address how the primary visual cortex represents object position we used a population approach that pools spiking activity of many neurones in cat area 17. In response to flashed stationary squares (0.4 deg) we obtained localized activity distributions in visual field coordinates, which we referred to as profiles across a ‘population receptive field’ (PRF). We here show how motion trajectories can be derived from activity across the PRF and how the representation of moving and flashed stimuli differs in position. We found that motion was represented by peaks of population activity that followed the stimulus with a speed-dependent lag. However, time-to-peak latencies were shorter by ∼16 ms compared to the population responses to stationary flashes. In addition, motion representation showed a directional bias, as latencies were more reduced for peripheral-to-central motion compared to the opposite direction. We suggest that a moving stimulus provides ‘preactivation’ that allows more rapid processing than for a single flash event.

Most female birds have only a left ovary and associated oviduct. The entry to the oviduct is on the left side of the urodeum of the cloaca. This arrangement may favor males that mount females from the left during copulation if it results in sperm being placed closer to the opening of the oviduct. Therefore, we predicted a left-sided directional bias of cloacal contacts during House Sparrow (Passer domesticus) copulations. Cloacal contacts from the left outnumbered those from the right 74 to 25 (3:1) during 25 bouts of copulation at 11 House Sparrow nests. While this pattern suggests that a left-sided bias in mounting by males during copulation may be related to the asymmetry of the female reproductive tract, it also might be related to brain lateralization.

Triturus alpestris has been found to be adept at homing, and previous studies have found that its orientation behaviour during breeding migration can be explained, at least in part, by the use of olfactory cues from the breeding pond. Nonetheless, the use of chemical cues from the pond probably does not support a guidance strategy when the newts are far from the pond. Hence, T. alpestris may rely on other orientation cues. In this study, alpine newts were tested in a circular arena to determine the sensory cues used to locate breeding ponds. Animals were collected from a permanent pond situated in northern Spain, taken to the experimental site 9020 m distant, and tested for orientation under a variety of conditions (i.e., orientation under a clear night sky, orientation under dark conditions, and orientation under a clear night sky in the presence of an altered geomagnetic field). The possibility of a non-homing directional bias was also tested. Newts chose a compass course in the direction of their breed...

Sensorimotor integration regulates goal-directed movements. We study the signaling mechanisms underlying sensorimotor integration in C. elegans during olfactory steering, when the sinusoidal movements of the worm generate an in-phase oscillation in the concentration of the sampled odorant. We show that cholinergic neurotransmission encodes the oscillatory sensory response and the motor state of head undulations by acting through an acetylcholine-gated channel and a muscarinic acetylcholine receptor, respectively. These signals converge on two axonal domains of an interneuron RIA, where the sensory-evoked signal suppresses the motor-encoding signal to transform the spatial information of the odorant into the asymmetry between the axonal activities. The asymmetric synaptic outputs of the RIA axonal domains generate a directional bias in the locomotory trajectory. Experience alters the sensorimotor integration to generate specific behavioral changes. Our study reveals how cholinergic neurotransmission, which can represent sensory and motor information in the mammalian brain, regulates sensorimotor integration during goal-directed locomotions.

International audience; The present study (N=56) investigated spatio-temporal accuracy of horizontal reaching movements controlled visually through a vertical video monitor. Direct vision of the hand was precluded and the direction of hand trajectory, as perceived on the video screen, was varied by changing the angle of the camera. The orientation of the visual scene displayed on the fronto-parallel plane was thus congruent (0 degrees condition) or non-congruent (directional bias of 15 degrees, 30 degrees or 45 degrees counterclockwise) according to the horizontal working space. The goal of this study was to determine whether local learning of a directional bias can be transferred to other locations in the working space, but taking into account the magnitude of the directional bias (15 degrees, 30 degrees or 45 degrees ), and the position of the successive objectives (targets at different distances (TDD) or different azimuths (TDA)). Analysis of the spatial accuracy of pointing movements showed that when introducing a directional bias, terminal angular error was linearly related to the amount of angular perturbation (around 30%). Seven trials were, on average, necessary to eliminate this terminal error, whatever the magnitude of the directional bias and the position of the successive targets. When changing the location of the spatial objective, transfer of adaptation was achieved in the TDD condition but remained partial in the TDA condition. Furthermore, initial orientation of the trajectory suggested that some participants used a hand-centred frame of reference whereas others used an external one to specify movement vector. The adaptation process differed as a function of the frame of reference used, but only in the TDA condition. Adaptation for participants using a hand-centred frame of reference was more concerned with changes in the shape of the trajectory, whereas participants using an external frame of reference adapted their movement by up-dating the initial direction of hand trajectory. As a whole, these findings suggest that the processes involved in remote visual control of hand movement are complex with the result that tasks requiring video-controlled manipulation like video-controlled surgery require specific spatial abilities in actors and consequential plasticity of their visuo-motor system, in particular concerning the selection of the frame of reference for action.

Myosin V is a two-headed molecular motor that binds six light chains per heavy chain, which creates unusually long lever arms. This motor moves processively along its actin track in discrete 36-nm steps. Our model is that one head of the two-headed myosin V tightly binds to actin and swings its long lever arm through a large angle, providing a stroke. We created single-headed constructs with different-size lever arms and show that stroke size is proportional to lever arm length. In a two-headed molecule, the stroke provides the directional bias, after which the unbound head diffuses to find its binding site, 36 nm forward. Our two-headed construct with all six light chains per head reconstitutes the 36-nm processive step seen in tissue-purified myosin V. Two-headed myosin V molecules with only four light chains per head are still processive, but their step size is reduced to 24 nm. A further reduction in the length of the lever arms to one light chain per head results in a motor that is unable to walk processively. This motor produces single small ≈6-nm strokes, and ATPase and pyrene actin quench measurements show that only one of the heads of this dimer rapidly binds to actin for a given binding event. These data show that for myosin V with its normal proximal tail domain, both heads and a long lever arm are required for large, processive steps.

This study investigated the physical and physiological response of individual setae on the antennule of Gaussia princeps. We found significant differences in the physical and physiological responses of the setae to various intensities of water flow. No physiological evidence was found to suggest that individual setae are dually innervated; however, directional bias in both the displace- ment and subsequent physiological responses was evident. Although more easily displaced by fluid flow, the shortest hairs were physiologically less sensitive to angular deflection than were the longer setae, so that slow flows produced a greater neural response in the long seta. The combination of high resistance to movement and acute physiological sensitivity allows the long seta to respond to biolog- ically driven, low-intensity flows while filtering out high-frequency background noise. This suggests that the most prominent, long, distal setae function as low-flow detectors whereas the short hairs respond to more rapid fluid motion. Each seta responds to only a portion of the overall range of water velocity in the copepod's habitat. Thus, the entire sensory appendage, which consists of an ensemble of setae of different morphologies and lengths, may function as a unit to code the intensity and direc- tionality of complex fluid disturbances.

A mathematical model is presented for the growth of yeast that incorporates both dimorphic behaviour and nutrient diffusion. The budding patterns observed in the standard and pseudohyphal growth modes are represented by a bias in the direction of cell proliferation. A set of spatial indices is developed to quantify the morphology and compare the relative importance of the directional bias to nutrient concentration and diffusivity on colony shape. It is found that there are three different growth modes: uniform growth, diffusion-limited growth (DLG) and an intermediate region in which the bias determines the morphology. The dimorphic transition due to nutrient limitation is investigated by relating the directional bias to the nutrient concentration, and this is shown to replicate the behaviour observedin vivo. Comparisons are made with experimental data, from which it is found that the model captures many of the observed features. Both DLG and pseudohyphal growth are found to be capable of generating observed experimental morphologies.

Cover time measures the time (or number of steps) required for a mobile agent to visit each node in a network (graph) at least once. A short cover time is important for search or foraging applications that require mobile agents to quickly inspect or monitor nodes in a network, such as providing situational awareness or security. Speed can be achieved if details about the graph are known or if the agent maintains a history of visited nodes, however, these requirements may not be feasible for agents with limited resources, they are difficult in dynamic graph topologies, and they do not easily scale to large networks. This paper introduces a set-based form of heading (directional bias) that allows an agent to more efficiently explore any connected graph, static or dynamic. When deciding the next node to visit, agents are discouraged from visiting nodes that neighbor both their previous and current locations. Modifying a traditional movement method, e.g., random walk, with this concept encourages an agent to move toward nodes that are less likely to have been previously visited, reducing cover time. Simulation results with grid, scale-free, and minimum distance graphs demonstrate heading can consistently reduce cover time as compared to non-heading movement techniques.

This article documents a systematic bias in surface wind directions between the TAO buoy measurements at 0°, 170°W and the ECMWF analysis and forecasts. This bias was of the order 10° and persisted from November 2008 to January 2010, which was consistent with a post-recovery calibration drift in the anemometer vane. Unfortunately, the calibration drift was too time-variant to be used to correct the data so the quality flag for this deployment was adjusted to reflect low data quality. The primary purpose of this paper is to inform users in the modelling and remote-sensing community about this systematic, persistent wind directional bias, which will allow users to make an educated decision on using the data and be aware of its potential impact to their downstream product quality. The uncovering of this bias and its source demonstrates the importance of continuous scientific oversight and effective user-data provider communication in stewarding scientific data. It also suggests the need for improvement in the ability of buoy data quality control procedures of the TAO and ECMWF systems to detect future wind directional systematic biases such as the one described here.

The history of life shows a clear trend in hierarchical organization, revealed by the successive emergence of organisms with ever greater numbers of levels of nestedness and greater development, or ‘individuation’, of the highest level. Various arguments have been offered which suggest that the trend is the result of a directional bias, or tendency, meaning that hierarchical increases are more probable than decreases among lineages, perhaps because hierarchical increases are favoured, on average, by natural selection. Further, what little evidence exists seems to point to a bias: some major increases are known – including the origin of the eukaryotic cell from prokaryotic cells and of animals, fungi and land plants from solitary eukaryotic cells – but no major decreases (except in parasitic and commensal organisms), at least at the cellular and multicellular levels. The fact of a trend, combined with the arguments and evidence, might make a bias seem beyond doubt, but here I argue that its existence is an open empirical question. Further, I show how testing is possible.

The weighted sum of order p , the l bp -norm, is a generalization of the well-known l p -norm used in predicting distances in a transportation network. The properties of the directional bias function and the unit balls for the l bp -norm are of theoretical and practical interest. We investigate these properties and compare them with the properties of the l p -norm's directional bias function and the unit balls. We find that the l bp -norm is better at capturing the nonlinearity in a transportation network than the weighted l p -norm. It is also shown that, in contrast to the weighted l p -norm, where the optimal parameter p value is confined to the interval (1,2), for the l bp -norm the parameter p can have an optimal value greater than 2.

ANCOVA and regression both exhibit a directional bias when measuring correlates of change. This bias confounds the comparison of changes between naturally occurring groups with large pretest differences (ANCOVA), or for identifying predictors of change when the predictor is correlated with pretest (regression). This bias is described in some detail. A computer simulation study is presented, which shows that properly identified structural equation models are not susceptible to this bias. Neither gain scores (posttest minus pretest) nor structural equation models exhibit the “regression bias.” Other factors, such as skewness, that may confound measurement of change are also discussed.

When patients with left-sided neglect are asked to bisect horizontal lines, they tend to place their marks to the right of the line's objective mid-point. However, when asked to bisect short lines they are either more accurate or paradoxically cross over and place their marks to the left of the objective mid-point. Previous explanations of the cross over phenomenon have considered specific aberrations of spatial attention. However, these explanations make no predictions about judgments of non-spatial stimuli. Two patients with right brain damage were asked to judge weights placed on both hands simultaneously. They were biased in reporting weights on the right as being heavier than those on the left. This rightward bias changed with lighter pairs of weights presented in the context of equal reference weights. In one patient the directional bias was eliminated and in the other the bias was reversed so that she was more likely to report the left weight as heavier than the right. These data suggest that a phenomenon analogous to cross over in line bisections also occurs with judgments of non-spatial stimuli. Representations of stimuli appear to be influenced by features of the stimuli encountered on-line and by memory traces of similar stimuli encountered previously. With an attentional deficit, memory traces influence the magnitude of the representation derived on-line disproportionately.

In his classic norm formation research, Sherif (1935) demonstrated convergence in group members' judgments of ambiguous perceptual stimuli. In the present study, we investigated convergence in group members' strategic orientations for solving problems, specifically riskiness and conservatism. According to Regulatory Focus Theory (Higgins, 1998), people in a “promotion focus” (who are sensitive to the presence and absence of positive outcomes and who desire accomplishments) adopt risky strategies for solving problems, whereas people in a “prevention focus” (who are sensitive to the absence and presence of negative outcomes and who desire security) adopt conservative strategies. Using a modified version of Sherif's classic paradigm, we introduced a subtle manipulation to induce promotion vs prevention focus in three-person groups working on a multitrial recognition memory task. We found evidence that group members' responses converged and that this convergence was associated with a directional bias in strategic orientation (i.e., promotion groups were riskier than prevention groups). Implications of these results for understanding shared reality in groups were discussed.

Two hundred and sixty four right-handed, 246 mixed-handed and 360 left-handed students were requested to indicate on five maps of cinema halls what place they would choose. All three handedness groups showed a preference for the right and a corresponding directional bias towards the left space. However, they differed significantly from each other on the magnitude of this bias which was most pronounced in right and less in left handers. It is assumed that lateralized mechanisms underlying such biases have developed evolutionarily and serve right-handed persons best. Non-dextrality considerably reduces their phenotypic expressions, but even left-handedness does not reverse the directional bias towards the left. It is also hypothesized that right, mixed and left handers differ in a large number of behavioral choices and strategies, modeled by cerebrally lateralized mechanisms and that the cinema seating preference is only one of them.

Directionality in right, mixed and left handers was studied, asking subjects to draw 6 familiar objects. All three handedness classes showed left directional bias, but they differed significantly in this respect, right handers being the most and left handers the least left directed. Directionality is related to handedness, but it seems to be governed by an autonomous underlying mechanism, which probably developed in the course of evolution to facilitate the perceptuo-motor relationships of the subject with the environment.

Clockwise and counterclockwise full turns are commonly used to assess lateralization in circling behavior. Although previous studies have reported that the rotatory swimming (ROSW) test is simple and reliable, little is known about lateralization of turns lower than 360 degrees and the amount of turning close to the wall, and even less is known about alternation of direction during a session. Here we investigated the effects of consistency of laterality and sex on 30 degree turns in center and in periphery of the swimming apparatus, and on alternation of direction upon three sessions. Approximately 80% of the turns occurred when mice swam along the wall. In side-consistent turners, this suggests the existence of an intrinsic sensorimotor asymmetry that determines the adhesion to the preferred side. Regarding categorization of side preferences, there was a high percentage of agreement between center and periphery, as well as between full turns and extra 30 degree turns (30 degree turns that do not contribute to full turns). Therefore, behavioral asymmetry in the ROSW can be assessed using 30 degree turns. There was no significant directional bias in the population, and side preference was found to be independent of sex. By contrast, after the second minute of each session, males exhibited a significantly higher number of reversal of direction (RD) as well as a higher number of RD per turn than females. The amount of RD presented by each animal is not predicted by the animal's side preference. Thus, RD is independent of preferred side of turning and depends on sex.

Motor proteins of the kinesin superfamily transport intracellular cargo along microtubules. Although different kinesin proteins share 30–50% amino-acid identity in their motor catalytic cores, some move to the plus end of microtubules whereas others travel in the opposite direction1,2. Crystal structures of the catalytic cores of conventional kinesin (a plus-end-directed motor involved in organelle transport) and ncd (a minus-end-directed motor involved in chromosome segregation) are nearly identical3,4; therefore, the structural basis for their opposite directions of movement is unknown. Here we show that the ncd ‘neck’, made up of 13 class-specific residues next to the superfamily-conserved catalytic core, is essential for minus-end-directed motility, as mutagenesis of these neck residues reverses the direction of ncd motion. By solving the 2.5 A structure of a functional ncd dimer, we show that the ncd neck (a coiled-coil) differs from the corresponding region in the kinesin neck (an interrupted β-strand)5,6, although both necks interact with similar elements in the catalytic cores. The distinct neck architectures also confer different symmetries to the ncd and kinesin dimers and position these motors with appropriate directional bias on the microtubule.

In this study, we investigated whether early deafness affects the typical pattern of hemispheric lateralization [i.e., right hemisphere (RH) dominance] in the control of spatial attention. To this aim, deaf signers, deaf non-signers, hearing signers, and hearing non-signers were required to bisect a series of centrally presented visual lines. The directional bisection bias was found to be significantly different between hearing and deaf participants, irrespective of sign language use. Hearing participants (both signers and non-signers) showed a consistent leftward bias, reflecting RH dominance. Conversely, we observed no evidence of a clear directional bias in deaf signers or non-signers (deaf participants overall showing a non-significant tendency to deviate rightward), suggesting that deafness may be associated to a more bilateral hemispheric engagement in visuospatial tasks.

Random walks have been proposed as a simple method of efficiently searching, or disseminating information throughout, communication and sensor networks. In nature, animals (such as ants) tend to follow correlated random walks, i.e., random walks that are biased towards their current heading. In this paper, we investigate whether or not complementing random walks with directional bias can decrease the expected discovery and coverage times in networks. To do so, we use a macro-level model of a directionally biased random walk based on Markov chains. By focussing on regular, connected networks, the model allows us to efficiently calculate expected coverage times for different network sizes and biases. Our analysis shows that directional bias can significantly reduce the coverage time, but only when the bias is below a certain value which is dependent on the network size.

Although sockeye salmon (Oncorhynchus nerka) spend 1-4 years in the ocean and accumulate 99% of adult body weight during this period, their migratory patterns in the Northeast Pacific are not yet well understood. A model of ocean migration based on conjecture from limited catch and tagging data has influenced work in sockeye ecology for the past 20 years. To evaluate this model, we constructed a spatially explicit individual-based model that used ocean surface currents and simple behavioural rules to simulate migration patterns for sockeye from the Fraser River system. We explored several modelled behaviours, including random swimming and swimming with a directional bias during some months. The simulations begin at the time when juveniles leave inside coastal waters and end when return migration begins (a few months before river reentry). We determined that simple undirected swimming for most of the ocean phase (except the first 4 months when smolts are near the coast) provided results that challenged the prevailing model but did not require complex assumptions. The migration patterns generated by these rules compare well both qualitatively and quantitatively with the existing empirical data on British Columbia sockeye distribution and migrations in the ocean.

The study of behavioral laterality in humans and nonhumans can contribute to our understanding of brain evolution and functional similarities across species. Few studies have focused on cetaceans. This report exams lateralized behaviors in two captive bottlenose dolphins (Tursiops truncatus). Observations were made by videotaping through a 90 × 150 cm underwater one-way Plexiglass mirror. Directional bias in swimming, “barrel-roll” maneuvers, and circular head movements was assessed for each subject. There was a strong clockwise bias in swimming direction and direction of “barrel-rolls,” but not circular head movements. The clockwise bias in swimming direction and “barrel-roll” maneuvers may be consistent with a rightward turning bias. Zoo Biol 16:173–177, 1997. © 1997 Wiley-Liss, Inc.

When drawing real scenes or copying simple geometric figures young children are highly sensitive to parallel cues and use them effectively. However, this sensitivity can break down in surprisingly simple tasks such as copying a single line where robust directional errors occur despite the presence of parallel cues. Before we can conclude that this directional bias is a limiting case it needs to be shown that any given parallel cues are indeed being processed. We achieved this by using a texture-defined contour where parallel cues are integral to the stimulus and thus cannot be ignored. Here we report that even when prolific parallel cues must have been processed, young children make robust directional errors when copying single lines. This finding demonstrates a major constraint on young children's spatial parallel coding.

International audience; Abstract Microsaccades are miniature saccades occurring once or twice per second during visual fixation. While microsaccades and saccades share similarities at the oculomotor level, the functional roles of microsaccades are still debated. In this study, we examined the hypothesis that the microsaccadic activity is affected by the type of noisy background during the execution of a particular discrimination task. Human subjects had to judge the orientation of a tilted stimulus embedded in static or dynamic backgrounds in a forced choice-task paradigm, as adapted from Rucci, Iovin, Poletti, and Santini (2007). Static backgrounds induced more microsaccades than dynamic ones only during the execution of the discrimination task. A directional bias of microsaccades, dictated by the stimulus orientation, was temporally coupled with this period of increased activity. Both microsaccade rates and orientations were comparable across background types after the response time although subjects maintained fixation until the end of the trial. This represents a background-specific modulation of the microsaccadic activity driven by attentional demands. The visual influence of microsaccades on discrimination performances was modeled at the retinal level for both types of backgrounds. A higher simulated microsaccadic activity was necessary for static backgrounds in order to achieve discrimination performance scores comparable to that of dynamic ones. Taken together, our experimental and theoretical findings further support the idea that microsaccades are under attentional control and represent an efficient sampling strategy allowing spatial information acquisition.

PURPOSE Optokinetic eye movements stabilize gaze by tracking motion of the visual scene during sustained movement of a creature's body. The purpose of this study was to describe vertical and horizontal optokinetic nystagmus (OKN) in nonhuman primates (NHPs) with normal binocular vision, and to compare their responses to NHPs with binocular maldevelopment induced by prism-rearing. METHODS Optical strabismus was created in infant macaques (n = 6) by fitting them with prism goggles. The goggles were removed after 3, 6, 9, or 12 weeks to determine the effects of increasing durations of binocular noncorrespondence. Infant NHPs (n = 2) reared wearing plano goggles served as controls. OKN was evoked by horizontal or vertical stripe motion. Eye movements were recorded by using binocular search coils. RESULTS NHPs reared in early infancy under conditions of binocular noncorrespondence for durations of 6 weeks or longer had horizontal OKN responses biased directionally in favor of nasalward motion. NHPs reared with prisms for any duration had vertical OKN responses more biased than normal NHPs in favor of upward motion. Diagonal "crosstalk" during horizontal or vertical OKN (vertical slow phases during horizontal stimulus motion, and vice versa) was present to some degree in all NHPs. However, crosstalk-upward during horizontal OKN and nasalward during vertical OKN-was most pronounced in NHPs reared with prism for durations long enough to induce a permanent esotropic strabismus (longer than 3 weeks). CONCLUSIONS With fusion maldevelopment, the OKN pathways retain a nasalward and upward bias. During forward locomotion, optic flow excites temporalward and downward visual motion in each eye. The OKN biases would act in counterbalance. The biases attenuate with emergence of fusion, but may persist and crosstalk when fusion is impeded.

Conventional shot domain migration constructs a subsurface image using the forward extrapolated (downgoing) wavefield from a source and reverse extrapolated (up-going) wavefield originating at the surface receiver positions. Similarly, sea surface related multiples can also be used to construct an image of the subsurface where the boundary data for the down-going and up-going wavefields are generated at the receiver locations via wavefield separation. After up-down separation the down-going and up-going wavefields act as the source and receiver surface wavefields and exist only at the receiver positions. To properly image the subsurface with the multiples, the down-going and up-going wavefields must be both recorded. Therefore, the streamer coverage, receiver density, source-receiver distribution geometry and acquisition shooting direction as well as target depth and subsurface dip are controlling factors in the effectiveness of imaging with multiples. For example, wide azimuth (WAZ) acquisition generates large streamer coverage and enhances the use of both the down-going (source) and up-going (receiver) wavefields. Anti-parallel shooting is typically required to reduce the source (down-going) wavefield directional bias and image both updip and downdip targets. Split-spread shooting geometry uses rays including downgoing and up-going wavefields recorded from different sides of the shot location and further enhances the subsurface illumination. In this paper, both synthetic and field data examples are used to demonstrate the challenges from acquisition geometry. A shallow water field data example shows the successful application of the technology to mitigate the acquisition footprint. The technology has the potential of reducing drilling hazard risks.

Injuries to the peripheral nervous system (PNS) affect numerous people worldwide. Endogenous electrical currents are important during development and may influence axonal re-growth to aid recovery following injury. Electrical stimulation for 8 hours with 50 mV/mm has been previously shown to influence neurite re-growth and this was further enhanced by co-stimulation with Schwann cells (SC). The optimal duration for electrical stimulation is not known and therefore this study examines neuronal morphology and outgrowth in response to electrically stimulated SC following a shorter 1 hour stimulation at 50 mV/mm. Primary dissociated dorsal root ganglion neurons were seeded on the electrically stimulated SC. Results indicate that the electrically stimulated SC elicited greater total neurite outgrowth by 2.05-fold compared to unstimulated control populations with no directional bias. Application of electrical stimulation in vivo could aid neuron regrowth to PNS injuries.

Developing practical computer programs to impose geologic interpretations on computer-generated contours has proven to be difficult. Today, complex data transformations, tedious contour editing, or both are used to achieve that goal. This paper introduces a new program for incorporating high-quality geologic interpretations into computer contouring. The program is robust, easy to implement, and easy to explain to potential users. The computational complexity of the program is high, but the results are worth the price.

Previous studies have demonstrated that the perception of shading is based upon assumptions about lighting direction, for example, light from above. However, it is not clear whether these assumptions are used in the perception of cast shadows. Moreover, it is unclear whether a perceptual interaction exists between shading and cast shadows because until now they have been studied separately. In this study, we investigated through three experiments whether the light-from-above (or another direction) assumption is used in interpreting ambiguous cast shadows, and whether shading information influences the interpretation of cast shadows. Our results indicate the existence of the light-from-above assumption in interpreting cast shadows. Consistent shading information enhanced the interpretation, and judgments of lighting direction were also based on both cast shadow and shading information. However, the perceptual determination of shape from shading was relatively independent of the cast shadow interpretation or the lighting direction judgments of the scene.

Structures of the human O6-alkylguanine-DNA alkyltransferase bound to substrate together with biochemical analysis provide clues to substrate acquisition and recognition, as well as details of the methyl transfer reaction catalyzed by this direct DNA repair protein.

We thoroughly respect the recent contributions of Jennions and Moller to the appropriate use of meta-analysis in Ecology and Evolution (Moller and Jennions 2001; Jennions and Moller 2002a, b). Therefore, we are surprised to have to point out the ‘wood’ among the ‘trees’ of their own data. Our point (Kotiaho and Tomkins 2002) was simply to raise the question: given that about 8.6% of studies report non-significant effects for the main hypothesis (Csada et al. 1996), can meta-analysis fail to find a significant overall effect size? Our conclusion was that where publication bias existed, it could not. Here we reply to the comments in Jennions et al.’s (this volume) ‘reply’ and support our original claim with evidence from a thorough empirical investigation of this subject by two of these authors (Jennions and Moller 2002a). We illustrated our point with a hypothetical example in which a new hypothesis was proposed but which was untrue (effect size zero). This hypothetical hypothesis nevertheless attracted ten publications. We calculated that, with a publication bias causing nine out of 10 publications to be significant, that, all things being equal (i.e. methodology and sample size), there would be a significant overall effect size. Jennions et al. (this volume) make two points concerning the validity of our example. The first point is that if the hypothetical true effect size really was zero, then there would be significant positive as well as significant negative effect sizes that were published among the nine significant studies. This would of course tend to render the overall effect size calculated as non-significant, rather than significant as we calculated by assuming all of the significant results fell in the same direction. Our assumption was not without foundation however, as publication bias not only manifests itself as a bias towards significant results but also and importantly, as a bias towards intuiti e results. This has been demonstrated a number of times recently in the form of paradigm shifts and publication biases in Ecology and Evolution (Alatalo et al. 1997, Palmer 1999, 2000, Simmons et al. 1999, Poulin 2000, Jennions and Moller 2002a). Indeed, a directional bias is used as an indication of publication bias when examining funnel plots (Light and Pillemer 1984, Begg 1994). Jennions et al.’s (this volume) second point is that unlike in our hypothetical study, all things are not equal, and that in reality, non-significant studies that are published are likely to have larger sample sizes than the published significant ones. This relationship between significance and sample size arises because publication bias favours the publication of small studies that are significant over small studies that are nonsignificant (Light and Pillemer 1984, Begg 1994). Hence by giving all of our studies the same sample size we weighted them equally in our estimation of true effect size, whereas the likelihood may be that the nine significant studies would have had smaller sample sizes and therefore be weighted less. Even so, in our example if all of the studies that were just significant (Z=1.96) had a sample size of 30, the study of zero effect (Z=0) would require a sample size in excess of 1914 to make the overall mean weighted Fishers zr non-significant (using equation 4.12 on page 71 in Rosenthal 1991 and equations 18-3 and 18-8 on pages 265 and 268, respectively, in Shaddish and Haddock 1994). Furthermore, a study that was just significant in the opposite (counterintuitive) direction would require a sample size in excess of 143 which is more than four times the magnitude of the nine significant studies to make the overall weighted Fishers zr non-significant. Hence the difference in sample size between the studies that were significant and non-significant or significant in the opposite direction would have to be extreme to invalidate our example. The extreme differences in sample sizes between significant and non-significant studies required to negate the effects that we were proposing are likely to be uncommon.

The aim of this cohort study was to evaluate the concordance of the Sickness Impact Profile for Nursing Homes (SIP- NH) and Sickness Impact Profile (SIP) in classifying change. Subjects consisted of 194 consecutive long- stay nursing home residents at one academic department of the V.A. and in 8 community proprietary nursing homes in San Antonio, Texas. They were to have more than 3 months residency; to be ⩾61 years; and to be dependent in at least 2 ADLs with an MMSE score of ⩾15. Subjects were administered a 128- item SIP and a reduced 66- item SIP- NH at baseline and 4, 8, and 12- month follow- up. At each follow- up, subjects were classified into 3 mutually exclusive change categories using a change score of ⩾5 points. Concordance of the classification of subjects by the SIP- NH and SIP was evaluated. The misclassification rate as well as its direction was also assessed. Both instruments classified a little over one- quarter of the subjects as better, over a third as being unchanged, and another third as being worse at the four- month follow- up. More subjects were classified as worse by both instruments at 8 and 12 months. All kappas ranged from 0.52 to 0.78, indicating good to excellent agreement. Overall, the SIP- NH characterized persons as changed more often than the SIP with no systematic directional bias. In conclusion, the SIP- NH was concordant with the SIP in classifying change in subjects. However, we cannot say which of the two is better for detecting change. Future research must focus on defining a change score which has clinical meaning, and evaluate responsiveness to change. (Aging Clin. Exp. Res. 7: 228–233, 1995)