Fixation and the stereokinetic phenomenon

One of two circles on a rotating disk appears to execute a planetary motion about the other circle. It is shown that the fixated circle serves as the center of rotation for the nonfixated circle. The effect of fixation is absent when polygons replace the circles. However, when one corner of an isolated square is fixated, the remaining corners rotated about the fixated corner. These planetary effects are consistent with the retinal paths followed by the elements of a display during fixation. This is not unlike the failure of position constancy associated with smooth pursuit of linearly moving targets in environments lacking a stationary visual frame of reference. In the present instance, however, the “retinal” responses occur during tracking of circularly moving targets, even in the presence of a visual frame of reference. These results are discussed in relation to the stereokinetic phenomenon. It is also shown that there is a strong interaction between the effects of fixation and the configurational features of the display. When a circle and a square are overlapping on a rotating disk, fixation of the square does not produce the perception of planetary motion. However, when the circle is fixated, the square is readily perceived as executing a planetary path about the circle. The possibility that position constancy in general is attributable to the geometry of the scene rather than to a “discounting” of information about eye movements is mentioned.     

Test of models of achromatic transparency

Consider an achromatic disk transparent on an achromatic background formed by two adjoining rectangles, with the common border of the rectangles dividing the disk in half. Current models of achromatic transparency contend that the perceived extent of transparency of the disk depends on the luminance contrast inside the disk and on the luminance contrast in the background outside the disk. Here, a model is proposed which contends that this perceived extent is determined only by the luminance contrasts inherent in the disk: inside the disk and between the disk and the background. Two experiments were designed to determine which luminance contrasts influence transparency. In the first experiment, subjects rated the perceived extent of transparency of the disk for different combinations of the luminances of the disk and of the background. The results strengthen the view that the perceived extent of transparency depends on the luminance contrasts inherent in the disk. In the second experiment, a test was made of the possibility that luminance contrasts between adjoining areas of the background outside the disk are nonessential for transparency. The results show that transparency occurred both when the areas of the background outside the transparent region adjoined one another and when they were separated, confirming that the perceived extent of transparency depended only on luminance contrasts between adjoining areas inherent in the disk.     

Attentional Modulation of Size Contrast

A test circle surrounded by smaller context circles appears larger if presented in isolation, whereas a test circle surrounded by large context circles is seen as smaller than in isolation. Two experiments are reported indicating that this phenomenon, the Ebbinghaus illusion, depends on whether subjects are attending to the context circles. Subjects first saw a reference circle and then a briefly presented (150 msec) test circle. Their task was to determine whether the test circle was larger or smaller than the reference. The test circle was surrounded by smaller context circles of one colour arrayed along a horizontal axis centred on the test, and larger context circles of a different colour arrayed along a vertical axis centred on the test. Subjects judged both the size of the test and the colours of either the small or large context circles. Perceived test size changed systematically, depending on which context circles were task-relevant.     

Scaling movement amplitude: adaptation of timing and amplitude control in a bimanual task

Participants traced two circles simultaneously and the diameter of one circle was scaled as the diameter of the other circle remained constant. When the scaled circle was larger, amplitude error shifted from overshooting to undershooting, while shifting from undershooting to overshooting when this circle was smaller. Asymmetric coordination was unstable when the left arm traced a circle larger than the right arm, yet stable when the left arm traced a smaller circle. When producing symmetric coordination and the left arm traced the larger circle, relative phase shifted by 30°, but a right arm lead predominated. When the left arm traced the smaller circle and symmetric coordination was required, a 30° shift in relative phase occurred, but hand lead changed from left to right. The modulation of movement amplitude and relative phase emerged simultaneously as a result of neural crosstalk effects linked to initial amplitude conditions and possibly visual feedback of the hands' motion.     

Memory for locations within regions: Spatial biases and visual hemifield differences

Memory for location of a dot inside a circle was investigated with the circle in the center of a computer screen (Experiment 1) or with the circle presented in either the left or the right visual field (Experiment 2). In both experiments, as in Huttenlocher, Hedges, and Duncan’s (1991) study, the task was to relocate the dot by marking the remembered location. When errors in angular and radial estimates were considered separately, it was found that, in both experiments, the angular locations of estimates of the dots’ positions regressed toward different locations inside each quadrant of the circle; the radial locations of the estimates of dots’ positions tended to regress toward locations near the circumference. These variations in the direction of bias appeared to reflect a general shift of estimates toward the upper left arc of the circle. The second experiment replicated the preceding effects but also revealed that the regressions within quadrants of angular values were stronger after right visual field than after left visual field presentations. We interpret the dissociation between visual fields as evidence that memory for categorical spatial relations (Kosslyn, 1987) is more dependent on left-hemisphere than on right-hemisphere processing.     

Visual evoked potentials to the geometric forms in the randomized presentation

Two outlined geometric figures, an equilateral triangle and a circle, of equal contour length, were randomly presented at a fixed position in the lower or upper part of the visual field (LVF and UVF). Transient visual evoked potentials (VEPs) were recorded monopolarly from the inion (I), 5, 10, 15 cm above it (I5, I10, I15) and Fz, for 12 subjects. Grand-averaged VEPs were computed. A negative (N) wave (averaged peak latency 155 ms) was identified in the LVF and a positive (P) wave (130 ms) in the UVF. In the LVF, the N amplitude of the triangle was significantly larger than that of the circle at I5 and I. Regarding the P wave in the UVF, the triangle was of a significantly longer latency than the circle at I15, I10 and I5. The enhancement of the N amplitude for the triangle in the LVF is not attributable to the arousal caused by the preparatory state for the figure, since the subject could not predict the figure to be presented next or its position.     

主题情境和信任特质对大学生信任圈的影响

以395名大学生为被试,采用2×4×2的混合设计考察了主题情境(内容和风险等级)和信任特质对大学生信任圈规模和成分的影响。结果表明:(1)主题情境的内容对信任圈的规模和成分均有影响,在借钱情境下的信任圈规模显著大于分享负面信息情境,且两者的信任对象排序也有所不同;(2)随着主题情境的风险等级提高,两种情境下的信任圈规模均减少,但借钱情境下的信任圈规模减少更多,四种风险下信任圈成分无显著变化;(3)信任特质对两种主题情境下的大学生信任圈规模均有显著影响,高信任的被试信任圈规模较大,但对信任圈成分无显著影响;(4)信任圈成分总体呈现出亲人、熟人和陌生人的差序格局。     

不同主题和风险下的人际信任:“信任圈”的中、加比较

在人际关系网络中,那些被信任者构成了个体的"信任圈",信任圈的规模可以代表个体表现出的信任水平。本研究考察了在不同交流主题(借钱、正面和负面信息交流)和风险等级下,中国人和加拿大人信任圈规模的差异。对202名中国和加拿大成年被试的调查表明,交流主题对信任水平有影响,在借钱和交流正面信息时信任圈明显大于交流负面信息时;风险等级越高,信任圈越小,在借钱时人们对风险等级尤其敏感;无论分享正面还是负面信息时,中国人的信任圈都比加拿大人更小,而在借钱方面中国人比加拿大人的信任圈更大。可见,人际信任与主题、风险和文化因素及其交互作用有关,这些结果对于理解信任的文化差异和跨文化交往实践非常有意义。     

Comparing upward and speeding up. Motivational consequences of nonsocial comparison for speed-accuracy trade-offs

Comparison is one of the most ubiquitous and versatile components in human information processing. Social comparisons in particular have multifaceted judgmental, affective, behavioral, and motivational consequences. Initially, the consequences of nonsocial comparisons may appear to be less complex than the consequences of social comparisons. Comparing a smaller circle with a larger circle, for example, has little motivational relevance. Across two studies, however, we demonstrated that different types of nonsocial comparisons influence the motivational underpinnings of participants' subsequent performance. Participants who were perceptually or numerically induced to compare upward (e.g., to compare a smaller stimulus with a larger stimulus) in a first task traded accuracy for speed in a subsequent unrelated performance task. Conversely, participants who had compared downward traded speed for accuracy. These trade-offs are indicative of promotion- and prevention-focused motivational orientations, respectively. Comparing a geometric circle with a "superior" (e.g., larger) circle seems to yield promotion-focused strategic orientations similar to those produced by comparing oneself to a person one perceives as superior. These findings demonstrate the surprising motivational power of nonsocial comparisons.     

Perception of the Ebbinghaus illusion in 5- to 8-month-old infants

The Ebbinghaus illusion is a geometric illusion based on a size-contrast between a central circle and surrounding circles. A central circle surrounded by small inducing circles is perceived as being larger than a central circle surrounded by large inducing circles. In the present study we investigated 5- to 8-month-old infants' perception of the Ebbinghaus illusion using a preferential-looking paradigm. We measured the preference between a central circle surrounded by small inducing circles (overestimated figure) and a central circle surrounded by large inducing circles (underestimated figure). Infants showed a significant preference for the overestimated figure when the central circle was flashing, but not when it was static. Furthermore, there was no preference between the two figures when the central circles were removed. These results suggest that infants' preference reflects their perception of the size illusion of the central circle. There is a possibility that 5- to 8-month-old infants perceive the Ebbinghaus illusion.     

A new method for determining the personal constants in the Luneburg theory of binocular visual space

Based on the Luneburg theory of binocular visual space, the equation for a visual circle (an apparent circle) was derived to estimate the personal constants, o and K, in this theory. Using small points of light in an otherwise dark room, five observers were asked to construct a visual circle on the horizontal plane with a standard radius of 50 or 100 cm in the median plane. The observation distance for the small circle was 250, 450, or 700 cm, and that for the large circle was 700, 1,030, 1,300, or 1,600 cm. The personal constants calculated from the radii of six directions in each circle were found to be inconsistent with those expected from this theory. The os obtained were remarkably larger than those observed in earlier studies and increased systematically as the observation distance increased. Almost all Ks were negative, with most being less than minus one. Possible factors responsible for these inconsistencies are discussed with reference to the results of previous experiments.     

Multidimensional scaling of subjective colors by color-blind observers

Temporal coding theories of color vision suggest explanations of flicker-induced subjective colors such as those that appear on Benham’s disk. If color blindness were due simply to photopigment anomalies, then subjective colors might be elicited by central patterns of neural activity in color-blind observers that mimic those which the cones normally produce in colornormal observers. We had color-normal and color-blind observers scale subjective colors like those on Benham’s disk for similarity. The inferred color spaces for six normal observers resembled the familiar hue circle, but the spaces for five red-green-deficient observers were compressed along the red-green axis. This is consistent with the position that flicker colors are due to retinal processes, and suggests that color blindness may involve variations of the central nervous system in addition to photopigment anomalies.     

Expanding the moral circle: Inclusion and exclusion mindsets and the circle of moral regard

The human tendency to draw boundaries is pervasive. The ‘moral circle’ is the boundary drawn around those entities in the world deemed worthy of moral consideration. Three studies demonstrate that the size of the moral circle is influenced by a decision framing effect: the inclusion-exclusion discrepancy. Participants who decided which entities to exclude from the circle (exclusion mindset) generated larger moral circles than those who decided which to include (inclusion mindset). Further, people in an exclusion mindset showed “spill-over” effects into subsequent moral judgments, rating various outgroups as more worthy of moral treatment. The size of the moral circle mediated the effects of mindset on subsequent moral judgment. These studies offer an important first demonstration that decision framing effects have substantial consequences for the moral circle and related moral judgments.     

APPARENT SIZE AS A DETERMINER OF FIGURAL AFTER-EFFECTS. II

K olehmainen , K. Apparent size as a determiner of figural after-effects. II. Scand. J. Psychol . 1968, 9, 237—240.—A brightly illuminated circle (TF) was flashed at distance d . The subject projected the after-image of TF on a screen placed at distance d/2, and fixated the after-image, which appeared to be half the size of the stimulus figure. Then TF and a comparison circle (CF) of equal size were shown, faintly illuminated, at distance d . A clear-cut figural after-effect occurred TF was perceived to be larger. It is suggested that TF appeared dimmer after the fixation and was perceived to be farther away than CF. As a consequence of this TF looked larger.     

Visual search for size-defined target objects is modulated by the Ebbinghaus apparent-size illusion: facilitatory and inhibitory effects of the context objects

Five experiments were carried out to investigate under which conditions the apparent size of objects is computed and exploited optimally in visual search for size-defined targets. Observers searched for a target test circle that was retinally larger than the distractor test circles, with both types of circles surrounded by context circles modulating the apparent size of the test circles (Ebbinghaus illusion). RTs were the faster the better test circles could be differentiated from the context circles, ie with smaller numbers of context circles, larger distances, and higher lightness (or colour) contrast between test and context circles. Apparent-size modulation had a strong influence on search RTs, resulting in faster RTs with smaller, and slower RTs with larger, context circles. A model assuming overall facilitatory effects of the apparent-size modulation and interference effects arising from decreasing test-context circle discriminability can explain the present results.     

Visual Evoked Potentials to Geometric Forms: Effects of Spatial Orientation

Five outlined geometric figures of equal contour length were presented monocularly below the fixation point (FP); an upright equilateral triangle (upright triangle), an inverted equilateral triangle (inverted triangle), an upright square (square), a 45°-tilted square (diamond) and a circle. The angular separation between FP and the top of the figures was held constant. Transient visual evoked potentials (VEPs) were recorded monopolarly from inion, 4, 7, 10 cm above it (l, l4, l7, l10) and Cz for ten subjects. The grand-averaged subtracted waves were obtained between the figure and blank (control) conditions. N1 (mean peak latency: 155 ms) and P2 (240 ms) waves were identified. ANOVAs were conducted for the latency and amplitude values. Main results were as follows: On the N1 amplitude at l4 and l, the upright triangle, inverted triangle and diamond figures evoked significantly larger responses than did the square and the circle. However, no significant difference was found among the former three figures. These findings on the N1 amplitude suggest that the effect of a triangle is orientation-free and that of a square is orientation-bound.     

Effects of contour proximity and lightness on Delboeuf illusions created by circumscribed letters

32 observers judged the size of a letter, either an "A" or an "S," which was surrounded by a circle. Both letters were overestimated, but larger surrounding circles reduced the illusion. Decreasing the lightness contrast of the surrounding circle relative to the central letter diminished the illusion. The results suggest that, like the Delboeuf illusion, these circumscribed letters illusions are produced by interactions among size-coding neurons.     

Binocular rivalry and surface-boundary processing

Theoretical and empirical studies show that the visual system relies on boundary contours and surface features (e.g. textures) to represent 3-D surfaces. When the surface to be represented has little texture information, or has a periodic texture pattern (grating), the boundary contour information assumes a larger weight in representing the surface. Adopting the premise that the mechanisms of 3-D surface representation also determine binocular rivalry perception, the current paper focuses on whether boundary contours have a similar role in binocular rivalry. In experiment 1, we tested the prediction that the visual system prefers selecting an image/figure defined by boundary contours for rivalry dominance. We designed a binocular rivalry stimulus wherein one half-image has a boundary contour defined by a grating disk on a background with an orthogonal grating orientation. The other half-image consists solely of the (same orientation) grating background without the grating disk, ie no boundary contour. Confirming our prediction, the predominance for the half-image with the grating disk is approximately 90%, despite the fact that the grating disk corresponds to an area with orthogonal grating in the fellow eye. The advantage of the grating disk is dramatically reduced to about 50% predominance when a boundary contour is added to the background-only half-image at the location corresponding to the grating disk. We attribute this reduced advantage to the formation of a corresponding binocular boundary contour. In experiment 2 the grating background was substituted by a random-dot background in a similar stimulus design. We found that the perceptual salience of the corresponding binocular boundary contours extracted by the interocular matching process is an important factor in determining the dynamics of binocular rivalry. Experiment 3 showed that vertical lines with uneven thickness and spacing as the background reduce the contribution of the monocular boundary contour of the grating disk in binocular rivalry, possibly through the formation of binocular boundary contours between the local edges (vertical components) of the vertical lines and the corresponding grating disk.     

The subjective size of visual stimuli affects the perceived duration of their presentation

The perception of time spent looking at a stimulus is lengthened or shortened when its physical attributes, such as area, differ from those of a comparison stimulus. We measured the perceived presentation duration of a visual object whose apparent area was altered by the Ebbinghaus illusion while its physical size remained invariant, so that a central circle surrounded by larger inducers appeared smaller than a same-size central circle surrounded by smaller inducers. The results showed that the perceived duration of presentation for apparently larger circles was longer than that of apparently smaller circles, although the actual area remained invariant across all circles. We concluded that the time perception process receives input from later visual processing.     

The role of part structure in the perceptual localization of a shape

The process of object localization may be accomplished with respect to a particular reference location, such as the center of gravity, COG (eg Vishwanath and Kowler, 2003 Vision Research 43 1637-1653). Here, we investigated how part structure affects an object's reference location. The reference location was evaluated with a measure of the illusory displacement of an internal target element embedded within a larger object (Morgan et al, 1990 Vision Research 30 1793-1810). To examine whether the reference location is different for shapes with part structure, two shapes were tested: circle (small and large; no part structure) and bell (shape with two parts, one larger than the other). Results were examined with respect to two predictions: either the location of an object is based on its shape as a whole, disregarding part structure (ie a single, overall COG), or the parts are processed separately (different COGs). With the circles, the results showed a systematic illusory displacement of the internal target toward the COG. With the bell, the illusion was significantly weaker than with both circles--even though the main part of the bell had the same size as the small circle, and its horizontal axis had the same extent as the large circle. Moreover, the distance judgments for the bell were consistent with a (weaker) reference point being located at the COG of the larger part, rather than at the COG of the entire bell. These results show that the part structure of a shape plays a role in the representation of its location, and that for complex shapes the perceived location of an embedded element depends more on the parts within which it is embedded, rather than on the whole shape.