Experimental phenomenology has demonstrated that perception is much richer than stimulus. As is seen in color perception, one and the same stimulus provides more than several modes of appearance or perceptual dimensions. Similarly, there are various perceptual dimensions in form perception. Even a simple geometrical figure inducing visual illusion gives not only perceptual impressions of size, shape, slant, depth, and orientation, but also affective or aesthetic impressions. The present study reviews our experimental phenomenological work on visual (...) class='Hi'>illusion and experimental aesthetics, and examines how aesthetic preference is influenced by stimulus factors determining visual illusions including anomalous surface and transparency as well as geometrical illusion. Along with line figures producing geometrical illusions, illusory surface figures inducing neon color spreading and transparency effects were used as test patterns. Participants made both of psychophysical judgments and of aesthetic judgments for the same test pattern. Both of geometrical illusions and aesthetic preferences were found to change similarly as a function of stimulus variables such as the number of filling lines and the size ratio of the inner and outer figural components. Also, following specific stimulus variables such as lightness contrast ratio and spatial interval between inducing figural elements (so called ``packmen''), strong effects of color spreading and transparency were accompanied with strong preferences. It seems that the paradigm to investigate aesthetic phenomena along with perceptual dimensions is useful to bridge the gap between experimental phenomenology and experimental aesthetics. (shrink)

Direct realism in one form or another is gaining traction as an approach to perception. With the hope of bolstering such positions, we offer a framework upon which to base an argument for direct realism in matters of perception. Better yet, we offer an empirically supported framework. The framework on offer is that of ecological psychology. With the framework in place, we then discuss how it can address visual illusions, one of the major challenges facing proponents of direct realism.

Visual illusions provide important evidence for the co-existence of unconscious and conscious representations. Objects surrounded by other figures are consciously perceived as different in size, while the visuo-motor system supposedly uses an unconscious representation of the discs’ true size for grip size scaling. Recent evidence suggests other factors than represented size, e.g., surrounding rings conceived as obstacles, affect grip size. Use of the diagonal illusion avoids visual obstacles in the path of the reaching hand. Results support the (...) dual representation theory. Grip size scaling follows actual size independent of illusory effects, which clearly bias conscious perception in direct comparisons of lengths and in finger-thumb span indications of perceived length. (shrink)

In the reported, experiment participants hit a ball to aim at the vertex of a Müller–Lyer configuration. This configuration either remained stable, changed its shaft length or the orientation of the tails during movement execution. A significant illusion bias was observed in all perturbation conditions, but not in the stationary condition. The illusion bias emerged for perturbations shortly after movement onset and for perturbations during execution, the latter of which allowed only a minimum of time for making adjustments (...) . These findings indicate that allocentric information is exploited for online control when people make rapid adjustments in response to a sudden change in the environment and not when people guide their limb movements to interact with a stable environment. (shrink)

Some data concerning visual illusions are hardly compatible with the perception–action model, assuming that only the perception system is influenced by visual context. The planning–control dichotomy offers an alternative that better accounts for some controversy in experimental data. We tested the two models by submitting the patient I. G. to the induced Roelofs effect. The similitude of the results of I. G. and control subjects favoured Glover's model, which, however, presents a paradox that needs to be clarified.

Why have core knowledge? Standard answers typically emphasize the difficulty of learning core knowledge from experience, or the benefits it confers for learning about the world. Here, we suggest a complementary reason: Core knowledge is critical for learning not just about the external world, but about the mind itself.

A simple experimental paradigm creates the powerful illusion that one is touching one’s own hand even when the two hands are separated by 15 cm. The participant uses her right hand to administer stimulation to a prosthetic hand while the Examiner provides identical stimulation to the participant’s receptive left hand. Change in felt position of the receptive hand toward the prosthetic hand has previously led to the interpretation that the participant experiences self-touch at the location of the prosthetic hand, (...) and experiences a sense of ownership of the prosthetic hand. Our results argue against this interpretation. We assessed change in felt position of the participant’s receptive hand but we also assessed change in felt position of the participant’s administering hand. Change in felt position of the administering hand was significantly greater than change in felt position of the receptive hand. Implications for theories of ownership are discussed. (shrink)

A simple experimental paradigm creates the powerful illusion that one is touching one’s own hand even when the two hands are separated by 15 cm. The participant uses her right hand to administer stimulation to a prosthetic hand while the Examiner provides identical stimulation to the participant’s receptive left hand. Change in felt position of the receptive hand toward the prosthetic hand has previously led to the interpretation that the participant experiences self-touch at the location of the prosthetic hand, (...) and experiences a sense of ownership of the prosthetic hand. Our results argue against this interpretation. We assessed change in felt position of the participant’s receptive hand but we also assessed change in felt position of the participant’s administering hand. Change in felt position of the administering hand was significantly greater than change in felt position of the receptive hand. Implications for theories of ownership are discussed. (shrink)

A fundamental question in the psychological sciences is the degree to which culture shapes core cognitive processes — perhaps none more foundational than how we perceive the world around us. A dramatic and oft-cited “case study” of culture’s power in this regard is the Müller-Lyer illusion, which depicts two lines of equal length but with arrowheads pointing either inward or outward, creating the illusion that one line is longer than the other. According to a line of research stretching (...) back over a century, depending on the society you were raised in (and how much carpentry you were exposed to), you may not see the illusion at all — an ambitious and influential research program motivating claims that seemingly basic aspects of visual processing may actually be “culturally evolved byproducts”. This Cultural Byproduct Hypothesis bears on foundational issues in the science, philosophy, and sociology of psychology, and remains popular today. Yet, here we argue that it is almost certainly false. We synthesize evidence from diverse fields which demonstrate that: (1) the illusion is not limited to humans, appearing in non-human animals from diverse ecologies; (2) the statistics of natural scenes are sufficient to capture the illusion; (3) the illusion does not require straight lines typical of carpentry (nor even any lines at all); (4) the illusion arises in sense modalities other than vision; and (5) the illusion arises even in congenitally blind subjects. Moreover, by reexamining historical data and ethnographic descriptions from the original case studies, we show that the evidence for cultural variation and its correlation with key cultural variables is in fact highly inconsistent, beset by questionable research practices, and misreported by later discussions. Together, these considerations undermine the most popular and dramatic example of cultural influence on perception. We further extend our case beyond this phenomenon, showing that many of these considerations apply to other visual illusions as well, including similarly implicated visual phenomena such as the Ebbinghaus, Ponzo, Poggendorf, and Horizontal-Vertical illusions. We conclude by outlining future approaches to cross-cultural research on perception, and we also point to other potential sources of cultural variation in visual processing. (shrink)

We often feel that our perceptual experience is richer than what we can express. For instance, when flashed with a large set of letters, we feel that we can see them all, while we can report only a few. However, the nature of this subjective impression remains highly debated: while many favour a dissociation between two forms of consciousness , others contend that the richness of phenomenal experience is a mere illusion. Here we addressed this question with a classical (...) partial-report paradigm now modified to include unexpected items in the unreported parts of the stimuli. We show that even in the presence of unexpected pseudo-letters, participants still felt that there were only letters. Additionally, we show that this feeling reflects an illusion whereby participants reconstruct letters using partial letter-like information. We propose that the feeling of seeing emerges from the interplay between partially accessible information and expectations. (shrink)

In this paper I explore a brand of scepticism about perceptual experience that takes its start from recent work in psychology and philosophy of mind on change blindness and related phenomena. I argue that the new scepticism rests on a problematic phenomenology of perceptual experience. I then consider a strengthened version of the sceptical challenge that seems to be immune to this criticism. This strengthened sceptical challenge formulates what I call the problem of perceptual presence. I show how this problem (...) can be addressed by drawing on an enactive or sensorimotor approach to perceptual consciousness. Our experience of environmental detail consists in our access to that detail thanks to our possession of practical knowledge of the way in which what we do and sensory stimulation depend on each other. (shrink)

The question of whether the visual world is a grand illusion is addressed and answered negatively. The question only arises because of the recent work on Inattentional Blindness , Change Blindness and the Attentional Blink which establishes that attention is necessary for perception. It is argued that IB occurs only when attention is narrowly focussed and not when attention is more broadly distributed, which is the more typical attentional state. Under conditions of distributed attention we are likely to (...) have a fuller, if less detailed, impression of the visual scene, which may be why we are so surprised by demonstrations of IB, AB and CB. It is also argued that the question about the possible illusory quality of our perceptual world cannot be avoided by denying that inattention causes blindness and asserting instead that it causes amnesia. This argument is grounded on the similarity between these phenomena and visual neglect and by evidence that priming by the unseen stimuli occurs in each case indicating that the stimuli to which we are functionally blind are processed and represented in implicit memory. The adaptive utility of this information is discussed. (shrink)

Investigating perceptual and cognitive abilities of zoo animals might help to improve their husbandry and enrich their daily life with new stimuli. Developing new environmental enrichment programs and devices is hence necessary to promote species-specific behaviours that need to be maintained in controlled environments. As far as we are aware, no study has ever tested the potential benefits of motion illusions as visual enrichment for zoo animals. Starting from a recent study showing that domestic cats are spontaneously attracted by (...) a well-known motion illusion, the Rotating Snake (RS) illusion, we studied whether this illusion could be used as a visual enrichment for big cats. We observed the spontaneous behaviour of three lionesses when three different visual stimuli were placed in their environment: the RS illusion and two control stimuli. The study involved two different periods: the baseline and the RS period, in which the visual stimuli were provided to the lionesses. To assess whether the lionesses were specifically attracted by the RS illusion, we collected data on the number of interactions with the stimuli, as well as on the total time spent interacting with them. To investigate the effect of the illusion on the animals’ welfare, individual and social behaviours were studied and compared between the two periods. The results showed that two lionesses out of three interacted more with the RS stimulus than with the two control stimuli. The fact that the lionesses seemed to be more inclined to interact with the RS stimulus indirectly suggests the intriguing possibility that they were attracted by the illusory motion. Moreover, behavioural changes between the two periods were reported for one of the lionesses, highlighting a reduction in self-directed behaviours and an increase in attentive behaviours, suggesting positive welfare implications. Thus, behavioural observations made before and during the presentation of the stimuli showed that our visual enrichment actually provided positive effects in lionesses. These results call for the development of future studies on the use of visual illusions in the enrichment programs of zoo animals. (shrink)

This paper questions two prima facie plausible claims concerning switching in the presence of ambiguous figures. The first is the claim that reversing is an instantaneous process. The second is the claim that the ability to reverse demonstrates the interpretive, inferential and constructive nature of visual processing. Empirical studies show that optical and cerebral events related to switching protract in time in a way that clashes with its perceived instantaneity. The studies further suggest an alternative theory of reversing: according (...) to such alternative, seeing the same thing in multiple ways is a matter of uncovering what is already present to the senses through visual search. (shrink)

Berkeley and Helmholtz proposed different indirect mechanisms for size perception: Berkeley, that size was conditioned to various cues, independently of perceived distance; Helmholtz, that it was unconsciously calculated from angular size and perceived distance. The geometrical approach cannot explain size-distance paradoxes (e.g., moon illusion). The dorsal/ventral solution is dubious for close displays and untestable for far displays.

Jerry Fodor has consistently cited the persistence of illusions--especially the M.

Perceived size is a function of viewing distance, retinal images size, and various contextual cues such as linear perspective and the size and location of neighboring objects. Recently, we demonstrated that illusion magnitudes of classic visual size illusions may be greatly enhanced or reduced by adding dynamic elements. Specifically, a dynamic version of the Ebbinghaus illusion (classically considered a “size contrast” illusion) led to a greatly enhanced illusory effect, whereas a dynamic version of the Corridor (...) class='Hi'>illusion (a “size constancy” illusion) led to a greatly diminished illusory effect. Although these differences may arise from the different processes underlying these illusions (size contrast vs. size constancy), the dynamic variants we tested in our previous work also differed in the nature of the dynamic elements; specifically, whereas the Dynamic Ebbinghaus included a moving target and inducers that changed size and position, the Dynamic Corridor only included a moving target on a static background. Here, we explore further dynamic versions of the Ebbinghaus illusion and the Corridor and Ponzo illusions by separately manipulating three types of dynamic elements: target motion, context translation, and dynamic changes in context. Across five experiments examining 21 dynamic illusory configurations, adding target motion or a dynamically changing context separately resulted in little-to-no illusory effect. In contrast, the combination of target motion and a dynamically changing context led to a robust size illusion, consistent with an interactive effect. However, illusory effects that exceeded the matched classic, static illusory configuration were only observed for the dynamic versions of the Ebbinghaus illusion and the Revealed Ponzo illusions, in which the contextual elements changed size. We conclude that the combination of target motion and a dynamically changing context are necessary to produce dynamic size illusions, but that enhancement above and beyond static illusions may be largely specific to size contrast effects. Our results have important implications for the integration of motion signals, a ubiquitous environmental stimulus, in the perception of object size. (shrink)

I argue that we sometimes visually perceive the intentions of others. Just as we can see something as blue or as moving to the left, so too can we see someone as intending to evade detection or as aiming to traverse a physical obstacle. I consider the typical subject presented with the Heider and Simmel movie, a widely studied ‘animacy’ stimulus, and I argue that this subject mentally attributes proximal intentions to some of the objects in the movie. I further (...) argue that these attributions are unrevisable in a certain sense and that this result can be used to as part of an argument that these attributions are not post-perceptual thoughts. Finally, I suggest that if these attributions are visual experiences, and more particularly visual illusions, their unrevisability can be satisfyingly explained, by appealing to the mechanisms which underlie visual illusions more generally. (shrink)

David Milner and Melvyn Goodale, and the many psychologists and philosophers who have been influenced by their work, claim that ‘the visual system that gives us our visual experience of the world is not the same system that guides our movements in the world’. The arguments that have been offered for this surprising claim place considerable weight on two sources of evidence — visual form agnosia and the reaching behaviour of normal subjects when picking up objects that (...) induce visual illusions. The present article shows that, if we are careful to consider the possibility that a demonstrative gesture can contribute content to a conscious experience, then neither source of evidence is compelling. (shrink)

There is a traditional scepticism about whether the world "out there" really is as we perceive it. A new breed of hyper-sceptics now challenges whether we even have the perceptual experience we think we have. According to these writers, perceptual consciousness is a kind of false consciousness. This view grows out of the discovery of such phenomena as change blindness and inattentional blindness, which show that we can all be quite blind to changes taking place before our very eyes. Such (...) radical scepticism has acute and widespread implications for the study of perception and consciousness. The writings collected in this volume explore these implications. The contributors are scientists and philosophers at the forefront of this research, and include well-known authors such as psychologists Susan Blackmore and Arien Mack, and philosophers Andy Clark and Daniel Dennett. They have an gift for bringing these paradoxical issues to life and sharing their excitement with the non-specialist. (shrink)

A cluster of experiments on “Change Blindness”, “Inattentional Blindness” and associated phenomena appear to demonstrate extremely counter intuitive results. According to one plausible characterisation, these results show that we consciously take in far less of the visual world than it seems we are aware of. It is worth briefly summarising the results of two recent sets of experiments, in order to give a flavour of this work. In ‘Gorillas in our Midst’ (Simons, D. and Chabris, C., Perception, 1999, 28), (...) subjects were asked to perform a task that involved watching a video of a casual basketball game that lasts for about a minute. The task involves counting the number of consecutive passes between members of the one of the teams. While the basketball is being thrown from player to player, something unexpected takes place: a person dressed in a black gorilla-suit walks through the play, stops briefly in the centre of the picture, thumps his chest, and then walks off. Although most subjects correctly record the number of passes made by the team, at least half of these subjects fail to notice the gorilla-suited interloper, who is visible for about nine seconds. When shown the video sequence a second time they are amazed to observe what they had previously overlooked. (shrink)

The purpose of this paper is to defend what I call the action-oriented coding theory (ACT) of spatially contentful visual experience. Integral to ACT is the view that conscious visual experience and visually guided action make use of a common subject-relative or 'egocentric' frame of reference. Proponents of the influential two visual systems hypothesis (TVSH), however, have maintained on empirical grounds that this view is false (Milner & Goodale, 1995/2006; Clark, 1999; 2001; Campbell, 2002; Jacob & Jeannerod, (...) 2003; Goodale & Milner, 2004). One main source of evidence for TVSH comes from behavioral studies of the comparative effects of size-contrast illusions on visual awareness and visuo- motor action. This paper shows that not only is the evidence from illusion studies inconclusive, there is a better, ACT-friendly interpretation of the evidence that avoids serious theoretical difficulties faced by TVSH. (shrink)

In recent years, a pair of intriguing phenomena has caused researchers working on vision and visual attention to reevaluate many of their assumptions. These phenomena, which have come to be called change blindness (CB) and inattentional blindness (IB), have led many to the conclusion that ordinary perceivers labor under a ``grand illusion'' concerning perception - an illusion that is..