A Remarkable Depth Confusion in Images of the Incomplete Statues of Bruno Catalano

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.publishedVersio

On the nature of simultaneous colour contrast

The subject of the present thesis is the phenomenon of simultaneous colour contrast: As is well known, the perceived colour of a given light stimulus depends almost as strongly on the stimulation of neighbouring regions of the visual field as on the local stimulus itself. Thus, the perceived colour of a target stimulus can be manipulated either by changing the colour co-ordinates of the target itself, or, alternatively, by changing the colour co-ordinates of the surround. Classical models of simultaneous contrast are based on the implicit assumption that the changes in perceived colour brought about by these two kinds of manipulation are basically of the same kind, and thus may compensate each other. This ‘compensation assumption’ is equivalent to the widespread assumption that the space of perceived colours is three-dimensional. In principle, though, the well-established facts of trichromatic theory are compatible with a dimensionality of the space of perceived colours higher than three (namely three times the number of differently coloured regions in the visual field). One of the central results of the present investigations is that the compensation assumption seems to be unwarranted in the case of simple centre-surround stimuli. This instilled the expectation that classical methods for measuring simultaneous contrast effects, such as grey settings and asymmetric colour matching, may sometimes be inappropriate, and thus yield misleading results. In further experiments it is shown that this is indeed the case when uniformly coloured surrounds are used. In the case of variegated surrounds, however, matters appear to be much less complicated. This difference seems to be due to impressions of perceptual transparency being evoked by uniform surrounds, but not by variegated ones

The illusion of absence in magic tricks

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 either 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.publishedVersio

Is neuroimaging measuring information in the brain?

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.This work was supported by postdoctoral fellowships to LdW and VE from the Research Foundation Flanders (FWO) and long-term structural funding from the Flemish Government (METH/08/02 and METH/14/02) awarded to JW.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.3758/s13423-016-1002-

A Perceptual Illusion of Empty Space Can Create a Perceptual Illusion of Levitation

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.publishedVersio

General practitioners’ management of depression symptoms in Somali refugee and Norwegian patients: a film vignette experiment

Objectives Refugees in comparison with non-refugee patients may face higher unmet mental healthcare needs. The mechanisms underlying these disparities are still poorly understood. The general practitioner (GP) plays a vital role in refugees’ mental health (MH), managing complaints within primary care and acting as gatekeeper to specialist services. However, GPs have reported feeling uncertain about working with refugee patients. Somalis make up one of the largest refugee groups in Norway and use primary care services more than the majority population for physical health, although not for MH. The current study examines GPs’ management of MH complaints in Somali refugee versus Norwegian vignette characters and the role of GP clinical uncertainty. Design We distributed an online experimental survey to GPs in Norway (n=133), who were randomised to watch a simulated consultation with a female Norwegian, female Somali, male Norwegian or male Somali vignette character, presenting the same symptoms of depression. GPs indicated which diagnoses, assessments and treatments they would endorse for the patient and their level of certainty. Outcome measures We calculated Simpson indices to measure inter-rater reliability and 2×2 analysis of variances as well as Bayesian estimation to examine clinical certainty based on patient background and gender. Results GPs’ clinical decisions about Somali and Norwegian vignette characters were similar, with a few exceptions. There was less consensus regarding the first prioritised diagnosis for Somali characters (Simpson index=0.129) versus Norwegian characters (Simpson index=0.208), (p=0.011, one-tailed). Somalis more frequently received diagnoses of post-traumatic stress disorder (PTSD), while Norwegians received diagnoses of feeling depressed. GPs endorsed sick leave more often for Norwegian characters and medication for physical complaints for Somali characters. There were no substantial differences in GPs’ self-reported certainty. Conclusions We found few and relatively small effects of patient background and gender on GPs’ clinical decisions. Nevertheless, the validity of certain diagnoses and prescription of sick leave need to be considered by clinicians and in future research.publishedVersio

Illusions of Imagery and Magical Experiences

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

How Visual Perception of the Inside of Things Creates the Impossible Dovetail

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

A Remarkable Depth Confusion in Images of the Incomplete Statues of Bruno Catalano

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 illusion of absence in magic tricks

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 either 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