Figural Aftereffects Research Articles

A Sensorimotor Numerosity System.

Incoming sensory input provides information for the planning and execution of actions, which yield motor outcomes that are themselves sensory inputs. One dimension where action and perception strongly interact is numerosity perception. Many non-human animals can estimate approximately the number of external elements as well as their own actions, and neurons have been identified that respond to both. Recent psychophysical adaptation studies on humans also provide evidence for neural mechanisms responding to both the number of externally generated events and self-produced actions. Here we advance the idea that these strong connections may arise from dedicated sensorimotor mechanisms in the brain, part of a more generalized system interfacing action with the processing of other quantitative magnitudes such as space and time.

Examination of the Attraction Theory in the Weight Figural Aftereffect

Examination of the Attraction Theory in the Weight Figural Aftereffect

Attending to Race (or Gender) Does Not Increase Race (or Gender) Aftereffects.

Recent research has shown that attention can influence the strength of face aftereffects. For example, attending to changes in facial features increases the strength of identity and figural aftereffects relative to passive viewing (Rhodes et al., 2011). Here, we ask whether attending to a specific social dimension of a face (such as race or gender) influences the strength of face aftereffects along that dimension. Across three experiments, participants completed many single-shot face adaptation trials. In each trial, participants observed a computer-generated adapting face for 5 s while instructed to focus on either the race or gender of that adapting face. Adapting faces were either Asian and female or Caucasian and male. In Experiment 1, all trials included an intermediate question (IQ) following each adaptation period, soliciting a rating of the adapting face on the attended dimension (e.g., race). In Experiment 2, only half of the trials included this IQ, and in Experiment 3 only a quarter of the trials did. In all three experiments, participants were subsequently presented with a race- and gender-neutral face and asked to rate it on either the attended dimension (e.g., race, attention-congruent trials) or the unattended dimension (e.g., gender, attention-incongruent trials) using a seven-point scale. Overall, participants showed significant aftereffects in all conditions, manifesting as (i) higher Asian ratings of the neutral faces following Caucasian vs. Asian adapting faces and (ii) higher female ratings of neutral faces following male vs. female adapting faces. Intriguingly, although reaction times were shorter during attention-congruent vs. attention-incongruent trials, aftereffects were not stronger along attention-congruent than attention-incongruent dimensions. Our results suggest that attending to a facial dimension such as race or gender does not result in increased adaptation to that dimension.

Adults with autism spectrum disorder show evidence of figural aftereffects with male and female faces

The norm-based coding model of face perception posits that face perception involves an implicit comparison of observed faces to a representation of an average face (prototype) that is shaped by experience. Using some methods, observers with autism spectrum disorder (ASD) have shown atypical face perception, but other methods suggest preserved face perception. Here, we used a figural aftereffects paradigm to test whether adults with ASD showed evidence of norm-based coding of faces, and whether they encode separate prototypes for male and female faces, as typical observers do. Following prolonged exposure to distorted faces that differ from their stored prototype, neurotypical adults show aftereffects: their prototype shifts in the direction of the adapting face. We measured aftereffects following adaptation to one distorted gender. There were no significant group differences in the size or direction of the aftereffects; both groups showed sex-selective aftereffects after adapting to expanded female faces but showed aftereffects for both sexes after adapting to contracted face of either sex, demonstrating that adults with and without ASD show evidence of partially dissociable male and female face prototypes. This is the first study to examine sex-selective prototypes using figural aftereffects in adults with ASD and replicates the findings of previous studies examining aftereffects in adults with ASD. The results contrast with studies reporting diminished adaptation in children with ASD.

Children's face identity representations are no more view specific than those of adults.

Face recognition performance improves during childhood, not reaching adult levels until late adolescence, yet the source of this improvement is unclear. Recognition of faces across changes in viewpoint appears particularly slow to develop. Poor cross-view recognition suggests that children's face representations may be more view specific than those of adults and is consistent with arguments that extensive experience with faces may be required to form representations that are robust to view changes. We conducted the first direct test of the view specificity of children's face representations by using face aftereffects to investigate whether children's face aftereffects transfer across changes in viewpoint. Using both the figural aftereffect (E1) and the identity aftereffect (E2) we showed that 8-year-old children's aftereffects transferred across substantial changes in viewpoint and that children did not differ from adults in the amount of transfer across viewpoint. These results suggest that children's coding of identity is no more view specific than that of adults and are consistent with a growing body of evidence indicating that the key perceptual mechanisms of face recognition emerge early in life.

Atypical updating of face representations with experience in children with autism

Face identity aftereffects are significantly diminished in children with autism relative to typical children, which may reflect reduced perceptual updating with experience. Here, we investigated whether this atypicality also extends to non-face stimulus categories, which might signal a pervasive visual processing difference in individuals with autism. We used a figural aftereffect task to measure directly perceptual updating following exposure to distorted upright faces, inverted faces and cars, in typical children and children with autism. A size-change between study and test stimuli limited the likelihood that any processing atypicalities reflected group differences in adaptation to low-level features of the stimuli. Results indicated that, relative to typical children, figural aftereffects for upright faces, but not inverted faces or cars, were significantly attenuated in children with autism. Moreover, the group difference was amplified when we isolated the 'face-selective' component of the aftereffect, by partialling out the mid-level shape adaptation common to upright and inverted face stimuli. Notably, the aftereffects of typical children were disproportionately larger for upright faces than for inverted faces and cars, but the magnitude of aftereffects of autistic children was not similarly modulated according to stimulus category. These findings are inconsistent with a pervasive adaptive coding atypicality relative to typical children, and suggest that reduced perceptual updating may constitute a high-level, and possibly face-selective, visual processing difference in children with autism.

Global face distortion aftereffects tap face-specific and shape-generic processes

Face aftereffects are commonly used to investigate the mechanisms underlying face processing, based on the assumption that they tap processes involved specifically with face-level coding (e.g., face space). However, face aftereffects could potentially arise from many levels of the visual system, and recent research has shown that one figural aftereffect (eye height) has both face-level and shape-generic components. Another very widely used figural manipulation is global face distortion. Here we investigate whether a global face distortion aftereffect (vertical compression) transfers to nonface stimuli, and if so, to what extent. Arguing for a mid- or high-level shape-generic component to our face aftereffect, we found significant face-to-object transfer even after minimizing retinotopic components. Arguing for an additional face-specific component, we found, first, that face-to-face aftereffects were significantly larger than face-to-object aftereffects and second, that this occurred only when the adaptor face was whole and intact rather than scrambled. Our results argue that global face distortion aftereffects are a useful tool for investigating face-space but that, to do so unambiguously, requires developing methods to minimize or account for the shape-generic contribution.

Ignored Faces Produce Figural Face Aftereffects

Following adaptation to faces with contracted (or expanded) internal features, faces previously perceived as normal appear distorted in the opposite direction. This figural face aftereffect suggests face-coding mechanisms adapt to changes in the spatial relations of features and/or the global structure of faces. Here, we investigated whether the figural aftereffect requires spatial attention. Participants ignored a distorted adapting face and performed a highly demanding letter-count task. Before and after adaptation, participants rated the normality of morphed distorted faces ranging from 50% contracted through undistorted to 50% expanded. A robust aftereffect was observed. These results suggest that the figural face aftereffect can occur in the absence of spatial attention, even when the attentional demands of the relevant task are high.

Effects of normal and abnormal visual experience on the development of opposing aftereffects for upright and inverted faces

We used opposing figural aftereffects to investigate whether there are at least partially separable representations of upright and inverted faces in patients who missed early visual experience because of bilateral congenital cataracts (mean age at test 19.5 years). Visually normal adults and 10-year-olds were tested for comparison. Adults showed the expected opposing aftereffects for upright and inverted faces. Ten-year-olds showed an adultlike aftereffect for upright faces but, unlike the adult group, no aftereffect for inverted faces. Patients failed to show an aftereffect for either upright or inverted faces. Overall, the results suggest that early visual input is necessary for the later development of (at least partially) separable representations of upright and inverted faces, a developmental process that takes many years to reach an adult-like refinement.

Adaptive face space coding in congenital prosopagnosia: Typical figural aftereffects but abnormal identity aftereffects

People with congenital prosopagnosia (CP) report difficulty recognising faces in everyday life and perform poorly on face recognition tests. Here, we investigate whether impaired adaptive face space coding might contribute to poor face recognition in CP. To pinpoint how adaptation may affect face processing, a group of CPs and matched controls completed two complementary face adaptation tasks: the figural aftereffect, which reflects adaptation to general distortions of shape, and the identity aftereffect, which directly taps the mechanisms involved in the discrimination of different face identities. CPs displayed a typical figural aftereffect, consistent with evidence that they are able to process some shape-based information from faces, e.g., cues to discriminate sex. CPs also demonstrated a significant identity aftereffect. However, unlike controls, CPs impression of the identity of the neutral average face was not significantly shifted by adaptation, suggesting that adaptive coding of identity is abnormal in CP. In sum, CPs show reduced aftereffects but only when the task directly taps the use of face norms used to code individual identity. This finding of a reduced face identity aftereffect in individuals with severe face recognition problems is consistent with suggestions that adaptive coding may have a functional role in face recognition.

Contrast dependence of figural aftereffects for faces

Contrast dependence of figural aftereffects for faces

Adaptation modulates the electrophysiological substrates of perceived facial distortion: Support for opponent coding

In two experiments we determined the electrophysiological substrates of figural aftereffects in face adaptation using compressed and expanded faces. In Experiment 1, subjects viewed a series of compressed and expanded faces. Results demonstrated that distortion systematically modulated the peak amplitude of the P250 event-related potential (ERP) component. As the amount of perceived distortion in a face increased, the peak amplitude of the P250 component decreased, regardless of whether the physical distortion was compressive or expansive. This provided an ERP metric of the degree of perceived distortion. In Experiment 2, we examined the effects of adaptation on the P250 amplitude by introducing an adapting stimulus that affected the subject's perception of the distorted test faces as measured through normality judgments. The results demonstrate that perception adaptation to compressed or expanded faces affected not only the behavioral normality judgments but also the electrophysiological correlates of face processing the window of 190–260 ms after stimulus onset.

Rapid changes in visual-spatial attention distort object shape

Shifts of attention due to rapid cue onsets have been shown to distort the perceived location of objects, but are there also systematic distortions in the perceived shapes of the objects themselves from such shifts? The present study demonstrates that there are. In three experiments, oval contours were presented that varied in width and height. Two brief, bright white dots were presented as cues and were positioned horizontally or vertically either inside or outside the oval contour. Observers had to judge whether the oval was taller than wide. The results show that the perceived shape of an oval was changed by visual cues such that the oval contours were repelled by the cues (Exp. 1). This effect only occurred when the cues preceded the ovals, providing sufficient time between the presentations to attract involuntary attention (Exp. 2). Moreover, an explanation based on figural aftereffects was ruled out (Exp. 3).

The Effect of Familiarity on Face Adaptation

Face aftereffects can provide information on how faces are stored by the human visual system (eg Leopold et al, 2001 Nature Neuroscience 4 89-94), but few studies have used robustly represented (highly familiar) faces. In this study we investigated the influence of facial familiarity on adaptation effects. Participants were adapted to a series of distorted faces (their own face, a famous face, or an unfamiliar face). In experiment 1, figural aftereffects were significantly smaller when participants were adapted to their own face than when they were adapted to the other faces (ie their own face appeared significantly less distorted than a famous or unfamiliar face). Experiment 2 showed that this 'own-face' effect did not occur when the same faces were used as adaptation stimuli for participants who were unfamiliar with them. Experiment 3 replicated experiment 1, but included a pre-adaptation baseline. The results highlight the importance of considering facial familiarity when conducting research on face aftereffects.

Sustained effects of adaptation on the perception of familiar faces.

Figural aftereffects are commonly believed to be transient and to fade away in the course of milliseconds. We tested face aftereffects using familiar faces and found sustained effects lasting up to 1 week. In 3 experiments, participants were first exposed to distorted pictures of famous persons and then had to select the veridical face in a 2-alternative forced choice task. Veridicality aftereffects were found in a direction opposite to the adapting distortion; these effects generalized to other pictures of the same individual and also to pictures of celebrities that had not been shown during adaptation. The findings support hierarchical theories of norm-based face coding and suggest that face adaptation effects have a representational basis. They also point toward multiple timescales in the operation of adaptation mechanisms, thereby providing a link between high-level adaptation and more general aspects of neuro-cognitive plasticity, that is, learning and memory.

Adaptation modulates the electrophysiological substrates of perceived facial distortion: Support for opponent coding

In two experiments we determined the electrophysiological substrates of figural aftereffects in face adaptation using compressed and expanded faces. In Experiment 1, subjects viewed a series of compressed and expanded faces. Results demonstrated that distortion systematically modulated the peak amplitude of the P250 event-related potential (ERP) component. As the amount of perceived distortion in a face increased, the peak amplitude of the P250 component decreased, regardless of whether the physical distortion was compressive or expansive. This provided an ERP metric of the degree of perceived distortion. In Experiment 2, we examined the effects of adaptation on the P250 amplitude by introducing an adapting stimulus that affected the subject's perception of the distorted test faces as measured through normality judgments. The set of test faces was held constant and the adapting stimulus was systematically varied across experimental days. Adapting to a compressed face made a less compressed test face appear more normal and an expanded test face more distorted as measured by normality ratings. We found that the adaptation conditions that increased the perceived distortion of the distorted test faces also decreased the amplitude of the P250. Likewise, adaptation conditions that decreased the perceived distortion of the distorted test faces also increased the amplitude of the P250. The results demonstrate that perceptual adaptation to compressed or expanded faces affected not only the behavioral normality judgments but also the electrophysiological correlates of face processing in the window of 190–260ms after stimulus onset.

Figural aftereffects transfer, but are also contingent on, race categories

Figural aftereffects transfer, but are also contingent on, race categories

Gender aftereffects in the perception of silhouetted face profiles

Recent studies have shown figural aftereffects in the perception of faces, including gender, race, and identity aftereffects (e.g., Leopold et al., 2001; Webster et al., 2004; Witthoft & Winawer, 2005). In such studies, prolonged exposure to a face with a particular characteristic (e.g., female) temporarily biases subsequent perception of faces in the opposite direction in face-space (e.g., male). Here we report such adaptation in a brief, implicit adaptation paradigm using parameterized silhouetted face profiles that rely on 18 landmark points to specify each face (Davidenko, 2004). We constructed a set of 8 male and 8 female face silhouettes, and a gender-neutral silhouette produced by averaging 20 male and 20 female silhouettes. Subjects were unaware that there were separate adaptation and test conditions; they simply rated each of 9 silhouettes on one of four dimensions: age, race, attractiveness, or gender. The first 8 silhouettes were either all female (Condition 1) or all male (Condition 2), and the 9th face was gender-neutral. Gender was only rated on the 9th face. We report a dramatic gender aftereffect with face silhouettes: 97% of subjects in Condition 1 (57 of 59) labeled the neutral silhouette as male, compared to 39% in Condition 2 (24 of 62). To our knowledge, this is the first report of face adaptation using profiles. In addition, these effects further validate Davidenko's silhouette face-space.

Orientation-sensitivity of face identity aftereffects

Our ability to recognize faces despite their similarity as visual patterns depends on high-level face-coding mechanisms that are strongly tuned to upright faces. If face aftereffects reflect adaptation of these mechanisms, as widely assumed, then they should be sensitive to face orientation. Previous studies have not supported this hypothesis, but have generally used a figural aftereffect paradigm, which may not optimally engage expert face-coding mechanisms. Here, we used an identity aftereffect paradigm, which requires identification of target faces, to provide a stronger test of the hypothesis. We measured identity aftereffects for upright and inverted faces, with and without eliminating low-level retinotopic adaptation. Baseline identification performance was substantially better for upright than inverted faces, confirming that our task tapped orientation-selective face expertise. With orientation varied between participants, aftereffects were almost twice as large for upright as inverted faces, on three different aftereffect measures (change in threshold, change in overall proportion correct, change in perceived identity of the average face). With orientation varied within participants, the results were less clear. We suggest that adaptation of expert face-coding mechanisms can contribute to face identity aftereffects, although the effect may not be very robust.

Broadly tuned, view-specific coding of face shape: Opposing figural aftereffects can be induced in different views

Face aftereffects are sensitive to changes in viewpoint, suggesting view-specific face coding, yet are not entirely eliminated by changes in viewpoint, suggesting view-invariance. To determine whether broad view-tuning can account for these findings we measured the reduction of a figural face aftereffect induced in one view by concurrent adaptation to an opposite distortion in a second viewpoint, varying the angle between these views. To the degree that the same neural population codes both viewpoints, the opposing aftereffects should cancel. Cancellation increased monotonically as the angle between two adapting views decreased, consistent with broadly tuned, view-specific coding of face shape.