Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1 -- 1905 2023-07-17 17:51:50 |
2 update layout + 15 word(s) 1920 2023-07-18 04:58:42 |

Video Upload Options

Do you have a full video?

Confirm

Are you sure to Delete?
Cite
If you have any further questions, please contact Encyclopedia Editorial Office.
Makin, A.D.J.; Roccato, M.; Karakashevska, E.; Tyson-Carr, J.; Bertamini, M. Symmetry Perception and Psychedelic Experience. Encyclopedia. Available online: https://encyclopedia.pub/entry/46880 (accessed on 22 June 2024).
Makin ADJ, Roccato M, Karakashevska E, Tyson-Carr J, Bertamini M. Symmetry Perception and Psychedelic Experience. Encyclopedia. Available at: https://encyclopedia.pub/entry/46880. Accessed June 22, 2024.
Makin, Alexis D. J., Marco Roccato, Elena Karakashevska, John Tyson-Carr, Marco Bertamini. "Symmetry Perception and Psychedelic Experience" Encyclopedia, https://encyclopedia.pub/entry/46880 (accessed June 22, 2024).
Makin, A.D.J., Roccato, M., Karakashevska, E., Tyson-Carr, J., & Bertamini, M. (2023, July 17). Symmetry Perception and Psychedelic Experience. In Encyclopedia. https://encyclopedia.pub/entry/46880
Makin, Alexis D. J., et al. "Symmetry Perception and Psychedelic Experience." Encyclopedia. Web. 17 July, 2023.
Symmetry Perception and Psychedelic Experience
Edit

Neuroscientific studies on symmetry perception have accumulated in the last 20 years. Functional MRI and EEG experiments have conclusively shown that regular visual arrangements, such as reflectional symmetry, Glass patterns, and the 17 wallpaper groups all activate the extrastriate visual cortex. This activation generates an event-related potential (ERP) called sustained posterior negativity (SPN).

Psychophysics Neuroscience Preattentive Processing Nature-Nurture Aesthetics Psychedelics Symmetry Regularity

1. Introduction

Symmetry perception has been studied since the early observations of Ernst Mach, who noticed that reflectional symmetry is more salient than translation or rotation, particularly when the axis is vertical (Figure 1). The Makin et al. [1] review on symmetry perception has six parts: 1) psychophysics, 2) neuroimaging, 3) automaticity, 4) innateness, 5) beauty, and 6) psychedelic experience.

Figure 1. Dot patterns with different kinds of visual symmetry.

1.1. Part 1: Psychophysical Research on Symmetry Perception

In a typical psychophysical experiment, the participants view many trials with abstract patterns (like those in Figure 1). On some trials the patterns are symmetrical, on some trials they are random. The participant’s task is to discriminate between these categories as quickly and accurately as possible. Response times are faster for more salient kinds of symmetry, such as vertical reflection.

Another typical psychophysical procedure is the 2-interval forced choice task. Here each trial involves two brief intervals. Symmetry is presented in one interval, and asymmetry in the other. The task is to determine which interval contained more symmetry – first or second. The symmetry-asymmetry difference is then systematically varied to determine discrimination thresholds (e.g., 75% correct). Discrimination thresholds are lower for more salient symmetries, such as vertical reflection [2].

Reflectional symmetry detection is very efficient and noise tolerant [3]. Perfect reflectional symmetry can be discriminated from complete asymmetry within a single screen refresh (e.g., 16.67 ms on a 60Hz monitor) or a single fixation [4]. However, the difference between perfect reflection and slightly imperfect reflection is not perceptually obvious and may only be noticed with serial visual search [5] [6].

Psychophysical procedures have often been used in studies supporting filter models of symmetry perception. The early visual system is like a retinotopic array of spatial frequency and orientation tuned filters [7]. When an image is subject to such filtering, any region with reflectional symmetry will yield mid-point-colinear blobs orthogonal to the global axis. This is true whether the symmetrical region is caused by an abstract pattern or a real object. Universal symmetry detection could be a matter of estimating blob alignment [8]. Early work in this field found that low frequency reflection dominates high frequency reflection when the two are superimposed at different orientations [9] and that filtered information in an elongated ‘integration region’ around the axis particularly important [10]. There have been many proposed filter models [11][12][13], and comparable accounts of Glass pattern detection have also been advanced [14].

Filter models have biological plausibility allow precise simulations, but there are many facts about symmetry detection they cannot explain (Figure 2). First, without modification, they cannot explain sensitivity to some kinds of anti-symmetry, where luminance is reversed across the axis [15]. Second, filter models cannot explain the well-established interaction between regularity and objecthood: Contour reflection is more salient when the contours belong to one object, while contour translation is more salient when they belong to two separate objects [16] [17]. Third, filter models cannot explain sensitivity to extraretinal symmetry, caused by partial occlusion [18] or perspective distortion [19]. Finally, different mechanisms are required to detect symmetry in radial frequency contours [14] or optic flow fields [20]. In summary, filter models can explain some, but not all aspects of symmetry detection.

Figure 2. Examples of symmetry and anti-symmetry (top) and symmetrical polygons seen from different view angles. The stimuli on the right are less obviously symmetrical, and they are a challenge for filter models.

1.2. Part 2: Neural Responses to Visual Symmetry

The brain response to visual symmetry has been studied extensively in the last 20 years [21]. Functional MRI work has shown that symmetry activates a network of regions in the extrastriate visual cortex, centred on V4 and the lateral occipital complex [22][23][24][25][26]. This extrastriate symmetry response can also be measured with EEG (Figure 3). Both symmetrical and asymmetrical stimuli generate event related potentials (ERPs) at posterior electrodes. After the P1 and N1 components of the visual evoked potential, amplitude is lower for symmetrical stimuli. This symmetry-asymmetry difference wave was observed by Jacobsen and Höfel [27], and is now called the Sustained Posterior Negativity (SPN) [28]. When symmetry is presented on one visual hemifield, the SPN is generated in the contralateral hemisphere [29]. A high amplitude SPN is one where the symmetry-asymmetry difference wave falls far below zero. As seen in Figure 3, SPN amplitude scales with the proportion of symmetry in the image and with the perceptual goodness of different visual regularities [30]. However, the SPN is robust to experimental manipulations of task [31].

Figure 3. The grand-average ERPs are shown in the upper left panel and difference waves (reflection-random) are shown in the lower left panel. A large SPN is a difference wave that falls a long way below zero. Topographic difference maps are shown on the right, aligned with the representative stimuli (black background). The difference maps depict a head from above, and the SPN appears as blue at the back. Purple labels indicate electrodes used for ERP waves [PO7, O1, O2 and PO8]. Note that SPN amplitude increases (that is, becomes more negative) with the proportion of symmetry in the image. In this experiment, the SPN increased from 0 to ~-3.5 microvolts as symmetry increased from 20% to 100%.

The SPN is closely related to a negativity extracted from steady state visual evoked potential methods [32][33][34].

Many SPN data sets are now available on a public databased called The Complete Liverpool SPN Catalogue (https://osf.io/2sncj/). This database houses EEG data and analysis scripts from all SPN projects at University of Liverpool, both published and unpublished.

1.3. Part 3: Symmetry Detection Can be Automatic, Preattentive and Unconscious

Symmetry does not pop out in classic visual search tasks [35] and it often go unnoticed in priming studies [36]. Despite these observations, researchers believe that stronger kinds of visual symmetry are sometimes processed automatically, preattentively, and unconsciously. There are several lines of evidence for this. First, insects use symmetry to guide adaptive behaviour [37] and insects are probably unconscious. Second, specific neurons in area V4 respond to specific kinds of symmetry in unconscious anesthetised monkeys [38]. Third, hemispatial neglect patients unconsciously use symmetry in figure-ground segmentation, even though half the object is subjectively absent [39]. Finally, symmetry is a gestalt grouping principle [40] [41] and resulting representations presumably guide thousands of judgments, saccades, and actions per day. These routine sensory-motor object interactions happen without anyone consciously attending to the symmetry itself.

Claims about the automaticity of symmetry detection should always be qualified by specifying the type of symmetry in question. For instance, what is true of single axis symmetry may not be true of double axis symmetry.

1.4. Part 4: Reflectional Symmetry Sensitivity is Innate

Perhaps reflectional symmetry perceptually special because genes hardwire the brain with innate reflection detectors? Good answers to nature-nurture questions are always likely to be subtle, but this bold nature claim might be a reasonable first approximation. After all, there is evidence for reflectional symmetry sensitivity in newly hatched poultry chicks [42]. Meanwhile, preferential looking and habituation studies on human infants suggest symmetry sensitivity at 4 months [43] [44]. Pornstein and Krinsky [45] found that infants are more sensitive to vertical reflection than other regularities. In contrast, Deep Neural Networks (DNNs) struggle to classify reflectional symmetry in exemplars outside their training set [46]. Many lines of research suggest DNNs overweight local cues, and are insensitive to global, configural properties [47]. Symmetry is a paradigm example of a configural property.

1.5. Part 5: Aesthetic Significance of Symmetry

Many animals seek mates with symmetrical phenotypic features. This is possibly because symmetry indicates health and genetic fitness [48], although there are alternative evolutionary explanations[49][50]. Humans are attracted to symmetrical faces and bodies [51] [52], although it can be difficult to separate facial symmetry and prototypicality.

Many studies in empirical aesthetics show that symmetry adds to the appeal of abstract patterns [53] [54] [55]. It is unclear whether innate sexual attraction to facial symmetry overgeneralizes to abstract patterns (in the same way that the innate 'cuteness' reaction to babies overgeneralizes to miniature objects). It is possible that symmetry-phiia in the face domain and symmetry-philia in the abstract pattern domain are two distinct psychological phenomena [56]. While the neural response to symmetry is preattentive, aesthetic evaluation of symmetry may only happen when symmetry is attended and classified [57] [58]. Symmetry may be an aesthetic primitive, which is appreciated in all cultures. However, artists and art experts may cultivate a taste for abstract asymmetry [59].

1.6. Part 6: Symmetry and Psychedelic Experience

Visual symmetry is prominent in hallucinations induced by the psychedelic drug N, N-dimethyltryptamine (DMT). DMT is an ingredient in the potent South American hallucinogen ayahuasca, and it is pharmacologically related to other more famous serotonergic drugs like LSD and Psilocybin (the active ingredient in magic mushrooms). Unlike LSD, DMT is an endogenous neurotransmitter found in healthy brains. It could be that individual differences in endogenous DMT signalling contribution to individual differences in aesthetic sensitivity and religiosity.

DMT experience was analysed by Lawrence et al. [60], who found that symmetry and fractal geometry are common hallucinations. A qualitative interview study by Cott and Rock [61] corroborates this. One participant reported that:

“The entire room was crawling with beautiful geometric hallucinations.”

Another participant reported:

“The room erupted in incredible neon colors, and dissolving into the most elaborate incredibly detailed fractal patterns that i [sic] have ever seen”.

The abundance of geometry is obvious in DMT inspired art (https://www.alexgrey.com/).

A representative account of DMT phenomenology was compiled by Gomez-Emilsson [62], who discussed six stages of the DMT trip. At stage 1 (Threshold) colours become vivid and visual acuity subjectively sharpens. At stage 2 (The chrysanthemum), colourful slowly rotating kaleidoscopes and mandalas are salient when users close their eyes. If you keep your eyes open, surfaces ‘symmetrify beyond belief’. At stage 3 (The magic eye) surfaces may develop autostereogram properties, where depth separation breaks up the 2D surface. Any regular structure is prone to overflow and fractalize. At Stage 4 (The waiting room) immersion hyperspace becomes intense, and there is a subjective sense of communicating with supernatural beings. At Stage 5 (The breakthrough) impossible hyper dimensionality and space-time tunnelling are experienced. The telepathic agents melt from human form are fuse with the hyper-dimensional geometry. The new universe feels palpably panpsychic, as if made of sentient material. Stage 6 (Amnesia) is apparently indescribable, because no visual representations or linguistic descriptions are adequate, and without these familiar cognitive tools, it is hard to reconstruct memories.

It is unlikely that all DMT users have the same six stage trip, but this account is representative, and it highlights the salience of symmetry in DMT hallucinations.

As research into psychedelic drugs becomes mainstream again, researchers anticipate more interest in hallucinatory symmetry. One possibility is that DMT reduces backward travelling alpha waves, so that the visual cortex is disinhibited, and internally generated representations cascade up the visual hierarchy [63].

Visual flicker is a cheaper and safer way to experience hallucinatory symmetry. Spatially unstructured flickering light often produces simple geometry, such as fans, tunnels, and spirals (Figure 4)[64]. Such patterns, labelled as ‘form constants’, could be an emergent property of overexcited retinotopic visual maps [65].

Figure 4. Artistic representations of form constants: a) tunnel/funnel; b) spiral; c) honeycomb; d) cobweb.

2. Summary

As researchers concluded in the review paper, the psychedelic renaissance opens new doors for symmetry perception research.

What would the extrastriate symmetry network do if there was no sensory input, and no top-down inhibition? Perhaps it would not simply remain silent by default. Instead, it may spontaneously generate a kaleidoscope of colourful, geometrical representations. Psychedelic drugs may disinhibit the extrastriate cortex, so the internal kaleidoscope intrudes on conscious experience.

References

  1. Alexis D. J. Makin; Marco Roccato; Elena Karakashevska; John Tyson-Carr; Marco Bertamini; Symmetry Perception and Psychedelic Experience. Symmetry 2023, 15, 1340.
  2. Elena Gheorghiu; Frederick A. A. Kingdom; Aaron Remkes; Hyung-Chul O. Li; Stéphane Rainville; The role of color and attention-to-color in mirror-symmetry perception. Scientific Reports 2016, 6, 29287.
  3. H.B. Barlow; B.C. Reeves; The versatility and absolute efficiency of detecting mirror symmetry in random dot displays. Vision Research 1979, 19, 783-793.
  4. Matthias Sebastian Treder; Behind the Looking-Glass: A Review on Human Symmetry Perception. Symmetry 2010, 2, 1510-1543.
  5. Jennifer Freyd; Barbara Tversky; Force of Symmetry in Form Perception. The American Journal of Psychology 1984, 97, 109.
  6. Bosco S. Tjan; Zili Liu; Symmetry impedes symmetry discrimination. Journal of Vision 2005, 5, 10-10.
  7. F. W. Campbell; J. G. Robson; Application of fourier analysis to the visibility of gratings. The Journal of Physiology 1968, 197, 551-566.
  8. S.C. Dakin; R.J. Watt; Detection of bilateral symmetry using spatial filters. Spatial Vision 1994, 8, 393-413.
  9. Bela Julesz; Jih-Jie Chang; Symmetry Perception and Spatial-Frequency Channels. Perception 1979, 8, 711-718.
  10. Dakin, S. C., & Herbert, A. M The spatial region of integration for visual symmetry detection. Proceedings of the Royal Society of Biological Sciences 1998, 265, 659-664.
  11. Steven C. Dakin; Robert F. Hess; The spatial mechanisms mediating symmetry perception. Vision Research 1997, 37, 2915-2930.
  12. D. Osorio; Symmetry detection by categorization of spatial phase, a model. Proceedings of the Royal Society B: Biological Sciences 1996, 263, 105-110.
  13. Frédéric J. A. M. Poirier; Hugh R. Wilson; A biologically plausible model of human shape symmetry perception. Journal of Vision 2010, 10, 9-9.
  14. Hugh R Wilson; Frances Wilkinson; Symmetry perception: a novel approach for biological shapes. Vision Research 2001, 42, 589-597.
  15. Sandra Mancini; Sharon L. Sally; Rick Gurnsey; Detection of symmetry and anti-symmetry. Vision Research 2005, 45, 2145-2160.
  16. Gordon C. Baylis; Jon Driver; Obligatory edge assignment in vision: The role of figure and part segmentation in symmetry detection.. Journal of Experimental Psychology: Human Perception and Performance 1995, 21, 1323-1342.
  17. Marco Bertamini; Jay D. Friedenberg; Michael Kubovy; Detection of symmetry and perceptual organization: The way a lock-and-key process works. Acta Psychologica 1997, 95, 119-140.
  18. Giulia Rampone; Alexis D.J. Makin; Semir Tatlidil; Marco Bertamini; Representation of symmetry in the extrastriate visual cortex from temporal integration of parts: An EEG/ERP study. Neuroimage 2019, 193, 214-230.
  19. Celia B. Fisher; Janet P. Szlyk; Irvin Rock; Level of processing in the perception of symmetrical forms viewed from different angles. Spatial Vision 1995, 9, 139-150.
  20. Robert H Wurtz; Optic flow: A brain region devoted to optic flow analysis?. Current Biology 1998, 8, 554-556.
  21. Marco Bertamini; Juha Silvanto; Anthony M. Norcia; Alexis D.J. Makin; Johan Wagemans; The neural basis of visual symmetry and its role in mid- and high-level visual processing. Annals of the New York Academy of Sciences 2018, 1426, 111-126.
  22. Bruce D. Keefe; André D. Gouws; Aislin A. Sheldon; Richard J. W. Vernon; Samuel J. D. Lawrence; Declan J. McKeefry; Alex R. Wade; Antony B. Morland; Emergence of symmetry selectivity in the visual areas of the human brain: fMRI responses to symmetry presented in both frontoparallel and slanted planes. Human Brain Mapping 2018, 39, 3813-3826.
  23. Peter J. Kohler; Alasdair Clarke; Alexandra Yakovleva; Yanxi Liu; Anthony M. Norcia; Representation of Maximally Regular Textures in Human Visual Cortex. Journal of Neuroscience 2016, 36, 714-729.
  24. Yuka Sasaki; Wim Vanduffel; Tamara Knutsen; Christopher Tyler; Roger Tootell; Symmetry activates extrastriate visual cortex in human and nonhuman primates. Proceedings of the National Academy of Sciences of the United States of America 2005, 102, 3159-3163.
  25. Christopher W. Tyler; Heidi A. Baseler; Leonid L. Kontsevich; Lora T. Likova; Alex R. Wade; Brian A. Wandell; Predominantly extra-retinotopic cortical response to pattern symmetry. Neuroimage 2005, 24, 306-314.
  26. Chayenne Van Meel; Annelies Baeck; Céline R. Gillebert; Johan Wagemans; Hans P. Op de Beeck; The representation of symmetry in multi-voxel response patterns and functional connectivity throughout the ventral visual stream. Neuroimage 2019, 191, 216-224.
  27. Thomas Jacobsen; Lea Höfel; Descriptive and evaluative judgment processes: Behavioral and electrophysiological indices of processing symmetry and aesthetics. Cognitive, Affective, & Behavioral Neuroscience 2003, 3, 289-299.
  28. Alexis D.J. Makin; Moon M Wilton; Anna Pecchinenda; Marco Bertamini; Symmetry perception and affective responses: A combined EEG/EMG study. Neuropsychologia 2012, 50, 3250-3261.
  29. Damien Wright; Alexis D.J. Makin; Marco Bertamini; Electrophysiological responses to symmetry presented in the left or in the right visual hemifield. Cortex 2017, 86, 93-108.
  30. Alexis D.J. Makin; Damien Wright; Giulia Rampone; Letizia Palumbo; Martin Guest; Rhiannon Sheehan; Helen Cleaver; Marco Bertamini; An Electrophysiological Index of Perceptual Goodness. Cerebral Cortex 2016, 26, 4416-4434.
  31. Alexis D. J. Makin; Giulia Rampone; Anna Pecchinenda; Marco Bertamini; Electrophysiological responses to visuospatial regularity. Psychophysiology 2013, 50, 1045-1055.
  32. Peter J. Kohler; Alasdair D. F. Clarke; The human visual system preserves the hierarchy of two-dimensional pattern regularity. Proceedings of the Royal Society B: Biological Sciences 2021, 288, 20211142.
  33. Anthony M. Norcia; T. Rowan Candy; Mark W. Pettet; Vladimir Y. Vildavski; Christopher W. Tyler; Temporal dynamics of the human response to symmetry. Journal of Vision 2002, 2, 1-1.
  34. Sadanori Oka; Jonathan D. Victor; Mary M. Conte; Toshio Yanagida; VEPs elicited by local correlations and global symmetry: Characteristics and interactions. Vision Research 2007, 47, 2212-2222.
  35. Christian N. L. Olivers; Peter A. Van Der Helm; Symmetry and selective attention: A dissociation between effortless perception and serial search. Perception & Psychophysics 1998, 60, 1101-1116.
  36. Dina Devyatko; Ruth Kimchi; Visual Awareness Is Essential for Grouping Based on Mirror Symmetry. Symmetry 2020, 12, 1872.
  37. Anne E. Wignall; Astrid M. Heiling; Ken Cheng; Marie E. Herberstein; Flower Symmetry Preferences in Honeybees and their Crab Spider Predators. Ethology 2006, 112, 510-518.
  38. J. L. Gallant; C. E. Connor; S. Rakshit; J. W. Lewis; D. C. Van Essen; Neural responses to polar, hyperbolic, and Cartesian gratings in area V4 of the macaque monkey. Journal of Neurophysiology 1996, 76, 2718-2739.
  39. Jon Driver; Gordon C. Baylis; Robert D. Rafal; Preserved figure-ground segregation and symmetry perception in visual neglect. Nature 1992, 360, 73-75.
  40. Bart Machilsen; Maarten Pauwels; Johan Wagemans; The role of vertical mirror symmetry in visualshape detection. Journal of Vision 2009, 9, 11-11.
  41. Andrew J. Mojica; Mary A. Peterson; Display-wide influences on figure–ground perception: The case of symmetry. Attention, Perception, & Psychophysics 2014, 76, 1069-1084.
  42. Elena Mascalzoni; Daniel Osorio; Lucia Regolin; Giorgio Vallortigara; Symmetry perception by poultry chicks and its implications for three-dimensional object recognition. Proceedings of the Royal Society B: Biological Sciences 2011, 279, 841-846.
  43. Marc H. Bornstein; Kay Ferdinandsen; Charles G. Gross; Perception of symmetry in infancy.. Developmental Psychology 1981, 17, 82-86.
  44. Marc H. Bornstein; Joan Stiles-Davis; Discrimination and memory for symmetry in young children.. Developmental Psychology 1984, 20, 637-649.
  45. Marc H Pornstein; Sharon J Krinsky; Perception of symmetry in infancy: The salience of vertical symmetry and the perception of pattern wholes. Journal of Experimental Child Psychology 1985, 39, 1-19.
  46. Shobhita Sundaram, Darius Sinha, Matthew Groth, Tomotake Sasaki, Xavier Boix Symmetry Perception by Deep Networks: Inadequacy of Feed-Forward Architectures and Improvements with Recurrent Connections. arXiv:2112.04162 2022, 2112, 04162.
  47. Dietmar Heinke; Peter Wachman; Wieske van Zoest; E. Charles Leek; A failure to learn object shape geometry: Implications for convolutional neural networks as plausible models of biological vision. Vision Research 2021, 189, 81-92.
  48. Moller; Thornhill; Bilateral Symmetry and Sexual Selection: A Meta-Analysis. The American Naturalist 1998, 151, 174-192.
  49. Magnus Enquist; Anthony Arak; Symmetry, beauty and evolution. Nature 1994, 372, 169-172.
  50. Magnus Enquist; Rufus A. Johnstone; Generalization and the evolution of symmetry preferences. Proceedings of the Royal Society B: Biological Sciences 1997, 264, 1345-1348.
  51. Anthony C. Little; Benedict C. Jones; Lisa M. DeBruine; Facial attractiveness: evolutionary based research. Philosophical Transactions B 2011, 366, 1638-1659.
  52. Gillian Rhodes; Fiona Proffitt; Jonathon M. Grady; Alex Sumich; Facial symmetry and the perception of beauty. Psychonomic Bulletin & Review 1998, 5, 659-669.
  53. Frans Boselie; Emanuel Leeuwenberg; Birkhoff Revisited: Beauty as a Function of Effect and Means. The American Journal of Psychology 1985, 98, 1–39. .
  54. Alexis David James Makin; Anna Pecchinenda; Marco Bertamini; Implicit affective evaluation of visual symmetry.. Emotion 2012, 12, 1021-1030.
  55. Stephen E. Palmer; Karen B. Schloss; Jonathan Sammartino; Visual Aesthetics and Human Preference. Annual Review of Psychology 2013, 64, 77-107.
  56. Alexis Dj Makin; Mai Helmy; Marco Bertamini; Visual cortex activation predicts visual preference: Evidence from Britain and Egypt. The Quarterly Journal of Experimental Psychology 2018, 71, 1771-1780.
  57. Marco Bertamini; Alexis Makin; Anna Pecchinenda; Testing Whether and When Abstract Symmetric Patterns Produce Affective Responses. PLoS ONE 2013, 8, e68403.
  58. Lea Höfel; Thomas Jacobsen; Electrophysiological Indices of Processing Symmetry and Aesthetics. Journal of Psychophysiology 2007, 21, 9-21.
  59. Helmut Leder; Pablo P. L. Tinio; David Brieber; Tonio Kröner; Thomas Jacobsen; Raphael Rosenberg; Symmetry Is Not a Universal Law of Beauty. Empirical Studies of the Arts 2018, 37, 104-114.
  60. David Wyndham Lawrence; Robin Carhart-Harris; Roland Griffiths; Christopher Timmermann; Phenomenology and content of the inhaled N, N-dimethyltryptamine (N, N-DMT) experience. Scientific Reports 2022, 12, 1-22.
  61. Cott, C; Rock, A.J; Phenomenology of N,N-Dimethyltryptamine Use: A Thematic Analysis. Journal of Scientific Exploration 2008, 22, 359-370.
  62. The hyperbolic geometry of DMT experiences: Symmetries, Sheets and Saddled Scenes . https://www.qri.org. Retrieved 2023-7-17
  63. Andrea Alamia; Christopher Timmermann; David J Nutt; Rufin VanRullen; Robin L Carhart-Harris; DMT alters cortical travelling waves. Elife 2020, 9, e59784.
  64. Varg T. Königsmark; Johanna Bergmann; Reshanne R. Reeder; The Ganzflicker experience: High probability of seeing vivid and complex pseudo-hallucinations with imagery but not aphantasia. Cortex 2021, 141, 522-534.
  65. G. B. Ermentrout; J. D. Cowan; A mathematical theory of visual hallucination patterns. Biological Cybernetics 1979, 34, 137-150.
More
Information
Subjects: Psychology
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register : , , , ,
View Times: 390
Revisions: 2 times (View History)
Update Date: 18 Jul 2023
1000/1000
Video Production Service