{{Short description|Visual perception phenomenon}} The '''face inversion effect''' is a phenomenon in which identifying upside-down faces compared to upright faces is much more difficult than doing the same for non-facial objects.<ref>{{Cite book|url=https://www.researchgate.net/publication/281640103|title=The face inversion effect—Parts and wholes: Individual features and their configuration|last1=Civile|first1=Ciro|last2=Mclaren|first2=Rossy|last3=Mclaren|first3=I.P.L.|date=2013-09-23|volume=67}}</ref><ref>{{Cite journal|last=Yin|first=Robert K.|date=1969|title=Looking at upside-down faces.|journal=Journal of Experimental Psychology|volume=81|issue=1|pages=141–145|doi=10.1037/h0027474|issn=0022-1015}}</ref>
A typical study examining the face inversion effect would have images of the inverted and upright object presented to participants and time how long it takes them to recognise that object as what it actually is (i.e. a picture of a face as a face). The face inversion effect occurs when, compared to other objects, it takes a disproportionately longer time to recognise faces when they are inverted as opposed to upright.<ref>{{Cite journal|last1=Farah|first1=M. J.|last2=Wilson|first2=K. D.|last3=Drain|first3=H. M.|last4=Tanaka|first4=J. R.|date=1995|title=The inverted face inversion effect in prosopagnosia: evidence for mandatory, face-specific perceptual mechanisms |journal=Vision Research|volume=35|issue=14|pages=2089–2093|issn=0042-6989|pmid=7660612|doi=10.1016/0042-6989(94)00273-O|doi-access=free}}</ref><ref>{{Cite journal|last1=Thornton|first1=Ian|last2=Mullins|first2=Emma|last3=Banahan|first3=Kara|date=2011 |title=Motion can amplify the face-inversion effect |journal=Psihologija|volume=44|issue=1|pages=5–22|doi=10.2298/psi1101005t |doi-access=free}}</ref>
Faces are normally processed in the special face-selective regions of the brain, such as the fusiform face area.<ref name="Kanwisher 2006">{{Cite journal|last1=Kanwisher|first1=Nancy|last2=Yovel|first2=Galit|date=2006-12-29|title=The fusiform face area: a cortical region specialized for the perception of faces 9|journal=Philosophical Transactions of the Royal Society of London B: Biological Sciences |volume=361|issue=1476|pages=2109–2128|doi=10.1098/rstb.2006.1934 |pmc=1857737|pmid=17118927}}</ref> However, processing inverted faces involves both face-selective regions and additional visual areas such as mid-level visual areas <ref name="Gilaie-Dotan 2010">{{Cite journal|last1=Gilaie-Dotan|first1=Sharon|last2=Gelbard-Sagiv|first2=Hagar| last3=Malach|first3=Rafael|date=2010-04-01|title=Perceptual shape sensitivity to upright and inverted faces is reflected in neuronal adaptation |journal=NeuroImage |volume=50|issue=2|pages=383–395|doi=10.1016/j.neuroimage.2009.12.077 |pmc=3221039|pmid=20044007}}</ref> and high-level scene-sensitive and object-sensitive regions of the parahippocampal place area and lateral occipital cortex.<ref name="Epstein 1998" /><ref name="Malach 1995" /> There seems to be something different about inverted faces that requires them to also involve these mid-level and high-level scene and object processing mechanisms.<ref name="Pitcher 2011">{{Cite journal|last1=Pitcher|first1=David|last2=Duchaine|first2=Bradley|last3=Walsh|first3=Vincent|last4=Yovel|first4=Galit|last5=Kanwisher|first5=Nancy|date=2011|title=The role of lateral occipital face and object areas in the face inversion effect|journal=Neuropsychologia|volume=49|issue=12|pages=3448–3453|doi=10.1016/j.neuropsychologia.2011.08.020|pmid=21896279|s2cid=6834054|issn=0028-3932}}</ref>
The most supported explanation for why faces take longer to recognise when they are inverted is the configural information hypothesis. The configural information hypothesis states that faces are processed with the use of configural information to form a holistic (whole) representation of a face. Objects, however, are not processed in this configural way. Instead, they are processed featurally (in parts). Inverting a face disrupts configural processing, forcing it to instead be processed featurally like other objects. This causes a delay since it takes longer to form a representation of a face with only local information.<ref name="Freire 2000" />
== Neural systems of face recognition == thumb|Location of the Fusiform Face AreaFaces are processed in separate areas of the brain to other stimuli, such as scenes or non-facial objects. For example, the fusiform face area (FFA) is a face-selective region in the brain that is only used for facial processing.<ref name="Kanwisher 2006" /> The FFA responds more to upright but not inverted faces, demonstrating that inverted faces are not detected the same way that upright faces are.<ref name="Yovel 2005">{{Cite journal|last1=Yovel|first1=Galit|last2=Kanwisher|first2=Nancy|date=2005|title=The Neural Basis of the Behavioral Face-Inversion Effect|journal=Current Biology|volume=15|issue=24|pages=2256–2262|doi=10.1016/j.cub.2005.10.072|pmid=16360687|issn=0960-9822|doi-access=free|bibcode=2005CBio...15.2256Y }}</ref>
The scene-selective parahippocampal place area (PPA) processes places, or scenes of the visual environment.<ref name="Epstein 1998">{{Cite journal|last1=Epstein|first1=Russell|last2=Kanwisher|first2=Nancy|date=1998|title=A cortical representation of the local visual environment|journal=Nature|volume=392|issue=6676|pages=598–601|doi=10.1038/33402|pmid=9560155|bibcode=1998Natur.392..598E|s2cid=920141|issn=0028-0836}}</ref> The object recognition area in the lateral occipital cortex (LOC) is involved in the processing of objects.<ref name="Malach 1995">{{Cite journal|last1=Malach|first1=R|last2=Reppas|first2=J B|last3=Benson|first3=R R|last4=Kwong|first4=K K|last5=Jiang|first5=H|last6=Kennedy|first6=W A|last7=Ledden|first7=P J|last8=Brady|first8=T J|last9=Rosen|first9=B R|date=1995-08-29|title=Object-related activity revealed by functional magnetic resonance imaging in human occipital cortex.|pmc=41110|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=92|issue=18|pages=8135–8139|issn=0027-8424|pmid=7667258|doi=10.1073/pnas.92.18.8135|bibcode=1995PNAS...92.8135M|doi-access=free}}</ref> Together, these regions are used to process inverted, but not upright faces. This suggests that there is something special about inverted compared to upright faces that requires them to involve object and scene processing regions.<ref name="Pitcher 2011" />
There is still some activity in face recognition regions when viewing inverted faces.<ref name="Haxby 1999">{{Cite journal|last1=Haxby|first1=James V|last2=Ungerleider|first2=Leslie G|last3=Clark|first3=Vincent P|last4=Schouten|first4=Jennifer L|last5=Hoffman|first5=Elizabeth A|last6=Martin|first6=Alex|date=1999|title=The Effect of Face Inversion on Activity in Human Neural Systems for Face and Object Perception|journal=Neuron|volume=22|issue=1|pages=189–199|doi=10.1016/s0896-6273(00)80690-x|pmid=10027301|issn=0896-6273|doi-access=free}}</ref> Evidence has found that a face-selective region in the brain known as the occipital face area (OFA) is involved in the processing of both upright and inverted faces.<ref name="Pitcher 2011" /><ref name="Yovel 2005" />
Overall, face and object processing mechanisms seem to be separate in the brain. Recognising upright faces involves special facial recognition regions, but recognising inverted faces involves both face and non-facial stimuli recognition regions.
== Face vs. object recognition processes == === Face recognition ===
==== Configural information ==== Configural information, also known as relational information, helps people to quickly recognise faces. It involves the arrangement of facial features, such as the eyes and nose. There are two types of configural information: first-order relational information and second-order relational information.<ref name="Civile 2016">{{Cite journal|last1=Civile|first1=Ciro|last2=McLaren|first2=Rossy|last3=McLaren|first3=Ian P. L.|date=2016|title=The Face Inversion Effect: Roles of First and Second-Order Configural Information|jstor=10.5406/amerjpsyc.129.1.0023|journal=The American Journal of Psychology|volume=129|issue=1|pages=23–35|doi=10.5406/amerjpsyc.129.1.0023|pmid=27029104|hdl=10871/19932|hdl-access=free}}</ref>
First-order relational information consists of the spatial relationships between different features of the face. These relationships between facial features are common to most people, for example, having the mouth located under the nose. First-order relational information therefore helps to identify a face as a face and not some other object.<ref name="Civile 2016" />
Second-order relational information is the size of the relationships between the features of the face, relative to a prototype (a model of what a face should look like). This type of information helps to distinguish one face from another because it differs between different faces.<ref name="Civile 2016" />
==== Holistic processing ==== The holistic processing of faces describes the perception of faces as wholes, rather than the sum of their parts. This means that facial features (such as the eyes or nose) are not explicitly represented in the brain on their own, rather, the entire face is represented.<ref name="Tanaka 1993">{{Cite journal|last1=Tanaka|first1=James W.|last2=Farah|first2=Martha J.|date=1993|title=Parts and wholes in face recognition|journal=The Quarterly Journal of Experimental Psychology|volume=46|issue=2|pages=225–245|doi=10.1080/14640749308401045|pmid=8316637|s2cid=33396424}}</ref>
According to the configural information hypothesis of face recognition, recognising faces involves two stages that use configural information to form holistic representations of faces.<ref name="Taubert 2011">{{Cite journal|last1=Taubert|first1=Jessica|last2=Apthorp|first2=Deborah|last3=Aagten-Murphy|first3=David|last4=Alais|first4=David|date=2011|title=The role of holistic processing in face perception: Evidence from the face inversion effect|journal=Vision Research|volume=51|issue=11|pages=1273–1278|doi=10.1016/j.visres.2011.04.002|pmid=21496463|issn=0042-6989|doi-access=free}}</ref>
A study demonstrated that face-selective activity in the brain was delayed when the configural information of faces was disrupted (for example, when faces were inverted).<ref>{{Cite journal|date=1999-07-01|title=Spatio-temporal localization of the face inversion effect: an event-related potentials study|journal=Biological Psychology|volume=50|issue=3|pages=173–189|doi=10.1016/S0301-0511(99)00013-7|pmid=10461804|issn=0301-0511|last1=Rossion|first1=B|s2cid=18206643}}</ref> This means that it took longer for the participants to recognise the faces they were viewing as faces and not other (non-facial) objects. The configural information explanation for facial recognition is therefore supported by the presence of the face inversion effect (a delay when faces are inverted).
==== Stages of face recognition ==== The first stage of recognising faces in the configural information hypothesis is first-level information processing. This stage uses first-order relational information to detect a face (i.e. to determine that a face is actually a face and not another object). Building a holistic representation of a face occurs at this early stage of face processing, to allow faces to be detected quickly.<ref name="Taubert 2011" />
The next stage, second-level information processing, distinguishes one face from another with the use of second-order relational information.<ref name="Taubert 2011" />
=== Object recognition === Smaller inversion effects occur for non-facial objects, suggesting that faces and other objects are not processed in the same way.
Face recognition involves configural information to process faces holistically. However, object recognition does not use configural information to form a holistic representation. Instead, each part of the object is processed independently to allow it to be recognised. This is known as a featural recognition method.<ref name="Civile 2016" /> Additionally, an explicit representation of each part of the object is made, rather than a representation of the object as a whole.<ref name="Tanaka 1993" />
== Theories == === Configural information hypothesis === According to the configural information hypothesis, the face inversion effect occurs because configural information can no longer be used to build a holistic representation of a face. Inverted faces are instead processed like objects, using local information (i.e. the individual features of the face) instead of configural information.
A delay is caused when processing inverted faces compared to upright faces. This is because the specific holistic mechanism (see holistic processing) that allows faces to be quickly detected is absent when processing inverted faces. Only local information is available when viewing inverted faces, disrupting this early recognition stage and therefore preventing faces from being detected as quickly. Instead, independent features are put together piece-by-piece to form a representation of the object (a face) and allow the viewer to recognise what it is.<ref name="Freire 2000">{{Cite journal|last1=Freire|first1=Alejo|last2=Lee|first2=Kang|last3=Symons|first3=Lawrence A|date=2000|title=The Face-Inversion Effect as a Deficit in the Encoding of Configural Information: Direct Evidence|journal=Perception|volume=29|issue=2|pages=159–170|doi=10.1068/p3012|pmid=10820599|s2cid=19695957|issn=0301-0066}}</ref>
=== Alternate hypotheses === Although the configural processing hypothesis is a popular explanation for the face inversion effect, there have been some challenges to this theory. In particular, it has been suggested that faces and objects are both recognised using featural processing mechanisms, instead of holistic processing for faces and featural processing for objects.<ref name="Matsuyoshi 2015">{{Cite journal|last1=Matsuyoshi|first1=Daisuke|last2=Morita|first2=Tomoyo|last3=Kochiyama|first3=Takanori|last4=Tanabe|first4=Hiroki C.|last5=Sadato|first5=Norihiro|last6=Kakigi|first6=Ryusuke|date=2015-03-11|title=Dissociable Cortical Pathways for Qualitative and Quantitative Mechanisms in the Face Inversion Effect|journal=Journal of Neuroscience|volume=35|issue=10|pages=4268–4279|doi=10.1523/JNEUROSCI.3960-14.2015|issn=0270-6474|pmid=25762673|pmc=6605288}}</ref> The face inversion effect is therefore not caused by delay from faces being processed as objects. Instead, another element is involved. Two potential explanations follow.
==== Perceptual learning ==== Perceptual learning is a common alternative explanation to the configural processing hypothesis for the face inversion effect. According to the perceptual learning theory, being presented with a stimulus (for example, faces or cars) more often makes that stimulus easier to recognise in the future.<ref name="Wallis 2013">{{Cite journal|last=Wallis|first=Guy|date=2013|title=Toward a unified model of face and object recognition in the human visual system|journal=Frontiers in Psychology|language=English|volume=4|pages=497|doi=10.3389/fpsyg.2013.00497|pmid=23966963|pmc=3744012|issn=1664-1078|doi-access=free}}</ref>
Most people are highly familiar with viewing upright faces. It follows that highly efficient mechanisms have been able to develop to the quick detection and identification of upright faces.<ref>{{Cite journal|last1=Gold|first1=J.|last2=Bennett|first2=P. J.|last3=Sekuler|first3=A. B.|date=1999|title=Signal but not noise changes with perceptual learning|journal=Nature|volume=402|issue=6758|pages=176–178|doi=10.1038/46027|pmid=10647007|bibcode=1999Natur.402..176G|s2cid=4426137|issn=0028-0836}}</ref> This means that the face inversion effect would therefore be caused by an increased amount of experience with perceiving and recognising upright faces compared to inverted faces.<ref name="Sekuler 2004">{{Cite journal|last1=Sekuler|first1=Allison B|last2=Gaspar|first2=Carl M|last3=Gold|first3=Jason M|last4=Bennett|first4=Patrick J|date=2004|title=Inversion Leads to Quantitative, Not Qualitative, Changes in Face Processing|journal=Current Biology|volume=14|issue=5|pages=391–396|doi=10.1016/j.cub.2004.02.028|pmid=15028214|issn=0960-9822|doi-access=free|bibcode=2004CBio...14..391S }}</ref>
==== Face-scheme incompatibility ==== The face-scheme incompatibility model has been proposed in order to explain some of the missing elements of the configural information hypothesis. According to the model, faces are processed and assigned meaning by the use of schemes and prototypes.<ref name="Rakover 2013">{{Cite journal|last=Rakover|first=Sam S.|date=2013-08-01|title=Explaining the face-inversion effect: the face–scheme incompatibility (FSI) model|journal=Psychonomic Bulletin & Review|volume=20|issue=4|pages=665–692|doi=10.3758/s13423-013-0388-1|pmid=23381811|issn=1069-9384|doi-access=free}}</ref>
The model defines a scheme as an abstract representation of the general structure of a face, including characteristics common to most faces (i.e. the structure of and relationships between facial features). A prototype refers to an image of what an average face would look like for a particular group (e.g. humans or monkeys). After being recognised as a face with the use of a scheme, new faces are added to a group by being evaluated for their similarity to that group's prototype.<ref name="Rakover 2013" />
There are different schemes for upright and inverted faces: upright faces are more frequently viewed and thus have more efficient schemes than inverted faces. The face inversion effect is thus partly caused by less efficient schemes for processing the less familiar inverted form of faces.<ref name="Rakover 2013" /> This makes the face-scheme incompatibility model similar to the perceptual learning theory, because both consider the role of experience important in the quick recognition of faces.<ref name="Sekuler 2004" /><ref name="Rakover 2013" />
=== Integration of theories === Instead of just one explanation for the face inversion effect, it is more likely that aspects of different theories apply. For example, faces could be processed with configural information but the role of experience may be important for quickly recognising a particular type of face (i.e. human or dog) by building schemes of this facial type.<ref name="Matsuyoshi 2015" />
== Development == The ability to quickly detect and recognise faces was important in early human life, and is still useful today. For example, facial expressions can provide various signals important for communication.<ref name="Schmidt 2001">{{Cite journal|last1=Schmidt|first1=Karen L.|last2=Cohn|first2=Jeffrey F.|date=2001|title=Human Facial Expressions as Adaptations: Evolutionary Questions in Facial Expression Research|journal=American Journal of Physical Anthropology|volume=Suppl 33|pages=3–24|doi=10.1002/ajpa.20001|issn=0002-9483|pmc= 2238342|pmid=11786989}}</ref><ref>{{Cite journal|last1=Goldman|first1=Alvin I.|last2=Sripada|first2=Chandra Sekhar|date=2005|title=Simulationist models of face-based emotion recognition|journal=Cognition|volume=94|issue=3|pages=193–213|doi=10.1016/j.cognition.2004.01.005|pmid=15617671|s2cid=12794842|issn=0010-0277}}</ref> Highly efficient facial recognition mechanisms have therefore developed to support this ability.<ref name="Wallis 2013" />
As humans get older, they become more familiar with upright human faces and continuously refine the mechanisms used to recognise them.<ref name="Passarotti 2007">{{Cite journal|last1=Passarotti|first1=A.M.|last2=Smith|first2=J.|last3=DeLano|first3=M.|last4=Huang|first4=J.|date=2007|title=Developmental differences in the neural bases of the face inversion effect show progressive tuning of face-selective regions to the upright orientation|journal=NeuroImage|volume=34|issue=4|pages=1708–1722|doi=10.1016/j.neuroimage.2006.07.045|pmid=17188904|s2cid=18661084|issn=1053-8119}}</ref> This process allows people to quickly detect faces around them, which helps with social interaction.<ref name="Schmidt 2001" />
By about the first year of life, infants are familiar with faces in their upright form and are thus more prone to experiencing the face inversion effect. As they age, they get better at recognising faces and so the face inversion effect becomes stronger.<ref name="Passarotti 2007" /> The increased strength of the face inversion effect over time supports the perceptual learning hypothesis, since more experience with faces results in increased susceptibility to the effect.<ref name="Sekuler 2004" />
The more familiar a particular type of face (e.g. human or dog) is, the more susceptible one is to the face inversion effect for that face. This applies to both humans and other species. For example, older chimpanzees familiar with human faces experienced the face inversion effect when viewing human faces, but the same result did not occur for younger chimpanzees familiar with chimpanzee faces.<ref>{{Cite journal|last1=Dahl|first1=Christoph D.|last2=Rasch|first2=Malte J.|last3=Tomonaga|first3=Masaki|last4=Adachi|first4=Ikuma|date=2013-08-27|title=The face inversion effect in non-human primates revisited - an investigation in chimpanzees (Pan troglodytes)|journal=Scientific Reports|volume=3|issue=1|pages=2504|doi=10.1038/srep02504|issn=2045-2322|pmc=3753590|pmid=23978930|bibcode=2013NatSR...3E2504D}}</ref> The face inversion effect was also stronger for dog faces when they were viewed by dog experts.<ref name="Civile 2016" /> This evidence demonstrates that familiarity with a particular type of face develops over time and appears to be necessary for the face inversion effect to occur.
== Exceptions == There are a number of conditions that may reduce or even eliminate the face inversion effect. This is because the mechanism used to recognise faces by forming holistic representations is absent or disrupted. This can cause faces to be processed the same way as other (non-facial) objects.
=== Prosopagnosia === Prosopagnosia is a condition marked by an inability to recognize faces.<ref name="Busigny 2010">{{Cite journal|last1=Busigny|first1=Thomas|last2=Rossion|first2=Bruno|date=2010|title=Acquired prosopagnosia abolishes the face inversion effect|journal=Cortex|volume=46|issue=8|pages=965–981|doi=10.1016/j.cortex.2009.07.004|pmid=19683710|s2cid=16844554|issn=0010-9452}}</ref> When those with prosopagnosia view faces, the fusiform gyrus (a facial recognition area of the brain) activates differently to how it would in someone without the condition.<ref>{{Cite journal|last1=Grüter|first1=Thomas|last2=Grüter|first2=Martina|last3=Carbon|first3=Claus-Christian|date=2008|title=Neural and genetic foundations of face recognition and prosopagnosia|journal=Journal of Neuropsychology|volume=2|issue=1|pages=79–97|doi=10.1348/174866407x231001|pmid=19334306|issn=1748-6645|citeseerx=10.1.1.571.9472}}</ref> Additionally, non-facial object recognition areas (such as the ventral occipitotemporal extrastriate cortex) are activated when viewing faces, suggesting that faces and objects are processed similarly.<ref name="Haxby 1999" />
Individuals with prosopagnosia can be unaffected or even benefit from face inversion in facial recognition tasks.<ref name="Busigny 2010" /><ref>{{Cite journal|date=1995-07-01|title=The inverted face inversion effect in prosopagnosia: Evidence for mandatory, face-specific perceptual mechanisms|journal=Vision Research|volume=35|issue=14|pages=2089–2093|doi=10.1016/0042-6989(94)00273-O|pmid=7660612|issn=0042-6989|last1=Farah|first1=Martha J|last2=Wilson|first2=Kevin D|last3=Maxwell Drain|first3=H|last4=Tanaka|first4=James R|doi-access=free}}</ref> Normally, they process upright faces featurally, like objects. Inverted faces are also processed featurally rather than holistically.<ref>{{Cite journal|last1=Avidan|first1=Galia|last2=Tanzer|first2=Michal|last3=Behrmann|first3=Marlene|date=2011|title=Impaired holistic processing in congenital prosopagnosia |journal=Neuropsychologia|volume=49|issue=9|pages=2541–2552|doi=10.1016/j.neuropsychologia.2011.05.002 |pmc=3137703|pmid=21601583}}</ref> This demonstrates that there is no difference between the processing of upright and inverted faces, which explains why there is no disproportionate delay for recognizing inverted faces.<ref name="Haxby 1999" />
===Autism spectrum disorder=== Like those with prosopagnosia, individuals with autism spectrum disorder (ASD) do not use a configural processing mechanism to form a holistic representation of a face.<ref>{{Cite journal|last1=van der Geest|first1=J.N.|last2=Kemner|first2=C.|last3=Verbaten|first3=M.N.|last4=van Engeland|first4=H.|date=2002|title=Gaze behavior of children with pervasive developmental disorder toward human faces: a fixation time study|journal=Journal of Child Psychology and Psychiatry|volume=43|issue=5|pages=669–678|doi=10.1111/1469-7610.00055|pmid=12120862|issn=0021-9630}}</ref> Instead, they tend to process faces with the use of local or featural information.<ref>{{Cite journal|last1=Behrmann|first1=Marlene|last2=Avidan|first2=Galia|last3=Leonard|first3=Grace Lee|last4=Kimchi|first4=Rutie|last5=Luna|first5=Beatriz|last6=Humphreys|first6=Kate|last7=Minshew|first7=Nancy|date=2006|title=Configural processing in autism and its relationship to face processing |journal=Neuropsychologia|volume=44|issue=1|pages=110–129|doi=10.1016/j.neuropsychologia.2005.04.002 |pmid=15907952|url=http://repository.cmu.edu/cgi/viewcontent.cgi?article=1114&context=psychology|citeseerx=10.1.1.360.7141|s2cid=6407530}}</ref> This means that the same featural mechanisms are used between processing upright faces, inverted faces, and objects. Consequentially, the face inversion effect is less likely to occur in those with ASD.<ref>{{Cite journal|last=Falck-Ytter|first=Terje|date=2008|title=Face inversion effects in autism: a combined looking time and pupillometric study |journal=Autism Research|volume=1|issue=5|pages=297–306|doi=10.1002/aur.45 |pmid=19360681|s2cid=1123044}}</ref>
However, there is some evidence that the development of a holistic facial recognition mechanism in those with ASD is simply delayed, rather than missing. This would mean that there would actually be a difference between the processing of upright and inverted faces. Those with ASD may therefore eventually become susceptible to the face inversion effect.<ref>{{Cite journal|last1=Hedley|first1=Darren|last2=Brewer|first2=Neil|last3=Young|first3=Robyn|date=2014-10-31|title=The Effect of Inversion on Face Recognition in Adults with Autism Spectrum Disorder|journal=Journal of Autism and Developmental Disorders|volume=45|issue=5|pages=1368–1379|doi=10.1007/s10803-014-2297-1|pmid=25358250|s2cid=12284026|issn=0162-3257}}</ref>
==See also== * Autism Spectrum Disorder * Face perception * Prosopagnosia * Thatcher effect
==References== {{Reflist|32em}}
Category:Cognition Category:Face perception