Cognitive reliability of the sense of touch confronted with the thinning effect

The dependence of the cognitive function of the sense of touch of the area sensorium was investigated by means of the thinning illusion produced by rotating the cylindrical rod between the thumb and the forefinger. The genetic phases of this illusion were traced from sensations to perceptions and to meaningful cognition converting the rod's objective convexity into an apparent concavity, running seemingly around the rod. Adult subjects (N = 52) experimentally checked all variables on their optimum degree for producing this illusion, which showed an effective way for using illusions for a thorough investigation of mental synthetic processes.     

Instructions, illusory self-tilt and the rod-and-frame test

If an illusion of self-tilt is involved in rod-and-frame test performance, then instructions to adjust the rod to the body midline (egocentric instructions) should result in less rod adjustment error than the standard instructions for the rod-and-frame test to adjust the rod to the gravitational vertical. Two experiments were designed to examine this possibility. The results of the first experiment indicate that the tilted rod-and-frame display induces an illusion of self-tilt in the opposite direction. Significant differences between instructional conditions were found in the second experiment as expected. Other rod-and-frame studies are discussed in view of these findings.     

The discursive form of human understanding as the source of the transcendental illusion

Kant famously claims that pure reason is subject to a transcendental illusion in which the subjective validity and the regulative use of a principle of reason are conflated with its objective validity and constitutive use. His doctrine of transcendental illusion is puzzling for he insists that this illusion is natural as well as necessary. The two dominant interpretation strategies cannot make sense of this puzzle because they turn out to be either too strong or too weak: they either struggle to account for the legitimate, regulative use of the transcendental principle of reason or fall short of explaining the necessity of the transcendental illusion. In contrast, I shall argue that it is possible to account for the fact that the transcendental illusion is natural and necessary because it has its source in the discursive form of our human understanding, and that this illusion can nevertheless be known to be illusory because our discursive nature can be recognised as a merely particular form of understanding by comparing it with a possible, intuitive form of understanding in an act of critical self-reflection.     

A tactile illusion: The rotating hourglass

A new tactile (more properly termed haptic) illusion, the rotating hourglass, was investigated in the laboratory by rotating a rod end for end between the S’s thumb and forefinger. This illusion, which is an apparent decrease in the diameter of the rod at the point of contact with the fingers, was easily observed by 19 of the 20 Ss. When the illusion was studied as a function of time, the magnitude of the illusion increased over time with a mean decrease in apparent diameter of 52.3% from the beginning to the end of the 38-sec trials. A theory of differential adaptation of the skin is postulated to explain the rotating hourglass illusion and a similar illusion.     

Power and the Illusion of Transparency in Negotiations

This study examines how the illusion of transparency in negotiation differs depending on whether one is the powerful or less powerful negotiator. The illusion of transparency is the tendency for individuals to overestimate the extent to which their internal states and intentions are apparent to an outside observer. Thus, this illusion equals the difference between perceived and actual transparency. We predict that less powerful negotiators experience more perceived transparency than do powerful negotiators and that powerful negotiators exhibit greater actual transparency than do less powerful negotiators. The main hypothesis that the illusion of transparency is greater for less powerful negotiators than for powerful negotiators was supported.     

Reconsidering evidence for the suppression model of the octave illusion

The octave illusion is elicited by a sequence of tones presented to each ear that continuously alternate in frequency by one octave, but with high and low frequencies always in different ears. The percept for most listeners is a high pitch in one ear, alternating with a low pitch in the other ear. The influentialsuppression model of the illusion proposed by Deutsch and Roll (1976) carries three postulates: first, that listeners perceive only the pitch of the tones presented to their dominant ear; second, that this pitch is heard in whichever ear received the higher frequency tone; and third, that this apparent dissociation betweenwhat andwhere mechanisms arises from sequential interactions between the tones. In the present article, we reappraise evidence for the suppression model and demonstrate (1) the incompatibility of the theory with the existing literature on pitch perception, sound localization, and ear dominance and (2) methodological limitations in studies that have claimed to provide support for the suppression model. We conclude by proposing an alternative theory of the octave illusion that is based on established principles of fusion, rather than suppression, between ears.     

Observer pitch and roll influence: The rod and frame illusion

Observers misperceive the orientation of a vertical rod when it is viewed in the context of a tilted frame (therod and frame illusion, or RFI). The pitch and roll of the surrounding surfaces have independent influences on this illusion (Nelson & Prinzmetal, 2003). Experiment 1 measured the RFI when the pitch and roll of the floor that supported the observer was varied, and the observer was either seated in a chair or standing upright. There were additive influences of pitch and roll on the RFI of seated but not standing observers. Experiments 2 and 3 decoupled body roll and head roll in order to isolate the vestibular and proprioceptive contributions to these effects. The results are interpreted in support of a hierarchy of influence on the RFI: Visual input is given top priority, followed by vestibular input, and then proprioceptive input.     

Color Illusion

As standardly conceived, an illusion is an experience of an object o appearing F where o is not in fact F. Paradigm examples of color illusion, however, do not fit this pattern. A diagnosis of this uncovers different sense of appearance talk that is the basis of a dilemma for the standard conception. The dilemma is only a challenge. But if the challenge cannot be met, then any conception of experience, such as representationalism, that is committed to the standard conception is false. Perhaps surprisingly, naïve realism provides a better account of color illusion.

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The Illusion of Exclusivity

It is widely held that when you are deliberating about whether to believe some proposition p, only considerations relevant to the truth of p can be taken into account as reasons bearing on whether to believe p and motivate you accordingly. This thesis of exclusivity has significance for debates about the nature of belief, about control of belief, and about certain forms of evidentialism. In this paper I distinguish a strong and a weak version of exclusivity. I provide reason to think that strong exclusivity is an illusion and that weak exclusivity may also be an illusion. I describe a number of cases in which exclusivity seems not to hold, and I show how an illusion of exclusivity may be generated by a rather different feature of doxastic deliberation, which I call demandingness.     

Hierarchical organisation in perception of orientation

According to Rock [1990, in The Legacy of Solomon Asch (Hillsdale, NJ: Lawrence Erlbaum Associates)], hierarchical organisation of perception describes cases in which the orientation of an object is affected by the immediately surrounding elements in the visual field. Various experiments were performed to study the hierarchical organisation of orientation perception. In most of them the rod-and-frame-illusion (RFI: change of the apparent vertical measured on a central rod surrounded by a tilted frame) was measured in the presence/absence of a second inner frame. The first three experiments showed that, when the inner frame is vertical, the direction and size of the illusion are consistent with expectancies based on the hierarchical organisation hypothesis. An analysis of published and unpublished data collected on a large number of subjects showed that orientational hierarchical effects are independent from the absolute size of the RFI. In experiments 4 to 7 we examined the perceptual conditions of the inner stimulus (enclosure, orientation, and presence of luminance borders) critical for obtaining a hierarchical organisation effect. Although an inner vertical square was effective in reducing the illusion (experiment 3), an inner circle enclosing the rod was ineffective (experiment 4). This indicates that definite orientation is necessary to modulate the illusion. However, orientational information provided by a vertical or horizontal rectangle presented near the rod, but not enclosing it, did not modulate the RFI (experiment 5). This suggests that the presence of a figure with oriented contours enclosing the rod is critical. In experiments 6 and 7 we studied whether the presence of luminance borders is important or whether the inner upright square might be effective also if made of subjective contours. When the subjective contour figure was salient and the observers perceived it clearly, its effectiveness in modulating the RFI was comparable to that observed with luminance borders.     

Shattering the illusion of control: Multi-shot versus single-shot gambles

The illusion of control refers to a phenomenon whereby people believe their chances of success at a task are greater than would be warranted by objective analysis. This article raises two questions. First, how robust is the illusion of control? Second, how might the illusion be ‘shattered?’ Previous experimental demonstrations involved situations that can be likened to unique or single-shot gambles. If, however, the phenomenon is robust, it should occur in repeated or multi-shot gambles in which the outcome depends on a series of gambles involving the same underlying random process. It should also appear in single-shot gambles that are framed so as to superficially resemble multi-shot gambles. We label this the strong illusion of control hypothesis. On the other hand, because people have a better appreciation of probabilistic concepts in tasks they are able to represent as relative frequencies, the introduction of a multi-shot or ‘pseudo-multi-shot’ context might cue people to the random nature of the task, thereby shattering the illusion. The weak illusion of control hypothesis holds that the illusion of control will occur in single-shot but not in multi-shot or pseudo-multi-shot gambles. Two studies are reported that support the weak hypothesis. Alternative explanations are considered and implications are discussed.     

The illusion of clarity: Image segmentation and edge attribution without filling-in

It comes as no surprise that viewing a high-resolution photograph through a screen reduces its clarity. Yet when a coarsely quantized (i.e., pixelated) version of the same photo is seen through a screen its clarity is increased. Six experiments investigated this illusion of clarity. First, the illusion was quantified by having participants rate the clarity of quantized images with and without a screen (Experiment 1). Interestingly, the illusion occurs both when the wires of the screen are aligned with the blocks of the quantized image and when they are shifted horizontally and vertically (Experiments 2 and 3), casting doubt on the hypothesis that a local filling-in process is involved. The finding that no illusion occurs when the photo is blurred rather than quantized (Experiment 4) and that the illusion is sharply reduced when visual attention is divided (Experiment 5) argue for an image segmentation process that falsely attributes the edges of the quantized blocks to the screen. Finally, the illusion is larger when participants adopt an active rather than a passive cognitive strategy (Experiment 6), pointing to the importance of cognitive control in the illusion.     

Ontogeny of the Ponzo illusion: Effects of age,schooling, and environment(1)

Subjects were 384 Moroccan males (age range 6–22 yrs.), divided into 16 equal groups, according to the factorial design: age (4) × schooling (2) × environment (2). Subjects were tested on four Ponzo configurations (differing in contextual information) from Leibowitz et al. (1969), the Ponzo perspective stimulus from Segall et al. (1966), the CEFT from Witkin et al. (1971), and a measure of pictorial depth perception. Individual measures of contact with mass-media and urban life were collected on each subject. Analyses indicated that all main factors of age, schooling, and environment played important, and differing, roles in inducing illusion susceptibility. Piaget's (1969) theory of primary and secondary illusions was found useful in understanding the results of the Ponzo configurations used in the study. Primary illusion configurations were found to be relatively insensitive to experiential variables, and illusion susceptibility decreased with chronological age. In contrast, secondary illusion configurations were affected by many experiential factors, and illusion susceptibility was mediated through perceptual development and pictorial depth perception rather than chronological age. It was concluded that single-factor theories of ontogenetic change in illusion susceptibility were inadequate to explain the complex interactions found in this study.     

Recent developments in the experimental investigation of the illusion of control. A meta‐analytic review

The present study analyzes recent developments in the experimental investigation of the illusion of control by using the methods of meta‐analysis. The aim of the study was to estimate the effect sizes associated with different factors thought to induce the illusion of control considering different conceptualizations of the phenomenon. The overall weighted mean effect size (D) was.62, with the 95% confidence interval about the mean.49 to.75. Generally, experiments tend to obtain moderate to large effect sizes, and the illusion of control is constantly present as an effect of several situational and psychological factors. Nevertheless, the large heterogeneity of the studies in terms of dependent measures suggests that the underlying phenomena can be of a different nature.     

Apparent distance reduction with moving stimuli (Tandem Effect): Evidence for an attention-shifting model

Summary When two vertical rods move through a horizontal window in close succession, the Tandem Effect can be observed. It consists of a spatial illusion (distance between the rods looking smaller than it actually is) and a temporal illusion (under certain conditions both rods are seen simultaneously in the window, though the first rod has left the window before the second rod enters it). We report six experiments that explored the distance-reduction illusion and tested an attentional model of the effect. It assumes that attention is initially focused on the first rod and then shifted to the second, when it enters the window. The percept of the pair of rods is integrated from the first rod's position at the beginning, and the second rod's position at the end, of the focus shift. Consequently their subjective distance will be smaller than their physical distance by the distance that they travel during the focus shift. Experiments 1 and 2 established the Tandem Effect as an empirical phenomenon and showed that its size depends on stimulus parameters such as window size and movement speed. Experiments 3–5 tested specific predictions from the attentional model. Experiment 6 examined a further illusion, the Fröhlich Effect, and showed that it can be subsumed under the model. The experiments produced some unexpected effects and some predictions from the model were only partly confirmed. It is shown that the main findings can be combined into two quantitative functions that describe the course of focusing. One implication is that visual attention does not move from one object to another; rather all attention shifts originate in the fovea. We discuss several alternative interpretations of our data and show that they are less satisfactory than the attentional model.     

Varieties of Pictorial Illusion

This article focuses on a potentially perplexing aspect of our interactions with pictorial representations (including film, paintings, pictures, drawings, photographs, even video games): in some cases, it seems that visual representations can play tricks on our cognitive faculties. We may either come to believe that objects represented in pictures are real or perhaps perceive them as such. The possibility of widespread pictorial illusions has been oft discussed, and discarded, in the aesthetics literature. I support this stance. However, the nature of the illusion is more complicated than is usually considered. I argue that there are five different types of potential illusions and present reasons for rejecting each. I also explore in detail the most persistent illusion: the “object recognition perceptual illusion thesis,” which states that we undergo a perceptual illusion while viewing pictorial representations simply in virtue of seeing objects in the representation. I contend that a rejection of this thesis depends on the nature of perceptual content, an issue with far‐reaching consequences in aesthetics.     

Orientation contrast effects in the rod-and-frame test

Previous research indicates that a tilted visual display is capable of inducing eye torsion and an illusion of self-tilt in objectively upright observers. These effects may contribute to performance errors on the rod-and-frame test by rotating the perceived axes of visual space toward the tilted frame. The kinesthetic-matching method was used in the present study to see whether an effect of the visual orientation contrast between red and frame sides might also contribute to rod-and-frame test performance. Observers aligned invisible hand-held rods with the visual rod at various tilts under a control condition when the frame was absent, and under experimental conditions with the frame upright or set at 45°. The frame induced matching errors in the direction away from the frame sides which were most nearly parallel to the rod. Since no rotation of apparent visual axes should occur under these conditions, the data suggest that an orientation contrast effect is involved in the rod-and-frame test.     

The Visuomotor System Resists the Horizontal-Vertical Illusion

The effect of the horizontal-vertical illusion on the visual and visuomotor systems was investigated. Participants (N = 8) viewed horizontal and vertical lines in an inverted-T stimulus and judged whether the two line segments were the same or different lengths. Participants also reached out and grasped either the vertical or the horizontal line segment of the stimulus. Perceptually, participants succumbed to the illusion; that is, they judged Ts of equal horizontal and vertical line lengths to be different and Ts of unequal line lengths to be the same. When reaching toward the same stimuli, however, the size of their grip aperture was scaled appropriately for the various line lengths. Thus, whereas the perceptual system succumbed to the illusion, the visuomotor system did not. Those results support a model proposed by M. A. Goodale and A. D. Milner (1992), who posited separate cortical pathways for visual perception and visually guided action.     

The effect of variation of frame shape on the angular function of the rod-and-frame illusion

The angular function of the rod-and-frame illusion was studied under conditions of variation in frame shape. The results support predictions arising from the hypothesis that as a frame is varied in tilt, vertical settings of a rod will be in error in the direction of the major frame axis closest to true vertical.     

The effect of density and diameter on haptic perception of rod length

Three experiments on the effect of density and diameter on haptic perception of rod length are reported. In Experiment 1, the subjects wielded visually occluded rods of different densities. Perceived length was found to be affected by the density of the rod regardless of the actual length. In Experiment 2, three aluminum rods of different lengths with handles of four different diameters were wielded. Perceived length of the rod was found to be shorter as the diameter of the handle with which it was wielded increased. A diameter—length illusion was thereby produced. In Experiment 3, visually occluded rods of different diameters but of the same moment of inertia about thex-axis were wielded with the right hand, and tubes of different diameters were felt with the left hand. The subjects were instructed that their right hand was grasping a handle, and that the actual diameter of the rod could be felt with the left hand. Rods were perceived to be shorter if a larger diameter was felt with the left hand. The results showed that perceived length is not just a function of actual rod length, and that it is not accounted for by inertia only. The results are further discussed in terms of the nature of invariants and the effect of knowledge on perception.