Face Inversion Effect Research Articles

The role of experience-based perceptual learning in the face inversion effect

Perceptual learning of the type we consider here is a consequence of experience with a class of stimuli. It amounts to an enhanced ability to discriminate between stimuli. We argue that it contributes to the ability to distinguish between faces and recognize individuals, and in particular contributes to the face inversion effect (better recognition performance for upright vs inverted faces). Previously, we have shown that experience with a prototype defined category of checkerboards leads to perceptual learning, that this produces an inversion effect, and that this effect can be disrupted by Anodal tDCS to Fp3 during pre-exposure. If we can demonstrate that the same tDCS manipulation also disrupts the inversion effect for faces, then this will strengthen the claim that perceptual learning contributes to that effect. The important question, then, is whether this tDCS procedure would significantly reduce the inversion effect for faces; stimuli that we have lifelong expertise with and for which perceptual learning has already occurred. Consequently, in the experiment reported here we investigated the effects of anodal tDCS at Fp3 during an old/new recognition task for upright and inverted faces. Our results show that stimulation significantly reduced the face inversion effect compared to controls. The effect was one of reducing recognition performance for upright faces. This result is the first to show that tDCS affects perceptual learning that has already occurred, disrupting individuals’ ability to recognize upright faces. It provides further support for our account of perceptual learning and its role as a key factor in face recognition.

Face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects.

Studies investigating event-related potentials have reported on face-sensitive P1 and N170 components, as well as object-related N170 components. Face-sensitive N170 is also sensitive to face inversion, which has been defined as the face-inversion effect. This study aimed to directly compare the relationship between face-sensitive N170 during face perception (upright and inverted faces) and object-related N170 during object perception (two-dimensional and three-dimensional objects). More specifically, the purpose was to clarify whether face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects. Electroencephalography was performed in participants who were shown one of the four types of stimuli: upright faces, inverted faces, two-dimensional objects, or three-dimensional objects. The results revealed that the latency of P1 for three-dimensional objects was significantly longer than that for two-dimensional objects, the latency of N170 for three-dimensional objects was significantly longer than that for two-dimensional objects, and the latency of N170 for inverted faces was significantly longer than that for upright faces. These findings suggest that face-sensitive P1 and N170 components are related to the perception of two-dimensional and three-dimensional objects. Moreover, the results suggest that, similar to the face-inversion effect of face-sensitive N170 affected by mental rotation of the face, the object-related N170 of three-dimensional objects was affected by the mental rotation of two-dimensional objects. This suggests the novel possibility that face-sensitive P1 and N170 components can be used as an index for the perception of two-dimensional and three-dimensional objects.

Inversion effects for faces and objects in developmental prosopagnosia: A case series analysis

The disproportionate face inversion effect (dFIE) concerns the finding that face recognition is more affected by inversion than recognition of non-face objects; an effect assumed to reflect that face recognition relies on special operations. Support for this notion comes from studies showing that face processing in developmental prosopagnosia (DP) is less affected by inversion than it is in normal subjects, and that DPs may even display face inversion superiority effects, i.e. better processing of inverted compared to upright faces. To date, however, there are no reports of direct comparisons between inversion effects for faces and objects, investigating whether the altered inversion effect in DP is specific to faces. We examined this question by comparing inversion effects for faces and cars in two otherwise identical recognition tasks in a group of DPs (N = 16) and a matched control group, using a case series design. Although both groups showed inversion effects for both faces and cars, only the control group exhibited a significant dFIE, i.e. a larger inversion effect for faces than cars. In comparison, the DPs were not significantly more affected by inversion than the control group when assessed with a face processing task that did not require recognition. Importantly, in both settings the DPs are better with upright than with inverted faces, and on the individual level no DP was found to perform significantly better with inverted than with upright faces. In fact, the DPs are impaired relative to the control group with both upright and inverted faces and to a less extent also with upright and inverted cars. These results yield no evidence of inversion superiority in DP but rather suggest that their face recognition problem is not limited to operations specialized for upright faces.

The role of horizontal facial structure on the N170 and N250

Recent studies have shown that horizontal facial structure is important for face identification (Dakin and Watt, 2009; Goffaux and Dakin, 2010). Also, sensitivity to horizontal structure is associated with the size of the face inversion effect (Pachai et al., 2013). However, it is unclear how the N170 and N250, two components of visual event-related potentials ERPs that have been implicated in face perception, are modulated by oriented facial structure in an upright face identification task. Here, we recorded ERPs and behavioural accuracy from adult observers performing a 1-of-6 face identification task in conditions that parametrically manipulated the orientation structure of upright faces. Faces were filtered with ideal orientation filters centred on either 0 (horizontal) or 90 deg (vertical). Filter bandwidth was varied across conditions from ±45 to ±90 deg in steps of ±9 deg. As has been reported previously, response accuracy was significantly higher for faces that contained horizontal structure than vertical structure, and the horizontal-vertical difference was correlated with accuracy for unfiltered faces. In addition, the N170 and N250 were affected by the manipulation of horizontal facial structure. Furthermore, for the N250, but not the N170, the relative sensitivity to horizontal compared to vertical facial structure was significantly correlated with identification accuracy for unfiltered faces. We suggest that in a face identification task, the N250 but not the N170 is modulated by the amount of diagnostic information conveyed by horizontal structure.

External and internal facial features modulate processing of vertical but not horizontal spatial relations

Some years ago an asymmetry was reported for the inversion effect for horizontal (H) and vertical (V) relational face manipulations (Goffaux & Rossion, 2007). Subsequent research examined whether a specific disruption of long-range relations underlies the H/V inversion asymmetry (Sekunova & Barton, 2008). Here, we tested how detection of changes in interocular distance (H) and eye height (V) depends on cardinal internal features and external feature surround. Results replicated the H/V inversion asymmetry. Moreover, we found very different face cue dependencies for both change types. Performance and inversion effects did not depend on the presence of other face cues for detecting H changes. In contrast, accuracy for detecting V changes strongly depended on internal and external features, showing cumulative improvement when more cues were added. Inversion effects were generally large, and larger with external feature surround. The cue independence in detecting H relational changes indicates specialized local processing tightly tuned to the eyes region, while the strong cue dependency in detecting V relational changes indicates a global mechanism of cue integration across different face regions. These findings suggest that the H/V asymmetry of the inversion effect rests on an H/V anisotropy of face cue dependency, since only the global V mechanism suffers from disruption of cue integration as the major effect of face inversion.

Disordered high-frequency oscillation in face processing in schizophrenia patients.

Schizophrenia is a complex disorder characterized by marked social dysfunctions, but the neural mechanism underlying this deficit is unknown. To investigate whether face-specific perceptual processes are influenced in schizophrenia patients, both face detection and configural analysis were assessed in normal individuals and schizophrenia patients by recording electroencephalogram (EEG) data. Here, a face processing model was built based on the frequency oscillations, and the evoked power (theta, alpha, and beta bands) and the induced power (gamma bands) were recorded while the subjects passively viewed face and nonface images presented in upright and inverted orientations. The healthy adults showed a significant face-specific effect in the alpha, beta, and gamma bands, and an inversion effect was observed in the gamma band in the occipital lobe and right temporal lobe. Importantly, the schizophrenia patients showed face-specific deficits in the low-frequency beta and gamma bands, and the face inversion effect in the gamma band was absent from the occipital lobe. All these results revealed face-specific processing in patients due to the disorder of high-frequency EEG, providing additional evidence to enrich future studies investigating neural mechanisms and serving as a marked diagnostic basis.

The Bandwidth of Diagnostic Horizontal Structure for Face Identification.

Horizontally oriented spatial frequency components are a diagnostic source of face identity information, and sensitivity to this information predicts upright identification accuracy and the magnitude of the face-inversion effect. However, the bandwidth at which this information is conveyed, and the extent to which human tuning matches this distribution of information, has yet to be characterized. We designed a 10-alternative forced choice face identification task in which upright or inverted faces were filtered to retain horizontal or vertical structure. We systematically varied the bandwidth of these filters in 10° steps and replaced the orientation components that were removed from the target face with components from the average of all possible faces. This manipulation created patterns that looked like faces but contained diagnostic information in orientation bands unknown to the observer on any given trial. Further, we quantified human performance relative to the actual information content of our face stimuli using an ideal observer with perfect knowledge of the diagnostic band. We found that the most diagnostic information for face identification is conveyed by a narrow band of orientations along the horizontal meridian, whereas human observers use information from a wide range of orientations.

The role of the head in configural body processing: Behavioural and electrophysiological evidence from the inversion and scrambling effect.

The present study aimed to further explore the role of the head for configural body processing by comparing complete bodies with headless bodies and faceless heads (Experiment 1). A second aim was to further explore the role of the eye region in configural face processing (Experiment 2). Due to that, we conducted a second experiment with complete faces, eyeless faces, and eyes. In addition, we used two effects to manipulate configural processing: the effect of stimulus inversion and scrambling. The current data clearly show an inversion effect for intact bodies presented with head and faces including the eye region. Thus, the head and the eye region seem to be central for configural processes that are manipulated by the effect of stimulus inversion. Furthermore, the behavioural and electrophysiological body inversion effect depends on the intact configuration of bodies and is associated with the N170 as the face inversion effect depends on the intact face configuration. Hence, configural body processing depends not only on the presence of the head but rather on a complete representation of human bodies that includes the body and the head. Furthermore, configural face processing relies on intact and complete face representations that include faces and eyes.

The effect of scrambling upright and inverted faces on the N170.

The face inversion effect refers to a decrement in performance when we try to recognise familiar faces turned upside down (inverted), compared with familiar faces presented in their usual (upright) orientation. Recently, we have demonstrated that the inversion effect can also be found with checkerboards drawn from prototype-defined categories when the participants have been trained with these categories, suggesting that factors such as expertise and the relationships between stimulus features may be important determinants of this effect. We also demonstrated that the typical inversion effect on the N170 seen with faces is found with checkerboards, suggesting that modulation of the N170 is a marker for disruption in the use of configural information. In the present experiment, we first demonstrate that our scrambling technique greatly reduces the inversion effect in faces. Following this, we used Event-Related Potentials ( ERPs) recorded while participants performed an Old/New recognition study on normal and scrambled faces presented in both upright and inverted orientations to investigate the impact of scrambling on the N170. We obtained the standard robust inversion effect for normal faces: The N170 was both larger and delayed for normal inverted faces as compared with normal upright faces, whereas a significantly reduced inversion effect was recorded for scrambled faces. These results show that the inversion effect on the N170 is greater for normal compared with scrambled faces, and we interpret the smaller effect for scrambled faces as being due to the reduction in expertise for those faces consequent on scrambling.

About Face: Matching Unfamiliar Faces Across Rotations of View and Lighting.

Matching the identities of unfamiliar faces is heavily influenced by variations in their images. Changes to viewpoint and lighting direction during face perception are commonplace across yaw and pitch axes and can result in dramatic image differences. We report two experiments that, for the first time, factorially investigate the combined effects of lighting and view angle on matching performance for unfamiliar faces. The use of three-dimensional head models allowed control of both lighting and viewpoint. We found viewpoint effects in the yaw axis with little to no effect of lighting. However, for rotations about the pitch axis, there were both viewpoint and lighting effects and these interacted where lighting effects were found only for front views and views from below. The pattern of effects was similar regardless of whether view variation occurred as a result of head (Experiment 1) or camera (Experiment 2) suggesting that face matching is not purely image based. Along with face inversion effects in Experiment 1, the results of this study suggest that face perception is based on shape and surface information and draws on implicit knowledge of upright faces and ecological (top) lighting conditions.

Face inversion reveals holistic processing of peripheral faces

Face perception is accomplished by face-selective neural processes, involving holistic processing that enables highly efficient integration of facial features into a whole-face representation. It has been shown that in face-selective regions of the ventral temporal cortex (VTC), neural resources involved in holistic processing are primarily dedicated to the central portion of the visual field. These findings raise the intriguing possibility that holistic processing might be the privilege of centrally presented faces and could be strongly diminished in the case of peripheral faces. We addressed this question using the face inversion effect (FIE), a well-established marker of holistic face processing. The behavioral results revealed impaired identity discrimination performance for inverted peripheral faces scaled according to the V1 magnification factor, compared to upright presented faces. The size of peripheral FIE was comparable to that found for centrally displayed faces. Face inversion affected the early ERP responses to faces in two time intervals. The earliest FIE was most pronounced in the time window between 130 and 140 msec following stimulus presentation, for both centrally and peripherally displayed faces and in the latter case, it was present only over the contralateral hemisphere. The timing of the next component FIE corresponded closely with the temporal interval of the N170 ERP component and showed strong right hemisphere (RH) lateralization, both when faces were displayed in the left or right visual field (RVF). Furthermore, we also showed that centrally presented face masks impaired peripheral face identity discrimination performance, but did not reduce the magnitude of the FIE. These findings revealed robust behavioral and neural inversion effects for peripheral faces and thus suggest that faces are processed holistically throughout the visual field.

Holistic face representation is highly orientation-specific.

It has long been argued that face processing requires disproportionate reliance on holistic processing (HP), relative to that required for nonface object recognition. Nevertheless, whether the holistic nature of face perception is achieved via a unique internal representation or by the employment of an automated attention mechanism is still debated. Previous studies had used the face inversion effect (FIE), a unique face-processing marker, or the face composite task, a gold standard paradigm measuring holistic processing, to examine the validity of these two different hypotheses, with some studies combining the two paradigms. However, the results of such studies remain inconclusive, particularly pertaining to the issue of the two proposed HP mechanisms-an internal representation as opposed to an automated attention mechanism. Here, using the complete composite paradigm design, we aimed to examine whether face rotation yields a nonlinear or a linear drop in HP, thus supporting an account that face processing is based either on an orientation-dependent internal representation or on automated attention. Our results reveal that even a relatively small perturbation in face orientation (30 deg away from upright) already causes a sharp decline in HP. These findings support the face internal representation hypothesis and the notion that the holistic processing of faces is highly orientation-specific.

Comparing the face inversion effect in crows and humans

Humans show impaired recognition of faces that are presented upside down, a phenomenon termed face inversion effect, which is thought to reflect the special relevance of faces for humans. Here, we investigated whether a phylogenetically distantly related avian species, the carrion crow, with similar socio-cognitive abilities to human and non-human primates, exhibits a face inversion effect. In a delayed matching-to-sample task, two crows had to differentiate profiles of crow faces as well as matched controls, presented both upright and inverted. Because crows can discriminate humans based on their faces, we also assessed the face inversion effect using human faces. Both crows performed better with crow faces than with human faces and performed worse when responding to inverted pictures in general compared to upright pictures. However, neither of the crows showed a face inversion effect. For comparative reasons, the tests were repeated with human subjects. As expected, humans showed a face-specific inversion effect. Therefore, we did not find any evidence that crows—like humans—process faces as a special visual stimulus. Instead, individual recognition in crows may be based on cues other than a conspecific’s facial profile, such as their body, or on processing of local features rather than holistic processing.

Effects of social and non-social stress on social behavior in health and social anxiety disorder

High-level visual object processing is often assumed to be largely position-independent. Here we demonstrate that when faces and non-face objects simultaneously appear in opposite visual hemifields, the face-sensitive N170 component of the event-related brain potential (ERP) is exclusively generated in the contralateral hemisphere. The effects of face inversion on N170 amplitudes and latencies also show strong contralateral biases. These results reveal that retinotopic biases in low-level visual cortex extend well into category-selective high-level vision. We suggest that the contralateral organisation of face-sensitive visual processing results from generic competitive interactions between hemispheres during the simultaneous perception of visual objects.

The face-inversion effect in developmental prosopagnosia

The face-inversion effect in developmental prosopagnosia

Super-recognition in development: A case study of an adolescent with extraordinary face recognition skills

ABSTRACTFace recognition abilities vary widely. While face recognition deficits have been reported in children, it is unclear whether superior face recognition skills can be encountered during development. This paper presents O.B., a 14-year-old female with extraordinary face recognition skills: a “super-recognizer” (SR). O.B. demonstrated exceptional face-processing skills across multiple tasks, with a level of performance that is comparable to adult SRs. Her superior abilities appear to be specific to face identity: She showed an exaggerated face inversion effect and her superior abilities did not extend to object processing or non-identity aspects of face recognition. Finally, an eye-movement task demonstrated that O.B. spent more time than controls examining the nose - a pattern previously reported in adult SRs. O.B. is therefore particularly skilled at extracting and using identity-specific facial cues, indicating that face and object recognition are dissociable during development, and that super recognition can be detected in adolescence.

Revealing the mechanisms of human face perception using dynamic apertures

Faces are notoriously hard to perceive when turned upside-down. It is often claimed that perceptual decrements reflect a qualitative switch from parallel whole-face processing, to a serial analysis of individual features. To test this view, we examined observers’ ability to categorize faces presented in their entirety, or viewed through a dynamic aperture that moved incrementally across the facial image. Exposing faces region-by-region disrupts holistic processing, but permits serial analysis of local features. In line with the holistic accounts, we predicted that aperture viewing would greatly impair judgements of upright, but not inverted faces. As expected, identity, gender, age, and expression were categorized more precisely when faces were presented upright and in their entirety. Contrary to holistic accounts, however, the detrimental effects of inversion seen in the whole-face condition were no greater than in the aperture condition. Moreover, we found comparable aperture effects for upright and inverted faces; observers exhibited less decision noise when faces were viewed in their entirety, than when viewed through the aperture, irrespective of orientation. We replicate these findings in control experiments and show that the same pattern is seen irrespective of the direction of aperture transition or the nature of the fill used to replace the occluded regions of the to-be-judged image. These results challenge holistic accounts of the face inversion effect and support an alternative interpretation. First, in line with previous findings, they indicate that perceptual decrements when viewing upside-down faces result from impoverished descriptions of local regions, not the loss of whole-face processing. Second, when interpreting inverted faces, access to the wider face context appears to be far more important than currently believed.

3D faces are recognized more accurately and faster than 2D faces, but with similar inversion effects

Recognition of faces typically occurs via holistic processing where individual features are combined to provide an overall facial representation. However, when faces are inverted, there is greater reliance on featural processing where faces are recognized based on their individual features. These findings are based on a substantial number of studies using 2-dimensional (2D) faces and it is unknown whether these results can be extended to 3-dimensional (3D) faces, which have more depth information that is absent in the typical 2D stimuli used in face recognition literature. The current study used the face inversion paradigm as a means to investigate how holistic and featural processing are differentially influenced by 2D and 3D faces. Twenty-five participants completed a delayed face-matching task consisting of upright and inverted faces that were presented as both 2D and 3D stereoscopic images. Recognition accuracy was significantly higher for 3D upright faces compared to 2D upright faces, providing support that the enriched visual information in 3D stereoscopic images facilitates holistic processing that is essential for the recognition of upright faces. Typical face inversion effects were also obtained, regardless of whether the faces were presented in 2D or 3D. Moreover, recognition performances for 2D inverted and 3D inverted faces did not differ. Taken together, these results demonstrated that 3D stereoscopic effects influence face recognition during holistic processing but not during featural processing. Our findings therefore provide a novel perspective that furthers our understanding of face recognition mechanisms, shedding light on how the integration of stereoscopic information in 3D faces influences face recognition processes.

The Impact of Face Inversion on Animacy Categorization

Face animacy perception is categorical: Gradual changes in the real/artificial appearance of a face lead to nonlinear behavioral responses. Neural markers of face processing are also sensitive to face animacy, further suggesting that these are meaningful perceptual categories. Artificial faces also appear to be an “out-group” relative to real faces such that behavioral markers of expert-level processing are less evident with artificial faces than real ones. In the current study, we examined how categorical processing of real versus doll faces was impacted by the face inversion effect, which is one of the most robust markers of expert face processing. We examined how explicit categorization of faces drawn from a real/doll morph continuum was affected by face inversion (Experiment 1) and also how the response properties of the N170 were impacted by face animacy and inversion. We found that inversion does not change the position or steepness of the category boundary measured behaviorally. Further, neural markers of face processing are equally impacted by inversion regardless of whether they are elicited by real faces or doll faces. On balance, our results indicate that inversion has a limited impact on the categorical perception of face animacy.

Individual recognition and the 'face inversion effect' in medaka fish (Oryzias latipes).

Individual recognition (IR) is essential for maintaining various social interactions in a group, and face recognition is one of the most specialised cognitive abilities in IR. We used both a mating preference system and an electric shock conditioning experiment to test IR ability in medaka, and found that signals near the face are important. Medaka required more time to discriminate vertically inverted faces, but not horizontally shifted faces or inverted non-face objects. The ability may be comparable to the classic 'face inversion effect' in humans and some other mammals. Extra patterns added to the face also did not influence the IR. These findings suggest the possibility that the process of face recognition may differ from that used for other objects. The complex form of recognition may promote specific processing adaptations, although the mechanisms and neurological bases might differ in mammals and medaka. The ability to recognise other individuals is important for shaping animal societies.