Judgments Of Position Research Articles

Does representational momentum reflect a distortion of the length or the endpoint of a trajectory?

Observers viewed a moving target, and after the target vanished, indicated either the initial position or the final position of the target. In Experiment 1, an auditory tone cued observers to indicate either the initial position or the final position; in Experiment 2, different groups of observers indicated the initial position or the final position. Judgments of the initial position were displaced backward in the direction opposite to motion, and judgments of the final position were displaced forward in the direction of motion. The data suggest that the remembered trajectory is longer than the actual trajectory, and the displacement pattern is not consistent with the hypothesis that representational momentum results from a distortion of memory for the location of a trajectory.

Effects of stimulus material on the Fröhlich illusion

In the Fröhlich illusion, judgements of the first position of a moving object are typically displaced in the direction of motion. The illusion has been obtained with linear motion of a small target, and with rotary motion of a spatially extended line. We compared judgements of the initial orientation of a small dot and a line that rotated around the point of fixation. The illusion was absent with the dot, whereas it was reliably obtained with the line. When the density of the line was reduced to two dots, the illusion persisted. However, the illusion was absent when a half-line extending to only one side from fixation was presented. We discuss the results with respect to two attentional accounts of the Fröhlich illusion and an account based on spatiotemporal integration.

The use of 2D and 3D displays for shape-understanding versus relative-position tasks.

Research on when and how to use three-dimensional (3D) perspective views on flat screens for operational tasks such as air traffic control is complex. We propose a functional distinction between tasks: those that require shape understanding versus those that require precise judgments of relative position. The distortions inherent in 3D displays hamper judging relative positions, whereas the integration of dimensions in 3D displays facilitates shape understanding. We confirmed these hypotheses with two initial experiments involving simple block shapes. The shape-understanding tasks were identification or mental rotation. The relative-position tasks were locating shadows and determining directions and distances between objects. We then extended the results to four experiments involving complex natural terrain. We compare our distinction with the integral/separable task distinction of Haskel and Wickens (1993). Applications for this research include displays for air traffic control, geoplots for military command and control, and potentially, any display of 3D information.

Deficit of auditory space perception in patients with visuospatial neglect

There have been many studies of visuospatial neglect, but fewer studies of neglect in relation with other sensory modalities. In the present study we investigate the performance of six right brain damaged (RBD) patients with left visual neglect and six RBD patients without neglect in an auditory spatial task. Previous work on sound localisation in neglect patients adopted measure of sound localisation based on directional motor responses (e.g., pointing to sounds) or judgement of sound position with respect to the body midline (auditory midline task). However, these measures might be influenced by non-auditory biases related with motor and egocentric components. Here we adopted a perceptual measure of sound localisation, consisting in a verbal judgement of the relative position (same or different) of two sequentially presented sounds. This task was performed in a visual and in a blindfolded condition. The results revealed that sound localisation performance of visuospatial neglect patients was severely impaired with respect to that of RBD controls, especially when sounds originated in contralesional hemispace. In such condition, neglect patients were always unable to discriminate the relative position of the two sounds. No difference in performance emerged as a function of the visual condition in either group. These results demonstrate a perceptual deficit of sound localisation in patients with visuospatial neglect, suggesting that the spatial deficits of these patients can arise multimodally for the same portion of external space.

The role of perception in the mislocalization of the final position of a moving target.

The judged final position of a moving stimulus has been suggested to be shifted in the direction of motion because of mental extrapolation (representational momentum). However, a perceptual explanation is possible: The eyes overshoot the final position of the target, and because of a foveal bias, the judged position is shifted in the direction of motion. To test this hypothesis, the authors replicated previous studies, but instead of having participants indicate where the target vanished, the authors probed participants' perceptual focus by presenting probe stimuli close to the vanishing point. Identification of probes in the direction of target motion was more accurate immediately after target offset than it was with a delay. Another experiment demonstrated that judgments of the final position of a moving target are affected by whether the eyes maintain fixation or follow the target. The results are more consistent with a perceptual explanation than with a memory account.

Postmodern-Postcolonial Criticism and Pro-Democracy Enlightenment

This emphasis on the importance of democracy as a player in Chinas project of modernization constituted the core of what I call It is a position that has been eclipsed even discredited in the post-Tiananmen era. In the current environment of retrenched political authoritarianism and intellectual quietism the permanence of certain social orders-undemocratic ones-has acquired a kind of self-evidence and attractiveness and democratic change as prescribed in 1980s discourses about and now seems unrealistic. For some intellectuals in present-day China the only worth cherishing is a depoliticized one; for others enlightenment and modernity are ideas whose realization would simply be inappropriate for their nation and evidence of a submissive relationship with the hegemonic West. Although they differ in their judgments of both critical positions rely on an ahistorical framework which allows them erroneously perhaps to write off the uncomfortable notion that China might need pro-democracy enlightenment. (excerpt)

Separate simultaneous processing of egocentric and relative positions

It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating the processing of different attributes could also allow highly related attributes to evolve independently, so that they end up being judged on the basis of different types of information. Here, we examine the case of egocentric and relative localisation. For judging egocentric positions, the orientation of the eyes has to be taken into account. This is not so for judging relative positions. We demonstrate that these two attributes can be processed separately by showing that simultaneous judgements of relative and egocentric position differ in their dependency on eye orientation. Subjects pursued a moving dot. We flashed either single targets, or pairs of targets with a 67 ms interval between them, directly below the subjects’ gaze. As the eyes were moving during the 67 ms interval, the retinal separation between pairs of targets was different from their actual separation. Subjects indicated the position at which they saw the targets with reasonable reproducibility, with a consistent bias in the direction of the eye movement. However, when two targets were flashed, the indicated separation between them usually coincided with their retinal separation, rather than with their actual separation. We conclude that egocentric and relative spatial positions can be estimated separately and simultaneously, on the basis of different types of information.

Proprioception and stimulus-response compatibility.

Sixteen subjects pressed a left or right key in response to lateralized visual stimuli, in uncrossed (left index finger on left key, right finger on right key) and crossed conditions (left finger on right key and vice versa), with varying finger separations. Visual, tactile, or "efference copy" cues about relative finger positions were unavailable. Subjects had to press the key on the same side as (compatible group) or opposite side to the stimulus (incompatible group). Separate proprioceptive judgements of the relative finger positions were obtained. Findings of an overall reaction time (RT) advantage for compatible instructions and for uncrossed hands were replicated. With decreasing finger separation the RT advantage for compatible instructions decreased, and the probability of responding with either hand increased. The compatibility effect disappeared completely at the 6-cm crossed position, not at the position that was hardest to judge proprioceptively. This suggests that two forms of neural activation are summed: automatic activation of the anatomically same-side limb, and an integrated, rule-based activation. The results further demonstrate that independent proprioceptive cues from each limb, unassociated with skin contact between the limbs, can mediate the determination of relative position for response selection in stimulus-response compatibility tasks.

Proprioception and Stimulus-Response Compatibility

Sixteen subjects pressed a left or right key in response to lateralised visual stimuli, in uncrossed (left index finger on left key, right finger on right key) and crossed conditions (left finger on right key and vice versa), with varying finger separations. Visual, tactile, or efference copy cues about relative finger positions were unavailable. Subjects had to press the key on the same side as (compatible group) or opposite side to the stimulus (incompatible group). Separate proprioceptive judgements of the relative finger positions were obtained. Findings of an overall reaction time (RT) advantage for compatible instructions and for uncrossed hands were replicated. With decreasing finger the RT advantage for compatible instructions decreased and the probability of responding with either hand increased. The compatibility effect disappeared completely at the six cm crossed position, not at the position that was hardest to judge proprioceptively. This suggests that two forms of neural activation are summed: automatic activation of the anatomically same-side limb, and an integrated, rule-based activation. The results further demonstrate that independent proprioceptive cues from each limb, unassociated with skin contact between the limbs, can mediate the determination of relative position for response selection in stimulus-response compatibility tasks.

Expert judgements of party policy positions: uses and limitations in political research

Expert judgements of party policy positions: uses and limitations in political research

Human auditory cortex electrophysiological correlates of the precedence effect: Binaural echo lateralization suppression

Echoes lagging shortly after a sound and originating from a different location blend with the sound source perceptually. The location of the fused “source+echoes” is dominated by the source, suggesting suppression of echo localization. This effect is diminished monaurally, implying involvement of binaural processing. The neural substrates underlying the echo localization suppression are still unclear. The electrophysiological indications of primary auditory cortex involvement in binaural suppression of echo lateralization are presented. Position judgment and auditory-evoked potentials (AEPs) were recorded to single- and pairs of binaural and monaural clicks. The pairs simulated a source and its echo. The binaural source+echo position judgment was dominated by the source at small echo lags. With lag increase, it shifted toward the echo. The AEPs were studied for binaural processes specific to a “real” echo, as opposed to an identical single sound (a “virtual” echo). A reduction in binaural peak amplitude and area and an increase in binaural peak latency were detected specifically in the real echo-evoked middle-latency component Pa. The binaural echo Pa suppression depended upon echo lag, although less strongly than the psychoacoustic position judgment. Pa is associated with primary auditory cortex activity, thus suggesting primary cortical involvement in echo-lateralization suppression.

Perceiving limb position in normal and abnormal control: An equilibrium point perspective

Two potential sources of information allow the nervous system to determine limb position in egocentric space: (i) limb kinaesthesis and (ii) extraretinal cues to direction and distance. We argue that both of these information sources arise from essentially similar physiological origins – copies of the central commands issued by the nervous system together with afferent discharge fed back from the relevant peripheral effectors. A number of studies have demonstrated that judgements of limb position are more accurate when limb kinaesthesis is combined with extraretinal cues. We review some recent studies which suggest that the weighting attached to these two sources of information varies as a function of the amount of retinal detail present within the environment. We conclude by considering how the perception of limb position may be affected in cases of abnormal movement control. PsycINFO classification: 2221; 3250; 3299

Acoustic flow perception in cf-bats: properties of the available cues.

Signal design in cf-bats is hypothesized to be commensurate with the evaluation of time-variant echo parameters, imposed by changes in the sound channel occurring as the bat flies by a target. Two such parameters, the proportional changes in Doppler frequency and sound pressure amplitude, are surveyed, employing a simplified acoustic model in order to assess their fitness for target localization given a translational movement within a plane. This is accomplished by considering the properties of the scalar fields given by the value of these putative sensory variables as a function of position in a plane. The considered criteria are: existence and extent of ambiguity areas (i.e., multiple solutions for target position), magnitude of the variables (relevant with regard to perceptual thresholds), as well as magnitude and orthogonality of the gradients (relevant to localization accuracy). It is concluded that these properties render the considered variables compatible with gross judgements of target position. This may be sufficient for behavioral contexts like obstacle avoidance, where adoption of suitable safety margins could compensate for the variance and bias associated with estimates of target location.

Visual-proprioceptive mapping in children with developmental coordination disorder.

Developmental coordination disorder (DCD) occurs in a small but significant proportion of children who present with impaired body-eye coordination and show poor acquisition of motor skills. This study investigated the visual-proprioceptive mapping ability of children with DCD from a small selected group, with particular reference to the use of vision in matching tasks. The children with DCD in this study were significantly poorer than control children on all matching tasks. They seemed to have particular difficulty in cross-modal judgements that required the use of visual information to guide proprioceptive judgements of limb position. A distinction is drawn between tasks that can be achieved purely through sensory matching and those that require body-centred spatial judgements, suggesting that it is the latter that posits a particular difficulty for children with DCD.

Visual–proprioceptive mapping in children with developmental coordination disorder

Developmental coordination disorder (DCD) occurs in a small but significant proportion of children who present with impaired body–eye coordination and show poor acquisition of motor skills. This study investigated the visual–proprioceptive mapping ability of children with DCD from a small selected group, with particular reference to the use of vision in matching tasks. The children with DCD in this study were significantly poorer than control children on all matching tasks. They seemed to have particular difficulty in cross‐modal judgements that required the use of visual information to guide proprioceptive judgements of limb position. A distinction is drawn between tasks that can be achieved purely through sensory matching and those that require body‐centred spatial judgements, suggesting that it is the latter that posits a particular difficulty for children with DCD.

Sequential effects in rudimentary auditory and visual tasks.

Three experiments examined sequential effects in choice reaction time tasks. On each trial, a right/left positional judgment was made to a either a pure tone or a luminance increment in a visual array of box elements. In the first two experiments, a preparatory signal was presented prior to each imperative signal to indicate the relevant stimulus modality. At a short stimulus onset asynchrony (SOA) between the preparatory and the imperative signal (i.e., 60 msec), subjects were quicker to repeat the same response than to change their response when presented with successive tones, although no such repetition effect occurred on the visual target trials. Subjects were impaired if the stimulus modality changed across successive trials regardless of the modality of the target. At a longer SOA (i.e., 500 msec), these sequential effects were abolished; subjects were assumed to be able to prepare for the relevant modality because of the presentation of the preparatory signal. When the preparatory signals were omitted, in a final experiment, the modality-switching costs were still evident, but now inhibition of return occurred on both the auditory and the visual target trials-subjects were now impaired in responding when the target reappeared at its immediately previous location. It seems, therefore, that the repetition effect and modality-switching effects do dissociate. The data revealed clear differences between orienting attention to a particular spatial locale and focusing attention to a particular sensory modality.

A psychophysical study of leg‐before‐wicket judgments in cricket

Certain decisions made by officials in sport are suited to study by the techniques of psychophysics. These techniques were applied to one aspect of the leg‐before‐wicket decision in cricket. Participants were presented with simulated stimuli depicting a ball travelling down a cricket pitch and being intercepted. In a three‐alternative forced‐choice task, participants were required to decide whether the ball would have (had it not been obstructed) struck the wicket or whether it would have missed to the left or to the right. The participants' responses were used to make estimates of their random and systematic errors when extrapolating the flight of the ball to the plane of the wicket. It was found that participants were unable to fully allow for variations in the point from which the ball was released by the bowler and for variations in the lateral acceleration (swing) of the ball. The random error of the participants' judgments of the ball's future position had a standard deviation of around 3 cm in the plane of the wicket. The significance of this value is discussed with reference to umpires' error rates, and with reference to the umpire's decision strategy given the accepted practice of giving batsmen the benefit of any doubt.

Spatial uncertainty and sampling efficiency in amblyopic position acuity

Spatial uncertainty and undersampling are two of the major hypotheses for the losses of amblyopic spatial vision. To test these two hypotheses, equivalent spatial uncertainty and spatial integration efficiency in spatial position judgments were quantified with a spatial perturbation paradigm. Specifically, three-line bisection thresholds were measured for the amblyopic eyes of two strabismic and two anisometropic amblyopes, and for normal controls. The horizontal stimulus lines comprised discrete dark dots distributed randomly around the mean line position according to a gaussian function. Line separation, the number of dots on each line ( N), stimulus contrast ( C), and the vertical standard deviation ( σ e) of the dot distribution were varied. An ideal observer analysis quantified the magnitude of equivalent spatial uncertainty ( σ s), the effective number of dots used ( k), and spatial integration efficiency ( k N ). At the optimal separation, equivalent spatial uncertainty ( σ s) is approximately ten-fold higher in both types of amblyopic visual systems than in control observers, even when stimulus visibility is accounted for. This apparent increase in σ s is largely due to a shift in spatial scale of analysis in the amblyopic eye. Integration efficiency ( k N ) increases in proportion to stimulus contrast or visibility (in units of detection threshold). Unlike σ s, k N is different between the two types of amblyopia. For the anisometropic observers, k N is quantitatively similar to that of control observers. For the strabismic observers, on the other hand, k N is reduced even after taking stimulus visibility into account. The decreased spatial integration efficiency in the strabismic visual system suggests that spatial undersampling may occur at a secondary stage of visual processing, beyond the detection stage.

Effects of Generation on Memory for Order

Seven experiments are reported on memory for order of stimuli either generated by the subject or presented to the subject. When subjects were required to assign items to precise positions, a generation decrement was obtained, with subjects showing worse memory for order when they had generated the items. However, no generation decrement in accuracy was obtained when subjects were asked for relative recency judgments. This suggests that judgments of absolute and relative position are made using somewhat different memory processes.

Joint position sense in the recurrently sprained ankle

Functional instability of the ankle joint following an acute sprain has been well documented. The present study measured joint position sense of the ankle in subjects who had sustained recurrent ankle sprains but no sprain for at least three months prior to testing, and compared them with uninjured subjects. The testing device, a pedal goniometer, attempted to replicate the most common position of ankle injury (plantarflexion/inversion). Joint position sense was assessed using active and passive methods for reproducing predetermined positions in ankle inversion in plantarflexion. In both groups, passive judgment of joint position was more accurate than active judgment. Significant differences were recorded with the recurrently sprained ankle demonstrating greater errors in joint position sense for all passive testing positions.