Evidence for working memory storage operations in perceptual cortex

Isolating the short-term storage component of working memory (WM) from the myriad of associated executive processes has been an enduring challenge. Recent efforts have identified patterns of activity in visual regions that contain information about items being held in WM. However, it remains unclear (1) whether these representations withstand intervening sensory input and (2) how communication between multimodal association cortex and the unimodal perceptual regions supporting WM representations is involved in WM storage. We present evidence that the features of a face held in WM are stored within face-processing regions, that these representations persist across subsequent sensory input, and that information about the match between sensory input and a memory representation is relayed forward from perceptual to prefrontal regions. Participants were presented with a series of probe faces and indicated whether each probe matched a target face held in WM. We parametrically varied the feature similarity between the probe and target faces. Activity within face-processing regions scaled linearly with the degree of feature similarity between the probe face and the features of the target face, suggesting that the features of the target face were stored in these regions. Furthermore, directed connectivity measures revealed that the direction of information flow that was optimal for performance was from sensory regions that stored the features of the target face to dorsal prefrontal regions, supporting the notion that sensory input is compared to representations stored within perceptual regions and is subsequently relayed forward. Together, these findings indicate that WM storage operations are carried out within perceptual cortex.     

The Thatcher illusion in squirrel monkeys (Saimiri sciureus)

Like humans, Old World monkeys are known to use configural face processing to distinguish among individuals. The ability to recognize an individual through the perception of subtle differences in the configuration of facial features plays an important role in social cognition. To test this ability in New World monkeys, this study examined whether squirrel monkeys experience the Thatcher illusion, a measure of face processing ability in which changes in facial features are difficult to detect in an inverted face. In the experiment, the monkeys were required to distinguish between a target face and each of the three kinds of distracter faces whose features were altered to be different from those of the target. For each of the pairs of target and distracter faces, four rotation-based combinations of upright and inverted face presentations were used. The results revealed that when both faces were inverted and the eyes of the distracter face were altered by rotating them at an angle of 180° from those of the target face, the monkeys' discrimination learning was obstructed to a greater extent than it was under the other conditions. Thus, these results suggest that the squirrel monkey does experience the Thatcher illusion. Furthermore, it seems reasonable to assume that squirrel monkeys can utilize information about facial configurations in individual recognition and that this facial configuration information could be useful in their social communications.     

Differentiating falsely recognized faces from incompletely remembered faces

This study describes an experimental method for determining whether people who recognize a face containing both some target features and some new features are falsely recognizing the face or whether they are incompletely remembering it. Twenty min. after studying a target face either one time or a third time, 136 participants were instructed to examine six test faces similar to the target and to select two test faces sharing only target features and no unstudied features. The likelihood of selecting two test faces sharing four target features and no incorrect features was significantly greater than chance only for the 67 participants who studied the target three times. Because the two faces selected as containing only target features did not share any unstudied features, they were not falsely recognized; instead, they were indicative of correct but incomplete memory for the thrice-studied target.     

The attentional boost effect really is a boost: Evidence from a new baseline

In the attentional boost effect, participants encode images into memory as they perform an unrelated target-detection task. Later memory is better for images that coincided with a target rather than a distractor. This advantage could reflect a broad processing enhancement triggered by target detection, but it could also reflect inhibitory processes triggered by distractor rejection. To test these possibilities, in four experiments we acquired a baseline measure of image memory when neither a target nor a distractor was presented. Participants memorized faces presented in a continuous series (500- or 100-ms duration). At the same time, participants monitored a stream of squares. Some faces appeared on their own, and others coincided with squares in either a target or a nontarget color. Because the processes associated with both target detection and distractor rejection were minimized when faces appeared on their own, this condition served as a baseline measure of face encoding. The data showed that long-term memory for faces coinciding with a target square was enhanced relative to faces in both the baseline and distractor conditions. We concluded that detecting a behaviorally relevant event boosts memory for concurrently presented images in dual-task situations.     

An examination of simultaneous lineup identification decision processes using eye tracking

Decision processes in simultaneous lineups (an array of faces in which a ‘suspect’ face is displayed along with foil faces) were examined using eye tracking to capture the length and number of times that individual faces were visually analysed. The similarity of the lineup target face relative to the study face was manipulated, and face dwell times on the first visit and on return visits to the individual lineup faces were measured. On first visits, positively identified faces were examined for a longer duration compared to faces that were not identified. When no face was identified from the lineup, the suspect was visited for a longer duration compared to a foil face. On return visits, incorrectly identified faces were examined for a longer duration and visited more often compared to correctly identified faces. The results indicate that lineup decisions can be predicted by face dwell time and the number of visits made to faces. Copyright © 2010 John Wiley & Sons, Ltd.     

How faces differ--a new comparative technique

It can be argued that the process of recognizing faces progresses in two stages: first, the realisation that a perceived image contains patterns that may most reasonably be interpreted as forming a discrete face; second, correct and positive identification by noting the particular features that differentiate one face from all others. A novel technique which explored the latter process in the particular case of four different (male) faces is described. The experiment took the form of a four-alternatives forced-choice presentation of faces behind masks which contained a number of randomly positioned apertures. The percentage of correct responses for each separate aperture was then computed after a large number of 1 s presentations to four observers. This novel form of experiment suggested an equally novel form of pictorial data presentation that, literally, highlights the salient features of each individual face and thereby allows detailed intercomparison merely by inspection. Summing over all targets and observers reveals a strong preference for eyes and eyebrows, followed closely by the hairline above the temples. Next in order of preference comes the mouth and upper-lip area, followed by the lateral hairline beside each temple. Individual differences are strong, however, and the variations are such as to suggest that the uncritical application of generalised feature saliency lists is neither useful nor appropriate.     

Visual search for a socially defined feature: what causes the search asymmetry favoring cross-race faces?

Levin (1996, 2000) reported that white subjects search for black targets more quickly than they search for white targets, suggesting that black faces are perceived as having a feature that is lacking in white faces. Here we test one of the implications of this asymmetry by having subjects search for same-race (SR) and cross-race (CR) faces that are distorted to look less like each other (producing caricatures that enhance race-specifying features), or are distorted to look more like each other (a prototypical distortion expected to reduce the salience of race-specifying features). Experiments 1 and 2 show that caricaturing the feature-positive CR distractors speeds search for the SR face and that prototypical distortion slows this search. The same distortions in SR faces did not affect the search slopes. However, these distortions also eliminated the overall advantage for CR faces. Experiment 3 shows that trial-to-trial variation in the specific distractors in each display can eliminate the asymmetry and suggests that this asymmetry depends on the subjects' ability to set a consistent a priori perceptual criterion when searching for a CR target, while the distortion effects emphasize the importance of distractor-rejection processes in determining the form of a serial search asymmetry.     

Face value: testing the utility of contextual face cues for face recognition

The presence of multiple faces during a crime may provide a naturally-occurring contextual cue to support eyewitness recognition for those faces later. Across two experiments, we sought to investigate mechanisms underlying previously-reported cued recognition effects, and to determine whether such effects extended to encoding conditions involving more than two faces. Participants studied sets of individual faces, pairs of faces, or groups of four faces. At test, participants in the single-face condition were tested only on those individual faces without cues. Participants in the two and four-face conditions were tested using no cues, correct cues (a face previously studied with the target test face), or incorrect cues (a never-before-seen face). In Experiment 2, associative encoding was promoted by a rating task. Neither hit rates nor false-alarm rates were significantly affected by cue type or face encoding condition in Experiment 1, but cuing of any kind (correct or incorrect) in Experiment 2 appeared to provide a protective buffer to reduce false-alarm rates through a less liberal response bias. Results provide some evidence that cued recognition techniques could be useful to reduce false recognition, but only when associative encoding is strong.     

Tolerance for distorted faces: Challenges to a configural processing account of familiar face recognition

Face recognition is widely held to rely on ‘configural processing’, an analysis of spatial relations between facial features. We present three experiments in which viewers were shown distorted faces, and asked to resize these to their correct shape. Based on configural theories appealing to metric distances between features, we reason that this should be an easier task for familiar than unfamiliar faces (whose subtle arrangements of features are unknown). In fact, participants were inaccurate at this task, making between 8% and 13% errors across experiments. Importantly, we observed no advantage for familiar faces: in one experiment participants were more accurate with unfamiliars, and in two experiments there was no difference. These findings were not due to general task difficulty – participants were able to resize blocks of colour to target shapes (squares) more accurately. We also found an advantage of familiarity for resizing other stimuli (brand logos). If configural processing does underlie face recognition, these results place constraints on the definition of ‘configural’. Alternatively, familiar face recognition might rely on more complex criteria – based on tolerance to within-person variation rather than highly specific measurement.     

Perceptual learning in face processing: Comparison facilitates face recognition

Theoretical analyses of perceptual learning suggest that comparison between similar stimuli aids subsequent discrimination between them. The current studies examined whether the opportunity to compare a target face to other similar faces during a preexposure phase facilitated performance on a matching task. Performance was better when the target face had been presented in alternation with similar comparator faces than if that target had not been exposed before test. Exposure to the target face without comparators, or exposure alternating with dissimilar faces, improved performance relative to the nonexposed control but performance was not as good as when target exposure was given in alternation to similar comparison faces. The effects were not influenced by image changes between exposure and test. It is suggested that exposure to a face in comparison to similar stimuli focuses the central representation of a face on its unique features. In practical terms these results suggest that reliable identification of an individual from their photograph would be improved by viewing that photograph in comparison with photographs of similar people.     

Angry faces are tracked more easily than neutral faces during multiple identity tracking

We investigated whether and how emotional facial expressions affect sustained attention in face tracking. In a multiple-identity and object tracking paradigm, participants tracked multiple target faces that continuously moved around together with several distractor faces, and subsequently reported where each target face had moved to. The emotional expression (angry, happy, and neutral) of the target and distractor faces was manipulated. Tracking performance was better when the target faces were angry rather than neutral, whereas angry distractor faces did not affect tracking. The effect persisted when the angry faces were presented upside-down and when surface features of the faces were irrelevant to the ongoing task. There was only suggestive and weak evidence for a facilitatory effect of happy targets and a distraction effect of happy distractors in comparison to neutral faces. The results show that angry expressions on the target faces can facilitate sustained attention on the targets via increased vigilance, yet this effect likely depends on both emotional information and visual features of the angry faces.     

Encoding differences affect the number and precision of own-race versus other-race faces stored in visual working memory

Other-race faces are discriminated and recognized less accurately than own-race faces. Despite a wealth of research characterizing this other-race effect (ORE), little is known about the nature of the representations of own-race versus other-race faces. This is because traditional measures of this ORE provide a binary measure of discrimination or recognition (correct/incorrect), failing to capture potential variation in the quality of face representations. We applied a novel continuous-response paradigm to independently measure the number of own-race and other-race face representations stored in visual working memory (VWM) and the precision with which they are stored. Participants reported target own-race or other-race faces on a circular face space that smoothly varied along the dimension of identity. Using probabilistic mixture modeling, we found that following ample encoding time, the ORE is attributable to differences in the probability of a face being maintained in VWM. Reducing encoding time, a manipulation that is more sensitive to encoding limitations, caused a loss of precision or an increase in variability of VWM for other-race but not own-race faces. These results suggest that the ORE is driven by the inefficiency with which other-race faces are rapidly encoded in VWM and provide novel insights about how perceptual experience influences the representation of own-race and other-race faces in VWM.

     

本族和异族面孔的视觉工作记忆容量:面孔特征的影响

采用延迟探测刺激匹配再认任务,考察面孔种族和内外部特征是否会影响面孔视觉工作记忆容量。被试先识记2或4张中国人或白人的真实面孔图片,一半有内部特征(眼睛、鼻子和嘴巴),另一半有内部和外部特征(脸型、发型),再进行面孔再认判断。采用Cowan’s K值的分析显示,我国被试对本族和异族面孔的视觉工作记忆容量没有差异,但面孔数量与特征多少会影响面孔工作记忆容量,表明对本族和异族面孔的视觉加工不同。     

Emotional priming of pop-out in visual search

When searching for a discrepant target along a simple dimension such as color or shape, repetition of the target feature substantially speeds search, an effect known as feature priming of pop-out (V. Maljkovic and K. Nakayama, 1994). The authors present the first report of emotional priming of pop-out. Participants had to detect the face displaying a discrepant expression of emotion in an array of four face photographs. On each trial, the target when present was either a neutral face among emotional faces (angry in Experiment 1 or happy in Experiment 2), or an emotional face among neutral faces. Target detection was faster when the target displayed the same emotion on successive trials. This effect occurred for angry and for happy faces, not for neutral faces. It was completely abolished when faces were inverted instead of upright, suggesting that emotional categories rather than physical feature properties drive emotional priming of pop-out. The implications of the present findings for theoretical accounts of intertrial priming and for the face-in-the-crowd phenomenon are discussed.     

Exploring recognition with interchanged facial features

Any attempt to unravel the mechanism underlying the process of human face recognition must begin with experiments that explore human sensitivity to differences between a perceived image and an original memory trace. A set of three consecutive experiments are reported that were collectively designed to measure the relative importance of different facial features. The method involved the use of image-processing equipment to interchange cardinal features among frontally viewed target faces. Observers were required to indicate which of the original target faces most resembled the modified faces. The results clearly establish the dominant influence of the head outline as the major recognition feature. Next in importance is the eye/eyebrow combination, followed by the mouth, and then the nose. As a recognition feature in a frontally presented face, the nose is hardly noticed. The number of apparently random responses to some faces indicates that a surprisingly different face can sometimes arise from a fortuitous combination of the old features.     

Evolutionary Psychology of Facial Attractiveness

The human face communicates an impressive number of visual signals. Although adults' ratings of facial attractiveness are consistent across studies, even cross-culturally, there has been considerable controversy surrounding attempts to identify the facial features that cause faces to be judged attractive or unattractive. Studies of physical attractiveness have attempted to identify the features that contribute to attractiveness by studying the relationships between attractiveness and (a) symmetry, (b) averageness, and (c) nonaverage sexually dimorphic features (hormone markers). Evolutionary psychology proposes that these characteristics all pertain to health, suggesting that humans have evolved to view certain features as attractive because they were displayed by healthy individuals. However, the question remains how single features that are considered attractive relate to each other, and if they form a single ornament that signals mate quality. Moreover, some researchers have recently explained attractiveness preferences in terms of individual differences that are predictable. This article briefly describes what is currently known from attractiveness research, reviews some recent advances, and suggests areas for future researchers' attention.     

Line‐up Misidentifications: When Being ‘Prototypically Black’ is Perceived as Criminal

Eyewitness misidentifications are the leading factor contributing to wrongful convictions. Black men, more than any other racial group, are disproportionately affected by this, thus elevating the importance of identifying factors that contribute to the false recollection of unseen faces. In the current studies, we tested whether misplaced familiarity and subsequent misidentification of Black faces was underpinned by the degree to which target faces were considered ‘prototypical’ (i.e., representative) of the Black race category. First, results revealed that Black faces with stereotypical facial features were accurately categorized as ‘Black’ quicker than faces with nonstereotypical features (Experiment 1). Moreover, identification errors were higher for both face recognition (Experiment 2) and line‐up identification (Experiment3) for stereotypical‐featured than nonstereotypical‐featured faces. Overall, results suggest that stereotypical Black faces are representative of the category ‘Black’ and facilitated feelings of familiarity and the endorsement of memory errors that may underpin eyewitness misidentifications. Copyright © 2013 John Wiley & Sons, Ltd.     

Two routes to face perception: evidence from psychophysics and computational modeling

The aim of this study was to separately analyze the role of featural and configural face representations. Stimuli containing only featural information were created by cutting the faces into their parts and scrambling them. Stimuli only containing configural information were created by blurring the faces. Employing an old-new recognition task, the aim of Experiments 1 and 2 was to investigate whether unfamiliar faces (Exp. 1) or familiar faces (Exp. 2) can be recognized if only featural or configural information is provided. Both scrambled and blurred faces could be recognized above chance level. A further aim of Experiments 1 and 2 was to investigate whether our method of creating configural and featural stimuli is valid. Pre-activation of one form of representation did not facilitate recognition of the other, neither for unfamiliar faces (Exp. 1) nor for familiar faces (Exp. 2). This indicates a high internal validity of our method for creating configural and featural face stimuli. Experiment 3 examined whether features placed in their correct categorical relational position but with distorted metrical distances facilitated recognition of unfamiliar faces. These faces were recognized no better than the scrambled faces in Experiment 1, providing further evidence that facial features are stored independently of configural information. From these results we conclude that both featural and configural information are important to recognize a face and argue for a dual-mode hypothesis of face processing. Using the psychophysical results as motivation, we propose a computational framework that implements featural and configural processing routes using an appearance-based representation based on local features and their spatial relations. In three computational experiments (Experiments 4–6) using the same sets of stimuli, we show how this framework is able to model the psychophysical data.     

Evidence for holistic processing of faces viewed as photographic negatives

Inversion and photographic negation both impair face recognition. Inversion seems to disrupt processing of the spatial relationship between facial features ('relational' processing) which normally occurs with upright faces and which facilitates their recognition. It remains unclear why negation affects recognition. To find out if negation impairs relational processing, we investigated whether negative faces are subject to the 'chimeric-face effect'. Recognition of the top half of a composite face (constructed from top and bottom halves of different faces) is difficult when the face is upright, but not when it is inverted. To perform this task successfully, the bottom half of the face has to be disregarded, but the relational processing which normally occurs with upright faces makes this difficult. Inversion reduces relational processing and thus facilitates performance on this particular task. In our experiments, subjects saw pairs of chimeric faces and had to decide whether or not the top halves were identical. On half the trials the two chimeras had identical tops; on the remaining trials the top halves were different. (The bottom halves were always different.) All permutations of orientation (upright or inverted) and luminance (normal or negative) were used. In experiment 1, each pair of 'identical' top halves were the same in all respects. Experiment 2 used differently oriented views of the same person, to preclude matches being based on incidental features of the images rather than the faces displayed within them. In both experiments, similar chimeric-face effects were obtained with both positive and negative faces, implying that negative faces evoke some form of relational processing. It is argued that there may be more than one kind of relational processing involved in face recognition: the 'chimeric-face effect' may reflect an initial 'holistic' processing which binds facial features into a 'Gestalt', rather than being a demonstration of the configurational processing involved in individual recognition.