Effects of contextual and local factors on Ponzo illusion magnitude

Ponzo illusion has been explained by considering either just the inducing elements present in a restricted area of the visual field, the same area in which the test elements are located, or the stimulus configuration as a whole in which even the most distal figural elements – i.e., the external converging lines, here called “Ponzo wedge”– play a crucial role. The two studies reported here aimed at showing that both global configurational characteristics and inducing elements locally interacting with the test stimuli can independently affect the illusory effect. This hypothesis was tested using stimuli in which graphic-inducing elements giving rise to a herringbone pattern (Coren & Girgus, 1978) were drawn in the same area of the test segments. Results of Exp. 1 confirmed the effect of the two factors. In particular, both factors proved to determine the illusion, since they induced illusory effects either in isolation or in the same/opposite direction. In Exp. 2 the relative weight of these two factors was evaluated in relation to the width of the angle of the inducing elements and to the distance of the test segments from the vertex. Results showed no linear relationships between the distance of the test segments from the external inducing elements and the weight of the Ponzo wedge factor. Received: 25 June 1996 / Accepted: 1 October 1997     

The Ponzo illusion with auditory substitution of vision in sighted and early-blind subjects

We tested the effects of using a prosthesis for substitution of vision with audition (PSVA) on sensitivity to the Ponzo illusion. The effects of visual experience on the susceptibility to this illusion were also assessed. In one experiment, both early-blind and blindfolded sighted volunteers used the PSVA to explore several variants of the Ponzo illusion as well as control stimuli. No effects of the illusion were observed. The results indicate that subjects focused their attention on the two central horizontal bars of the stimuli, without processing the contextual cues that convey perspective in the Ponzo figure. In a second experiment, we required subjects to use the PSVA to consider the two converging oblique lines of the stimuli before comparing the length of the two horizontal bars. Here we were able to observe susceptibility to the Ponzo illusion in the sighted group, but to a lesser extent than in a sighted non-PSVA control group. No clear effect of the ilusion was obtained in early-blind subjects. These results suggest that, at least in sighted subjects, perception obtained with the PSVA shares perceptual processes with vision. Visual experience appears mandatory for a Ponzo illusion to occur with the PSVA.     

Response confidence and the Ponzo illusion.

The number of longer line judgments and the ratings of confidence in these judgements were significantly higher when the comparison line was located near the apex of the Ponzo wedge but only confidence ratings were affected by the orientation of the wedge (ns = 24 men, 24 women). Differences between the two measures suggest that perceptual and nonperceptual processes may be involved in the illusion.     

Temporal processing characteristics of the Ponzo illusion

Many visual illusions result from assumptions of our visual system that are based on its long-term adaptation to our visual environment. Thus, visual illusions provide the opportunity to identify and learn about these fundamental assumptions. In this paper, we investigate the Ponzo illusion. Although many previous studies researched visual processing of the Ponzo illusion, only very few considered temporal processing aspects. However, it is well known that our visual percept is modulated by temporal factors. First, we used the Ponzo illusion as prime in a response priming task to test whether it modulates subsequent responses to the longer (or shorter) of two target bars. Second, we used the same stimuli in a perceptual task to test whether the Ponzo illusion is effective for very short presentation times (12 ms). We observed considerable priming effects that were of similar magnitude as those of a control condition. Moreover, the variations in the priming effects as a function of prime-target stimulus-onset asynchrony were very similar to that of the control condition. However, when analyzing priming effects as a function of participants’ response speed, effects for the Ponzo illusion increased in slower responses. We conclude that although the illusion is established rapidly within the visual system, the full integration of context information is based on more time-consuming and later visual processing.     

Perception of the Ponzo illusion by rhesus monkeys, chimpanzees, and humans: Similarity and difference in the three primate species

In Experiment 1, 3 rhesus monkeys and 1 chimpanzee were tested for their susceptibility to the Ponzo illusion. The subjects were first trained to report the length of the target bar presented at the center of the computer display by touching either of the two choice locations designated as “long” or “short.” When inverted-V context lines were superimposed on the target bar, the subjects tended to report “long” more often as the apex of these upward-converging lines approached the target bar. The perception of the Ponzo illusion was thus demonstrated. In Experiment 2, the same 3 rhesus monkeys and 2 new chimpanzees were tested using two types of context lines that provided different strengths of linear perspective. The subjects showed a bias similar to that found in Experiment 1, but there was no difference in the magnitude of the bias between the two types of context in either species. This failed to support the classic account for the Ponzo illusion, the perspective theory, raised by Gregory (1963). In Experiment 3, the magnitude of the illusion was compared between the inverted-V context and the context consisting of short vertical lines having the same gap as the former in the same 3 rhesus monkeys and 2 of the chimpanzees from the preceding experiments. While the chimpanzees showed the illusion for both types of stimuli, the monkeys showed no illusion for the latter. In Experiment 4, 6 humans were tested in a comparable procedure. As in the nonhuman primates, the illusion was unaffected by the strength of linear perspective. On the other hand, the humans showed considerably larger illusion for the context consisting of vertical lines than for contexts consisting of converging lines. Thus, there was a great species difference in the effect of the gap itself on the magnitude of the Ponzo illusion. Similarity found at first turned out to be no more than superficial. Possible sources of this species difference are discussed.     

The adjacency principle and induced movement

The apparent movement of a stationary point of light was investigated as a function of the apparent distance of the point of light with respect to the inducing frame of frames. When two frames were presented simultaneously, they were at different distances and physically moved at opposite phase in frontoparallel planes. When one frame was presented alone, it was positioned at different times at each of the two distances. The point of light was presented stereoscopically at the distance of either the near or far frame or midway in depth between these distances. With the single frame, it was found that the magnitude of the induced movement decreassed as the point of light was increasingly far in front of a frame but decreased less or remained approximately constant for distances be hind a frame. With the two frames presented simultaneously, it was found that as the depth between a particular frame and the point of light decreased, the contribution of that frame to the induced movement increased. The results illustrate the interaction of perceptions, in this case perceived depth and perceived motion, and are consistent with the adjacency principle.     

The role of apparent depth and context in the perception of the Ponzo illusion

The role of apparent depth features and the proximity of the test lines to the adjacent contours in the actuation of the Ponzo illusion was examined. Six versions of the Ponzo figure were employed: a standard Ponzo figure and five modified figures in which the test lines varied in orientation (horizontal or vertical) and in location (inside or outside the converging contours). Both manipulations resulted in a significant decrease in the magnitude of the illusion in comparison to the standard Ponzo figure. The results suggest that the Ponzo illusion is significantly affected by contextual factors.     

Effects of test line position and age on the magnitude of the Ponzo illusion

An earlier study by Quina and Pollack (1971) suggested that the two test lines of the classical Ponzo figure underwent simultaneous distortion in opposite directions. In the present study, test lines were shown individually with comparison lines outside the influence of the wedge to 70 school children in Grades 2–8 and to 10 adults. The apical test line was overestimated by all age groups, and the distal line was consistently underestimated. Dissimilar age trends were found, supporting the concept of the Ponzo illusion as the product of two distinct processes.     

Spatial attention in Ponzo-like patterns

A variant of Ponzo’s pattern was devised by drawing converging oblique lines at the ends of each of two horizontal lines that were located directly one above the other. Pairs of converging or diverging fins (either between or outside the horizontal shafts) were systematically removed. The results showed that, as predicted by integrative field theory, oblique lines between the shafts produced more distortion than did oblique lines outside the shafts. Also, it was shown that the attentive field construct in integrative field theory was crucial for predicting patterns of means and variances in this experiment. The modified Ponzo effect was shown to have much in common with the classical Müller-Lyer illusion. The subtle differences between the two were explained by proposing that the size of the optimum attentive field was larger in the Ponzo tasks than in the Müller-Lyer tasks because expansion fins are found onboth shafts in the Ponzo-like figure.     

The effect of frame figure type and frame size on the line and the circle Ponzo illusions

Abstract:   To examine the determinants of the Ponzo illusion, we compared the perceived size of lines and circles presented within three different frames: two converging lines, two circles, and two squares. Twenty stimulus figures, consisting of two types of objects (lines/circles) × three types of frame figures (Ponzo/circles/squares) × three sizes of lower frames (small/medium/large), and two control figures were presented on a personal computer display. Twelve students performed three measurements (upper-object/lower-object/illusion) for each stimulus figure using the method of adjustment. To analyze the relationship between single object perception and the Ponzo illusion, we compared the calculated values of overestimation magnitude differences between the upper and lower objects with the actual obtained illusion values of the six object-frame conditions. The calculated values of the circle and the square frame figures corresponded to the difference between the upper single object and the lower single object. In contrast, the results of the Ponzo figure need an additional factor to explain the differences between the obtained and the calculated values. These results indicate that two factors are involved in the Ponzo illusion: (a) the framing effect affects the perceived size of the individual single objects, and (b) the comparison factor affects the comparison process of the two objects within the converging lines.     

The relationship between vertical stimulation and horizontal attentional asymmetries

The original aim was to examine the effect of perceived distance, induced by the Ponzo illusion, on left/right asymmetries for line bisection. In Experiment 1, university students (n?=?29) made left/right bisection judgements for lines presented in the lower or upper half of the screen against backgrounds of the Ponzo stimuli, or a baseline. While the Ponzo illusion had relatively little effect on line bisection, elevation in the baseline condition had a strong effect, whereby the leftward bias was increased for upper lines. Experiment 2 (n?=?17) eliminated the effect of elevation by presenting the line in the middle and moving the Ponzo stimuli relative to the line. Despite this change, the leftward bias was still stronger in the upper condition in the baseline condition. The final experiment (n?=?17) investigated whether upper/lower visual stimulation, which was irrelevant to the task, affected asymmetries for line bisection. The results revealed that a rectangle presented in the upper half of the screen increased the leftward line bisection bias relative to a baseline and lower stimulation condition. These results corroborate neuroimaging research, showing increased right parietal activation associated with shifts of attention into the upper hemispace. This increased right parietal activation may increase the leftward attentional bias—resulting in a stronger leftward bias for line bisection.     

社会场景下联合表征的整合机制

人们在交互过程中会同时表征自我和他人相关的信息,形成社会性联合表征.然而,自我和他人相关信息是以整合还是分离的形式存在,这一问题尚未厘清.本研究以工作记忆蓬佐错觉为指标展开了探讨.实验中要求两名被试分别记忆部分构成蓬佐错觉的线段并回忆.结果发现,竞争和合作场景下的个体不仅表征了他人相关的信息,还将其和自身相关的信息进行了整合,形成工作记忆蓬佐错觉效应,表明社会交互条件下会自动整合成社会性共同表征.     

Ponzo错觉解释的合理性：倾斜恒常性理论的局限

倾斜恒常性理论是一种新的解释Ponzo错觉的理论,但是似乎存在一些局限。本研究采用调节法通过两个实验考察了四种Ponzo错觉版本在各种条件(视角和水平线段间距)下的错觉量情况,以此来检验倾斜恒常性理论。实验一中,对称Ponzo错觉变异版本在50mm时的错觉量情况和Prinzmetal(2001)的结果相似,但是在85mm和120mm时得到了较多的错觉量,这和倾斜恒常性理论的理论预期不符。实验二对不对称Ponzo错觉的考察得到了和实验一类似的结果,只有50mm时的情形符合倾斜恒常性理论预期。通过以上实验得到水平线间距和视角因素都是产生Ponzo错觉的重要因素,而倾斜恒常性理论过分强调了背景线的倾斜诱导效应,忽略了其他结构因素对Ponzo错觉的影响,所以倾斜恒常性理论具有一定的局限性,不能有效地解释Ponzo错觉的产生机制。     

Attention without awareness: Attentional modulation of perceptual grouping without awareness

Perceptual grouping is the process through which the perceptual system combines local stimuli into a more global perceptual unit. Previous studies have shown attention to be a modulatory factor for perceptual grouping. However, these studies mainly used explicit measurements, and, thus, whether attention can modulate perceptual grouping without awareness is still relatively unexplored. To clarify the relationship between attention and perceptual grouping, the present study aims to explore how attention interacts with perceptual grouping without awareness. The task was to judge the relative lengths of two centrally presented horizontal bars while a railway-shaped pattern defined by color similarity was presented in the background. Although the observers were unaware of the railway-shaped pattern, their line-length judgment was biased by that pattern, which induced a Ponzo illusion, indicating grouping without awareness. More importantly, an attentional modulatory effect without awareness was manifested as evident by the observer’s performance being more often biased when the railway-shaped pattern was formed by an attended color than when it was formed by an unattended one. Also, the attentional modulation effect was shown to be dynamic, being more pronounced with a short presentation time than a longer one. The results of the present study not only clarify the relationship between attention and perceptual grouping but also further contribute to our understanding of attention and awareness by corroborating the dissociation between attention and awareness.

     

Spatial attention in Ponzo-like patterns.

A variant of Ponzo's pattern was devised by drawing converging oblique lines at the ends of each of two horizontal lines that were located directly one above the other. Pairs of converging or diverging fins (either between or outside the horizontal shafts) were systematically removed. The results showed that, as predicted by integrative field theory, oblique lines between the shafts produced more distortion than did oblique lines outside the shafts. Also, it was shown that the attentive field construct in integrative field theory was crucial for predicting patterns of means and variances in this experiment. The modified Ponzo effect was shown to have much in common with the classical Müller-Lyer illusion. The subtle differences between the two were explained by proposing that the size of the optimum attentive field was larger in the Ponzo tasks than in the Müller-Lyer tasks because expansion fins are found on both shafts in the Ponzo-like figure.     

Illusion in a three-dimensional Hering figure in relation to viewing distance

Two groups of 34 Ss each judged the amount of illusion in a three-dimensional Hering figure at three viewing distances (9, 18, and 36 ft). The horizontal bars could be located in the foremost frontal plane of the three-dimensional display or could be recessed within it. Group C-F began at the close distance and Group F-C at the furthest distance. Amount of illusion increased with viewing distance and was greater with the bars recessed within the display. At the furthest distance, but not at the other distances, amount of illusion was greater for Group F-C. The results confirm predictions from Gregory’s theory of primary constancy scaling but are also interpretable in terms of local effects at the intersections of parallel bars and background lines.     

Leonardo's constraint: two opaque objects cannot be seen in the same direction

Given Leonardo's constraint that 2 opaque objects cannot be seen in the same direction, how are the regions of objects occluded to 1 eye included in perception? To answer this question, the authors presented 3-dimensional stimuli, similar to the ones that concerned Leonardo, and measured the visual directions of their monocular and binocular regions. When the distance between near and far objects was large, the nonfixated object was seen as double and blurry. Leonardo's constraint was met by seeing the near object as double and transparent or the distant object as double and superimposed. When the distance between near and far objects was small, the constraint was met by a perceptual displacement and compression of parts of the nonfixated object.     

Influences of temporal factors on memory conjunction errors

Subjects viewed a series of faces presented two at a time for 16 seconds. Following either a 15‐minute (Experiment 1) or 24‐hour (Experiment 2) retention interval they received a recognition test that included old faces as well as faces constructed by recombining features from simultaneously presented study faces (simultaneous‐conjunction condition), faces from successive pairs (near‐conjunction condition), and faces that were two pairs apart (far‐conjunction condition). In Experiment 1, false alarm rates decreased as the temporal distance between the relevant study faces increased. In Experiment 2, the false alarm rate in the simultaneous‐conjunction condition was equal to the hit rate for old faces, and the false alarm rates for the other conditions was much lower. There was no effect of serial position during the study phase on the likelihood that parts of a face would later be miscombined to produce a recognition error in either experiment. The results suggest that witnesses to a crime are more likely to miscombine features of a to‐be‐remembered stimulus with those of another stimulus that was simultaneously present at the crime scene than with those of a stimulus encountered either earlier or later, especially when the test is delayed. Copyright © 2000 John Wiley & Sons, Ltd.     

Gender Differences in Illusion Response: The Influence of Spatial Strategy and Sex Ratio

Two experiments explored factors related to gender differences in Ponzo illusion susceptibility. In Experiment 1, 54 male and 54 female (predominantly white, middle class) undergraduates were administered Witkin's Embedded Figures Test (EFT) and, on 2 separate occasions, a form of the Ponzo illusion. Results showed the Ponzo to be quite reliable over several days. Females were significantly more field dependent (as shown by slower responses to the EFT), and significantly more susceptible to the Ponzo illusion, than males. Furthermore, EFT performance correlated significantly with Ponzo susceptibility for females, but not for males, suggesting that the difference between males and females in Ponzo response may be due not to differences in field independence per se, but rather to differences in the strategies used to solve the illusion task. In Experiment 2, 111 male and 148 female (predominantly white, middle class) undergraduates were administered the Ponzo illusion twice, the 2 administrations separated by about 90 min. Again, the illusion task showed good reliability, and females were significantly more susceptible to the illusion. Furthermore, the magnitude of the difference between males and females was systematically related to the sex ratio (the ratio of the number of males to the number of females) of the particular session in which each subject happened to be participating. It is suggested that social factors such as sex ratio might affect the strategies participants use when doing illusion tasks, and perhaps other spatial skills tasks as well.     

Apparent equivalence between perception and imagery in the production of various visual illusions

The ability of high and low imagers (as assessed by the Vividness of Visual Imagery Questionnaire) to utilize imagery in the production of a visual illusion was examined in three experiments. In Experiment 1, subjects were to imagine noninducing elements oi the Ponzo figure. In Experiment 2, subjects were asked to imagine the inducing angle of the Ponzo figure. Subjects were requested to imagine the inducing diagonals of the Hering and Wundt figures in Experiment 3. Regardless of which figure was presented, high imagers consistently reported an illusion whether it was produced by real or imagined lines. Also, the imagery-produced illusion was equivalent in magnitude to the actual illusion (when all lines are physically present). Low imagers reported an illusion only when lines were physically present. These results were interpreted in terms of Finke’s (1980) equivalence theory.