Showing papers in "I-perception in 2012"

Components of aesthetic experience: aesthetic fascination, aesthetic appraisal, and aesthetic emotion.

Abstract: In this paper aesthetic experience is defined as an experience qualitatively different from everyday experience and similar to other exceptional states of mind. Three crucial characteristics of aesthetic experience are discussed: fascination with an aesthetic object (high arousal and attention), appraisal of the symbolic reality of an object (high cognitive engagement), and a strong feeling of unity with the object of aesthetic fascination and aesthetic appraisal. In a proposed model, two parallel levels of aesthetic information processing are proposed. On the first level two sub-levels of narrative are processed, story (theme) and symbolism (deeper meanings). The second level includes two sub-levels, perceptual associations (implicit meanings of object's physical features) and detection of compositional regularities. Two sub-levels are defined as crucial for aesthetic experience, appraisal of symbolism and compositional regularities. These sub-levels require some specific cognitive and personality dispositions, such as expertise, creative thinking, and openness to experience. Finally, feedback of emotional processing is included in our model: appraisals of everyday emotions are specified as a matter of narrative content (eg, empathy with characters), whereas the aesthetic emotion is defined as an affective evaluation in the process of symbolism appraisal or the detection of compositional regularities.

The Role of Head Movements and Signal Spectrum in an Auditory Front/Back Illusion:

Abstract: We used a dynamic auditory spatial illusion to investigate the role of self-motion and acoustics in shaping our spatial percept of the environment. Using motion capture, we smoothly moved a sound source around listeners as a function of their own head movements. A lowpass filtered sound behind a listener that moved in the direction it would have moved if it had been located in the front was perceived as statically located in front. The contrariwise effect occurred if the sound was in front but moved as if it were behind. The illusion was strongest for sounds lowpass filtered at 500 Hz and weakened as a function of increasing lowpass cut-off frequency. The signals with the most high frequency energy were often associated with an unstable location percept that flickered from front to back as self-motion cues and spectral cues for location came into conflict with one another.

Crossmodal correspondences: Innate or learned?

Abstract: “Are Chimpanzees synaesthetic?” An affirmative answer to this question appeared recently in a Nature commentary on a study by Ludwig, Adachi, and Matzuzawa (2011) that demonstrated crossmodal correspondences in both chimpanzees and humans. Here we question the claim that chimpanzees are synaesthetic. We also question the claim that certain crossmodal correspondences are innate. We suggest an alternative account for the crossmodal correspondence between auditory pitch and visual lightness in terms of the internalization of correlations present in the environment. We highlight the limitations of such natural correlation approaches to the study of crossmodal correspondences as well as how such claims could potentially be tested in future research.

Using an Oculomotor Signature as an Indicator of Aesthetic Preference

Abstract: Eye movements are strongly influenced by the task given to an observer. The immediacy of such eye movements, which are difficult to control consciously, offers the potential to explore highly variable subjective evaluations, such as aesthetic preference, with reliable objective measures. We presented a variety of images in sets of 2, 4, or 8 items for different durations and analyzed oculomotor statistics such as cumulative fixation duration, refixations, and the sequence of fixations while participants searched for their preferred image, after which participants indicated their preference using a button press. The total amount of time spent looking at any image correlates with selection preference and does so increasingly well with longer presentation duration. For short presentations, the first and last fixations correlate better with image preference. All response measures become increasingly variable as the number and complexity of presented images are increased. A weighted combination of these measures can significantly improve the correlation with preference, suggesting a "signature" which could be used as a reliable indicator for task-free subjective evaluation of stimuli in visual psychophysics. Its role as an improved fitness function in visually driven evolutionary algorithms is discussed.

The cognitive neuroscience of crossmodal correspondences.

Abstract: In a recent article, N. Bien, S. ten Oever, R. Goebel, and A. T. Sack (2012) used event-related potentials to investigate the consequences of crossmodal correspondences (the “natural” mapping of features, or dimensions, of experience across sensory modalities) on the time course of neural information processing. Then, by selectively lesioning the right intraparietal cortex using transcranial magnetic stimulation, these researchers went on to demonstrate (for the first time) that it is possible to temporarily eliminate the effect of crossmodal congruency on multisensory integration (specifically on the spatial ventriloquism effect). These results are especially exciting given the possibility that the cognitive neuroscience methodology utilized by Bien et al. (2012) holds for dissociating between putatively different kinds of crossmodal correspondence in future research.

A comparison of two theories of perceived distance on the ground plane: The angular expansion hypothesis and the intrinsic bias hypothesis

Abstract: Two theories of distance perception—ie, the angular expansion hypothesis (Durgin and Li, 2011 Attention, Perception, & Psychophysics 73 1856-1870) and the intrinsic bias hypothesis (Ooi et al, 2006 Perception 35 605-624)—are compared. Both theories attribute exocentric distance foreshortening to an exaggeration in perceived slant, but their fundamental geometrical assumptions are very different. The intrinsic bias hypothesis assumes a constant bias in perceived geographical slant of the ground plane and predicts both perceived egocentric and exocentric distances are increasingly compressed. In contrast, the angular expansion hypothesis assumes exaggerations in perceived gaze angle and perceived optical slant. Because the bias functions of the two angular variables are different, it allows the angular expansion hypothesis to distinguish two types of distance foreshortening—the linear compression in perceived egocentric distance and the nonlinear compres- sion in perceived exocentric distance. While the intrinsic bias is proposed only for explaining distance biases, the angular expansion hypothesis provides accounts for a broader range of spatial biases.

Effects of memory colour on colour constancy for unknown coloured objects.

Abstract: The perception of an object's colour remains constant despite large variations in the chromaticity of the illumination-colour constancy. Hering suggested that memory colours, the typical colours of objects, could help in estimating the illuminant's colour and therefore be an important factor in establishing colour constancy. Here we test whether the presence of objects with diagnostical colours (fruits, vegetables, etc) within a scene influence colour constancy for unknown coloured objects in the scene. Subjects matched one of four Munsell papers placed in a scene illuminated under either a reddish or a greenish lamp with the Munsell book of colour illuminated by a neutral lamp. The Munsell papers were embedded in four different scenes-one scene containing diagnostically coloured objects, one scene containing incongruent coloured objects, a third scene with geometrical objects of the same colour as the diagnostically coloured objects, and one scene containing non-diagnostically coloured objects (eg, a yellow coffee mug). All objects were placed against a black background. Colour constancy was on average significantly higher for the scene containing the diagnostically coloured objects compared with the other scenes tested. We conclude that the colours of familiar objects help in obtaining colour constancy for unknown objects.

Artful terms: A study on aesthetic word usage for visual art versus film and music

Abstract: Despite the importance of the arts in human life, psychologists still know relatively little about what characterises their experience for the recipient. The current research approaches this problem by studying people's word usage in aesthetics, with a focus on three important art forms: visual art, film, and music. The starting point was a list of 77 words known to be useful to describe aesthetic impressions of visual art (Augustin et al 2012, Acta Psychologica 139 187–201). Focusing on ratings of likelihood of use, we examined to what extent word usage in aesthetic descriptions of visual art can be generalised to film and music. The results support the claim of an interplay of generality and specificity in aesthetic word usage. Terms with equal likelihood of use for all art forms included beautiful, wonderful, and terms denoting originality. Importantly, emotion-related words received higher ratings for film and music than for visual art. To our knowledge this is direct evidence that aesthetic experiences of visual art may be less affectively loaded than, for example, experiences of music. The results render important information about aesthetic word usage in the realm of the arts and may serve as a starting point to develop tailored measurement instruments for different art forms.

Perception while watching movies: Effects of physical screen size and scene type

Abstract: Over the last decade, television screens and display monitors have increased in size considerably, but has this improved our televisual experience? Our working hypothesis was that the audiences adopt a general strategy that “bigger is better.” However, as our visual perceptions do not tap directly into basic retinal image properties such as retinal image size (C. A. Burbeck, 1987), we wondered whether object size itself might be an important factor. To test this, we needed a task that would tap into the subjective experiences of participants watching a movie on different-sized displays with the same retinal subtense. Our participants used a line bisection task to self-report their level of “presence” (i.e., their involvement with the movie) at several target locations that were probed in a 45-min section of the movie “The Good, The Bad, and The Ugly.” Measures of pupil dilation and reaction time to the probes were also obtained. In Experiment 1, we found that subjective ratings of presence increased with physical screen size, supporting our hypothesis. Face scenes also produced higher presence scores than landscape scenes for both screen sizes. In Experiment 2, reaction time and pupil dilation results showed the same trends as the presence ratings and pupil dilation correlated with presence ratings, providing some validation of the method. Overall, the results suggest that real-time measures of subjective presence might be a valuable tool for measuring audience experience for different types of (i) display and (ii) audiovisual material.

The same old New Look: Publication bias in a study of wishful seeing.

Abstract: A recent study reported evidence of “wishful seeing,” where observers reported seeing a desired object as being closer than other objects. A statistical analysis of the experimental findings reveals evidence of publication bias in the study, so the existence of wishful seeing remains unproven.

Luminance distribution modifies the perceived freshness of strawberries.

Abstract: Material perception studies focus on the analysis of visual cues that may underlie the ability to distinguish between the different properties of an object. Herein, we investigated the effects of luminance distribution on the perceived freshness of a strawberry independent from its colour information. We took photographs of the degradation of a strawberry over 169 hours in a controlled environment, then presented cropped square patches of the original images to subjects who then rated the perceived freshness using a visual analogue scale. Freshness ratings were significantly highly correlated with statistical measures of the luminance and colour channels. To clarify which of these visual cues affects freshness perception, we created artificial images by modifying only the luminance distribution and keeping the colour information unchanged. The modification of luminance resulted in a highly correlated change in freshness perception, suggesting that luminance visual cues are essential to the freshness perception of strawberries. Finally, by eliminating the colour information from the images, we examined the contribution of luminance distribution independent of colour information and found that luminance information suffices for accurate estimation of strawberry freshness.

Aesthetic Preference for Spatial Composition in Multiobject Pictures

Abstract: Five experiments examined preferences for horizontal positions in multiobject pictures. In Experiment 1, each picture contained a fixed object and an object whose position could be adjusted to create the most (or least) aesthetically pleasing image. Observers placed the movable object closer to the fixed object when the objects were related than when they were unrelated (a relatedness bias) but almost never overlapped them (a separation bias). Experiment 2 showed that these results were not due to demand characteristics by replicating them almost exactly in a between-participants design. In Experiment 3, preference rankings revealed a strong relatedness bias together with an inward bias toward the spatial envelope of objects to point into the frame. A weak balance effect was evident in a multiple regression analysis. Experiment 4 replicated the inward bias for the spatial envelope using multiobject groups. Experiment 5 generalized the above findings for different objects when observers had to choose between image pairs that differed only in interobject distance or degree of balance. Strong relatedness effects were again present, but there was no evidence of any preference for balance.

Space-time disarray and visual awareness

Abstract: Local space-time scrambling of optical data leads to violent jerks and dislocations. On masking these, visual awareness of the scene becomes cohesive, with dislocations discounted as amodally occluding foreground. Such cohesive space-time of awareness is technically illusory because ground truth is jumbled whereas awareness is coherent. Apparently the visual field is a construction rather than a (veridical) perception

Temporal Patterns of Saccadic Eye Movements Predict Individual Variation in Alternation Rate during Binocular Rivalry

Abstract: Interindividual variation has been shown in the rates at which subjects alternate in perception during viewing of binocular rivalry and other ambiguous figures. A similar pattern of interindividual variation is evident in the rate of eye movements. The aim of this study was to determine whether individual differences in the rate of binocular rivalry predict individual differences in the rate of eye movements. First, participants reported changes in perception during contour rivalry. We found that the alternation rate during rivalry varied from 0.15 to 0.59/s between individuals. Next, participants viewed different visual displays while their eye movements were tracked. We found that the rate of saccadic eye movements varied by 1.9-4.4/s between individuals. Although the temporal characteristics of eye movements and binocular rivalry differed in their absolute rate, we found a significant positive correlation between these measures; that is, the frequency of saccadic eye movements can predict an individual's rate of perceptual alternation during rivalry. These findings suggest a potential link between the mechanisms involved in binocular rivalry and those processes involved in controlling eye movements.

Aesthetic judgment of triangular shape: compactness and not the golden ratio determines perceived attractiveness.

Abstract: Many studies over a period of more than a century have investigated the influence of the golden ratio on perceived geometric beauty. Surprisingly, very few of these studies used triangular shapes. In Experiment 1, we presented right triangles that differed in regard to their elongation determined by increasing the length of one side relative to another. Attractiveness ratings did not peak at the golden ratio, but there was a very strong influence of axis ratio overall. Participant ratings were a negative decreasing function of ratio. Triangles that pointed upward were judged as significantly more attractive than those that pointed down. We interpret these results according to a compactness hypothesis: triangles that are more compact are less likely to move or break and are thus considered more pleasing. Orientation also affects aesthetics. Upward-pointing triangles with a base parallel to the ground, regardless of their compactness, are also considered more perceptually stable and attractive. These findings were replicated across stimulus type in a second experiment with isosceles triangles and across testing procedure in a third experiment using a paired comparison technique.

Perceptual organization of shape, color, shade, and lighting in visual and pictorial objects

Abstract: The main questions we asked in this work are the following: Where are representations of shape, color, depth, and lighting mostly located? Does their formation take time to develop? How do they contribute to determining and defining a visual object, and how do they differ? How do visual artists use them to create objects and scenes? Is the way artists use them related to the way we perceive them? To answer these questions, we studied the microgenetic development of the object perception and formation. Our hypothesis is that the main object properties are extracted in sequential order and in the same order that these roles are also used by artists and children of different age to paint objects. The results supported the microgenesis of object formation according to the following sequence: contours, color, shading, and lighting.

Awareness of the light field: the case of deformation

Abstract: Human observers group local shading patterns into global super-patterns that appear to be illuminated in some unitary fashion. Many years ago, this was noticed for the case of uniform, unidirectional illumination. Recently, we found that it also applies to convergent and divergent illumination flows, but that human observers are blind to rotational light flow patterns (in the sense of being unable to group the local shading patterns). We now report that human observers are also blind to deformation patterns. This is perhaps interesting because convergent, divergent, rotational, and deformation patterns all occur in natural light fields. This is an idiosyncrasy of the human visual system, on par with the fact that visual awareness fails to present the observer with saddle shapes.

Aesthetic valence of visual illusions.

Abstract: Visual illusions constitute an interesting perceptual phenomenon, but they also have an aesthetic and affective dimension. We hypothesized that the illusive nature itself causes the increased aesthetic and affective valence of illusions compared with their non-illusory counterparts. We created pairs of stimuli. One qualified as a standard visual illusion whereas the other one did not, although they were matched in as many perceptual dimensions as possible. The phenomenal quality of being an illusion had significant effects on “Aesthetic Experience” (fascinating, irresistible, exceptional, etc), “Evaluation” (pleasant, cheerful, clear, bright, etc), “Arousal” (interesting, imaginative, complex, diverse, etc), and “Regularity” (balanced, coherent, clear, realistic, etc). A subsequent multiple regression analysis suggested that Arousal was a better predictor of Aesthetic Experience than Evaluation. The findings of this study demonstrate that illusion is a phenomenal quality of the percept which has measurable aesthetic and affective valence.

On the matching of seen and felt shape by newly sighted subjects

Abstract: How do we recognize identities between seen shapes and felt ones? Is this due to associative learning, or intrinsic connections these sensory modalities? We can address this question by testing the capacities of newly sighted subjects to match seen and felt shapes, but only if the subjects can see the objects well enough to form adequate visual representations of their shapes. In light of this, a recent study by R. Held and colleagues fails to demonstrate that their newly sighted subjects' inability to match seen and felt shape was due to a lack of intermodal connections rather than a purely visual deficit, as the subjects may not have been able visually to represent 3D shape in the perspective-invariant manner required for intermodal matching. However, the study could be modified in any of several ways to help avoid this problem.

Expert performance by athletes in the verbal estimation of spatial extents does not alter their perceptual metric of space

Abstract: Athletes often give more accurate estimates of egocentric distance along the ground than do non-athletes. To explore whether cognitive calibration was accompanied by perceptual change, athletes and non-athletes made verbal height and distance estimates and also did a perceptual matching task between perceived egocentric distances and frontal vertical extents. Both groups were well calibrated for height estimation for poles viewed frontally, but athletes were much better calibrated at estimating longer egocentric distances (which are systematically underestimated by non-athletes). Athletes were more likely to have learned specific units of ground distance from relevant sports contexts. Both groups reported using human height as a metric for vertical extent. For non-athletes, verbal underestimation of ground distance corresponded to predictions based on perceptual matches between egocentric distances and vertical extents in conjunction with human-height-based verbal estimates of vertical extents. For athletes, the verbal scaling of egocentric distances of 10 m or more was more accurate and was not predicted by their egocentric distance matches to vertical extents.

Grouping by closure influences subjective regularity and implicit preference.

Abstract: A reflection between a pair of contours is more rapidly detected than a translation, but this effect is stronger when the contours are closed to form a single object compared to when they are closed to form 2 objects with a gap between them. That is, grouping changes the relative salience of different regularities. We tested whether this manipulation would also change preference for reflection or translation. We measured preference for these patterns using the Implicit Association Test (IAT). On some trials, participants saw words that were either positive or negative and had to classify them as quickly as possible. On interleaved trials, they saw reflection or translation patterns and again had to classify them. Participants were faster when 1 button was used for reflection and positive words and another button was used for translation and negative words, compared to when the reverse response mapping was used (translation and positive vs. reflection and negative). This reaction time difference indicates an implicit preference for reflection over translation. However, the size of the implicit preference was significantly reduced in the Two-objects condition. We concluded that factors that affect perceptual sensitivity also systematically affect implicit preference formation.

Healthy Older Observers Cannot Use Biological-Motion Point-Light Information Efficiently within 4 m of Themselves:

Abstract: Healthy aging is associated with a number of perceptual changes, but measures of biological-motion perception have yielded conflicting results. Biological motion provides information about a walker, from gender and identity to speed, direction, and distance. In our natural environment, as someone approaches us (closer distances), the walker spans larger areas of our field of view, the extent of which can be underutilized with age. Yet, the effect of age on biological-motion perception in such real-world scenarios remains unknown. We assessed the effect of age on discriminating walking direction in upright and inverted biological-motion patterns, positioned at various distances in virtual space. Findings indicate that discrimination is worse at closer distances, an effect exacerbated by age. Older adults’ performance decreases at distances as far away as 4 m, whereas younger adults maintain their performance as close as 1 m (worse at 0.5 m). This suggests that older observers are limited in their capacity to integrate information over larger areas of the visual field and supports the notion that age-related effects are more apparent when larger neural networks are required to process simultaneous information. This has further implications for social contexts where information from biological motion is critical.

Empirical aesthetics, the beautiful challenge: An introduction to the special issue on Art & Perception.

Abstract: The i-Perception special issue Art & Perception is based on the Art & Perception Conference 2010 in Brussels. Our vision with this conference was to bring together artists and vision scientists from different backgrounds to exchange views and state-of-the-art knowledge on art perception and aesthetics. The complexity of the experience of art and of aesthetic phenomena, in general, calls for specific research approaches, for which interdisciplinarity seems to be key. Following this logic, the special issue Art & Perception contains contributions by artists and vision scientists with different methodological approaches. The contributions span a wide range of topics, but are all centred around two questions: How can one understand art perception and aesthetics from a psychological point of view, and how is this reflected in art itself?

Aesthetic judgement of orientation in modern art.

Abstract: When creating an artwork, the artist makes a decision regarding the orientation at which the work is to be hung based on their aesthetic judgement and the message conveyed by the piece. Is the impact or aesthetic appeal of a work diminished when it is hung at an incorrect orientation? To investigate this question, Experiment 1 asked whether naive observers can appreciate the correct orientation (as defined by the artist) of 40 modern artworks, some of which are entirely abstract. Eighteen participants were shown 40 paintings in a series of trials. Each trial presented all four cardinal orientations on a computer screen, and the participant was asked to select the orientation that was most attractive or meaningful. Results showed that the correct orientation was selected in 48% of trials on average, significantly above the 25% chance level, but well below perfect performance. A second experiment investigated the extent to which the 40 paintings contained recognisable content, which may have mediated orientation judgements. Recognition rates varied from 0% for seven of the paintings to 100% for five paintings. Orientation judgements in Experiment 1 correlated significantly with “meaningful” content judgements in Experiment 2: 42% of the variance in orientation judgements in Experiment 1 was shared with recognition of meaningful content in Experiment 2. For the seven paintings in which no meaningful content at all was detected, 41% of the variance in orientation judgements was shared with variance in a physical measure of image content, Fourier amplitude spectrum slope. For some paintings, orientation judgements were quite consistent, despite a lack of meaningful content. The origin of these orientation judgements remains to be identified.

The utility of defocus blur in binocular depth perception.

Abstract: The question of whether defocus blur is a quantitative cue for depth perception is a topic of renewed interest. A recent study suggests that relative defocus blur can be used in computing depth throughout the visual field, particularly in regions where disparity loses precision. However, elements of the study's experimental design and theoretical analysis appear to undermine this claim. First, the study did not provide evidence that blur can be used as a quantitative depth cue. It only measured blur discrimination thresholds, not perceived depth from for blur. Second, the study's conceptualization of the complementary use of blur and disparity, and related conjectures, are based on the specific viewing geometry and fixation distance tested. They do not appear to generalize to natural viewing situations and tasks. I suggest a different way in which defocus blur might affect depth perception. Because depth-of-focus blur is a cue to egocentric distance, it could contribute to quantitative depth perception by scaling depth relations specified by other relative depth cues.

Hearing mouth shapes: Sound symbolism and the reverse McGurk effect.

Abstract: In their recent article, Sweeny, Guzman-Martinez, Ortega, Grabowecky, and Suzuki (2012) demonstrate that heard speech sounds modulate the perceived shape of briefly presented visual stimuli. Ovals, whose aspect ratio (relating width to height) varied on a trial-by-trial basis, were rated as looking wider when a /woo/ sound was presented, and as taller when a /wee/ sound was presented instead. On the one hand, these findings add to a growing body of evidence demonstrating that audiovisual correspondences can have perceptual (as well as decisional) effects. On the other hand, they prompt a question concerning their origin. Although the currently popular view is that crossmodal correspondences are based on the internalization of the natural multisensory statistics of the environment (see Spence, 2011), these new results suggest instead that certain correspondences may actually be based on the sensorimotor responses associated with human vocalizations. As such, the findings of Sweeny et al. help to breathe new life into Sapir's (1929) once-popular "embodied" explanation of sound symbolism. Furthermore, they pose a challenge for those psychologists wanting to determine which among a number of plausible accounts best explains the available data on crossmodal correspondences.

Shape detection of Gaborized outline versions of everyday objects

Abstract: We previously tested the identifiability of six versions of Gaborized outlines of everyday objects, differing in the orientations assigned to elements inside and outside the outline. We found significant differences in identifiability between the versions, and related a number of stimulus metrics to identifiability (Sassi, M., Vancleef, K., Machilsen, B., Panis, S., & Wagemans, J. (2010). Identification of everyday objects on the basis of Gaborized outline versions. i-Perception, 1(3), 121-142). In this study, after retesting the identifiability of new variants of three of the stimulus versions, we tested their robustness to local orientation jitter in a detection experiment. In general, our results replicated the key findings from the previous study, and allowed us to substantiate our earlier interpretations of the effects of our stimulus metrics and of the performance differences between the different stimulus versions. The results of the detection task revealed a different ranking order of stimulus versions than the identification task. By examining the parallels and differences between the effects of our stimulus metrics in the two tasks, we found evidence for a trade-off between shape detectability and identifiability. The generally simple and smooth shapes that yield the strongest contour integration and most robust detectability tend to lack the distinguishing features necessary for clear-cut identification. Conversely, contours that do contain such identifying features tend to be inherently more complex and, therefore, yield weaker integration and less robust detectability.

View-based matching can be more than image matching: The importance of considering an animal's perspective

Abstract: Using vision for navigation is important for many animals and a common debate is the extent to which spatial performance can be explained by “simple” view-based matching strategies. We discuss, in the context of recent work, how confusion between image-matching algorithms and the broader class of view-based navigation strategies, is hindering the debate around the use of vision in spatial cognition. A proper consideration of view-based matching strategies requires an understanding of the visual information available to a given animal within a particular experiment.

The power of liking: Highly sensitive aesthetic processing for guiding us through the world

Abstract: Assessing liking is one of the most intriguing and influencing types of processing we experience day by day. We can decide almost instantaneously what we like and are highly consistent in our assessments, even across cultures. Still, the underlying mechanism is not well understood and often neglected by vision scientists. Several potential predictors for liking are discussed in the literature, among them very prominently typicality. Here, we analysed the impact of subtle changes of two perceptual dimensions (shape and colour saturation) of three-dimensional models of chairs on typicality and liking. To increase the validity of testing, we utilized a test-adaptation-retest design for extracting sensitivity data of both variables from a static (test only) as well as from a dynamic perspective (test-retest). We showed that typicality was only influenced by shape properties, whereas liking combined processing of shape plus saturation properties, indicating more complex and integrative processing. Processing the aesthetic value of objects, persons, or scenes is an essential and sophisticated mechanism, which seems to be highly sensitive to the slightest variations of perceptual input.

Looking at Op Art: Gaze Stability and Motion Illusions

Abstract: Various Op artists have used simple geometrical patterns to create the illusion of motion in their artwork. One explanation for the observed illusion involves retinal shifts caused by small involuntary eye movements that observers make while they try to maintain fixation. Earlier studies have suggested a prominent role of the most conspicuous of these eye movements, small rapid position shifts called microsaccades. Here, we present data that could expand this view with a different interpretation. In three experiments, we recorded participants' eye movements while they tried to maintain visual fixation when being presented with variants of Bridget Riley's Fall, which were manipulated such as to vary the strength of induced motion. In the first two experiments, we investigated the properties of microsaccades for a set of stimuli with known motion strengths. In agreement with earlier observations, microsaccade rates were unaffected by the stimulus pattern and, consequently, the strength of induced motion illusion. In the third experiment, we varied the stimulus pattern across a larger range of parameters and asked participants to rate the perceived motion illusion. The results revealed that motion illusions in patterns resembling Riley's Fall are perceived even in the absence of microsaccades, and that the reported strength of the illusion decreased with the number of microsaccades in the trial. Together, the three experiments suggest that other sources of retinal image instability than microsaccades, such as slow oculomotor drift, should be considered as possible factors contributing to the illusion.