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Illusory motion and depth of a rotating band. Illustrated are the instants just before and after FAS, with identical spatial distributions but opposite directions of motion. Top row: frontal views with two highlighted example dots (red and green). Middle and bottom rows: top views of the interpolated shapes, resulting from different combinations of illusory motion and illusory depth, again with two highlighted example dots (red and green). The arrows depict spontaneous reversals (green), reversals of illusory depth only (blue, constant illusory motion outcome of FAS), and reversals of illusory rotation only (red, illusory motion reversal outcome of FAS).
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Multiple dots moving independently back and forth on a flat screen induce a compelling illusion of a sphere rotating in depth (structure-from-motion). If all dots simultaneously reverse their direction of motion, two perceptual outcomes are possible: either the illusory rotation reverses as well (and the illusory depth of each dot is maintained), o...
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... Optical illusions have fascinated humans since the ancient times [1][2][3] and served as both object of inspiration in arts [4,5] and paradigmatic topic of research in the fields of psychology and behavioural science [6][7][8][9][10][11][12][13]. Nowadays, when artificial intelligence (AI) is all around, a question arises whether a computer or robotic system can recognise optical illusions similarly to a human. ...
Ambiguous optical illusions have been a paradigmatic object of fascination, research and inspiration in arts, psychology and video games. However, accurate computational models of perception of ambiguous figures have been elusive. In this paper, we design and train a deep neural network model to simulate human perception of the Necker cube, an ambiguous drawing with several alternating possible interpretations. Defining the weights of the neural network connection using a quantum generator of truly random numbers, in agreement with the emerging concepts of quantum artificial intelligence and quantum cognition, we reveal that the actual perceptual state of the Necker cube is a qubit-like superposition of the two fundamental perceptual states predicted by classical theories. Our results finds applications in video games and virtual reality systems employed for training of astronauts and operators of unmanned aerial vehicles. They are also useful for researchers working in the fields of machine learning and vision, psychology of perception and quantum–mechanical models of human mind and decision making.
... For the former, authors have used priming or suppressing effects (usually attributed to adaptation) (Kanai & Verstraten, 2005;Nawrot & Blake, 1989;Joel Pearson & Brascamp, 2008;Joel Pearson & Clifford, 2005), changes in retinal location (Long & Toppino, 2004), manipulation of the type of presentation (continuous-intermittent) (Leopold, Wilke, Maier, & Logothetis, 2002;Orbach, Ehrlich, & Heath, 1963), and direct manipulation of the properties of the stimulus, such as the intensity (Lynn, 1961) and completeness (Babich & Standing, 1981). In contrast, studies of high-level manipulations have focused on the effects of volition (Toppino, 2003;Van Ee, Van Dam, & Brouwer, 2005), expectation and prediction (Denison, Piazza, & Silver, 2011), attention (Chong & Blake, 2006;Dieter & Tadin, 2011;Stonkute, Braun, & Pastukhov, 2012), learning (Haijiang, Saunders, Stone, & Backus, 2006), mental imagery (Pearson, Clifford, & Tong, 2008), knowledge of reversibility (Rock, Hall, & Davis, 1994), and finally the preference for stimuli with a statistical structure similar to natural images (Baker & Graf, 2009;Dobbins & Grossmann, 2010;Zhou, Zhang, Liu, Yang, & Qu, 2010). However, the present study was not designed to test specific neural mechanisms, such as adaptation and noise. ...
When facing ambiguous images, the brain switches between mutually exclusive interpretations, a phenomenon known as bistable perception. Despite years of research, a consensus on whether bistability is driven primarily by bottom-up or top-down mechanisms has not been achieved. Here, we adopted a Bayesian approach to reconcile these two theories. Fifty-five healthy participants were exposed to an adaptation of the Necker cube paradigm, in which we manipulated sensory evidence and prior knowledge. Manipulations of both sensory evidence and priors significantly affected the way participants perceived the Necker cube. However, we observed an interaction between the effect of the cue and the effect of the instructions, a finding that is incompatible with Bayes-optimal integration. In contrast, the data were well predicted by a circular inference model. In this model, ambiguous sensory evidence is systematically biased in the direction of current expectations, ultimately resulting in a bistable percept.
... For the former, authors have used priming or suppressing effects (usually attributed to adaptation) [31][32][33][34], changes in retinal location [35], manipulation of the type of presentation (continuous-intermittent) [36,37], and direct manipulation of the properties of the stimulus, like intensity [38] and completeness [39]. In contrast, studies of high-level manipulations have focused on the effects of volition [40,41], expectation and prediction [42], attention [43][44][45], learning [46], mental imagery [47], knowledge of reversibility [48] and finally the preference for stimuli with a statistical structure similar to that of natural images [8,49,50]. Note however that the present study was not designed to test specific neural mechanisms such as adaptation and noise. ...
When facing fully ambiguous images, the brain cannot commit to a single percept and instead switches between mutually exclusive interpretations every few seconds, a phenomenon known as bistable perception. Despite years of research, there is still no consensus on whether bistability, and perception in general, is driven primarily by bottom-up or top-down mechanisms. Here, we adopted a Bayesian approach in an effort to reconcile these two theories. Fifty-five healthy participants were exposed to an adaptation of the Necker cube paradigm, in which we manipulated sensory evidence (by shadowing the cube) and prior knowledge (e.g., by varying instructions about what participants should expect to see). We found that manipulations of both sensory evidence and priors significantly affected the way participants perceived the Necker cube. However, we observed an interaction between the effect of the cue and the effect of the instructions, a finding incompatible with Bayes-optimal integration. In contrast, the data were well predicted by a circular inference model. In this model, ambiguous sensory evidence is systematically biased in the direction of current expectations, ultimately resulting in a bistable percept.
... First, attention may act as a modulatory influence that alters the dynamics of bistable perception. This manifests, for example, as changes in the rate of perceptual alternation (Alais et al., 2010;Kohler et al., 2008;Kornmeier, Hein, & Bach, 2009;Lack, 1978;Paffen et al., 2006;Pastukhov & Braun, 2007;Reisberg & O'Shaughnessy, 1984;Schölvinck & Rees, 2009;Stonkute et al., 2012;Suzuki & Grabowecky, 2007), or as a bias in perception in favor of an attended perspective (Chong, Tadin, & Blake, 2005;Dieter, Melnick, & Tadin, 2015;Hol, Koene, & van Ee, 2003;Meng & Tong, 2004;Mitchell, Stoner, & Reynolds, 2004;Ooi & He, 1999;Suzuki & Peterson, 2000;Toppino, 2003). These modulatory influences of attention on bistable perception have been reviewed previously (Dieter & Tadin, 2011;Paffen & Alais, 2011), and we return to some relevant points later in our essay. ...
... Here, perceptual disappearances were much more likely to be reported on the attended side. These findings suggest slowed dynamics outside of attention, a result that appears to generalize to other bistable figures when partially attended ( Fig. 1; Kohler et al., 2008;Pastukhov & Braun, 2007;Reisberg & O'Shaughnessy, 1984;Stonkute et al., 2012; but see Intaite et al., 2012). Given that slowed dynamics are also observed when BR is tracked as part of a dual-task paradigm (Alais et al., 2010;Paffen et al., 2006), this pattern of results suggests that slowed alternations under conditions of partially diverted attention are a general property shared by BR with other forms of perceptual bistability (Fig. 1). ...
... For one, several studies involving "complete inattention" achieved such conditions for only a few seconds, while bistable stimuli are often viewed for longer durations. In addition, we have already noted that studies utilizing a dual-task approach have found slowing of alternations across many forms of bistability including BR (Alais et al., 2010;Kohler et al., 2008;Paffen et al., 2006;Pastukhov & Braun, 2007;Reisberg & O'Shaughnessy, 1984;Schölvinck & Rees, 2009;Stonkute et al., 2012). Although there is a clear effect of attentional load in dual task conditions, one cannot be certain that attention was entirely diverted from the rival stimulus. ...
How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct—depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences.
... The dots were distributed on the surface of the illusory sphere in such a way as to ensure a specific minimal distance between pairs of left-and rightmoving dots at the time of the on-screen motion inversion (Stonkute et al., 2012). We used four interpair distances to systematically manipulate the strength of the motion transient and, therefore, the probability of successfully induced perceptual reversals. ...
... Conversely, T post ¼ 320 ms was the longest presentation interval, which provided observers with the best opportunity to observe and report a reversal of illusory rotation (T post ¼ 320 ms in Figure 2C). In agreement with prior work (Stonkute et al., 2012), a stronger motion transient due to the on-screen motion inversion produced more frequent switches of illusory rotation: P reversal (S1, 320 ms ...
... both their responses and, presumably, perception are qualitatively and quantitatively similar to that of an unperturbed stable illusory rotation (see Experiment 1). Earlier work showed that exogenously triggered reversals also occur in the (near) absence of attention (Stonkute et al., 2012). Therefore, we can conclude that neither awareness nor attention is necessary for exogenously triggered reversals of perceptual dominance in SFM. ...
Here, we characterize the duration of exogenously triggered perceptual switches in an ambiguously rotating structure-from-motion display and demonstrate their independence on visual awareness. To this end, we triggered a perceptual reversal by inverting the on-screen motion and systematically varied the posttrigger presentation duration, while collecting observers' reports about the initial and final directions of illusory rotation. We demonstrate that for the structure-from-motion display, perceptual transitions are extremely brief (≤20 ms) and can be considered instantaneous from an experimental perspective. We also report that although very brief posttrigger intervals (10-20 ms) reliably initiate a perceptual reversal, observers become aware of perceptual switches only if the posttrigger presentation continues for at least 80 ms. Additional experiments demonstrated that an observed lack of visual awareness for brief posttrigger presentation intervals cannot be attributed to either a systematic delay of visual awareness or to backward masking. Our results show that exogenously triggered perceptual reversal can occur in the absence of visual awareness, extending earlier work on spontaneous reversals that indicated that neither awareness nor attention may be required for multistable perception. Methodologically, the brevity and the short latency of induced perceptual reversals make them particularly suitable for finely timed experiments, such as magneto/electroencephalography studies.
... The display manipulation that is central to the measurement is a sudden inversion of the on-screen motion, schematically illustrated in Fig. 1 (see also Movie 2). It provides a transient signal for the change in motion, irrespective of which illusory rotation is currently dominant (Pastukhov, Vonau, & Braun, 2012;Stonkute, Braun, & Pastukhov, 2012). In contrast to some other methods that trigger perceptual reversals by temporarily biasing the display in favor of the suppressed percept (e.g. using stereoscopic depth for SFM or relative contrast for binocular rivalry (Blake, Westendorf, & Fox, 1990)), this method does not introduce any state-specific bias, since the onscreen motion before and after the reversal is ambiguous in a balanced way. ...
... The structure-from-motion (SFM, (Sperling & Dosher, 1994)) display consisted of 50 dots (see Movies 1-2). Dots were distributed pseudo-randomly over the surface of an illusory sphere in such a way as to ensure maximal distance between each left-moving dot and the nearest rightmoving dot and vice versa (see (Stonkute et al., 2012) for details). The diameter of the sphere was 5° and the rotation rate was 0.2 Hz. ...
... In the former case, the ambiguously rotating sphere was presented for a variable amount of time (T pre [20, 40, 80, 160, 320] ms) before the on-screen motion was inversed and the presentation continued unperturbed for another 320 ms (i.e. total presentation duration T on =T pre +T post [340, 360, 400, 480, 600] ms, see Fig. 2B and Movie 2). The purpose of the on-screen motion inversion was to induce a reversal in the direction of illusory rotation, see above Stonkute et al., 2012). As during the biasing sequence, observers reported the dominant direction of illusory rotation at the end of the presentation interval (D test ). ...
We investigated the relation between perception and sensory memory of multi-stable structure-from-motion displays. The latter is an implicit visual memory that reflects a recent history of perceptual dominance and influences only the initial perception of multi-stable displays. First, we established the earliest time point when the direction of an illusory rotation can be reversed after the display onset (29–114 ms). Because our display manipulation did not bias perception towards a specific direction of illusory rotation but only signaled the change in motion, this means that the perceptual dominance was established no later than 29–114 ms after the stimulus onset. Second, we used orientation-selectivity of sensory memory to establish which display orientation produced the strongest memory trace and when this orientation was presented during the preceding prime interval (80–140 ms). Surprisingly, both estimates point towards the time interval immediately after the display onset, indicating that both perception and sensory memory form at approximately the same time. This suggests a tighter integration between perception and sensory memory than previously thought, warrants a reconsideration of its role in visual perception, and indicates that sensory memory could be a unique behavioral correlate of the earlier perceptual inference that can be studied post hoc.
... Next, we considered whether repetition priming of transformations can be explained by selective attention. To this end, we reanalyzed the data of (Stonkute, Braun, & Pastukhov, 2012), where attention was distracted in every trial by a concurrent task at the time of the sudden change in the planar motion of an SFM display (see Figure 6A and (Stonkute et al., 2012) for details). This effectively precluded observers from exerting any sort of volitional control over how they perceived changes in the SFM display in individual trials, also ruling out attention to features/objects, parts/wholes, etc. ...
... Next, we considered whether repetition priming of transformations can be explained by selective attention. To this end, we reanalyzed the data of (Stonkute, Braun, & Pastukhov, 2012), where attention was distracted in every trial by a concurrent task at the time of the sudden change in the planar motion of an SFM display (see Figure 6A and (Stonkute et al., 2012) for details). This effectively precluded observers from exerting any sort of volitional control over how they perceived changes in the SFM display in individual trials, also ruling out attention to features/objects, parts/wholes, etc. ...
... respectively, t(4)=0.2, p= 0.53, paired sample t-test, see Figure 6BC and Experiments 4-5 in (Stonkute et al., 2012)). We conclude that priming of perceptual transformations is not the product of volitional control, nor a bias mediated by selective visual attention. ...
Retinal input is riddled with abrupt transients due to self-motion, changes in illumination, object-motion, etc. Our visual system must correctly interpret each of these changes to keep visual perception consistent and sensitive. This poses an enormous challenge, as many transients are highly ambiguous in that they are consistent with many alternative physical transformations. Here we investigated inter-trial effects in three situations with sudden and ambiguous transients, each presenting two alternative appearances (rotation-reversing structure-from-motion, polarity-reversing shape-from-shading, and streaming-bouncing object collisions). In every situation, we observed priming of transformations as the outcome perceived in earlier trials tended to repeat in subsequent trials and this repetition was contingent on perceptual experience. The observed priming was specific to transformations and did not originate in priming of perceptual states preceding a transient. Moreover, transformation priming was independent of attention and specific to low level stimulus attributes. In summary, we show how “transformation priors” and experience-driven updating of such priors helps to disambiguate sudden changes of sensory inputs. We discuss how dynamic transformation priors can be instantiated as “transition energies” in an “energy landscape” model of the visual perception.
... Non-rigid structure from motion (NRSFM) is the process of recovering the relative camera motion, and the time-varying 3D coordinates of feature points on a deforming object, by means of the corresponding 2D points in a sequence of images. In many cases, the recovered 3D shapes can effectively enhance the performances of existing systems in object recognition, face perception, etc. [1][2][3]. Nevertheless, in the NRSFM model, the objects generally undergo a series of shape deformations and pose variations. Thus, in the absence of necessary prior knowledge on shape deformation, recovering the 3D shape and motion of nonrigid objects from 2D point tracks remains a difficult and ill-posed problem. ...
In recent years, non-rigid structure from motion (NRSFM) has become one of the hottest issues in computer vision due to its wide applications. In practice, the number of available high-quality images may be limited in many cases. Under such a condition, the performances may not be satisfactory when existing NRSFM algorithms are applied directly to estimate the 3D coordinates of a small-size image sequence. In this paper, a sub-sequence-based integrated algorithm is proposed to deal with the NRSFM problem with small sequence sizes. In the proposed method, sub-sequences are first extracted from the original sequence. In order to obtain diversified estimations, multiple weaker estimators are constructed by applying the extracted sub-sequences to a recent NRSFM algorithm with a rotation-invariant kernel (RIK). Compared to other first-order statistics, the trimmed mean is a relatively robust statistic. Considering the fact that the estimations of some weaker estimators may have large errors, the trimmed means of the outputs for all the weaker estimators are computed to determine the final estimated 3D shapes. Compared to some existing methods, the proposed algorithm can achieve a higher estimation accuracy, and has better robustness. Experimental results on several widely used image sequences demonstrate the effectiveness and feasibility of the proposed algorithm.
... Ever since these early debates, the issue of voluntary control of ambiguous stimuli has recurrently attracted the interest of scientists until today (e.g., Washburn and Gillette, 1933;Washburn et al., 1934;Pelton and Solley, 1968;Lack, 1978;Peterson and Hochberg, 1983;Struber and Stadler, 1999;Suzuki and Peterson, 2000;Toppino, 2003;Meng and Tong, 2004;van Ee et al., 2005;Chong et al., 2005;Klink et al., 2008;Hugrass and Crewther, 2012;Stonkute et al., 2012). Among such studies a distinction can be traced between the observers' ability to switch between two alternative percepts and the ability to hold either of the two in visual awareness, as changes in reversal rate can occur without variations in relative dominance of either percept (van Ee et al., 2005). ...
... The discrepancy between the results of Pastukhov and Braun (2007) and Intaitè et al. (2013) and the results of Brascamp and Blake (2012) could be due on one hand to a difference between the types of stimuli inducing the perceptual conflict; on the other hand, the experimental manipulation disrupted visual awareness of the ambiguous stimuli in Brascamp and Blake's, but not in Pastukhov and Braun's nor in Intaitè and colleagues's study. Interestingly, Stonkute et al. (2012) showed that the withdrawal of spatial attention can also produce qualitative changes in the interpretation of a bistable stimulus. The authors studied the impact of sudden inversions of planar flow motion on the perception of ambiguous structurefrom-motion spheres: when all the dots composing the sphere reverse their motion direction, the perceptual outcome could be either an inversion of the illusory depth of each dot, with motion direction being maintained, or an inversion of motion direction, with conservation of illusory depth. ...
The world as it appears to the viewer is the result of a complex process of inference performed by the brain. The validity of this apparently counter-intuitive assertion becomes evident whenever we face noisy, feeble or ambiguous visual stimulation: in these conditions, the state of the observer may play a decisive role in determining what is currently perceived. On this background, ambiguous perception and its amenability to top-down influences can be employed as an empirical paradigm to explore the principles of perception. Here we offer an overview of both classical and recent contributions on how stable and transient states of the observer can impact ambiguous perception. As to the influence of the stable states of the observer, we show that what is currently perceived can be influenced (1) by cognitive and affective aspects, such as meaning, prior knowledge, motivation, and emotional content and (2) by individual differences, such as gender, handedness, genetic inheritance, clinical conditions, and personality traits and by (3) learning and conditioning. As to the impact of transient states of the observer, we outline the effects of (4) attention and (5) voluntary control, which have attracted much empirical work along the history of ambiguous perception. In the huge literature on the topic we trace a difference between the observer's ability to control dominance (i.e., the maintenance of a specific percept in visual awareness) and reversal rate (i.e., the switching between two alternative percepts). Other transient states of the observer that have more recently drawn researchers' attention regard (6) the effects of imagery and visual working memory. (7) Furthermore, we describe the transient effects of prior history of perceptual dominance. (8) Finally, we address the currently available computational models of ambiguous perception and how they can take into account the crucial share played by the state of the observer in perceiving ambiguous displays.
... Lissajous figures were originally studied by means of twin-oscillators and analog cathode ray oscillographs in the 1940s and 1950s (Fisichelli, 1947(Fisichelli, , 1951Fisichelli & Misiak, 1947;Philip, 1953;Philip & Fisichelli, 1945 In contrast to binocular rivalry, perceptual reversals of the Lissajous figure are virtually instantaneous, thus facilitating the construction of a perceptually equivalent ''replay'' condition (Weilnhammer et al., 2013). Similar to other bistable depthfrom-motion stimuli (Pastukhov, Vonau, & Braun, 2012;Stonkute, Braun, & Pastukhov, 2012), the rotating Lissajous figure elicits perceptual transitions only at critical stimulus configurations which are characterized by depth symmetry: during selfocclusions of the figure, the illusory 3D object is symmetrical with respect to the frontal plane. Here, we aimed to investigate how three parameters of the Lissajous figure -complexity, line width, and rotational speed -influence its perceptual dynamics. ...
... We investigated how three stimulus parameters -complexity, line width, and rotational speed -modulate the perceptual dynamics of a bistable rotating Lissajous figure. These parameters are related to the timing and duration of depth-symmetrical selfocclusions of the figure, which have been shown to be critical stimulus configurations for the perceptual transitions of similar bistable depth-from-motion stimuli (Pastukhov, Vonau, & Braun, 2012;Stonkute, Braun, & Pastukhov, 2012). ...
During bistable vision perception spontaneously "switches" between two mutually exclusive percepts despite constant sensory input. The endogenous nature of these perceptual transitions has motivated extensive research aimed at the underlying mechanisms, since spontaneous perceptual transitions of bistable stimuli should in principle allow for a dissociation of processes related to sensory stimulation from those related to conscious perception. However, transitions from one conscious percept to another are often not instantaneous, and participants usually report a considerable amount of mixed or unclear percepts. This feature of bistable vision makes it difficult to isolate transition-related visual processes. Here, we revisited an ambiguous depth-from-motion stimulus which was first introduced to experimental psychology more than 80 years ago. This rotating Lissajous figure might prove useful in complementing other bistable stimuli, since its perceptual transitions only occur at critical stimulus configurations and are virtually instantaneous, thus facilitating the construction of a perceptually equivalent replay condition. We found that three parameters of the Lissajous figure - complexity, line width, and rotational speed - differentially modulated its perceptual dominance durations and transition probabilities, thus providing experimenters with a versatile tool to study the perceptual dynamics of bistable vision.
