Symmetry Perception Research Articles

Neutrality and satisfaction in the mediation session: party and mediator perspectives

PurposeThis study aims to investigate the relationship between perceptions of mediators acting symmetrically (treating parties equally) and transparently (providing an explanation of past or future behavior) with parties’ assessments of the neutrality of their mediator and satisfaction with the mediation process.Design/methodology/approachThis mixed-method study surveyed parties and mediators from 35 naturally occurring mediation sessions at community mediation centers about their perceptions of neutrality, symmetry, transparency and satisfaction.FindingsThe results showed that parties overwhelmingly assessed their mediators as acting neutrally. Compared to parties’ assessments of mediator neutrality, mediators rated their own neutrality even higher. Symmetry and transparency were both positively correlated with parties’ assessment of mediator neutrality and also emerged as qualitative themes. Speaking order and talk time did not significantly correlate with perception of symmetry. Overall, symmetry appeared to be a more salient factor in parties’ assessment of mediator neutrality than transparency. Both neutrality and symmetry were positively correlated with party satisfaction with the mediation process, but transparency was not.Research limitations/implicationsThe present study provides a foundation for future research in understanding neutrality from both parties and mediators’ perspectives. The primary limitation was a small sample size and possible selection bias in achieving the sample.Practical implicationsThe study found that symmetry and transparency are useful strategies for managing party perceptions of mediator neutrality and party satisfaction with the mediation process.Originality/valueThis study is one of only a few empirical research studies that investigated the parties’ perspective of mediator neutrality. The study provides a foundation for future research in understanding neutrality from both parties and mediators’ perspectives.

Stimulus information supporting bilateral symmetry perception

A classification image (a psychophysical reverse-correlation) method was used to investigate what stimulus regions and information the visual system uses for bilateral symmetry perception. The stimuli were symmetric random-dot patterns with either low or high dot density. First, the spatial integration region supporting symmetry perception was estimated, by analyzing the trial-to-trial correlation between the spatial location of symmetric dots and the corresponding response. It was observed that the integration region was rather compact (3 deg2 with dense stimulus), vertically elongated and located near to the axis of symmetry. The size of the area was dependent on the pattern density, being larger with low-density stimulus. Next, the resolution of the symmetry matching was probed by estimating how close to the perfect symmetry the dots in two stimulus parts must be to be perceived as symmetric (classification image for symmetry tolerance). Dot pairings up to 6 arc min off from the mirror symmetry correlated with symmetry response, suggesting that the process underlying symmetry matching has large tolerance and low resolution. Outside the integration region, the symmetry tolerance classification image weights were essentially zero, suggesting that the lack of symmetry integration there is not a byproduct of high tolerance.

The representation of symmetry in multi-voxel response patterns and functional connectivity throughout the ventral visual stream

Several computational models explain how symmetry might be detected and represented in the human brain. However, while there is an abundance of psychophysical studies on symmetry detection and several neural studies showing where and when symmetry is detected in the brain, important questions remain about how this detection happens and how symmetric patterns are represented. We studied the representation of (vertical) symmetry in regions of the ventral visual stream, using multi-voxel pattern analyses (MVPA) and functional connectivity analyses. Our results suggest that neural representations gradually change throughout the ventral visual stream, from very similar part-based representations for symmetrical and asymmetrical stimuli in V1 and V2, over increasingly different representations for symmetrical and asymmetrical stimuli which are nevertheless still part-based in both V3 and V4, to a more holistic representation for symmetrical compared to asymmetrical stimuli in high-level LOC. This change in representations is accompanied by increased communication between left and right retinotopic areas, evidenced by higher interhemispheric functional connectivity during symmetry perception in areas V2 and V4.

A Force-Directed Algorithm for Drawing Directed Graphs Symmetrically

Symmetry is one of the most important aesthetic criteria on graph drawing. It is quite necessary to measure the extent to which the drawings can be considered symmetric. For this purpose, a symmetric metric based on vertex coordinate calculation is proposed in this paper. It is proven theoretically and experimentally that the proposed metric is robust to contraction, expansion, and rotation of drawings. This robustness conforms to human perception of symmetry. Star-subgraphs and cycles are two common structures in digraphs. Both of them have inherent symmetry which should be displayed in drawings. For this purpose, a force-directed algorithm named FDS is proposed which can draw star-subgraphs and cycles as symmetrically as possible. FDS algorithm draws cycles as circles whose positions are fixed to provide a scaffolding for overall layout, renders non-leaf vertices by a standard force-directed layout, and places leaf vertices on concentric circles via a deterministic strategy. A series of experiments are carried out to test FDS algorithm. The results show that FDS algorithm draws digraphs more symmetrically than the existing state-of-the-art algorithms and performs efficiency comparable to O(nlog⁡n) YFHu algorithm.

Influence of lighting direction on the perception of symmetry and attractiveness of faces

Influence of lighting direction on the perception of symmetry and attractiveness of faces

Symmetry perception for patterns defined by color and luminance.

Perception of visual symmetry is fast and efficient and relies on both early low-level and late mid- and high-level neural mechanisms. To test for potential influences of early low-level mechanisms on symmetry perception, we used isoluminant, achromatic, and combined (color + luminance) patterns in a psychophysical and an event-related-potential (ERP) experiment. In the psychophysical experiment, pattern contrast was fixed at individual symmetry-discrimination threshold. Participants then judged whether a pattern was symmetric or random. Stimuli at isoluminance were associated with a large bias toward symmetry, achromatic stimuli introduced the opposite bias, and stimuli containing a balance of both color and luminance were perceived without bias. These findings are in line with distinct contrast sensitivity functions for color and luminance, with color providing low-frequency information useful for symmetry detection and luminance providing high-frequency information useful for detection of detail. The subsequent ERP experiment was run at high contrasts to assess processing of symmetry in suprathreshold conditions. Sustained posterior negativity, a symmetry-sensitive ERP component, was observed in all conditions and showed the expected dependence on symmetry. However, interactions between symmetry and contrast type were not observed. In conclusion, while our findings at threshold support models that propose an important contribution of low-level mechanisms to symmetry perception, at suprathreshold these low-level contributions do not persist. Therefore, under everyday viewing conditions, symmetry perception engages a relatively broad cortical network that is not constrained by low-level inputs.

What Do Spatial Distortions in Patients' Drawing After Right Brain Damage Teach Us About Space Representation in Art?

The right cerebral hemisphere plays a crucial rule in spatial cognition, spanning from perception of elementary features, such as location, color, line orientation or shape to representation of different spaces (3D space, allocentric, egocentric, face, personal, peri-personal, or imaginal). One important aspect of its contribution concerns the perception of space symmetry and the representation of objects and scenes, with reference to the midline or body axis. This representation results from a balance between spatial attention processes depending from the two hemispheres. Healthy participants tend to show a discrete deviation of the midline plane representation toward the left side, that is likely to result from the predominance of the activity of the right cerebral hemisphere, mainly oriented toward the contralateral side of space. The visuospatial abilities of the right hemisphere, especially for the representation of the midline plane are crucially engaged in painting and drawing processes in artists. Interestingly, the distortions created by painters of the Cubism period, characterized by an asymmetry of objects and body representations, a specific enlargement or reduction of parts of space, or even by complex distortions of 3D space are analogous to those classically reported in right-brain-damaged patients (unilateral spatial neglect, hyperschematia, constructional apraxia). Understanding the pathological mechanisms of these representation disorders provides meaningful information to apprehend visual artist creations and esthetic perception of space.

Spatiotemporal and Luminance Contrast Properties of Symmetry Perception

Recent studies have shown that limiting the lifetime of pattern elements improves symmetry detection, potentially by increasing the number of element locations. Here, we investigate how spatial relocation, luminance contrast modulation and lifetime duration of elements affect symmetry perception in dynamic stimuli. Stimuli were dynamic dot-patterns containing varying amounts of symmetry about a vertical axis. Symmetrical matched-pairs were: (i) relocated to multiple successive, but random locations (i.e., multiple locations condition); (ii) relocated between the same two locations (i.e., two locations condition); (iii) not, relocated, but their luminance contrast was modulated at different temporal frequencies (i.e., one location condition), and (iv) not relocated, but a single pattern was presented at full contrast (i.e., static condition). In the dynamic conditions, we varied the elements’ lifetime duration and temporal frequency of contrast modulation. We measured symmetry detection thresholds using a two-interval forced choice procedure. Our results show improved performance for the multiple locations condition compared to two-location and static conditions, suggesting a cumulative process whereby weak symmetry information is integrated by spatiotemporal filters to increase overall symmetry signal strength. Performance also improved for the static, contrast modulated patterns, but this was explained by a reduction in perceived density. This suggests that different mechanisms mediate symmetry detection in dynamic stimuli and static contrast modulated patterns.

Temporal dynamics of mirror-symmetry perception.

Recent studies have suggested that temporal dynamics rather than symmetrical motion-direction contribute to mirror-symmetry perception. Here we investigate temporal aspects of symmetry perception and implicitly, its temporal flexibility and limitations, by examining how symmetrical pattern elements are combined over time. Stimuli were dynamic dot-patterns consisting of either an on-going alternation of two images (sustained stimulus presentation) or just two images each presented once (transient stimulus presentation) containing different amounts of symmetry about the vertical axis. We varied the duration of the two images under five temporal-arrangement conditions: (a) whole patterns in which a symmetric pattern alternated with a noise pattern; (b) delayed halves—the halves of the symmetric and noise patterns were presented with temporal delay; (c) matched-pairs—two alternating images each containing equal amounts of symmetrical matched-pairs; (d) delayed matched-pairs—the same as arrangement (c), but with matched-pairs presented with delay; and (e) static—both images presented simultaneously as one. We found increased sensitivity in sustained compared to transient stimulus presentations and with synchronous compared to delayed matched-pairs stimuli. For the delayed conditions, sensitivity decreased gradually with longer image durations (>60 ms), prominently for the transient stimulus presentations. We conclude that spatial correlations across-the-symmetry-midline can be integrated over time (∼120 ms), and symmetry mechanisms can tolerate temporal delays between symmetric dot-pairs of up to ∼60 ms.

Measuring Integration Processes in Visual Symmetry with Frequency-Tagged EEG

Symmetry is a highly salient feature of the natural world which requires integration of visual features over space. The aim of the current work is to isolate dynamic neural correlates of symmetry-specific integration processes. We measured steady-state visual evoked potentials (SSVEP) as participants viewed symmetric patterns comprised of distinct spatial regions presented at two different frequencies (f1 and f2). We measured intermodulation components, shown to reflect non-linear processing at the neural level, indicating integration of spatially separated parts of the pattern. We generated a wallpaper pattern containing two reflection symmetry axes by tiling the plane with a two-fold reflection symmetric unit-pattern and split each unit-pattern diagonally into separate parts which could be presented at different frequencies. We compared SSVEPs measured for wallpapers and control patterns for which both images were equal in terms of translation and rotation symmetry but reflection symmetry could only emerge for the wallpaper pattern through integration of the image-pairs. We found that low-frequency intermodulation components differed between the wallpaper and control stimuli, indicating the presence of integration mechanisms specific to reflection symmetry. These results showed that spatial integration specific to symmetry perception can be isolated through a combination of stimulus design and the frequency tagging approach.

The Effects of Ageing on Intergenerational Support Exchange: A New Look at the Hypothesis of Flow Reversal

There has been debate about whether the flow of intergenerational support reverses as parents age. One view is that in western countries, parents remain ‘net donors’ to children, even in very old age. Such a conclusion coincides with notions of parental altruism and would be in contrast to notions of exchange and reciprocity over the life course. This paper examines the thesis of flow reversal in a new way: it uses prospective longitudinal data, it combines data from samples of ageing parents and samples of adult children, it develops a way to create measures of balance from frequency items on support exchange, and it combines objective measures of support exchange with subjective perceptions of symmetry. The focus is limited to support that involves time and effort. The support that parents give to children declines with age, the support they receive increases, and at around age 75–76, parents become ‘net receivers’. The decline in downward support is stronger than the increase in upward support, suggesting that declining parental opportunities to give plays an important role in the flow reversal. In sum, the analyses provide evidence for what we can call delayed and parent-driven flow reversal. Evidence for flow reversal is stronger in the sample of adult children, pointing to the limitations of sampling ageing parents. Finally, there is correspondence between objective measures of support exchange and perceptions of symmetry, although on the whole, few parents regard themselves as ‘net receivers’.

The neural basis of visual symmetry and its role in mid- and high-level visual processing.

Symmetry is an important and prominent feature of the visual world. It has been studied as a basis for image segmentation and perceptual organization, but it also plays a role in higher level processes, such as face and object perception. Over the past decade, there has been progress in the study of the neural mechanisms of symmetry perception in humans and other animals. There is extended activity in the ventral stream, including the lateral occipital complex (LOC) and VO1; this activity starts in V3 and it occurs independently of the task (automatic response). Additionally, when the task requires processing of symmetry, the activation may emerge for objects that are symmetrical, even though they do not project a symmetrical image. There is also some evidence of hemispheric lateralization, especially for the LOC. We review the studies on the cortical basis of visual symmetry processing and its links to encoding of other aspects of the visual world, such as faces and objects.

Symmetry in Motion: Perception of Attractiveness Changes with Facial Movement

Facial symmetry is an index of developmental stability and shows a positive correlation with attractiveness assessment. However, the appearance of one’s facial symmetry is not always static and may change when there is facial movement while a person is speaking. This study examined whether viewing a dynamic image of a person speaking (where facial symmetry may alter) would elicit a different perception of attractiveness than viewing a static image of that person as a still photo. We examined changes in both measured and perceived facial symmetry in relation to attractiveness perception. We found that when facial movements created an appearance of overall greater facial symmetry while a person was speaking in a video, the person was rated as being more attractive than as a still photo. Likewise, those with facial movements measured and perceived as less symmetrical while speaking were rated as less attractive in a video clip than still photo. By examining the perception of faces in motion as we typically encounter others in real life rather than considering only static photos, we have extended the ecological validity of the study of the perception of bilateral symmetry in humans as it relates to attractiveness.

Neuromuscular Electrical Stimulation Superimposed on Movement Early after ACL Surgery.

Quadriceps weakness and asymmetrical loading of lower limbs are two major issues after anterior cruciate ligament reconstruction (ACLR). The aim of this study was to evaluate the effectiveness of a 6-wk training protocol involving neuromuscular electrical stimulations (NMES) of the quadriceps muscle superimposed on repeated sit-to-stand-to-sit exercises (STSTS), as an additional treatment to standard rehabilitation, from the 15th to the 60th day after ACLR. Sixty-three ACLR patients were randomly allocated to one of the three treatment groups: NMES superimposed on STSTS (NMES + STSTS), STSTS only, or no additional treatment (NAT) to standard rehabilitation. Maximal isometric strength of the knee extensor and flexor muscles was measured 60 and 180 d after surgery. Asymmetry in lower extremity loading was measured during a sit-to-stand movement at 15, 30, 60, and 180 d after surgery and during a countermovement jump 180 d after surgery by means of two adjacent force platforms placed under each foot. The NMES + STSTS participants showed higher muscle strength of the knee extensors, which was accompanied by lower perception of pain and higher symmetry in lower extremity loading compared with STSTS-only and NAT participants after both 60 and 180 d from surgery. Participants in the STSTS-only treatment group showed higher symmetry in lower extremity loading compared with those in the NAT group 60 d after surgery. These results suggest that an early intervention based on NMES superimposed to repeated STSTS exercises is effective for recovering quadriceps strength and symmetry in lower extremity loading by the time of return to sport.

Зрительное восприятие симметрии как фактор эстетического переживания

The article deals with the formation of aesthetic experience in connection with the perception of physical symmetry of objects and their images. An overview of modern works on the psychology of aesthetic perception in the context of the problem of the perception of symmetry is presented. The phenomenon of symmetry preference in visual perception is illustrated by arguments in its favor and data on its situationality. The ecological context of symmetry in animals and plants is touched in connection with the phenomenon of fluctuating asymmetry as an undirected deviation in the symmetry of a two-sided structure normally distributed in the population. Mathematical models of symmetry of forms and their multiscale representation are discussed. The analysis of the study of the Zen stone garden perceptual peculiarities from the position of the medial axes’ model is carried out.On the basis of the provisions of the transcendental psychology of perception, a hypothesis is advanced about the meta-sensory origin of the aesthetic sense, based on the process of interrelation of the internal symmetrical mechanisms of visual perception and the cognitive processes of creating figurative representations. The relation to the principle of symmetry in the context of the transcendental psychology of perception is shown.

Interview

Interview Charles Martin (bio) Ever since I first heard Charles Martin read, I've admired the crisp lucidity of his craft. But while preparing for our talk, which took place on September 8, 2017 at his home in Syracuse, New York, I started to suspect that he values a looser kind of insight too, like what Paul Klee described as "exactitude winged by intuition." I began by asking about a discovery he made in his early studies of Catullus—how a certain poem called "poem 64" was arranged symmetrically. Charles explained that this technique arose during a time when people were still writing poems on scrolls, so it made sense to try things like that since you could hold the two scenes together. The scene on the outside could be juxtaposed against its corresponding scene on the inside. But with books, he explained, we don't have that luxury … unless you tear the pages. Eric Berlin: So is symmetry something that listeners and readers can sense instinctively? Charles Martin: Not always. Dylan Thomas wrote a poem called "Prologue" at the beginning of his collected poems, and it's done in a chiasmic arrangement where A, the first line, rhymes with A, the last line, and it spans two or three pages so that by the time reader gets to the last line he's not going to remember oh, that's rhyming with the first line. As a structural device, chiasmus has its limitations over a period like that. James Merrill has a wonderful poem called "Pearl," a late poem, which is arranged chiasmically so the first and last lines rhyme, [End Page 417] and it's only about 30 lines long so it fits on a page, and readers will notice that, I think. Some will at least! EB: So there's a scope to the perception of symmetry. Within a single line maybe, like the so-called "golden line," which Ovid sometimes used, "in which a pair of adjectives and their respective nouns at either end enclose a verb in the middle." CM: Certainly, Latin readers would have responded to that and approved of that kind of thing, because you can hold it in your mind if it's a line long. EB: So what is it about symmetry that you think affects readers? Is it the presence of mind that we sense in it? CM: Probably so. But there are certain limitations to that, because the reader doesn't always get it. One of Catullus's editors noted that in a poem of his where he was supposed to be dying and he's calling out to Lesbia, most likely, to condemn her heartlessness, if you read down the left-hand side you find an anagram that translates "by nature, as hard as bronze." So here he is dying, and he still has the wit to put in a little acrostic verse. But it took about 2,000 years before anybody noticed that. So the little hidden stuff, the arrangement, the symmetrical arrangement of a long poem probably goes past most people. When I pointed out the symmetry in "poem 64," I got a lot of pushback. EB: You've said, "the poet's one who brings order to the world's waste bit by bit, letter by letter, And each laboriously traced / on his own flesh, until he's dressed in / an artful weave of self-expression." Whether that order is perceived by the reader or not, does it serve a purpose in the building of the poem? CM: I think it has to. You know, a lot of these things, even the order that Marianne Moore creates with her syllabic arrangement, may not [End Page 418] be apparent to anybody else. But it's got to be apparent to her as she writes the poem. As a result, it does create an order for that poem. EB: How do you avoid contrivance when you're consciously building formal structures out of words? CM: I don't know entirely that you do. That's one of those questions [laughing] that I would probably dodge. EB: So, how do you think readers react to form differently than...

Symmetric Objects Become Special in Perception Because of Generic Computations in Neurons

Symmetry is a salient visual property: It is easy to detect and influences perceptual phenomena from segmentation to recognition. Yet researchers know little about its neural basis. Using recordings from single neurons in monkey IT cortex, we asked whether symmetry—being an emergent property—induces nonlinear interactions between object parts. Remarkably, we found no such deviation: Whole-object responses were always the sum of responses to the object’s parts, regardless of symmetry. The only defining characteristic of symmetric objects was that they were more distinctive compared with asymmetric objects. This was a consequence of neurons preferring the same part across locations within an object. Just as mixing diverse paints produces a homogeneous overall color, adding heterogeneous parts within an asymmetric object renders it indistinct. In contrast, adding identical parts within a symmetric object renders it distinct. This distinctiveness systematically predicted human symmetry judgments, and it explains many previous observations about symmetry perception. Thus, symmetry becomes special in perception despite being driven by generic computations at the level of single neurons.

Factors Affecting the Perception of 3D Facial Symmetry from 2D Projections

Facial symmetry is believed to have an evolutionary significance and so its detection should be robust in natural settings. Previous studies of facial symmetry detection have used front views of faces where the decision could be made on 2D image properties rather than 3D facial properties. These studies also employed comparative judgements, which could be influenced by attractiveness rather than symmetry. Two experiments explored the ability to detect typical levels of 3D facial asymmetry (contrasted with wholly symmetrical faces) from 2D projections of faces. Experiment 1 showed that asymmetry detection was impaired by inversion but even more impaired by 90 degrees rotation demonstrating the importance of the vertical reflection. Asymmetry detection was also reduced by yaw rotation of the head but still above-chance at 30 degrees rotation. Experiment 2 explored the effect of asymmetrical lighting and yaw rotation up to 45 degrees. Detection of asymmetry was affected by asymmetrical lighting and yaw rotation in a non-additive manner. The results are discussed in terms of the special role that faces and vertical symmetry play in visual perception.

Measuring Integration Processes in Visual Symmetry with Frequency-tagged EEG

Symmetry is a highly salient feature of the natural world which requires integration of visual features over space. The aim of the current work is to isolate dynamic neural correlates of symmetry-specific integration processes. We measured steady-state visual evoked potentials (SSVEP) as participants viewed symmetric patterns comprised of distinct spatial regions presented at two different frequencies (f1 and f2). We measured intermodulation components, shown to reflect non-linear processing at the neural level, indicating integration of spatially separated parts of the pattern. We generated a wallpaper pattern containing two reflection symmetry axes by tiling the plane with a two-fold reflection symmetric unit-pattern and split each unit-pattern diagonally into separate parts which could be presented at different frequencies. We compared SSVEPs measured for wallpapers and control patterns for which both images were equal in terms of translation and rotation symmetry but reflection symmetry could only emerge for the wallpaper pattern through integration of the image-pairs. We found that low-frequency intermodulation components differed between the wallpaper and control stimuli, indicating the presence of integration mechanisms specific to reflection symmetry. These results showed that spatial integration specific to symmetry perception can be isolated through a combination of stimulus design and the frequency tagging approach.

Dentoskeletal parameters related to visual perception of facial asymmetry in patients with skeletal class III malocclusion after orthognathic surgery

The purpose of the study is to explore the critical parameters determining the visual perception of postoperative facial symmetry. This study retrospectively included 24 patients with skeletal class III malocclusion and double-jaw orthognathic surgery (OgS). The patients were classified according to the outcome of subjective visual perception scores (SVPS) based on the postoperative frontal images by 10 orthodontists: symmetrical surgical outcome (S group, n=12) and facial asymmetry after surgery (A group, n=12). The 3D dentofacial measurements from cone beam computed tomography, were compared between the S and A groups. The relationship of all variables in all patients with the SVPS was explored by Spearman correlation coefficient. Significant differences were observed in the midline parameters in the mandible, the B point, gnathion and menton, and the mandibular border axis as well as in the discrepancy of the chin morphology between the two groups (P<0.05). The findings demonstrated that the midline parameter deviation, shape of the mandibular border, and the contour of menton morphology play the major role in the visual perceptions of postoperative asymmetry.