Stereokinetic effect and its relation to the kinetic depth effect.

The stereokinetic effect (SKE) has been defined and studied by nested circular patterns rotating on a turntable. Circles must appear not to rotate as they revolve, which in turn results in their appearing to translate relative to one another. A powerful illusion of object depth results even though the individual circles do not undergo an appropriate foreshortening consistent with their apparent changes in slant. It is suggested and tested that the SKE is based on the changing positions between the nested contours despite the absence of any change within each contour, whereas the kinetic depth effect (KDE) entails both kinds of change. It follows that a turntable method of presentation is not necessary, and between-contour transformations can be simulated by computer animation. Displays consisting of simple translations were shown to evoke robust depth impressions as were patterns consisting of contours of varying shapes. Comparisons of the depth, compellingness, and rigidity of matched SKE and KDE displays are reported. The SKE is taken to be paradigmatic for how the visual system perceives depth when observing small object rotations that occur in everyday situations.     

Projective invariance and the kinetic depth effect.

Seven experiments test the assumption that, in the kinetic depth effect, observers have reliable and direct access to the equivalence of shapes in projective geometry. The assumption is implicit in 'inverse optics' approaches to visual form perception. Observers adjusted a comparison shape to match a standard shape; both standard and comparison were portrayed as in continuous rotation in space, using a graphics computer. The shapes were either plane quadrilaterals or solid prisms. The angular difference of the planes of the shapes was varied, as was the dot density of a texture in those planes. Departure from projective equivalence was measured in six studies by measuring the planar analogue of cross ratio, and in a seventh by measuring the cross ratio for points in space. Projective equivalence was not found to be perceived uniformly, except in one experiment that did not involve rotation in depth. Otherwise changes in orientation of up to 180 degrees about a single coordinate axis had no significant effect on matches in shape, while changes in orientation about more than one coordinate axis produced significant effects. The addition of texture and a change in rotation speed did not correct departures from projective equivalence.     

Early motion processes and the kinetic depth effect

It has been known for over 30 years that motion information alone is sufficient to yield a vivid impression of three-dimensional object structure. For example, a computer simulation of a transparent sphere, the surface of which is randomly speckled with dots, gives no impression of depth when presented as a stationary pattern on a visual display. As soon as the sphere is made to rotate in a series of discrete steps or frames, its 3-D structure becomes apparent. Three experiments are described which use this stimulus, and find that depth perception in these conditions depends crucially on the spatial and temporal properties of the display:

1. Depth is seen reliably only for between-frame rotations of less than 15°, using two-frame and four-frame sequences.

2. Parametric observations using a wide range of frame durations and inter-frame intervals reveal that depth is seen only for inter-frame intervals below 80 msec and is optimal when the stimulus can be sampled at intervals of about 40-60 msec.

3. Monoptic presentation of two frames of the stimulus is sufficient to yield depth, but the impression is destroyed by dichoptic presentation.

These data are in close agreement with the observed limits of direction perception in experiments using “short-range” stimuli. It is concluded that depth perception in the motion display used in these experiments depends on the outputs of low-level or “short-range” motion detectors.     

On the limits of perceptual complementarity in the kinetic depth effect

In a series of experiments, we have investigated the abilities of human observers to perceive geometric properties of moving three-dimensional objects as a function of their perspective and rotational complexities. The results indicate a decreasing ability of observers to extract metric, angular, and rigid motion as the perspectives and rotations depart from parallel projections and one-parameter central rotations. In this way, quantitative limits are suggested for the principle of perceptual complementarity suggested by Shepard (1981).     

Rigid and non-rigid kinetic depth effect with rotating discrete helices

Summary To examine the conditions in which human observers fail to recover the rigid structure of a three-dimensional object in motion we used simulations of discrete helices with various pitches undergoing either pure rotation in depth (rigid stimuli) or rotation plus stretching (non-rigid stimuli). Subjects had either to rate stimuli on a rigidity scale (Experiments 1 and 2) or to judge the amount of rotation of the helices (Experiments 3 and 4). We found that perceived rigidity depended on the pitch of the helix rather than on objective non-rigidity. Furthermore, we found that helices with a large pitch/radius ratio were perceived as highly non-rigid and that their rotation was underestimated. Experiment 5 showed that the detection of a pair of dots rigidly related (located on. the helix) against a background of randomly moving dots is easier at small phases in which the change of orientation across frames is also small. We suggest that this is because at small phases the grouping of dots in virtual lines does occur and that this may be an important factor in the perceived nonrigidity of the helices.This research was supported by MPI 60% (1987, 1988) and CNR (1986), 1987, 1988) grants to Clara Casco and Sergio Roncato and Grant CNR 90.01603.PS93 to Giorgio Ganis.     

Simple kinetic information for transparent depth

The present paper reports three investigations of new kinetic information for transparent depth using computer-generated dot patterns. An initial demonstration showed that separation in depth could be obtained by translating rectangular lattices of dots through one another like intersecting columns of marching soldiers. The first two experiments showed that diagonal interactions between lattices created significantly stronger separation than did horizontal or vertical interactions (horizontal was, in turn, stronger than vertical) and that patterns which translated through one another without any of the individual elements intersecting were better separated than those whose rows or columns intersected in register. The third experiment showed that random patterns interacting in any direction created the strongest separations of all the patterns observed. Results were taken to indicate that a unified theory of depth information, developed in the context of James Gibson’s ecological optics, must incorporate both spatial and kinetic structure in its specification of necessary and sufficient stimulus conditions.     

Ratings of kinetic depth in multidot displays

Subjects saw kinetic depth displays whose shape (sphere or cylinder) was defined by luminous dots distributed randomly on the surface or in the volume of the object. Subjects rated perceived 3-D depth, rigidity, and coherence. Despite individual differences, all 3 ratings increased with the number of dots. Dots in the volume yielded ratings equal to or greater than surface dots. Each rating varied with 3 of 4 factors (shape, distribution, numerosity, and perspective), but the ratings either between trials or between conditions were often uncorrelated. Object shape affected rigidity but not depth ratings. Veridically perceived polar displays had slightly lower rigidity but higher depth ratings than parallel projection displays. (Reversed polar displays were always grossly nonrigid.) The interaction of ratings and stimulus parameters requires theories and experiments in which different KDE ratings are not treated interchangeably.     

Seeing stereoscopic depth from disparity between kinetic edges

Traditionally, it is assumed that stereovision operates only on the positional difference (disparity) between luminance-defined features in the images in the left and the right eye. Here, I show that stereoscopic depth can be seen from disparity between edges created by relative motion of texture elements, and between edges created by correlated flicker of stationary texture elements. Luminance-based stereopsis was impossible since the texture was binocularly uncorrelated. Positional disparity of the centre of revolving patterns was not an efficient depth cue. Stereopsis from the stimuli presented here was possible even without binocular overlap of textured areas. The results provide evidence that positional disparity of kinetic edges, defined by correlated flicker or motion contrast alone, can be used as matching features to recover stereoscopic depth.     

Depth capture by kinetic depth and by stereopsis

The perceived depth of regions within a stereogram lacking explicit disparity information can be captured by the surface structure of regions where disparity is explicit: stereo capture. In two experiments, observers estimated surface curvature/depth of an untextured object (a 'ribbon') superimposed on a cylinder textured with dots, the cylinder curvature being defined by disparity (stereo depth) or by motion parallax (kinetic depth: KD). With the stereo-defined cylinder, depth capture was obtained under conditions where the disparity of the ribbon was ambiguous; with the KD, cylinder depth capture was obtained under conditions where the motion flow of the cylinder was in a direction parallel to that of the ribbon. These results demonstrate yet another similarity between KD and stereopsis.     

The role of perceptual organization in the depth perception of kinetic lattice displays

College student subjects were asked to judge perceived depth in computer-generated displays. In all displays, one lattice of points moved through a stationary lattice in either a rowwise or columnwise direction. No points of the two lattices ever touched. Two display variables, strain and shear, each had a significant effect on depth ratings. Shear, however, was only effective at the level of strain for which depth ratings were high. The results confirm earlier studies in which “topological breakage” information was found to affect depth perception. The outcome of this study suggests that principles of perceptual organization can influence the nature of effective breakage information.     

Linear vection in the central visual field facilitated by kinetic depth cues.

Illusory self-motion (vection) is thought to be determined by motion in the peripheral visual field, whereas stimulation of more central retinal areas results in object-motion perception. Recent data suggest that vection can be produced by stimulation of the central visual field provided it is configured as a more distant surface. In this study vection strength (tracking speed, onset latency, and the percentage of trials where vection was experienced) and the direction of self-motion produced by displays moving in the central visual field were investigated. Apparent depth, introduced by using kinetic occlusion information, influenced vection strength. Central displays perceived to be in the background elicited stronger vection than identical displays appearing in the foreground. Further, increasing the eccentricity of these displays from the central retina diminished vection strength. If the central and peripheral displays were moved in opposite directions, vection strength was unaffected, and the direction of vection was determined by motion of the central display on almost half of the trials when the centre was far. Near centres produced fewer centre-consistent responses. A complete understanding of linear vection requires that factors such as display size, retinal locus, and apparent depth plane are considered.     

Phases in Movement After-Effects and their relationship to the kinetic figural effect

Summary A Movement After-Effect (MAE) observed on a structured test figure contains generally two successive phases. The initial one is non-contingent upon the test figure and is assumed to result from an adaptation process. The second phase is shown to be contingent upon the features of the test figure and their similarity with those of the generating figure. A conditioning process is assumed to share in its appearance. In Experiment I, it is shown that the areal spread of MAE which may appear in the contingent phase is likely to result from a generalization process in which part of the test figure corresponding to an unstimulated area becomes transiently effective in generating a MAE. In Experiment II distributed practice of the MAE is shown to lead to an increase in the duration of the effect when the generating and test figures are similar. This last result suggests that the true conditioning stimulus is the generating figure as such.     

心理学怎样为邪教所用和怎样用心理学迎战邪教

没有系统研修过心理学的邪教教主,特别是邪教"法轮功"教主李洪志,却十分善于运用心理学的一些原理去大量捕获信徒,并使他们死心塌地地跟着他走。文章以需要理论、心理挫折理论、认识过程理论和群体心理动力理论为代表,又以作者在同邪教的实际斗争中获取的案例揭示了这些理论是怎样被邪教盗用来设置骗局,快速发展邪教组织,驾驭和控制邪教信徒,为自己罪恶目的服务的。文章认为,当邪教教主猖狂窃取心理学理论欺世骗人、谋财害命时,我们也应当针锋相对地挥舞心理学利剑,运用心理学的理论和方法迎战邪教,将被邪教捕获的痴迷者解救出来,文章还为此提供了可供参考的策略和方法。     

Absence of depth processing in the large-frame rod-and-frame effect

Attenuation of the rod-and-frame effect (RFE) with depth separation (Gogel & Newton, 1975) was investigated with the rod and frame in either intersecting or parallel depth planes (PDP). In the former case, in which either the top of the rod or the frame was inclined 45 deg away from the observer, no attenuation was found for frames projecting a retinal angle of 39.2 or 13.5 deg. In the PDP paradigm, the rod was optically 60 cm nearer the observer than was the frame. The depth adjacency effect of Gogel and Newton was replicated, but only for small retinal angles (7.2 and 6.8 deg) of the frame and for a 15-deg frame tilt, but not for larger retinal angles (39.2 and 12.7 deg) or for frames tilted at 22 deg. The absence of attenuation with depth separation in large frames and its presence in small frames is consistent with the identification of these phenomena with properties of the ambient and focal visual systems, respectively (Leibowitz & Post, 1982).     

How the brain responds to any: an MEG study

The word any may appear in some sentences, but not in others. For example, any is permitted in sentences that contain the word nobody, as in Nobody ate any fruit. However, in a minimally different context any seems strikingly anomalous: ^*Everybody ate any fruit. The aim of the present study was to investigate how the brain responds to the word any in such minimally different contexts - where it is permitted (licensed) and where it is not permitted (unlicensed). Brain responses were measured from adult readers using magnetoencephalography (MEG). The results showed significantly larger responses to permissible contexts in the left posterior temporal areas between 400-500 ms and 590-660 ms. These results clarify the anatomy and timing of brain processes that contribute to our judgment that a word such as any is or is not permitted in a given context.