Identity From Variation: Representations of Faces Derived From Multiple Instances

Research in face recognition has tended to focus on discriminating between individuals, or “telling people apart.” It has recently become clear that it is also necessary to understand how images of the same person can vary, or “telling people together.” Learning a new face, and tracking its representation as it changes from unfamiliar to familiar, involves an abstraction of the variability in different images of that person's face. Here, we present an application of principal components analysis computed across different photos of the same person. We demonstrate that people vary in systematic ways, and that this variability is idiosyncratic—the dimensions of variability in one face do not generalize well to another. Learning a new face therefore entails learning how that face varies. We present evidence for this proposal and suggest that it provides an explanation for various effects in face recognition. We conclude by making a number of testable predictions derived from this framework.     

Facial first impressions from another angle: How social judgements are influenced by changeable and invariant facial properties

First impressions made to photographs of faces can depend as much on momentary characteristics of the photographed image (within‐person variability) as on consistent properties of the face of the person depicted (between‐person variability). Here, we examine two important sources of within‐person variability: emotional expression and viewpoint. We find more within‐person variability than between‐person variability for social impressions of key traits of trustworthiness, dominance, and attractiveness, which index the main dimensions in theoretical models of facial impressions. The most important source of this variability is the emotional expression of the face, but the viewpoint of the photograph also affects impressions and modulates the effects of expression. For example, faces look most trustworthy with a happy expression when they are facing the perceiver, compared to when they are facing elsewhere, whereas the opposite is true for anger and disgust. Our findings highlight the integration of these different sources of variability in social impression formation.     

The development of expert face processing: are infants sensitive to normal differences in second-order relational information?

Sensitivity to second-order relational information (i.e., spatial relations among features such as the distance between eyes) is a vital part of achieving expertise with face processing. Prior research is unclear on whether infants are sensitive to second-order differences seen in typical human populations. In the current experiments, we examined whether infants are sensitive to changes in the space between the eyes and between the nose and the mouth that are within the normal range of variability in Caucasian female faces. In Experiment 1, 7-month-olds detected these changes in second-order relational information. Experiment 2 extended this finding to 5-month-olds and also found that infants detect second-order relations in upright faces but not in inverted faces, thereby exhibiting an inversion effect that has been considered to be a hallmark of second-order relational processing during adulthood. These results suggest that infants as young as 5 months are sensitive to second-order relational changes that are within the normal range of human variability. They also indicate that at least rudimentary aspects of face processing expertise are available early in life.     

Variability in photos of the same face

Psychological studies of face recognition have typically ignored within-person variation in appearance, instead emphasising differences between individuals. Studies typically assume that a photograph adequately captures a person’s appearance, and for that reason most studies use just one, or a small number of photos per person. Here we show that photographs are not consistent indicators of facial appearance because they are blind to within-person variability. Crucially, this within-person variability is often very large compared to the differences between people. To investigate variability in photos of the same face, we collected images from the internet to sample a realistic range for each individual. In Experiments 1 and 2, unfamiliar viewers perceived images of the same person as being different individuals, while familiar viewers perfectly identified the same photos. In Experiment 3, multiple photographs of any individual formed a continuum of good to bad likeness, which was highly sensitive to familiarity. Finally, in Experiment 4, we found that within-person variability exceeded between-person variability in attractiveness. These observations are critical to our understanding of face processing, because they suggest that a key component of face processing has been ignored. As well as its theoretical significance, this scale of variability has important practical implications. For example, our findings suggest that face photographs are unsuitable as proof of identity.     

Event-related potentials reveal the development of stable face representations from natural variability

Natural variability between instances of unfamiliar faces can make it difficult to reconcile two images as the same person. Yet for familiar faces, effortless recognition occurs even with considerable variability between images. To explore how stable face representations develop, we employed incidental learning in the form of a face sorting task. In each trial, multiple images of two facial identities were sorted into two corresponding piles. Following the sort, participants showed evidence of having learnt the faces performing more accurately on a matching task with seen than with unseen identities. Furthermore, ventral temporal event-related potentials were more negative in the N250 time range for previously seen than for previously unseen identities. These effects appear to demonstrate some degree of abstraction, rather than simple picture learning, as the neurophysiological and behavioural effects were observed with novel images of the previously seen identities. The results provide evidence of the development of facial representations, allowing a window onto natural mechanisms of face learning.     

A Rationale for Evidence-Based Clinical Supervision

Although modern mental health systems increasingly require evidence-based practice (EBP), clinicians continue to object to restrictions on their professional independence, which they may perceive as counterproductive, divisive and even demeaning. In the face of such deep-seated objections, do we really need to strive for an evidence-based approach to supervision? We believe so, and begin our argument by noting a colourful illustration of the problems that can exist in the absence of EBP, those of poor training, therapist drift and weak professional regulation. Next, we present EBP as a mechanism to reduce such unacceptable variability in the way that treatments are delivered. We then apply the lessons from this divisive situation to the practice of clinical supervision, outlining a rationale for an inclusive, synergistic way forward. A number of fundamental psychological motives for this integration are noted, including supervisor training that is informed by practice-based research, corrective feedback on supervision, and a supportive professional system. Illustrative examples are provided in each of these areas. It is concluded that the traditional gulf between research and practice can and should be bridged in relation to supervision.     

On the specificity of face cognition compared with general cognitive functioning across adult age

Face cognition is considered a specific human ability, clearly differentiable from general cognitive functioning. Its specificity is primarily supported by cognitive-experimental and neuroimaging research, but recently also from an individual differences perspective. However, no comprehensive behavioral data are available, which would allow estimating lifespan changes of the covariance structure of face-cognition abilities and general cognitive functioning as well as age-differences in face cognition after accounting for interindividual variability in general cognition. The present study aimed to fill this gap. In an age-heterogeneous (18-82 years) sample of 448 adults, we found no factorial dedifferentiation between face cognition and general cognition. Age-related differences in face memory were still salient after taking into account changes in general cognitive functioning. Face cognition thus remains a specific human ability compared with general cognition, even until old age. We discuss implications for models of cognitive aging and suggest that it is necessary to include more explicitly special social abilities in those models.     

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.     

Intersubject variability in fearful face processing: the linkbetween behavior and neural activation

Stimuli that signal threat show considerable variability in the extents to which they enhance behavior, even among healthy individuals. However, the neural underpinning of this behavioral variability is not well understood. By manipulating expectation of threat in an fMRI study of fearful versus neutral face categorization, we uncovered a network of areas underlying variability in threat processing in healthy adults. We explicitly altered expectations by presenting face images at three different expectation levels: 80 %, 50 %, and 20 %. Subjects were instructed to report as quickly and accurately as possible whether the face was fearful (signaled threat) or not. An uninformative cue preceded each face by 4 s. By taking the difference between reaction times (RTs) to fearful and neutral faces, we quantified an overall fear RT bias (i.e., faster to fearful than to neutral faces) for each subject. This bias correlated positively with late-trial fMRI activation (8 s after the face) during unexpected-fearful-face trials in bilateral ventromedial prefrontal cortex, the left subgenual cingulate cortex, and the right caudate nucleus, and correlated negatively with early-trial fMRI activation (4 s after the cue) during expected-neutral-face trials in bilateral dorsal striatum and the right ventral striatum. These results demonstrate that the variability in threat processing among healthy adults is reflected not only in behavior, but also in the magnitude of activation in medial prefrontal and striatal regions that appear to encode affective value.     

The improbable simplicity of the fusiform face area

The fusiform face area (FFA) is described as an easily identifiable module on the fusiform gyrus. However, the organization of face-selective regions in ventral temporal cortex (VTC) is more complex than this prevailing view. We highlight methodological factors contributing to these complexities and the extensive variability in how the FFA is identified. We suggest a series of constraints to aid researchers when defining any functionally specialized region with a pleasing realization: anatomy matters.     

Normative accuracy and response time data for the computerized Benton Facial Recognition Test (BFRT-<Emphasis Type="Italic">c</Emphasis>)

We report normative data from a large (N = 307) sample of young adult participants tested with a computerized version of the long form of the classical Benton Facial Recognition Test (BFRT; Benton & Van Allen, 1968). The BFRT-c requires participants to match a target face photograph to either one or three of six face photographs presented simultaneously. We found that the percent accuracy on the BFRT-c (81%–83%) was below ceiling yet well above chance level, with little interindividual variance in this typical population sample, two important aspects of a sensitive clinical test. Although the split-half reliability on response accuracy was relatively low, due to the large variability in difficulty across items, the correct response times measured in this version—completed in 3 min, on average—provide a reliable and critical complementary measure of performance at individual unfamiliar-face matching. In line with previous observations from other measures, females outperformed male participants at the BFRT-c, especially for female faces. In general, performance was also lower following lighting changes than following head rotations, in line with previous studies that have emphasized participants’ limited ability to match pictures of unfamiliar faces with important variations in illumination. Overall, this normative data set supports the validity of the BFRT-c as a key component of a battery of tests to identify clinical impairments in individual face recognition, such as observed in acquired prosopagnosia. However, this analysis strongly recommends that researchers consider the full test results: Beyond global indexes of performance based on accuracy rates only, they should consider the time taken to match individual faces as well as the variability in performance across items.     

Cues to personality and health in the facial appearance of chimpanzees (Pan troglodytes)

Humans (Homo sapiens) and chimpanzees (Pan troglodytes) can extract socially-relevant information from the static, non-expressive faces of conspecifics. In humans, the face is a valid signal of both personality and health. Recent evidence shows that, like humans, chimpanzee faces also contain personality information, and that humans can accurately judge aspects of chimpanzee personality relating to extraversion from the face alone (Kramer, King, and Ward, 2011). These findings suggest the hypothesis that humans and chimpanzees share a system of personality and facial morphology for signaling socially-relevant traits from the face. We sought to test this hypothesis using a new group of chimpanzees. In two studies, we found that chimpanzee faces contained health information, as well as information of characteristics relating to extraversion, emotional stability, and agreeableness, using average judgments from pairs of individual photographs. In a third study, information relating to extraversion and health was also present in composite images of individual chimpanzees. We therefore replicate and extend previous findings using a new group of chimpanzees and demonstrate two methods for minimizing the variability associated with individual photographs. Our findings support the hypothesis that chimpanzees and humans share a personality signaling system.     

Telling faces together: Learning new faces through exposure to multiple instances

We are usually able to recognize novel instances of familiar faces with little difficulty, yet recognition of unfamiliar faces can be dramatically impaired by natural within-person variability in appearance. In a card-sorting task for facial identity, different photos of the same unfamiliar face are often seen as different people. Here we report two card-sorting experiments in which we manipulate whether participants know the number of identities present. Without constraints, participants sort faces into many identities. However, when told the number of identities present, they are highly accurate. This minimal contextual information appears to support viewers in “telling faces together”. In Experiment 2 we show that exposure to within-person variability in the sorting task improves performance in a subsequent face-matching task. This appears to offer a fast route to learning generalizable representations of new faces.     

The effects of distinctiveness on memory and metamemory for face–name associations

We examined the influence of face and name distinctiveness on memory and metamemory for face–name associations. Four types of monitoring judgements were solicited during encoding and retrieval of face–name pairs that contained distinct or typical faces (Experiment 1) or names (Experiment 2). The beneficial effects of distinctiveness on associative memory were symmetrical between faces and names, such that relative to their typical counterparts, distinct faces enhanced memory for names, and distinct names enhanced memory for faces. These effects were also apparent in metamemory. Estimates of prospective and retrospective memory performance were greater for face–name associations that contained a distinct face or name compared with a typical face or name, regardless of whether the distinct item was a cue or target. Moreover, the predictive validity of prospective monitoring improved with name distinctiveness, whereas the predictive validity of retrospective monitoring improved with facial distinctiveness. Our results indicate that distinctiveness affects not only the strength of the association between a face and a name, but also the ability to monitor that association.     

Testosterone-to-oestradiol ratio is associated with female facial attractiveness

The relationship between facial shape and attractiveness has been extensively studied, yet few studies have investigated the underlying biological factors of an attractive face. Many researchers have proposed a link between female attractiveness and sex hormones, but there is little empirical evidence in support of this assumption. In the present study we investigated the relationship between circulating sex hormones and attractiveness. We created prototypes by separately averaging photographs of 15 women with high and low levels of testosterone, oestradiol, and testosterone-to-oestradiol ratio levels, respectively. An independent set of facial images was then shape transformed toward these prototypes. We paired the resulting images in such a way that one face depicted a female with high hormone level and the other one with a low hormone level. Fifty participants were asked to choose the more attractive face of each pair. We found that low testosterone-to-oestradiol ratio and low testosterone were positively associated with female facial attractiveness. There was no preference for faces with high oestradiol levels. In an additional experiment with 36 participants we confirmed that a low testosterone-to-oestradiol ratio plays a larger role than low testosterone alone. These results provide empirical evidence that an attractive female face is shaped by interacting effects of testosterone and oestradiol.     

Individual differences in holistic processing predict face recognition ability

Why do some people recognize faces easily and others frequently make mistakes in recognizing faces? Classic behavioral work has shown that faces are processed in a distinctive holistic manner that is unlike the processing of objects. In the study reported here, we investigated whether individual differences in holistic face processing have a significant influence on face recognition. We found that the magnitude of face-specific recognition accuracy correlated with the extent to which participants processed faces holistically, as indexed by the composite-face effect and the whole-part effect. This association is due to face-specific processing in particular, not to a more general aspect of cognitive processing, such as general intelligence or global attention. This finding provides constraints on computational models of face recognition and may elucidate mechanisms underlying cognitive disorders, such as prosopagnosia and autism, that are associated with deficits in face recognition.     

Dimensions of movement specific reinvestment in practice of a golf putting task

ObjectivesThis study aimed to investigate the role of the two dimensions of movement specific reinvestment (conscious motor processing and movement self-consciousness) in performance of a complex task early and later in practice. Furthermore, the study also examined the underlying kinematic mechanisms by which conscious motor processing and movement self-consciousness influence performance in practice.MethodsTrait measures of conscious motor processing and movement self-consciousness were obtained from participants using the Movement Specific Reinvestment Scale. Participants (n = 30) with no prior golf putting experience practiced 300 golf putts over the course of two days. Putting proficiency (number of putts holed) and variability of movement kinematics (SD impact velocity and SD putter face angle at impact) were assessed early and later in practice.ResultsMovement self-consciousness positively influenced putting proficiency early and later in practice by reducing variability of impact velocity and putter face angle at impact. Conscious motor processing positively influenced putting proficiency early in practice by reducing variability of impact velocity and putter face angle at impact. Later in practice, conscious motor processing was not associated with putting proficiency.ConclusionThe findings suggest that higher propensity for movement self-consciousness potentially influences performance early and later in practice by reducing variability of impact velocity and putter face angle at impact. A higher propensity for conscious motor processing benefits performance in a similar manner as movement self-consciousness early in practice but it does not seem to influence performance later in practice. The findings of the current study suggest that movement self-consciousness and conscious motor processing differentially influence performance at different stages in practice of a complex motor skill, suggesting that they might depict different types of conscious processing.     

Ensemble coding of facial identity is not refined by experience: Evidence from other-race and inverted faces

The ability to recognize identity despite within-person variability in appearance is likely a face-specific skill and shaped by experience. Ensemble coding – the automatic extraction of the average of a stimulus array – has been proposed as a mechanism underlying face learning (allowing one to recognize novel instances of a newly learned face). We investigated whether ensemble encoding, like face learning and recognition, is refined by experience by testing participants with upright own-race faces and two categories of faces with which they lacked experience: other-race faces (Experiment 1) and inverted faces (Experiment 2). Participants viewed four images of an unfamiliar identity and then were asked whether a test image of that same identity had been in the study array. Each test image was a matching exemplar (from the array), matching average (the average of the images in the array), non-matching exemplar (a novel image of the same identity), or non-matching average (an average of four different images of the same identity). Adults showed comparable ensemble coding for all three categories (i.e., reported that matching averages had been present more than non-matching averages), providing evidence that this early stage of face learning is not shaped by face-specific experience.     

Emerging adults’ sleep patterns and attentional capture: the pivotal role of consistency

College students face consistent cognitive demands and often get insufficient and/or irregular sleep. The current study investigated associations of sleep duration and sleep variability with attentional performance. Sleep duration variability was expected to moderate the association between duration and cognitive functioning. College students’ (n = 83) natural sleep patterns were recorded via wristband actigraphy across three consecutive nights during an academic term. The association between sleep duration and attentional capture was strongest for those whose sleep was the most consistent across the three nights preceding the attentional task (i.e., low sleep duration variability). For those with low sleep duration variability, less sleep was associated (B = ?0.25) with reduced ability to ignore irrelevant cues and redirect attention to target locations. In other words, consistently low sleep duration was associated with compromises in attention. Our results indicate the importance of consistent sleep routines as well as sufficient sleep duration in order to optimize attentional performance in college students.