Illusory Perceptions Research Articles

Five types of anomalous perceptions created by the same mirror-reflection process

The real world and its mirror image are plane symmetric to each other with respect to a mirror surface, but mirror images are often perceived differently due to optical illusions. This paper shows that there are at least five types of different illusory perceptions of mirror images of pictures, although they arise from the same optical process. In all five illusions, we place a 2D picture of a 3D object horizontally, and see its image reflected by a vertical mirror. In some cases, the left and the right are reversed (left-right reversal illusion), sometimes horizontal planes change their heights (height reversal illusion), sometimes a lying object rises up (lying-standing illusion), sometimes the object turns upside down as if having done a somersault (somersault illusion), and sometimes the object is replaced by a rather different object (replacement illusion). This paper examines why these illusions occur from geometrical and psychological points of view.

Changing Finger Movement Perception: Influence of Active Haptics on Visual Dominance

The perception of one’s own body is a complex mechanism that can be disturbed by conflicting sensory information and lead to illusory (mis-) perceptions. Prominent models of multisensory integration propose that sensory streams are integrated according to their reliability by approximating Bayesian inference. As such, when considering self-attribution of seen motor actions, previous works argue in favor of visual dominance over other sensations, and internal cues. In the present work, we use virtual reality and a haptic glove to investigate the influence of an active haptic feedback on one’s visual and agency judgments over a performed finger action under experimentally manipulated visual and haptic feedbacks. Data overall confirm that vision dominates for agency judgment in conditions of multisensory conflict. Interestingly, we also show that participants’ visual judgment over their finger action is sensitive to multisensory conflicts (vision, proprioception, motor afferent signals, and haptic perception), thus bringing an important nuance to the widely accepted view on a general visual dominance.

Depth Perception With Interocular Blur Differences Based on a Spiking Network

Visual depth perception is the basic function of the visual nervous system. To a stimulus in the stereo space, the visual nervous system could generate a perception about depth of its position. Experimental observations have demonstrated that interocular blur differences could lead to illusory perceptions about depths of moving stimuli. However, to stimuli with interocular blur differences, influences of different factors on illusory depth perceptions are still unclear. To explore these influences, this paper constructs a plastic two-layer k-winner-take-all (k-WTA) spiking network, simulating primary visual cortical responses. With incompatible stimuli presented into two eyes in experiments, binocular rivalry could occur in the primary visual cortex and interact with depth perception. To simulate binocular rivalry, the network consists of two parallel visual channels driven by left-eye and right-eye stimuli and competing with each other through mutual inhibition. In simulations, the horizontally moving stimulus is filtered with different Gaussian filters to generate paired monocular stimuli with interocular blur differences. The blurry strength, the moving direction and the moving speed perform as varying factors of moving stimuli. The network updates its dynamics through probabilistic inference, reflecting impacts of each factor on both neural responses and binocular rivalry. The modified responses could simulate illusory depth perceptions of stimuli as observed in experiments. To stimuli with interocular blur differences, varying factors could modify binocular rivalry in the network, inducing distinguishing illusory depth perceptions. Based on probabilistic inference, our model could provide possible explanations to illusory depth perceptions with interocular blur differences.

Unambiguous determinism in captivity of illusory perceptions

This article attempt to clarify whether the accusations brought by modern physics and probabilistic thinking against unambiguous determinism are justified. Is it incompatible with the existence of various possibilities, coincidences, free will, and certain laws of microcosm? Does it really lead to absolute predetermination? Is the perception of universality and fundamentality of unambiguous causation really outdated? Can the dynamic laws  be limited in their manifestation? Can they be replaced with probabilistic laws? At the same time, the logic of research is founded on determination of the essence of all the phenomena that are supposedly incompatible with the unambiguous determinism. In the course of research, the author adheres to gradual implementation of the principle of materialistic monism. The conclusion is made that the classical representation of universality and fundamentality of unambiguous causality remains relevant and is fully compatible with the presence of various possibilities, coincidences, free will, and probability. The author reveals the nature of possibilities and coincidences, as well as indicated inseparability of these phenomena from the predictive activity of a human. The article also determines inextricable link between the dynamic laws and the materiality of  the cognizable world, which testifies to their unlimited fundamentality. The nature of probabilistic laws and their inseparability from dynamic laws is underlined. The author provides arguments that unambiguous causality does not lead to absolute predomination of events, emphasizes the importance of the worldview criterion of validity of scientific representations; and clarifies the definition of matter.

The right thalamic ventral posterolateral nucleus seems to be determinant for macrosomatognosia: a case report

BackgroundMacrosomatognosiais the illusory sensation of a substantially enlarged body part. This disorder of the body schema, also called “Alice in wonderland syndrome” is still poorly understood and requires careful documentation and analysis of cases. The patient presented here is unique owing to his unusual macrosomatognosia phenomenology, but also given the unreported localization of his most significant lesion in the right thalamus that allowed consistent anatomo-clinical analysis.Case presentationThis 45-years old man presented mainly with long-lasting and quasi-delusional macrosomatognosia associated to sensory deficits, both involving the left upper-body, in the context of a right thalamic ischemic lesion most presumably located in the ventral posterolateral nucleus. Fine-grained probabilistic and deterministic tractography revealed the most eloquent targets of the lesion projections to be the ipsilateral precuneus, superior parietal lobule,but also the right primary somatosensory cortex and, to a lesser extent, the right primary motor cortex. Under stationary neurorehabilitation, the patient slowly improved his symptoms and could be discharged back home and, later on, partially return to work.ConclusionWe discuss deficient neural processing and integration of sensory inputs within the right ventral posterolateral nucleus lesion as possible mechanisms underlying macrosomatognosia in light of observed anatomo-clinical correlations. On the other hand, difficulty to classify this unique constellation of Alice in wonderland syndrome calls for an alternative taxonomy of cognitive and psychic aspects of illusory body-size perceptions.

When Left is One and Right is Double: An Experimental Investigation of Visual Allesthesia after Right Parietal Damage.

Illusory visual phenomena, such as palinopsia, polyopsia or allesthesia, are rare manifestations of posterior cortical damage. Symptoms are characterized by illusory perceptions, ranging from isolated stationary objects to scenes and moving persons. Such illusions may appear while the original object is still in view, or become manifest with a delay and last for minutes, hours or even days. Some authors have suggested a disinhibited cortical response underlying visual illusions, but experimental studies supporting this hypothesis are lacking. Here, we examined a rare patient who after focal right parietal injury consistently reported a second stimulus on the left when briefly shown a target in his right hemifield. The patient perceived the illusory stimulus as less intense, and therefore concluded that it must have a different shape than the original stimulus. A masking experiment revealed that the frequency of the illusion was inversely related to the visibility of the original stimulus, suggesting that it depended on early, feedforward visual processing. We propose that illusory perceptions reflect the interplay of two physiological processes: a fast and automatic activation of contralateral, homotopic visual cortex after unilateral stimulation, and the lack of top-down inhibition following damage to the posterior parietal cortex.

Multisensorial Perception in Chronic Migraine and the Role of Medication Overuse

Multisensory processing can be assessed by measuring susceptibility to crossmodal illusions such as the Sound-Induced Flash Illusion (SIFI). When a single flash is accompanied by 2 or more beeps, it is perceived as multiple flashes (fission illusion); conversely, a fusion illusion is experienced when more flashes are matched with a single beep, leading to the perception of a single flash. Such illusory perceptions are associated to crossmodal changes in visual cortical excitability. Indeed, increasing occipital cortical excitability, by means of transcranial electrical currents, disrupts the SIFI (ie, fission illusion). Similarly, a reduced fission illusion was shown in patients with episodic migraine, especially during the attack, in agreement with the pathophysiological model of cortical hyperexcitability of this disease. If episodic migraine patients present with reduced SIFI especially during the attack, we hypothesize that chronic migraine (CM) patients should consistently report less illusory effects than healthy controls; drugs intake could also affect SIFI. On such a basis, we studied the proneness to SIFI in CM patients (n = 63), including 52 patients with Medication Overuse Headache (MOH), compared to 24 healthy controls. All migraine patients showed reduced fission phenomena than controls (P < .0001). Triptan MOH patients (n = 23) presented significantly less fission effects than other CM groups (P = .008). This exploratory study suggests that CM – both with and without medication overuse – is associated to a higher visual cortical responsiveness which causes deficit of multisensorial processing, as assessed by the SIFI. PerspectiveThis observational study shows reduced susceptibility to the SIFI in CM, confirming and extending previous results in episodic migraine. MOH contributes to this phenomenon, especially in case of triptans.

A hard to read font reduces the causality bias

AbstractPrevious studies have demonstrated that fluency affects judgment and decision-making. The purpose of the present research was to investigate the effect of perceptual fluency in a causal learning task that usually induces an illusion of causality in non-contingent conditions. We predicted that a reduction of fluency could improve accuracy in the detection of non-contingency and, therefore, could be used to debias illusory perceptions of causality. Participants were randomly assigned to either an easy-to-read or a hard-to-read condition. Our results showed a strong bias (i.e., overestimation) of causality in those participants who performed the non-contingent task in the easy-to-read font, which replicated the standard causality bias effect. This effect was reduced when the same task was presented in a hard-to-read font. Overall, our results provide evidence for a reduction of the causality bias when presenting the problem in a hard-to-read font. This suggests that perceptual fluency affects causal judgments.

Do positive illusions of control foster happiness?

Positive emotions have been shown to benefit from optimistic perceptions, even if these perceptions are illusory (Seligman & Csikszentmihalyi, 2000). The current research investigated the effects of increases and decreases in illusory control on positive and negative emotions. In two studies we experimentally induced changes in illusory perceptions of control (increase vs. decrease of illusory control) and assessed the extent to which these changes, in turn, influenced participants' emotions. Extending prior research, the results of both studies revealed that whereas illusions of personal control over environmental outcomes mitigated the experience of negative emotions, they did not foster positive emotions. Perceiving a loss of illusory control, however, significantly reduced the experience of positive emotions, but had no effect on negative emotions. Implications for emotion theory and intervention programs are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Real and illusory perceptions of patients in induced coma.

To identify, in the scientific literature, real and illusory perceptions of adult patients in induced coma. This is an integrative review of 15 primary studies from the Medline, Web of Science, LILACS, CINAHL and SCOPUS databases. The main memories reported after induced coma were thirst, cold, and pain. In some studies, patients reported they were unable to tell whether they were awake or dreaming, whether it was real or unreal. Satisfactory memories were reported by patients related to the care received and the use of bedside journals. Evidence showed a number of studies aiming to identify delirium, but without a focus on analyzing real or illusory perceptions of patients after induced coma. Thus, this integrative review identified scientific evidence of memories related to perceptions of sedated patients in the intensive care unit.

A Protective Mechanism against Illusory Perceptions Is Amygdala-Dependent.

Most people have a clear sense of body ownership, preserving them from physical harm. However, perceptual body illusions - famously the rubber hand illusion (RHI) - can be elicited experimentally in healthy individuals. We hypothesize that the amygdala, a core component of neural circuits of threat processing, is involved in protective mechanisms against disturbed body perceptions. To test this hypothesis, we started by investigating two monozygotic human twin sisters with focal bilateral amygdala damage due to Urbach-Wiethe disease. Relative to 20 healthy women, the twins exhibited, on two occasions 1 year apart, augmented RHI responses in form of faster illusion onset and increased vividness ratings. Following up on these findings, we conducted a volumetric brain morphometry study involving an independent, gender-mixed sample of 57 healthy human volunteers (36 female, 21 male). Our results revealed a positive correlation between amygdala volume and RHI onset, i.e., the smaller the amygdala, the less time it took the RHI to emerge. This raised the question of whether a similar phenotype would result from experimental amygdala inhibition. To dampen amygdala reactivity, we intranasally administered the peptide hormone oxytocin to the same 57 individuals in a randomized trial before conducting the RHI. Compared with placebo, oxytocin treatment yielded enhanced RHI responses, again evident in accelerated illusion onset and increased vividness ratings. Together, the present series of experiments provides converging evidence for the amygdala's unprecedented role in reducing susceptibility to the RHI, thus protecting the organism from the potentially fatal threats of a distorted bodily self.SIGNIFICANCE STATEMENT Compelling evidence indicates that the amygdala is of vital importance for danger detection and fear processing. However, lethal threats can arise not only from menacing external stimuli but also from distortions in bodily self-perception. Intriguingly, the amygdala's modulatory role in such illusory body perceptions is still elusive. To probe the amygdala's involvement in illusory body experiences, we conducted a multi-methodological series of experiments in a rare human amygdala lesion model, complemented by a morphological and pharmaco-modulatory experiment in healthy volunteers. Our findings convergently suggest that the amygdala's integrity is indispensable for maintaining an unbiased, precise perception of our bodily self. Hence, the amygdala might shield us against distortions in self-perception and the resultant loss of behavioral control of our organism.

It's all in your head: Expectations create illusory perception in a dual-task setup.

Predictions about the world can guide our perception and action, but they can also misguide us. We developed novel dual-task setups where the participants are occupied by a primary task and are from time to time queried about the phenomenal contents of the auxiliary task. We show that "hallucinating" the presence of an actually absent stimulus is not an exception, but a common phenomenon (more than 90% of participants experienced illusory objects at least once). Additionally, in experiment 1 we found a negative correlation between the amount of illusory perceptions and the Autism Spectrum Quotient score. People who scored higher on the questionnaire, were less likely to experience illusory objects. Finally, we observed no effect of spatial attention on expectation-based illusory presence of an object. More generally our results demonstrate that expectations misguide perception when attention is diverted to another task.

Parkinson's disease alters multisensory perception: Insights from the Rubber Hand Illusion

BackgroundManipulation of multisensory integration induces illusory perceptions of body ownership. Patients with Parkinson's disease (PD), a neurodegenerative disorder characterised by striatal dopamine deficiency, are prone to illusions and hallucinations and have sensory deficits. Dopaminergic treatment also aggravates hallucinations in PD. Whether multisensory integration in body ownership is altered by PD is unexplored. ObjectiveTo study the effect of dopamine neurotransmission on illusory perceptions of body ownership. MethodsWe studied the Rubber Hand Illusion (RHI) in 21 PD patients (on- and off-medication) and 21 controls. In this experimental paradigm, synchronous stroking of a rubber hand and the subject's hidden real hand results in the illusory experience of ‘feeling’ the rubber hand, and proprioceptive mislocalisation of the real hand towards the rubber hand (‘proprioceptive drift’). Asynchronous stroking typically attenuates the RHI. ResultsThe effect of PD on illusory experience depended on the stroking condition (b = −2.15, 95% CI [−3.06, −1.25], p < .0001): patients scored questionnaire items eliciting the RHI experience higher than controls in the illusion-attenuating (asynchronous) condition, but not in the illusion-promoting (synchronous) condition. PD, independent of stroking condition, predicted greater proprioceptive drift (b = 15.05, 95% CI [6.05, 24.05], p = .0022); the longer the disease duration, the greater the proprioceptive drift. However, the RHI did not affect subsequent reaching actions. On-medication patients scored both illusion (critical) and mock (control) questionnaire items higher than when off-medication, an effect that increased with disease severity (log (OR) =.014, 95% CI [.01, .02], p < .0001). ConclusionPD affects illusory perceptions of body ownership in situations that do not typically induce them, implicating dopamine deficit and consequent alterations in cortico-basal ganglia-thalamic circuitry in multisensory integration. Dopaminergic treatment appears to increase suggestibility generally rather than having a specific effect on own-body illusions, a novel finding with clinical and research implications.

オクターブ錯聴における錯聴・非/不完全錯聴のfMRIによる検討

オクターブ錯聴における錯聴・非/不完全錯聴のfMRIによる検討

Seeing Inscriptions on the Shroud of Turin: The Role of Psychological Influences in the Perception of Writing

The Shroud of Turin (hereafter the Shroud) is one of the most widely known and widely studied artifacts in existence, with enormous historical and religious significance. For years, the Shroud has inspired worldwide interest in images on its fabric which appear to be of the body and face of a man executed in a manner consistent with crucifixion, and many believe that these images were formed in the Shroud’s fibers during the Resurrection of Jesus of Nazareth. But, more recently, other reports have suggested that the Shroud also contains evidence of inscriptions, and these reports have been used to add crucial support to the view that the Shroud is the burial cloth of Jesus. Unfortunately, these reports of inscriptions are based on marks that are barely visible on the Shroud, even when images are enhanced, and the actual existence of writing on the Shroud is still a matter of considerable debate. Here we discuss previous evidence concerning the psychological processes involved generally in the perception of writing, and especially when letters and words are indistinct. We then report two experiments in which the influence of religious context on perception of inscriptions was addressed specifically, using an image of woven fabric (modern linen) containing no writing and with no religious provenance. This image was viewed in two different contexts: in the Religious Context, participants were informed that the image was of a linen artifact that was important to the Christian faith whereas, in the non-religious Neutral Context, participants were informed that the image was of a simple piece of linen. Both groups were told that the image may contain faint words and were asked to report any words they could see. All participants detected words on the image, and indicated that these words were visible and were able to trace on the image the words they detected. In each experiment, more religious words were detected in the Religious Context condition than in the Neutral Context condition whereas the two contexts showed no effect on the number of non-religious words detected, indicating that religious context had a specific effect on the perception of illusory writing. Indeed, in the Neutral Context condition, no religious words at all were reported in either experiment. These findings suggest that images of woven material, like linen, inspire illusory perceptions of writing and that the nature of these perceptions is influenced considerably by the religious expectations of observers. As a consequence, the normal psychological processes underlying perception of writing, and the tendency of these processes to produce illusory perceptions, should be an essential consideration when addressing the existence of religious inscriptions on religious artifacts such as the Shroud of Turin.

Specific activation of operculum 3 (OP3) brain region during provoked tinnitus-related phantom auditory perceptions in humans.

The phantom sound perception mechanism by which a sound perception occurs without any external sound source is still enigmatic. According to our previous fMRI study, a small region in the parietal operculum 3 was hyperactivated as a function of tinnitus periodicity in subjects with acoustic trauma tinnitus sequelae. This region was localized in the vicinity of neural correlates of middle-ear tympano-ossicular chain movements due to pressure variations. Disturbed proprioceptors are known to trigger illusory perceptions; therefore, we hypothesized that a disturbance of middle-ear proprioceptors may originate phantom sound perceptions. We designed an fMRI study that aimed to stimulate middle-ear proprioceptors by repetitive vibrations using various rates of click trains. In this study, we report that exposure to specific rates of stimuli for a few minutes at comfortable intensity level in healthy subjects distinctly triggered transient tinnitus-like aftereffects. The fMRI neural correlates of the aftereffects were unequivocally localized in the same parietal region as in acoustic trauma tinnitus sufferers. Our results strongly suggest that a middle-ear kinesthetic/proprioceptive illusion exists at the origin of acoustic trauma tinnitus via a somatosensory pathway encompassing the trigeminal system.

Experts in Offside Decision Making Learn to Compensate for Their Illusory Perceptions

In association football, the flash-lag effect appears to be a viable explanation for erroneous offside decision making. Due to this spatiotemporal illusion, assistant referees (ARs) perceive the player who receives the ball ahead of his real position. In this experiment, a laboratory decision-making task was used to demonstrate that international top-class ARs, compared with amateur soccer players, do not have superior perceptual sensitivity. They clearly modify their decision criterion according to the contextual needs and, therefore, show a higher response bias toward not responding to the stimulus, in particular in the most difficult situations. Thus, international ARs show evidence for response-level compensation, resulting in a specific cost (i.e., more misses), which clearly reflects the use of particular (cognitive) strategies. In summary, it appears that experts in offside decision making can be distinguished from novices more on the cognitive or decision-making level than on the perceptual level.

Cognitive distortions and pathological gambling among Chinese youth

This study overviews Chinese youngsters’ fallacy regarding gambling, compares the illusory perceptions of control over gambling outcomes between problem gamblers and average Chinese youngsters and investigates the extent to which cognitive biases can predict pathological gambling. Scales for assessing irrational beliefs about gambling and tendencies to pathological gambling were administered to 801 Chinese students living in Hong Kong. The results indicate that the perceived intention to obtain desired outcomes, illusory control of the primary type and perceived loss of control over gambling behaviours serve as effective indicators of pathological gambling. In view of that, intervention strategies that zero in on cognitive distortions can constitute a pertinent approach for treating local problem gamblers.

Prestimulus Beta Power and Phase Synchrony Influence the Sound-Induced Flash Illusion

We investigated the sound-induced flash illusion, an example for the influence of auditory information on visual perception. It consists of the perception of 2 visual stimuli upon the presentation of a single visual stimulus alongside 2 auditory stimuli. We used magnetoencephalography to assess the influence of prestimulus oscillatory activity on varying the perception of invariant stimuli. We compared cortical activity from trials in which subjects perceived an illusion with trials in which subjects did not perceive the illusion, keeping the stimulation fixed. Subjects perceived the illusion in approximately 50% of trials. Prior to the illusion, we found stronger beta-band power in left temporal sensors, localized to the left middle temporal gyrus. Illusory perceptions were preceded by increased beta-band phase synchrony between the left middle temporal gyrus and auditory areas as well as by decreased phase synchrony with visual areas. Alpha-band phase synchrony between visual and temporal, parietal, and frontal cortical areas as well as alpha-band phase synchrony between auditory and visual areas were modulated. This supports and extends reports on the influence of brain states prior to stimulation on subsequent perception. We suggest that prestimulus local and network activities form predispositions if sensory streams will be integrated.

Basic points of the Antropic Attitude Theory

The reason for the introduction of the concept of attitude was the explanation of illusory perceptions. On the basis of experimental studies D. Uznadze demonstrated that the illusions of perception are connected not solely to the motor activity sphere. It can appear in every modality of perception. J. Piaget called the phenomenon identified in the above-mentioned method “the Uznadze effect” and used it for the characterization of specific stages of the development of intellect.Social attitude, in addition to the unprejudiced objective reality, implies disposition towards other people, social environment. Attitudes, besides differing by the content and components that are depicted in them, differ from each other by ways of formation.Characterization of social attitudes is performed according to what disposition exists towards the social values expressed through them. Its peculiarities are measured on a number scale. For this purpose we use an 11-point scale. On this scale, attitude is characterized by: valency – positive-negative disposition for social values; valency intensity – how more intensive is attitude valency according to positivity and negativity; the zone of acceptance, which expresses the intensity of attitudes acceptable for a person; the zone of toleration – a zone of the intensity of attitudes, which can be tolerated by a person; sharpness-diffusivity attitude, which shows by how many steps can the attitude of a person be characterized, etc.On the human being level of psyche development, conscious, cognitive, and moral behaviors emerge. Attitudes are actively involved in these processes as well. At the highest level of psyche development, the activity of a human being is determined by social attitudes.