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The reliance in psychology on verbal definitions means that psychological research is unusually moored to how humans think and communicate about categories. Psychological concepts (e.g., intelligence, attention) are easily assumed to represent objective, definable categories with an underlying essence. Like the "vital forces" previously thought to animate life, these assumed essences can create an illusion of understanding. By synthesizing a wide range of research lines from cognitive, clinical, and biological psychology and neuroscience, we describe a pervasive tendency across psychological science to assume that essences explain phenomena. Labeling a complex phenomenon can appear as theoretical progress before there is sufficient evidence that the described category has a definable essence or known boundary conditions. Category labels can further undermine progress by masking contingent and contextual relationships and obscuring the need to specify mechanisms. Finally, we highlight examples of promising methods that circumvent the lure of essences and suggest four concrete strategies for identifying and avoiding essentialist intuitions in theory development. [ABSTRACT FROM AUTHOR]

Many magic tricks rely solely on vision, but there are few, if any, that rely on auditory perception alone. Here, we question why this is so and argue that research focusing on this issue could provide deeper theoretical insights into the similarities and differences between our senses., Competing Interests: Declaration of interests The authors have no interests to declare., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We introduce a new illusory color phenomenon. The illusion is evoked by two alternating displays comprising various colored disks. Although the colors in the alternating displays are the same, the color appearance of the two displays are quite different. We suggest that apparent motion of the disks modulates the color percepts., Competing Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

In the art of conjuring, as well as in cognitive science, possibilities for designing magic tricks that are suitable for people who are blind or visually impaired have only rarely been considered. In this article, we argue that many magic tricks which are normally presented in a visual way, are not inherently based on visual processes, but instead on systematic illusions and limitations in visual imagery and mental simulations. Accordingly, it should be possible to adapt these tricks for presentation in a non-visual format, which should be suitable for people who are blind or visually impaired. As an initial test of this general approach, we adapted three magic tricks for non-visual presentation and presented them for blindfolded participants. Standard versions of the tricks were also presented to seeing participants. The participants in both groups were asked to indicate how magical they felt the tricks were, as well as whether they had any idea about the secrets behind them. The results suggest that the non-visual versions of the tricks are roughly comparable to the regular visual versions. We conclude that adapting magic tricks based on illusions of imagery for non-visual presentation appears to be a promising avenue for more universal design in the art of magic. We also argue that the illusions of imagery responsible for the experiences of magic evoked presents interesting challenges for basic cognitive science., Competing Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

When a Möbius loop is cut along the middle of the band, the result is a single connected loop, yet anecdotal evidence from science demonstrations and the use of this effect in magic tricks suggest that most people are thoroughly surprised by this because they strongly believe that the result should be two separate loops. Here, we present results from a behavioral experiment confirming this anecdotal evidence and discuss potential theoretical explanations for why this demonstration evokes strong, but misleading intuitions and a related illusion of impossibility., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2021.)

The purpose of the present note is to draw attention to the potential role of a recently discovered visual illusion in creating traffic accidents. The illusion consists in a compelling and immediate experience that the space behind an occluding object in the foreground is empty. Although the illusion refers to a region of space, which is invisible due to occlusion (a blind spot), there is evidence to suggest that it is nevertheless driven by visual mechanisms and that it can be just as deceptive and powerful as ordinary visual illusions. We suggest that this novel illusion can make situations involving blind spots in a road user's field of view even more dangerous than one would expect based on the lack of visibility by itself. This could be because it erroneously makes the road user feel that (s)he has actually seen everything there is to see, and thus has verified that the blind spot is empty. This hypothesis requires further testing before definitive conclusions can be drawn, but we wish to make researchers and authorities involved in the analysis of traffic accidents and on-the-spot crash investigations aware of its potential role in order to encourage registration of relevant data and facilitate further research.

Here, we consider a well-known wooden puzzle known as the impossible dovetail. We argue that an intriguing form of amodal completion, dealing with spontaneous interpretations of the inside of objects is the key to understanding why people find it difficult to see how the impossible dovetail is indeed possible., (© The Author(s) 2020.)

Recently, a curious illusion of absence has been described, where the space behind an occluder is compellingly experienced as empty. This illusion is similar to illusions based on amodal completion in the sense that it refers to occluded portions of a visual scene and informal observations suggest that it may also be largely impervious to conscious knowledge. The aim of the present experiment was to test the hypothesis that the illusion of absence is cognitively impenetrable in the same way as amodal completion. Participants viewed magic tricks based on amodal completion, the illusion of absence, or attentional and reasoning misdirection and tried to infer the secret behind the tricks after one, two, or three presentations. The results show that the tricks based on the illusion of absence are very difficult to debunk, even after repeated presentations. In this regard, they are similar to tricks based on amodal completion but different from tricks based on attentional and reasoning misdirection. The participants also rated how magical they felt the tricks were. Surprisingly, the magic ratings tended to be quite high even in trials where the participants had already discovered the secret behind the trick. This unexpected finding may be taken to suggest that there may be two magical moments in the lifetime of a magic trick: In addition to the magical experience evoked by trick itself, discovering the secret behind the trick may also evoke an experience of impossibility., (© The Author(s) 2020.)

A recent analysis of magic tricks suggests the existence of a perceptual illusion where the space hidden behind an occluding object is experienced as empty in a strangely compelling way. Here, we show that this illusion of absence is not just a trivial consequence of the lack of retinal stimulation but rather the result of an active process of perceptual construction. The results of a simple experiment show that this perceptual illusion of absence can in turn trigger perceptual processes which generate an immediate perceptual impression of levitation via a percept-percept coupling. This suggests that magical illusions of levitation are partially driven by an immediate perceptual impression of floating in thin air. The perceptual mechanisms underlying the illusion of absence are hitherto unknown, but our results provide support for a potential explanation based on the generic view principle., (© The Author(s) 2019.)

Images of Bruno Catalano's sculptures of incomplete bodies give rise to a remarkable depth confusion in which the background is partly pushed to the front. We argue that this confusion is related to what happens in the Kanizsa square, although the effect in the images of Catalano's sculpture appears to be driven by knowledge-based processing., (© The Author(s) 2019.)

The challenges raised in this article are not with information theory per se, but the assumptions surrounding it. Neuroscience isn't sufficiently critical about the appropriate 'receiver' or 'channel', focuses on decoding 'parts', and often relies on a flawed 'veridicality' assumption. If these problematic assumptions were questioned, information theory could be better directed to help us understand how the brain works.

In recent years, there has been a growing interest in the idea that we may gain new insights in cognitive science by studying the art of magic. Here, I offer a first exploratory overview and preliminary conceptual analysis of a class of magic tricks, which has been largely neglected in this pursuit, namely, a set of tricks that can be loosely defined as topological tricks. The deceptive powers of many of these tricks are difficult to understand in light of known psychological principles, which suggests that closer scientific scrutiny may raise interesting questions and challenges for cognitive science. I discuss a number of known and novel psychological principles that may explain why these tricks evoke the strong feelings of impossibility that are characteristic of magical experiences. A profound and detailed understanding of how topological tricks evoke magical experiences remains elusive, though, and more research on this topic could advance our understanding of perception, imagery and reasoning., (© The Author(s) 2019.)

In their quest for creating magical experiences, magicians rely on a host of psychological factors. Here, we compare tricks based on attentional misdirection with tricks based on amodal completion. Based on the notion that amodal completion is a cognitively impenetrable perceptual phenomenon, we predicted that the tricks based on this perceptual effect should-to a much larger extent than tricks based on attentional misdirection-retain their deceptive power when the tricks are repeated. The results of an experiment with four magic tricks involving attentional misdirection and four magic tricks based on amodal completion lend strong support to this prediction. Asking subjects to try to figure out the secret behind these tricks after one, two, or three presentations of each trick, we found that the observed solution rates for tricks based on attentional misdirection increased much more with repeated viewing than those for tricks based on amodal completion, which remained very low throughout. Thus, the results lend further support to the idea that amodal completion is based on cognitively impenetrable perceptual mechanisms.

We report results from an experiment showing that a tall pillar with a triangular base evokes radically different three-dimensional (3D) percepts depending on the vantage point from which it is observed. The base of the pillar is an isosceles right triangle, but the pillar is perceived as just a thin plane when viewed from some vantage points. Viewed from other vantage points, the perceived 3D shape of the pillar corresponds to a square or rectangular base. In general, our results suggest that the visual system uses a preference for rectangularity (or symmetry) to determine the 3D shape of objects. The amodal impressions of the invisible backside of the pillar are often quite compelling, and the corresponding illusions persist even when the observers know the true shape of the pillar. Interestingly, though, the compellingness and definiteness of the amodal impression of the pillar's backside depends on the vantage point. This is reflected in corresponding differences in the interobserver variability of the 3D shape judgments. We also discuss how variants of this illusion are used as a powerful tool in the art of magic.

A recently proposed model of sensory processing suggests that perceptual experience is updated in discrete steps. We show that the data advanced to support discrete perception are in fact compatible with a continuous account of perception. Physiological and psychophysical constraints, moreover, as well as our awake-primate imaging data, imply that human neuronal networks cannot support discrete updates of perceptual content at the maximal update rates consistent with phenomenology. A more comprehensive approach to understanding the physiology of perception (and experience at large) is therefore called for, and we briefly outline our take on the problem.

When magicians perform spectacles that seem to defy the laws of nature, they do so by manipulating psychological reality. Hence, the principles underlying the art of conjuring are potentially of interest to psychological science. Here, we argue that perceptual and cognitive principles governing how humans experience hidden things and reason about them play a central role in many magic tricks. Different from tricks based on many other forms of misdirection, which require considerable skill on the part of the magician, many elements of these tricks are essentially self-working because they rely on automatic perceptual and cognitive processes. Since these processes are not directly observable, even experienced magicians may be oblivious to their central role in creating strong magical experiences and tricks that are almost impossible to debunk, even after repeated presentations. We delineate how insights from perceptual psychology provide a framework for understanding why these tricks work so well. Conversely, we argue that studying magic tricks that work much better than one intuitively would believe provides a promising heuristic for charting unexplored aspects of perception and cognition.

Psychology moved beyond the stimulus response mapping of behaviorism by adopting an information processing framework. This shift from behavioral to cognitive science was partly inspired by work demonstrating that the concept of information could be defined and quantified (Shannon, 1948). This transition developed further from cognitive science into cognitive neuroscience, in an attempt to measure information in the brain. In the cognitive neurosciences, however, the term information is often used without a clear definition. This paper will argue that, if the formulation proposed by Shannon is applied to modern neuroimaging, then numerous results would be interpreted differently. More specifically, we argue that much modern cognitive neuroscience implicitly focuses on the question of how we can interpret the activations we record in the brain (experimenter-as-receiver), rather than on the core question of how the rest of the brain can interpret those activations (cortex-as-receiver). A clearer focus on whether activations recorded via neuroimaging can actually act as information in the brain would not only change how findings are interpreted but should also change the direction of empirical research in cognitive neuroscience.

Currently, we see the contours of a new research program emerging, where cognitive scientists study what magicians do and why it works. This research program may aid us in formulating interesting questions about central aspects of human experience and in gaining new perspectives on the relation between perception and cognition., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In a well-known magic trick known as multiplying balls, conjurers fool their audience with the use of a semi-spherical shell, which the audience perceives as a complete ball [1]. Here, we report that this illusion persists even when observers touch the inside of the shell with their own finger. Even more intriguingly, this also produces an illusion of bodily self-awareness in which the finger feels shorter, as if to make space for the purely illusory volume of the visually completed ball. This observation provides strong evidence for the controversial and counterintuitive idea that our experience of the hidden backsides of objects is shaped by genuine perceptual representations rather than mere cognitive guesswork or imagery [2]., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In magic tricks involving false transfer, the conjurer typically creates the illusion of transferring a coin from one hand into the other, which is then closed into a fist, while in reality the coin is kept hidden in the first hand. The magical experience occurs when the closed fist of the second hand is opened and shown to be empty. According to professional magicians, the magical experience evoked by this kind of tricks becomes noticeably weaker when the time interval between the false transfer and the opening of the fist increases. This observation is surprising, given that neither the length of this interval nor any obvious factors associated with it can be expected to change the spectators' intellectual conviction regarding the true location of the coin. We performed a controlled psychological experiment and obtained results corroborating these informal observations. Increasing the temporal interval from 1 to 32 s led to an average reduction of the strength of the magical experience of 38%. We discuss potential explanations of this curious phenomenon in terms of object persistence, object files and temporal amodal completion.

In many magic tricks, magicians fool their audience by performing a mock action (a so-called "ruse"), which merely serves the purpose of providing a seemingly natural explanation for visible movements that are actually part of the secret move they want to hide from the audience. Here, we discuss a special magic ruse in which the action of secretly putting something somewhere is "explained away" by the mock action of fetching something from the same place, or vice versa . Interestingly, the psychological principles underlying the amazing potency and robustness of this technique seem to be very similar to the general perceptual principles underlying figure-ground perception and the assignment of border ownership. This analogy may be useful for exploring the possibility that this and similar magical effects involve immediate "unconscious inferences" about intentions more akin to perceptual processing than to explicit deliberations based on a reflective "theory" of mind.

The Poggendorff illusion is one of the most exhaustively studied illusions. Can it be revived as an interesting problem? Perhaps by moving it to a slightly different domain. Here, we consider the occlusion of a subjectively linear ramp of tonal values. In a simple experiment, we find results closely resembling those of the geometrical Poggendorff. Yet, the "explanations" offered for the latter hardly apply to the former case. Depending upon one's perspective, this may be taken to "revive" the Poggendorff illusion.

In a popular magic routine known as "multiplying billiard balls", magicians fool their audience by using an empty shell that the audience believes to be a complete ball. Here, we present some observations suggesting that the spectators do not merely entertain the intellectual belief that the balls are all solid, but rather automatically and immediately perceive them as such. Our observations demonstrate the surprising potency and genuinely perceptual origin of amodal volume completion.

In the well-known gamut expansion effect, uniformly coloured target patches are perceived as more colourful when they are embedded in a uniform grey surround than when they are embedded in a variegated one. Here, we provide a demonstration showing that this effect can be inverted when the uniformly coloured target patches are replaced by variegated ones. This observation suggests that the gamut expansion effect is due to mechanisms of transparency perception rather than due to contrast adaptation.

The well-known simultaneous color contrast effect is traditionally explained in terms of visual color constancy mechanisms correcting for the confounding influence of ambient illumination on the retinal color signal. Recent research, however, suggests that the traditional gross quantitative laws of simultaneous color contrast, which are readily compatible with this functional explanation, should be revised and replaced by others, which are not readily understandable in terms of this perspective. Here, we show that the revised laws of simultaneous color contrast are well accounted for by an alternative theory explaining the simultaneous contrast effect in terms of mechanisms subserving the perception of transparent media.

In this article, we present evidence supporting the hypothesis that the local mechanism of simultaneous color contrast is the same as the mechanism responsible for the crispening effect and the gamut expansion effect. A theoretically important corollary of this hypothesis is that the basic characteristics of simultaneous contrast are at odds with traditional laws. First, this hypothesis implies that the direction of the simultaneous contrast effect in color space is given by the vector from surround to target and not--as traditionally assumed--by the hue complementary to that of the surround. Second, it implies that the size of the simultaneous contrast effect depends on the difference between the target and surround colors in a way that challenges Kirschmann's fourth law. The widespread belief in the traditional laws, we argue, is due to the confounding influence of temporal adaptation.

Several studies show that the perception of occlusion may affect various aspects of motion perception. Here we present data indicating that occlusion cues also influence the visual interpolation of sampled motion. Normally, sampled motion stimuli are perceived as less smooth and jerkier when the spatial gaps between successive presentations of the "moving" target stimulus increase. Adding surfaces occluding the spatial gaps, however, we found that the perceived smoothness of motion was not only better, but also independent of the gap width. We argue that this effect occurs because the visual system attributes the interruptions in the motion path to occlusion rather than to the moving object itself., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Drawing on many seemingly disparate and unrelated lines of evidence, we argue that the direction of the simultaneous contrast effect in three-dimensional colour space is given by the difference vector between target and surround ('direction hypothesis'). This challenges the traditional idea according to which the direction of the simultaneous contrast effect is complementary to the colour of the surround ('complementarity law'). We also argue that the size of the simultaneous contrast effect is either constant or decreases with the difference between target and surround in three-dimensional colour space. The latter proposal challenges Kirschmann's fourth law. Within our theoretical framework, the universally presumed validity of the complementarity law and Kirschmann's fourth law can be understood as resulting from the failure to take various confounding factors into account when interpreting empirical data, the most prominent of which is the influence of temporal von Kries adaptation.

We present the results of an experiment aiming to clarify the relation between simultaneous colour contrast and Brown and MacLeod's (1997) gamut expansion effect. These two context effects are often thought to be due to two different mechanisms, but this assumption has not previously been subjected to empirical test. Here we used inter-individual variability in the susceptibility to these effects to test this assumption. The individual variability was found to be quite substantial for both context effects. As would be expected if a common underlying mechanism contributes to both effects, a significant correlation across observers was found. It is suggested that this putatively common mechanism of 'crispening' accounts completely for the gamut expansion effect, and partially for the simultaneous colour contrast effect, which seems to depend on von Kries adaptation also., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Classical apparent motion stimuli exhibit an inherent ambiguity with respect to the onsets and offsets of the stimulus elements. Sigman and Rock (1974, Perception 3 9-28) presented evidence suggesting that occlusion cues are used to resolve this ambiguity. We present results from experiments designed to further test predictions of this hypothesis. As expected, we found that the apparent motion of a target stimulus is suppressed when a 'moving' occluder is positioned such that it rationalises the onsets and offsets of the stimulus elements constituting the target. Somewhat unexpectedly, though, we also observed a slight tendency for motion suppression under conditions where the target was only partially occluded. The expected motion suppression occurred both with solid occluders and purely virtual Kanizsa-like occluders, although it was not always observed in the latter case. Motion suppression was found to occur over a wide range of stimulus onset asynchronies. Finally, we used binocular disparity cues to test the occlusion account of the motion suppression phenomenon against an alternative explanation in terms of attentional factors. The results are in clear favour of the occlusion account.

Discrete sequences of sampled motion often appear flickering and jerky. We present evidence showing that a target in sampled motion is perceived as smoother when structure in the background appears and disappears synchronously with the target. Specifically, we found that target flicker is turned into permanent target visibility at short interstimulus intervals and jerkiness is replaced by smoothly accelerating and decelerating motion at longer ones. We argue that this "smoothening" effect is essentially a form of amodal completion in space-time being evoked by spatiotemporal cues to occlusion. The effect highlights the importance of amodal representations in perception.

We report experimental evidence for substantial individual differences in the susceptibility to simultaneous colour contrast. Interestingly, we found that not only the general amount of colour induction varies across observers, but also the general shape of the curves describing asymmetric matching data. A simple model based on von Kries adaptation and crispening describes the data rather well when we regard its free parameters as observer specific. We argue that the von Kries component reflects the action of a temporal adaptation mechanism, while the crispening component describes the action of the instantaneous, purely spatial mechanism most appropriately labeled simultaneous colour contrast. An interesting consequence of this view is that traditional ideas about the general characteristics of simultaneous contrast must be considered as misleading. According to Kirschmann's 4th law, for instance, the simultaneous contrast effect should increase with increasing saturation of the surround, but crispening predicts the converse. Based on this reasoning, we offer a plausible explanation for the mixed evidence on the validity of Kirschmann's 4th law. We also argue that simultaneous contrast, the crispening effect, Meyer's effect and the gamut expansion effect are just different names for the same basic phenomenon.

We describe how illusory apparent motion of one's own fingers and other body parts can easily be experienced in spite of grossly conflicting proprioceptive signals. This simple illusion may be used to shed light on the crossmodal integration of visual and proprioceptive signals. Our preliminary observations suggest that the visual and proprioceptive signals do not merge into a common crossmodal percept. Instead, mutually inconsistent visual and bodily sensations are experienced simultaneously.