Rapid extraction of mean identity from sets of faces

Recent evidence suggests that the notion that the visual system can rapidly extract summary statistics from complex scenes extends to representing sets of faces in terms of mean emotion or gender. Here we show that observers can also extract a mean identity from a set of faces with different identities. Observers first saw a set of four faces with different identities and were subsequently asked whether or not a single test face had been present in the preceding set. They were significantly more likely to respond that the test face had been present in the set if it was the morphed mean of all four set faces than when it was an actual set member. This finding suggests that representations based on summary statistics are available for face identity.     

Women's own-gender bias in face recognition memory

Women remember more female than male faces, whereas men do not seem to display an own-gender bias in face recognition memory. Why women remember female faces to a greater extent than male faces is unclear; one proposition is that women attend more to and thereby process female faces more effortfully than male faces during encoding. A manipulation that distracts attention and reduces effortful processing may therefore decrease women's own-gender bias by reducing memory for female faces relative to male faces. In three separate experiments, women and men encoded female and male faces for later recognition in full attention and divided attention conditions. Results consistently showed that women, in contrast to men, displayed a reliable own-gender bias. Importantly, the magnitude of women's own-gender bias was not reduced in divided attention conditions, indicating that it is not a result of effortful processing of female faces. We suggest these results reflect that women have greater perceptual expertise for female faces, facilitating recognition memory.     

Sex differences and the own-gender bias in face recognition: A meta-analytic review

We review the literature on sex differences and the own-gender bias in face recognition. By means of a meta-analysis, we found that girls and women remember more faces than boys and men do (g=0.36), and more female faces (g=0.55), but not more male faces (g=0.08); however, when only male faces are presented, girls and women outperform boys and men (g=0.22). In addition, there is female own-gender bias (g=0.57), but not a male own-gender bias (g= ? 0.03), showing that girls and women remember more female than male faces. It is argued that girls and women have an advantage in face processing and episodic memory, resulting in sex differences for faces, and that the female own-gender bias may stem from an early perceptual expertise for female faces, which may be strengthened by reciprocal interactions and psychological processes directing girls' and women's interest to other females.     

Efficient summary statistical representation when change localization fails

People are sensitive to the summary statistics of the visual world (e.g., average orientation/speed/facial expression). We readily derive this information from complex scenes, often without explicit awareness. Given the fundamental and ubiquitous nature of summary statistical representation, we tested whether this kind of information is subject to the attentional constraints imposed by change blindness. We show that information regarding the summary statistics of a scene is available despite limited conscious access. In a novel experiment, we found that while observers can suffer from change blindness (i.e., not localize where change occurred between two views of the same scene), observers could nevertheless accurately report changes in the summary statistics (or “gist”) about the very same scene. In the experiment, observers saw two successively presented sets of 16 faces that varied in expression. Four of the faces in the first set changed from one emotional extreme (e.g., happy) to another (e.g., sad) in the second set. Observers performed poorly when asked to locate any of the faces that changed (change blindness). However, when asked about the ensemble (which set was happier, on average), observer performance remained high. Observers were sensitive to the average expression even when they failed to localize any specific object change. That is, even when observers could not locate the very faces driving the change in average expression between the two sets, they nonetheless derived a precise ensemble representation. Thus, the visual system may be optimized to process summary statistics in an efficient manner, allowing it to operate despite minimal conscious access to the information presented.     

Eye-tracking the own-gender bias in face recognition: Other-gender faces are viewed differently to own-gender faces

Research on the own-gender bias in face recognition has indicated an asymmetrical effect: an effect found only in women. We investigated the own-gender bias, using an eye-tracker to examine whether the own-gender bias is associated with differential processing strategies. We found an own-gender bias in our female participants. Our eye-tracking analysis indicated different scanning behaviours when processing own- and other-gender faces, with longer and more fixations to the eyes when viewing own-gender faces. Our results favour the socio-cognitive model, whilst acknowledging the role of perceptual expertise in the own-gender bias.     

Understanding gender bias in face recognition: Effects of divided attention at encoding

Prior research has demonstrated a female own-gender bias in face recognition, with females better at recognizing female faces than male faces. We explored the basis for this effect by examining the effect of divided attention during encoding on females' and males' recognition of female and male faces. For female participants, divided attention impaired recognition performance for female faces to a greater extent than male faces in a face recognition paradigm (Study 1; N = 113) and an eyewitness identification paradigm (Study 2; N = 502). Analysis of remember–know judgments (Study 2) indicated that divided attention at encoding selectively reduced female participants' recollection of female faces at test. For male participants, divided attention selectively reduced recognition performance (and recollection) for male stimuli in Study 2, but had similar effects on recognition of male and female faces in Study 1. Overall, the results suggest that attention at encoding contributes to the female own-gender bias by facilitating the later recollection of female faces.     

Who are you looking at? The influence of face gender on visual attention and memory for own- and other-race faces

Previous research suggests that the own-race bias (ORB) in memory for faces is a result of other-race faces receiving less visual attention at encoding. As women typically display an own-gender bias in memory for faces and men do not, we investigated whether face gender and sex of viewer influenced visual attention and memory for own- and other-race faces, and if preferential viewing of own-race faces contributed to the ORB in memory. Participants viewed pairs of female or male own- and other-race faces while their viewing time was recorded. Afterwards, they completed a surprise memory test. We found that (1) other-race males received the initial focus of attention, (2) own-race faces were viewed longer than other-race faces over time, although the difference was larger for female faces, and (3) even though longer viewing time increased the probability of remembering a face, it did not explain the magnified ORB in memory for female faces. Importantly, these findings highlight that face gender moderates attentional responses to and memory for own- and other-race faces.     

Who are you looking at? The influence of face gender on visual attention and memory for own- and other-race faces

Previous research suggests that the own-race bias (ORB) in memory for faces is a result of other-race faces receiving less visual attention at encoding. As women typically display an own-gender bias in memory for faces and men do not, we investigated whether face gender and sex of viewer influenced visual attention and memory for own- and other-race faces, and if preferential viewing of own-race faces contributed to the ORB in memory. Participants viewed pairs of female or male own- and other-race faces while their viewing time was recorded. Afterwards, they completed a surprise memory test. We found that (1) other-race males received the initial focus of attention, (2) own-race faces were viewed longer than other-race faces over time, although the difference was larger for female faces, and (3) even though longer viewing time increased the probability of remembering a face, it did not explain the magnified ORB in memory for female faces. Importantly, these findings highlight that face gender moderates attentional responses to and memory for own- and other-race faces.     

The Headscarf Effect: Direct Evidence from the Eyewitness Identification Paradigm

Internal and external features dominate familiar and unfamiliar face recognition, respectively. However, this finding is not universal; Egyptians showed a robust internal‐feature advantage for processing unfamiliar faces (Megreya & Bindemann, 2009). This bias was speculatively attributed to their long‐term experiences for individuating female faces with headscarves, which completely cover the external features. Here, we provided an empirical test for this suggestion. Participants from Egypt and UK were presented with a staged crime, which was committed by an own‐race woman with or without a headscarf. All participants were then asked to identify the culprit from a line‐up involving 10 faces with or without headscarves. British participants showed an advantage when the culprit left her hair uncovered. In contrast, Egyptian observers showed an advantage when the culprit wore a headscarf. This Egyptian headscarf effect was also replicated using British faces, suggesting that it reflects a specific characteristic of participant nationality rather than face nationality. These results therefore provide evidence for how culture influences cognition. Copyright © 2011 John Wiley & Sons, Ltd.     

Redundancy effects in the perception and memory of visual objects

Is visual representation of an object affected by whether surrounding objects are identical to it, different from it, or absent? To address this question, we tested perceptual priming, visual short-term, and long-term memory for objects presented in isolation or with other objects. Experiment 1 used a priming procedure, where the prime display contained a single face, four identical faces, or four different faces. Subjects identified the gender of a subsequent probe face that either matched or mismatched with one of the prime faces. Priming was stronger when the prime was four identical faces than when it was a single face or four different faces. Experiments 2 and 3 asked subjects to encode four different objects presented on four displays. Holding memory load constant, visual memory was better when each of the four displays contained four duplicates of a single object, than when each display contained a single object. These results suggest that an object's perceptual and memory representations are enhanced when presented with identical objects, revealing redundancy effects in visual processing.     

Females, but not males, show greater pupillary response to direct- than deviated-gaze faces

Under suitable conditions, pupillary dilation is a reliable index of processing activity. Pupil size was tracked in male and female observers following the presentation of face stimuli for an age-judgment task. The eyes on the faces were either directed towards the observer or deviated to the side. Pupil dilation accompanied processing of the faces, but female observers showed significantly more sustained pupil dilation when viewing direct- than deviated-gaze faces over the period 3 to 7 s after stimulus onset, regardless of stimulus sex. In contrast, male observers did not show a consistent pattern in response to either the gaze or sex of the face stimuli. These findings indicate a sex difference in the processing of gaze direction and suggest that females, but not males, apply increased effort to processing socially relevant (direct-gaze) than irrelevant (deviated-gaze) faces. They also demonstrate that pupillary measurement can potentially provide new insights into the processing of even visual input, provided reflexes are sufficiently controlled.     

Culture variation in the average identity extraction: The role of global vs. local processing orientation

ABSTRACT

Research has shown that observers often spontaneously extract a mean representation from multiple faces/objects in a scene even when this is not required by the task. This phenomenon, now known as ensemble coding, has so far mainly been based on data from Western populations. This study compared East Asian and Western participants in an implicit ensemble-coding task, where the explicit task was to judge whether a test face was present in a briefly exposed set of faces. Although both groups showed a tendency to mistake an average of the presented faces as target, thus confirming the universality of ensemble coding, East Asian participants displayed a higher averaging tendency relative to the Westerners. To further examine how a cultural default can be adapted to global or local processing demand, our second experiment tested the effects of priming global or local processing orientation on ensemble coding via a Navon task procedure. Results revealed a reduced tendency for ensemble coding following the priming of local processing orientation. Together, these results suggest that culture can influence the proneness to ensemble coding, and the default cultural mode is malleable to a temporary processing demand.     

Sex differences in unfamiliar face identification: evidence from matching tasks

Research on sex differences in face recognition has reported mixed results, on balance suggesting an advantage for female observers. However, it is not clear whether this advantage is specific to face processing or reflects a more general superiority effect in episodic memory. The current study therefore examined sex differences with a face-matching task that eliminates memory demands. Across two experiments, female but not male observers showed an own-sex advantage on match trials, in which two pictures have to be identified as the same person. This advantage was present for whole faces and when only the internal or external facial features were shown. Female observers were also more accurate in these three conditions on mismatch encounters, in which two photographs have to be identified as different people, but this reflects a more general effect that is present for male and female faces. These findings converge with claims of a female advantage in face recognition and demonstrate that this effect persists when memory demands are eliminated.     

Facial aging, attractiveness, and distinctiveness.

A standard facial caricature algorithm has been applied to a three-dimensional (3-D) representation of human heads, those of Caucasian male and female young adults. Observers viewed unfamiliar faces at four levels of caricature--anticaricature, veridical, moderate caricature, and extreme caricature--and made ratings of attractiveness and distinctiveness (experiment 1) or learned to identify them (experiment 2). There were linear increases in perceived distinctiveness and linear decreases in perceived attractiveness as the degree of facial caricature (Euclidean distance from the average face in 3-D-grounded face space) increased. Observers learned to identify faces presented at either level of positive caricature more efficiently than they did with either uncaricatured or anticaricatured faces. Using the same faces, 3-D representation, and caricature levels, O'Toole, Vetter, Volz, and Salter (1997, Perception 26 719-732) had shown a linear increase in judgments of face age as a function of degree of caricature. Here it is concluded that older-appearing faces are less attractive, but more distinctive and memorable than younger-appearing faces, those closer to the average face.     

The whole is indeed more than the sum of its parts: perceptual averaging in the absence of individual item representation

We tested Ariely's (2001) proposal that the visual system represents the overall statistical properties of sets of objects against alternative accounts of rapid averaging involving sub-sampling strategies. In four experiments, observers could rapidly extract the mean size of a set of circles presented in an RSVP sequence, but could not reliably identify individual members. Experiment 1 contrasted performance on a member identification task with performance on a mean judgment task, and showed that the tasks could be dissociated based on whether the test probe was presented before or after the sequence, suggesting that member identification and mean judgment are subserved by different mechanisms. In Experiment 2, we confirmed that when given a choice between a probe corresponding to the mean size of the set and a foil corresponding to the mean of the smallest and largest items only, the former is preferred to the latter, even when observers are explicitly instructed to average only the smallest and largest items. Experiment 3 showed that a test item corresponding to the mean size of the set could be reliably discriminated from a foil but the largest item in the set, differing by an equivalent amount, could not. In Experiment 4, observers rejected test items dissimilar to the mean size of the set in a member identification task, favoring test items that corresponded to the mean of the set over items that were actually shown. These findings suggest that mean representation is accomplished without explicitly encoding individual items.     

You may look unhappy unless you smile: The distinctiveness of a smiling face against faces without an explicit smile

An expressionless face is often perceived as rude whereas a smiling face is considered as hospitable. Repetitive exposure to such perceptions may have developed stereotype of categorizing an expressionless face as expressing negative emotion. To test this idea, we displayed a search array where the target was an expressionless face and the distractors were either smiling or frowning faces. We manipulated set size. Search reaction times were delayed with frowning distractors. Delays became more evident as the set size increased. We also devised a short-term comparison task where participants compared two sequential sets of expressionless, smiling, and frowning faces. Detection of an expression change across the sets was highly inaccurate when the change was made between frowning and expressionless face. These results indicate that subjects were confused with expressed emotions on frowning and expressionless faces, suggesting that it is difficult to distinguish expressionless face from frowning faces.     

Effects of perceptual quality on the processing of human faces presented to the left and right cerebral hemispheres

Three experiments examined the effects of stimulus duration, retinal eccentricity, and visual noise on the processing of human faces presented to the left visual field/right hemisphere (LVF-RH) and right visual field/left hemisphere (RVF-LH). In Experiment 1 observers identified which of 10 similar male faces was presented on a screen. The single face was presented for 10, 55, or 100 ms at 1 degree, 4 degrees, or 9 degrees of visual angle to the left or right of fixation. Decreasing stimulus duration and increasing retinal eccentricity lowered face recognition. The effect of duration was the same for LVF-RH and RVF-LH trials, but the detrimental effect of increasing retinal eccentricity was larger on LVF-RH trials than on RVF-LH trials. In Experiment 2 observers indicated whether a single face from this same set was a member of a memorized set of five positive faces. The probe face on each trial was presented alone or embedded in visual noise. Visual noise increased the error rate more on LVF-RH trials than on RVF-LH trials. This effect was replicated in Experiment 3, which also required observers to make a much easier discrimination between male and female faces. In the male/female task visual noise tended to impair performance more on RVF-LH trials than on LVF-RH trials, opposite the effect for the male/male task. These results are discussed in terms of hemispheric asymmetry for global versus local features of faces, the level of feature analysis demanded by a task, and the level of feature analysis most disrupted by perceptual degradation.     

基于合成平均刺激的平均表征机制——来自平均面孔吸引力的证据

人类能够快速提取集合中的统计信息, 形成平均表征。对于平均表征的产生机制, 研究者提出整合集合成员以合成平均刺激, 或计算集合成员特征值的平均值两种观点。以往研究中合成的平均刺激的特征值和计算成员特征值的平均值两种方式的结果相似, 难以区分两种观点。由于多个面孔的吸引力评分的均值与用这些面孔合成的平均面孔的吸引力评分存在差异, 本研究使用经典的平均辨别任务(实验1和2)和吸引力评价任务(实验3和4)为平均表征的产生来源于合成平均刺激的观点提供了支持证据。4个实验分别采用大容量面孔集合和小容量面孔集合探讨平均表征的形成机制, 结果发现大、小集合都形成了平均刺激, 并且平均表征的评定和加工可能更多依赖合成的平均刺激, 而非简单的对成员特征值进行平均; 此外, 集合吸引力出现了高评现象, 但小集合高评现象更少出现, 说明平均刺激的作用受到集合大小的影响。本研究为集合平均表征的形成机制和面孔集合吸引力高评现象的产生机制提供了新证据。     

Fluency misattribution and visual hindsight bias

We tested a fluency-misattribution theory of visual hindsight bias, and examined how perceptual and conceptual fluency contribute to the bias. In Experiment 1a observers identified celebrity faces that began blurred and then clarified (Forward baseline), or indicated when faces that began clear and then blurred were no longer recognisable (Backward baseline). In surprise memory tests that followed, observers adjusted the degree of blur of each face to match what the faces looked like when identified in the corresponding baseline condition. Hindsight bias was observed in the Forward condition: During the memory test observers adjusted the faces to be more blurry than when originally identified during baseline. These same observers did not show hindsight bias in the Backward condition: Here, they adjusted faces to the exact blur level at which they identified the faces during baseline. Experiment 1b tested a combined condition in which faces were viewed in a Forward progression at baseline but in a Backward progression at test. Hindsight bias was observed in this condition but was significantly less than the bias observed in the Experiment 1a Forward condition. Experiments 1a and 1b provide support for the fluency-misattribution account of visual hindsight bias: When observers are made aware of why fluency has been enhanced (i.e., in the Backward condition) they are better able to discount it, and as a result show reduced or no hindsight bias. In Experiment 2, observers viewed faces in a Forward progression at baseline and then in a Forward upright or inverted progression at test. Hindsight bias occurred in both conditions, but was greater for upright than inverted faces. We conclude that both conceptual and perceptual fluency contribute to visual hindsight bias.     

Fluency misattribution and visual hindsight bias

We tested a fluency-misattribution theory of visual hindsight bias, and examined how perceptual and conceptual fluency contribute to the bias. In Experiment 1a observers identified celebrity faces that began blurred and then clarified (Forward baseline), or indicated when faces that began clear and then blurred were no longer recognisable (Backward baseline). In surprise memory tests that followed, observers adjusted the degree of blur of each face to match what the faces looked like when identified in the corresponding baseline condition. Hindsight bias was observed in the Forward condition: During the memory test observers adjusted the faces to be more blurry than when originally identified during baseline. These same observers did not show hindsight bias in the Backward condition: Here, they adjusted faces to the exact blur level at which they identified the faces during baseline. Experiment 1b tested a combined condition in which faces were viewed in a Forward progression at baseline but in a Backward progression at test. Hindsight bias was observed in this condition but was significantly less than the bias observed in the Experiment 1a Forward condition. Experiments 1a and 1b provide support for the fluency-misattribution account of visual hindsight bias: When observers are made aware of why fluency has been enhanced (i.e., in the Backward condition) they are better able to discount it, and as a result show reduced or no hindsight bias. In Experiment 2, observers viewed faces in a Forward progression at baseline and then in a Forward upright or inverted progression at test. Hindsight bias occurred in both conditions, but was greater for upright than inverted faces. We conclude that both conceptual and perceptual fluency contribute to visual hindsight bias.