Haptic parallelity perception on the frontoparallel plane: the involvement of reference frames

It has been established that spatial representation in the haptic modality is subject to systematic distortions. In this study, the haptic perception of parallelity on the frontoparallel plane was investigated in a bimanual matching paradigm. Eight reference orientations and 23 combinations of stimulus locations were used. The current hypothesis from studies conducted on the horizontal and midsagittal planes presupposes that what is haptically perceived as parallel is a product of weighted contributions from both egocentric and allocentric reference frames. In our study, we assessed a correlation between deviations from the veridical and hand/arm postures and found support for the role of an intermediate frame of reference in modulating haptic parallelity on the frontoparallel plane as well. Moreover, a subject-dependent biasing influence of the egocentric reference frame determines both the reversal of the oblique effect and a scaling effect in deviations as a function of bar position.     

Alleys on an extensive apparent frontoparallel plane: a second experiment

Small light points were presented, in the dark, around a point in the center which was fixed at a distance of about 3 m from the subject. In experiment 1, the subject adjusted the positions of points so that all were frontoparallel and in three horizontal series, each consisting of five points, with the middle series level with the eyes, to satisfy the following conditions: (i) the three series must appear straight and horizontally parallel; (ii) the points of each of the five triplets must appear equally separated vertically; (iii) the three points of each triplet must appear to move horizontally along straight and parallel paths; (iv) the three points of each triplet must appear to move horizontally with a constant vertical separation. The most distant points were about 0.51 rad to the left and right of center, and about 0.22 rad above and below. In experiment 2, with the configuration of points obtained in experiment 1, the subject assessed ratios of all perceptual distances between points and also from the subject to all points. From experiment 1 (three subjects used), Gaussian curvature K and a constant related to depth perception (sigma) were estimated under the assumption that the frontoparallel plane is a Riemannian plane of constant curvature K and that Luneburg's mapping functions between visual space and physical space hold. The analysis was made according to equations different from those used previously. The results of experiment 2 (two subjects used) were analyzed by a new computer program in which no preassumed mapping functions are necessary for the estimation of K. From both analyses it is clear that there is no need to assume any other value of K than 0 (Euclidean) to describe the geometry of the frontoparallel plane. This presents a striking contrast to the results from experiments on parallel and equidistance alleys running toward the subject on the horizontal plane.     

Distortions in the perceived lightness of faces: the role of race categories

Although lightness perception is clearly influenced by contextual factors, it is not known whether knowledge about the reflectance of specific objects also affects their lightness. Recent research by O. H. MacLin and R. Malpass (2003) suggests that subjects label Black faces as darker than White faces, so in the current experiments, an adjustment methodology was used to test the degree to which expectations about the relative skin tone associated with faces of varying races affect the perceived lightness of those faces. White faces were consistently judged to be relatively lighter than Black faces, even for racially ambiguous faces that were disambiguated by labels. Accordingly, relatively abstract expectations about the relative reflectance of objects can affect their perceived lightness.     

Distortions of perceived visual out of pictures

Two experiments are reported examining judgments from 16 subjects who indicated the apparent direction of a photographed pointer that was rotated to different physical positions while being photographed. The photographs themselves were rotated about a vertical axis to several positions with respect to the subjects’ central viewing axis. The results replicate the well-known distortion in apparent direction associated with photographed pointers positioned to project directly out of the plane of the photograph. This effect has been described by Goldstein (1979) as the “differential rotation effect” because its magnitude is reduced as the depicted angle of the pointer becomes less orthogonal to the photograph. Analysis of the two-dimensional properties of the projected images shows that this differential rotation is related to projected angles on the surface of the photograph. This analysis may explain why circular objects often do not appear to be correctly drawn in the periphery of geometrically correct projections.     

Two varieties of perceived length

The perception of length depends on the mode of stimulation. When Ss were asked to judge the apparent lengths of blocks presented either visually or proprioceptively (between thumb and finger of one hand), visual length was proportional to block length, whereas proprioceptive length was an accelerating function of block length. When both visual and proprioceptive stimulation occurred simultaneously (S both saw and felt a block), the visual input was preemptive.     

Belief in conspiracy theories: The influence of uncertainty and perceived morality

In the present research, we examined people's tendency to endorse or question belief in conspiracy theories. In two studies, we tested the hypothesis that the perceived morality of authorities influences conspiracy beliefs, particularly when people experience uncertainty. Study 1 revealed that information about the morality of oil companies influenced beliefs that these companies were involved in planning the war in Iraq, but only when uncertainty was made salient. Similar findings were obtained in Study 2, which focused on a bogus newspaper article about a fatal car accident of a political leader in an African country. It is concluded that uncertainty leads people to make inferences about the plausibility or implausibility of conspiracy theories by attending to morality information. Copyright © 2012 John Wiley & Sons, Ltd.     

The hidden impact of conspiracy theories: perceived and actual influence of theories surrounding the death of Princess Diana

The authors examined the perceived and actual impact of exposure to conspiracy theories surrounding the death of Diana, Princess of Wales, in 1997. One group of undergraduate students rated their agreement and their classmates' perceived agreement with several statements about Diana's death. A second group of students from the same undergraduate population read material containing popular conspiracy theories about Diana's death before rating their own and others' agreement with the same statements and perceived retrospective attitudes (i.e., what they thought their own and others' attitudes were before reading the material). Results revealed that whereas participants in the second group accurately estimated others' attitude changes, they underestimated the extent to which their own attitudes were influenced.     

One-dimensional and multi-dimensional studies of the exocentric distance estimates in frontoparallel plane, virtual space, and outdoor open field

The aim of this study is twofold: on the one hand, to determine how visual space, as assessed by exocentric distance estimates, is related to physical space. On the other hand, to determine the structure of visual space as assessed by exocentric distance estimates. Visual space was measured in three environments: (a) points located in a 2-D frontoparallel plane, covering a range of distances of 20 cm; (b) stakes placed in a 3-D virtual space (range = 330 mm); and (c) stakes in a 3-D outdoors open field (range = 45 m). Observers made matching judgments of distances between all possible pairs of stimuli, obtained from 16 stimuli (in a regular squared 4 x 4 matrix). Two parameters from Stevens' power law informed us about the distortion of visual space: its exponent and its coefficient of determination (R2). The results showed a ranking of the magnitude of the distortions found in each experimental environment, and also provided information about the efficacy of available visual cues of spatial layout. Furthermore, our data are in agreement with previous findings showing systematic perceptual errors, such as the further the stimuli, the larger the distortion of the area subtended by perceived distances between stimuli. Additionally, we measured the magnitude of distortion of visual space relative to physical space by a parameter of multidimensional scaling analyses, the RMSE. From these results, the magnitude of such distortions can be ranked, and the utility or efficacy of the available visual cues informing about the space layout can also be inferred.     

Perceived range, perceived velocity, and perceived duration of the body rotating in the frontal plane

We investigated perceived range, perceived velocity, and perceived duration of the body rotating in the frontal plane (in roll). Specifically, to examine how shear to the otoliths in the inner ears and tactile pressure to the trunk affect judgments of range and velocity, in two experiments, we manipulated rotating range (30°–160°), rotating velocity (1.8°/sec to 9.6°/sec), mean tilt of the body (?60°, 0°, and 60°), and exposure to the visual vertical. Thirty-three normal or blindfolded participants made verbal judgments of range, velocity, and duration for each combination of these factors. The exponents of the power functions fitted to these judgments were, as a first approximation, .94, .61, and .84 for range, velocity, and duration, respectively, and perceived velocity was proportional to the ratio of perceived range to perceived duration (r = .91). These results suggest that the vestibular and somatosensory inputs are effective on judgments of range, but less so on judgments of velocity, and that perceived velocity may be determined as a ratio of perceived range to perceived duration. In addition, we found that (1) when the range the body has traveled is constant, the perceived range increases as the objective velocity decreases (proprioceptive τ effect); (2) self-motion through the tilted roll sometimes enlarges perceived range and perceived duration but reduces perceived velocity; and (3) the exposure to the visual vertical reduces variability of judgments for range and velocity and also reduces perceived range and perceived velocity of self-motion within a small range through the vertical roll.     

Lay theories and intergroup relations: A social-developmental perspective

Abundant research suggests that the study of lay theories helps to explain intergroup relations. Building on this work as well as “interactionist” theories for understanding social behaviour from developmental and social psychology, we propose an integrative social-developmental perspective examining how lay perceivers' characteristics (e.g., age, race, psychological motivations) interact with the environments in which they are nested to impact lay theory use over time and during life transitions. Using this perspective to guide our investigation of the Protestant work ethic (PWE) and colourblind theory, we show that a single lay theory can have a socially tolerant or intolerant meaning. We review work with US children and adults (Asians, Blacks, Latinos, Whites) as well as research with Colombian children and adults (Mestizos), showing similarities and differences in perceivers' uses of PWE and the colourblind theory. Even when both meanings are prevalent in a given culture, they are not necessarily equally emphasised in all environments or for all people living in those environments, nor are they responded to in the same way by all people. We discuss the implications of these results for theorising on lay theories and offer directions for future work in this area.     

Coalition formation in characteristic function games: Competitive tests of three theories

Two experiments tested the bargaining, minimum resource, and minimum power theories of coalition formation in situations involving different payoffs for some of the winning coalitions (characteristic function games). In the first experiment, a triadic resource distribution was employed and payoffs for the coalitions were specified in such a way that each of the three theories predicted the formation of a different coalition. The coalition predicted by minimum power theory formed the most frequently, and the mean divisions of the payoffs among coalition members were also closest to the predictions of minimum power theory. However, the most frequent coalition was not only the one predicted by minimum power theory, it was also the one having the largest payoff per member. There-fore, a second experiment was conducted, which employed a tetradic resource distribution and specified the coalition payoffs in such a way that (a) each of the theories predicted the formation of a different coalition and (b) none of the predicted coalitions was the one with the largest payoff per member. Although the mean payoff divisions in the coalitions in this experiment were closest to those predicted by bargaining theory, the coalition that formed most frequently was not one of those predicted by any of the theories. Rather, it was the one having the largest payoff per member. None of the three theories is able to account adequately for the results of both experiments. The difficulties that the theories have in dealing with coalition formation in situations in which there are different payoffs for winning are discussed.     

Distortions of temporal integration and perceived order caused by the interplay between stimulus contrast and duration

Stimulus contrast and duration effects on visual temporal integration and order judgment were examined in a unified paradigm. Stimulus onset asynchrony was governed by the duration of the first stimulus in Experiment 1, and by the interstimulus interval in Experiment 2. In Experiment 1, integration and order uncertainty increased when a low contrast stimulus followed a high contrast stimulus, but only when the second stimulus was 20 or 30 ms. At 10 ms duration of the second stimulus, integration and uncertainty decreased. Temporal order judgments at all durations of the second stimulus were better for a low contrast stimulus following a high contrast one. By contrast, in Experiment 2, a low contrast stimulus following a high contrast stimulus consistently produced higher integration rates, order uncertainty, and lower order accuracy. Contrast and duration thus interacted, breaking correspondence between integration and order perception. The results are interpreted in a tentative conceptual framework.     

Perceptual plane geometry: collinearity judgments probe the perceived orientation of an angle's sides

The task was to position a dot to lie one line length beyond the vertex of an angle by mentally extending one line segment forming the angle (and later the other line segment). Eight angles, variously oriented, provided judgmental errors attributable to the size of the subtended angle and line orientation. Collinearity errors are consistent with the hypothesis that the sizes of all subtended angles are underestimated. Horizontal-vertical assimilation describes the line-orientation effect. The largest error component is associated with the interaction of the two independent variables. Judgmental errors were modeled by a set of theoretically meaningful additive terms. Modeling was facilitated by symmetry assumptions (associated with odd and even mathematical functions) about the absolute magnitude and sign of judgmental errors that lead to the comparison of judgments derived from "interesting pairs" of stimuli.     

Intensity dependence of perceived duration: data, theories, and neural integration

Evaluates 2 theoretical models suggested to explain studies of the effect of stimulus intensity on the perceived duration of brief light flashes. Some studies found a direct relationship between the 2 variables; others found an indirect relationship. Each model suggests that an additional variable interacts with stimulus intensity. Proposed variables have included the nature of the judgment and the absolute intensity. The present evaluation indicates that both of the proposed variables play a role and that a melding of the models could best account for this phenomenon. The melding incorporates known time- and intensity-dependent characteristics of neural integration into the behavioral performance. The evaluation also indicates that future experiments on this problem will be most informative if they (a) give particular attention to the role of instructions, (b) explore an adequate range of intensities, and (c) strictly control adaptive state.     

The effect of texture on tactually perceived length

A curvilinear relationship between texture and perceived length was investigated in. two experiments. In Experiment 1 the perceived lengths of four grades of emery cloth and an untextured stimulus were compared in a forced-choice procedure. Generally, as predicted, fine-texture stimuli were perceived as longer than coarse-textured stimuli. Experiment 2 attempted to modify the biasing effect of texture by employing preliminary training with fine or coarse textures. Although unsuccessful in modifying the bias, the curvilinear relationship between texture and perceived length was agmn supported. Some implications for constructing teaching materials for the blind are discussed.