Egocentric and allocentric visual cues influence the specification of movement distance and direction

The authors investigated whether visuomotor transformations that support the computation of movement distance (i.e., extent) and movement direction rely differentially on integration of egocentric and allocentric visual information. To accomplish that objective, the authors factorially arranged 17 participants' open-loop reaching movements from 2 movement-start locations with mediolateral (ML) and anteroposterior (AP) variants of the induced Roelofs effect (IRE). The 2 movement-start locations in combination with the 2 IRE configurations enabled the authors to examine the impact of illusory movement pertaining to distance (i.e., AP-IRE) and direction (i.e., ML-IRE) information. AP-IRE and ML-IRE configurations across the 2 movement-start locations reliably influenced reaching endpoints in a direction consistent with the perceptual effects of the illusion. These findings suggest that unitary visual information involving interactive egocentric and allocentric visual cues supports the specification of both movement distance and movement direction.     

Egocentric/allocentric and coordinate/categorical haptic encoding in blind people

In this research, the impact of visual experience on the capacity to use egocentric (body-centered) and allocentric (object-centered) representations in combination with categorical (invariant non-metric) and coordinate (variable metric) spatial relations was examined. Participants memorized through haptic (congenitally blind, adventitiously blind, and blindfolded) and haptic + visual (sighted) exploration triads of 3D objects and then they were asked to judge: "which object was closest/farthest to you?" (egocentric-coordinate); "which object was on your left/right?" (egocentric-categorical); "which object was closest/farthest to a target object (e.g., cone)?" (allocentric-coordinate); "which object was on the left/right of the target object (e.g., cone)?" (allocentric-categorical). The results showed a slowdown in processing time when congenitally blind people provided allocentric-coordinate judgments and adventitiously blind people egocentric-categorical judgments. Moreover, in egocentric judgments, adventitiously blind participants were less accurate than sighted participants. However, the overall performance was quite good and this supports the idea that the differences observed are more quantitative than qualitative. The theoretical implications of these results are discussed.     

Egocentric or allocentric frameworks for the evaluation of other people's reachability

The adoption of egocentric and allocentric frameworks in the perception of other people’s reachability was investigated. In study 1, 24 adults (12 experienced and 12 inexperienced dealing with children) judged vertical reachability for themselves and for two children. In study 2, 37 parents judged vertical reachability for themselves and their children. Absolute errors (|estimate-actual reachability|), absolute percent errors (|1-judgement/actual reachability| × 100), and error tendency (underestimations, right judgments, or overestimations) were calculated. Adults were quite accurate in perceiving their own reachability (absolute percent errors ranging from 2.20% in study 1 to 3.12% in study 2) and clearly less precise when estimating children’s reachability. Results indicated a tendency for adults to overestimate reachability of the younger child (study 1) and a tendency for parents to overestimate their children’s reachability (study 2). No correlation between judgement errors for the self and for the children in any of the studies was observed. Results support the existence of an allocentric and not an egocentric framework when evaluating other people’s affordances.     

Numerical distance effects in visual search

We present three experiments in which observers searched for a target digit among distractor digits in displays in which the mean numerical target?Cdistractor distance was varied. Search speed and accuracy increased with numerical distance in both target-present and target-absent trials (Exp. 1A). In Experiment 1B, the target 5 was replaced with the letter S. The results suggest that the findings of Experiment 1A do not simply reflect the fact that digits that were numerically closer to the target coincidentally also shared more physical features with it. In Experiment 2, the numerical distance effect increased with set size in both target-present and target-absent trials. These findings are consistent with the view that increasing numerical target?Cdistractor distance affords faster nontarget rejection and target identification times. Recent neurobiological findings (e.g., Nieder, 2011) on the neuronal coding of numerosity have reported a width of tuning curves of numerosity-selective neurons that suggests graded, distance-dependent coactivation of the representations of adjacent numbers, which in visual search would make it harder to reject numerically closer distractors as nontargets.     

Predictive visual search: Role of environmental regularities in the learning of context cues

Repeatedly searching through invariant spatial arrangements in visual search displays leads to the buildup of memory about these displays (contextual-cueing effect). In the present study, we investigate (1) whether contextual cueing is influenced by global statistical properties of the task and, if so, (2) whether these properties increase the overall strength (asymptotic level) or the temporal development (speed) of learning. Experiment 1a served as baseline against which we tested the effects of increased or decreased proportions of repeated relative to nonrepeated displays (Experiments 1b and 1c, respectively), thus manipulating the global statistical properties of search environments. Importantly, probability variations were achieved by manipulating the number of nonrepeated (baseline) displays so as to equate the total number of repeated displays across experiments. In Experiment 1d, repeated and nonrepeated displays were presented in longer streaks of trials, thus establishing a stable environment of sequences of repeated displays. Our results showed that the buildup of contextual cueing was expedited in the statistically rich Experiments 1b and 1d, relative to the baseline Experiment 1a. Further, contextual cueing was entirely absent when repeated displays occurred in the minority of trials (Experiment 1c). Together, these findings suggest that contextual cueing is modulated by observers’ assumptions about the reliability of search environments.     

Relative cues and absolute distance perception

It is possible, in theory, for the simultaneous occurrence of several different relative cues of distances to increase the veridicality of the perception of absolute distance. To test whether this actually occurs, a three-dimensional display was viewed monocularly while moving the head laterally, under conditions in which some error in perceived absolute distance was expected. The perceived absolute distance of the display was measured with the number of relative cues of distance within the display varied. No systematic reduction was found in the error in perceived absolute distance as a consequence of the variation in the number of relative cues. The study provides no evidence that the potential source of absolute distance information provided by relative cues is utilized by the visual system.     

Keeping one's distance: the influence of spatial distance cues on affect and evaluation

Current conceptualizations of psychological distance (e.g., construal-level theory) refer to the degree of overlap between the self and some other person, place, or point in time. We propose a complementary view in which perceptual and motor representations of physical distance influence people's thoughts and feelings without reference to the self, extending research and theory on the effects of distance into domains where construal-level theory is silent. Across four experiments, participants were primed with either spatial closeness or spatial distance by plotting an assigned set of points on a Cartesian coordinate plane. Compared with the closeness prime, the distance prime produced greater enjoyment of media depicting embarrassment (Study 1), less emotional distress from violent media (Study 2), lower estimates of the number of calories in unhealthy food (Study 3), and weaker reports of emotional attachments to family members and hometowns (Study 4). These results support a broader conceptualization of distance-mediated effects on judgment and affect.     

Dissociation between visual perception of allocentric distance and visually directed walking of its extent

Walking without vision to previously viewed targets was compared with visual perception of allocentric distance in two experiments. Experimental evidence had shown that physically equal distances in a sagittal plane on the ground were perceptually underestimated as compared with those in a frontoparallel plane, even under full-cue conditions. In spite of this perceptual anisotropy of space, Loomis et al (1992 Journal of Experimental Psychology. Human Perception and Performance 18 906-921) found that subjects could match both types of distances in a blind-walking task. In experiment 1 of the present study, subjects were required to reproduce the extent of allocentric distance between two targets by either walking towards the targets, or by walking in a direction incompatible with the locations of the targets. The latter condition required subjects to derive an accurate allocentric distance from information based on the perceived locations of the two targets. The walked distance in the two conditions was almost identical whether the two targets were presented in depth (depth-presentation condition) or in the frontoparallel plane (width-presentation condition). The results of a perceptual-matching task showed that the depth distances had to be much greater than the width distances in order to be judged to be equal in length (depth compression). In experiment 2, subjects were required to reproduce the extent of allocentric distance from the viewing point by blindly walking in a direction other than toward the targets. The walked distance in the depth-presentation condition was shorter than that in the width-presentation condition. This anisotropy in motor responses, however, was mainly caused by apparent overestimation of length oriented in width, not by depth compression. In addition, the walked distances were much better scaled than those in experiment 1. These results suggest that the perceptual and motor systems share a common representation of the location of targets, whereas a dissociation in allocentric distance exists between the two systems in full-cue conditions.     

Egocentric search for disappearing objects in domestic dogs: evidence for a geometric hypothesis of direction

In several species, the ability to locate a disappearing object is an adaptive component of predatory and social behaviour. In domestic dogs, spatial memory for hidden objects is primarily based on an egocentric frame of reference. We investigated the geometric components of egocentric spatial information used by domestic dogs to locate an object they saw move and disappear. In experiment 1, the distance and the direction between the position of the animal and the hiding location were put in conflict. Results showed that the dogs primarily used the directional information between their own spatial coordinates and the target position. In experiment 2, the accuracy of the dogs in finding a hidden object by using directional information was estimated by manipulating the angular deviation between adjacent hiding locations and the position of the animal. Four angular deviations were tested: 5, 7.5, 10 and 15°. Results showed that the performance of the dogs decreased as a function of the angular deviations but it clearly remained well above chance, revealing that the representation of the dogs for direction is precise. In the discussion, we examine how and why domestic dogs determine the direction in which they saw an object disappear.     

Memory search following valid and invalid abrupt-onset cues

The impact of abrupt-onset cues on memory search was investigated, where the abrupt-onset cue was a valid (Experiment 1), random (Experiment 2), or irrelevant (Experiment 3) predictor of the location containing the test probe. In Experiment 4, the abrupt-onset cue either preceded or followed the test probe. Sternberg-like functions were obtained in Experiments 1 and 2, with the effects of the abrupt-onset cue localized primarily in the intercept rather than the slope. Experiment 3 demonstrated that a spatially separated and irrelevant abrupt-onset cue increased latency even when all memory probes occurred at the fixation point. In Experiment 4, the robust impact of an abrupt-onset cue vanished, regardless of stimulus onset asynchrony, when it followed the target. We concluded that abrupt-onset cues captured attention regardless of their predictability, manifested as a delaying of search. However, once attention was captured by the target, a subsequent abrupt-onset stimulus had no effect. These results were discussed in terms of diffuse attention and contingent capture models of attention.     

Memory for movement: Interaction of location and distance cues and imagery ability

The present experiments examined the role of imagery ability in recall of either the terminal location or the distance of a preselected horizontal linear movement following changes in the recall starting position. Subjects were selected on the basis of their scores on a shortened version of the Betts Questionnaire upon Mental Imagery (Betts Q.M.I., Sheehan 1967). Both high and low imagers were assigned to one of four groups, HIL, LIL, HID, LID, the last letter indicating the movement cue (terminal location or distance moved) to be recalled. Recall of the appropriate movement cue from one of four new recall starting positions occurred after either a 5-sec or 30-sec unfilled retention interval. Analysis of constant error indicated all groups were unable to recall the specified movement cue independent of the other source of information, even when subjects were given explicit instructions to utilise an imagery strategy. The data corroborate our earlier findings that memory for self paced movements is based on an interaction of location and distance cues derived from the criterion movement.     

The effects of familiar size on judgments of size and distance: An interaction of viewing attitude with spatial cues

Two hypotheses about the effects of familiar size on judgments of size and distance, the cue-conflict hypothesis and the viewing-attitude hypothesis, were examined. In Experiment 1, observers estimated the size and distance of familiar targets with apparent or assumptive instructions under three different spatial cue conditions. In Experiment 2, observers performed tasks similar to those of Experiment 1 with no specific instructions. The main results were: (1) Assumptive instructions facilitate the effects of familiar size in both size and distance judgments, but reducing spatial cues does not, and (2) viewing attitude changes from the apparent to the assumptive when available spatial cues are reduced. Thus, it was concluded that the viewing-attitude hypothesis gives a better account of the effects of familiar size, but that the cue-conflict hypothesis cannot be abandoned, because the number of conflicting cues contributes to the formation of viewing attitude.     

The contributions of static visual cues, nonvisual cues, and optic flow in distance estimation

By systematically varying cue availability in the stimulus and response phases of a series of same-modality and cross-modality distance matching tasks, we examined the contributions of static visual information, idiothetic information, and optic flow information. The experiment was conducted in a large-scale, open, outdoor environment. Subjects were presented with information about a distance and were then required to turn 180 before producing a distance estimate. Distance encoding and responding occurred via: (i) visually perceived target distance, or (ii) traversed distance through either blindfolded locomotion or during sighted locomotion. The results demonstrated that subjects performed with similar accuracy across all conditions. In conditions in which the stimulus and the response were delivered in the same mode, when visual information was absent, constant error was minimal; whereas, when visual information was present, overestimation was observed. In conditions in which the stimulus and response modes differed, a consistent error pattern was observed. By systematically comparing complementary conditions, we found that the availability of visual information during locomotion (particularly optic flow) led to an 'under-perception' of movement relative to conditions in which visual information was absent during locomotion.     

Counting bones: environmental cues that decrease food intake

At an all-you-can eat buffet in a sports bar, it was tested whether people would eat less if they knew how much they had already eaten. 50 graduate students (34 women; M age = 24.1 yr.) were seated at 21 tables randomly assigned to be bussed (leftover wings removed) or unbussed (wings left on table). The 31 students at the bussed tables ate more than those at the unbussed tables (7 wings vs. 5.5 wings), with the effect being stronger for men than women. In distracting eating environments, environmental cues may provide an effective means of reducing consumption. Implications for controlling alcohol intake were also noted.     

Egocentric spatial framework effects from single and multiple points of view

In three experiments, we tested the one-place, one-perspective rule formulated by Franklin, Tversky, and Coon (1992). This rule proposes that subjects take a neutral, external perspective when they must use multiple viewpoints to make decisions about the locations of objects in memorized scenes. We compared responding from a single viewpoint with responding from two viewpoints. In Experiments 1 and 2, we used a sentence verification procedure, and in Experiment 3, we compared a true-false verification procedure with a six-alternative forced-choice procedure. Under these various conditions, we observed egocentric spatial framework effects in that above-below judgments were faster than front-back judgments and front-back judgments were faster than right-left judgments. When responding from two points of view in a single place, our subjects took multiple intrinsic perspectives rather than one neutral external perspective as proposed by the one-place, one-perspective rule.     

An indirect measure of perceived distance from oculomotor cues

The sensitivity of an indirect method of measuring perceived distance was compared in two experiments with the direct procedure of eliciting verbal reports of distance. Perceived distance was varied by varying the oculomotor cues to object distance. The indirect method, called the “adjustable pivot method,” uses an apparatus that physically moves the stimulus object laterally concomitantly with the lateral motion of the head. The magnitude and direction of this concomitant motion determines the distance of the point around which the direction of gaze to the object rotates (the pivot distance) as the head is moved. The pivot distance at which the object appears stationary with head movement measures the apparent distance of the object. Both types of measures were found to vary systematically with the oculomotor distance of the object for points of light (Experiment 1) and extended objects (Experiment 2). A previous study has shown that the adjustable pivot method avoids cognitive errors that can distort verbal reports of distance. The present study, by demonstrating the discriminative capability of this method under conditions in which differences in perceived distance were expected to occur, provides clear evidence that the adjustable pivot method is a sensitive and useful procedure for measuring perceived distance.     

A comparison of accommodative and fusional convergence as cues to distance

The effectiveness of fusional as compared with accommodative convergence (with accommodation present in both cases) in determining perceived distance was investigated in this study. Luminous frames of two different visual angles at a nearly constant distance were viewed binocularly to provide fusional convergence and monocularly to provide accommodative convergence. Although some differences in reported size and distance of the frames occurred on the first presentations for binocular as compared to monocular observation, the most systematic differences between these two types of observation were present for the second (successive) presentations of the two frame sizes to the same Os. This is attributed to the relative size cue to distance occurring as a function of the different retinal sizes on the successive presentations. It was found that this relative size cue was more effective in modifying the perceived size and distance of the second presentations for monocular than for binocular observation. It is suggested that this reflects the greater effectiveness as a cue to distance of fusional as compared with accommodative convergence. This conclusion is of importance for studies concerned with the evaluation of convergence as a determiner of perceived distance.     

Absolute and relative cues for the auditory perception of egocentric distance

Three experiments were performed to examine the reverberation cue to egocentric auditory distance and to determine the extent to which such a cue could provide 'absolute', as contrasted with 'relative', information about distance. In experiment 1 independent groups of blindfolded observers (200 altogether) were presented with broadband noise from a speaker at one of five different distances (0.55 to 8 m) in a normal hard-walled room. Half of each group of observers were presented with the sound at 0 deg azimuth, followed (after a delay) by the identical sound at 90 deg azimuth. The order of presentation was reversed for the remaining observers. Perceived distance varied significantly as a function of the physical distance to the speaker, even for the first presentations. The change in the binaural information between the 0 deg and 90 deg presentations did not significantly modify the results. For both orientations, near distances were overestimated and far distances were underestimated. Experiment 2 and 3 were designed to evaluate how much prior auditory exposure to the laboratory environment was necessary. A 200 Hz square-wave signal was presented from one of three distances (1, 2, or 6 m) to observers who had either minimal room information or an exposure which included talking within the room. Perceived distance varied significantly with physical distance regardless to exposure condition.