Editing Symmetry (section)

===In psychology and neuroscience===
{{Further|Visual perception}}

For a human observer, some symmetry types are more salient than others, in particular the most salient is a reflection with a vertical axis, like that present in the human face. [[Ernst Mach]] made this observation in his book "The analysis of sensations" (1897),<ref>{{cite book |title = Symmetries and Group Theory in Particle Physics: An Introduction to Space-Time and Internal Symmetries | first1 = Ernst |last1 = Mach | publisher = Open Court Publishing House |year = 1897}}</ref> and this implies that perception of symmetry is not a general response to all types of regularities. Both behavioural and neurophysiological studies have confirmed the special sensitivity to reflection symmetry in humans and also in other animals.<ref>{{cite journal|author1=Wagemans, J.|title=Characteristics and models of human symmetry detection|journal=[[Trends in Cognitive Sciences]]|volume=1|issue=9|pages=346–352| year=1997|doi= 10.1016/S1364-6613(97)01105-4|pmid=21223945|s2cid=2143353|url=https://lirias.kuleuven.be/handle/123456789/207060}}</ref> Early studies within the [[Gestalt psychology|Gestalt]] tradition suggested that bilateral symmetry was one of the key factors in perceptual [[Principles of grouping|grouping]]. This is known as the [[Gestalt psychology#Law of Symmetry|Law of Symmetry]]. The role of symmetry in grouping and figure/ground organization has been confirmed in many studies. For instance, detection of reflectional symmetry is faster when this is a property of a single object.<ref>{{cite journal | author1=Bertamini, M.| title=Sensitivity to reflection and translation is modulated by objectness | journal=[[Perception (journal)|Perception]]| volume=39|pages=27–40| year=2010| issue=1 | doi=10.1068/p6393| pmid=20301844 | s2cid=22451173 }}</ref> Studies of human perception and psychophysics have shown that detection of symmetry is fast, efficient and robust to perturbations. For example, symmetry can be detected with presentations between 100 and 150 milliseconds.<ref>{{cite journal|author1=Barlow, H.B.|author2=Reeves, B.C.|title=The versatility and absolute efficiency of detecting mirror symmetry in random dot displays|journal=[[Vision Research]]|volume=19|issue=7|pages=783–793|year=1979|doi= 10.1016/0042-6989(79)90154-8|pmid=483597|s2cid=41530752}}</ref>

More recent neuroimaging studies have documented which brain regions are active during perception of symmetry. Sasaki et al.<ref>{{cite journal |author1=Sasaki, Y.|author2=Vanduffel, W.|author3=Knutsen, T.|author4=Tyler, C.W.|author5=Tootell, R.|title=Symmetry activates extrastriate visual cortex in human and nonhuman primates |journal=[[Proceedings of the National Academy of Sciences of the USA]]|volume=102|issue=8|pages=3159–3163|year=2005|doi= 10.1073/pnas.0500319102|pmid=15710884|pmc=549500|bibcode=2005PNAS..102.3159S|doi-access=free}}</ref> used functional magnetic resonance imaging (fMRI) to compare responses for patterns with symmetrical or random dots. A strong activity was present in extrastriate regions of the occipital cortex but not in the primary visual cortex. The extrastriate regions included V3A, V4, V7, and the lateral occipital complex (LOC). Electrophysiological studies have found a late posterior negativity that originates from the same areas.<ref>{{cite journal |author1=Makin, A.D.J. |author2=Rampone, G. |author3= Pecchinenda, A. |author4= Bertamini, M. |title= Electrophysiological responses to visuospatial regularity |journal=[[Psychophysiology]]| volume=50| pages= 1045–1055|year=2013|issue=10 |doi=10.1111/psyp.12082|pmid=23941638 }}</ref> In general, a large part of the visual system seems to be involved in processing visual symmetry, and these areas involve similar networks to those responsible for detecting and recognising objects.<ref>{{cite journal |author1=Bertamini, M.|author2=Silvanto, J. |author3=Norcia, A.M. |author4=Makin, A.D.J. |author5= Wagemans, J. |title=The neural basis of visual symmetry and its role in middle and high-level visual processing |journal=[[Annals of the New York Academy of Sciences]]|volume=132|pages=280–293|year=2018|issue=1 |doi=10.1111/nyas.13667|pmid=29604083 |bibcode=2018NYASA1426..111B |doi-access=free|hdl=11577/3289328 |hdl-access=free }}</ref>