Finding an unfamiliar face in a line-up: Viewing multiple images of the target is beneficial on target-present trials but costly on target-absent trials

When viewing unfamiliar faces, photographs of the same person often are perceived as belonging to different people and photographs of different people as belonging to the same person. Identity matching of unfamiliar faces is especially challenging when the photographs are of a person whose ethnicity differs from that of the observer. In contrast, matching is trivial when viewing familiar faces, regardless of race. Viewing multiple images of an own-race target identity improves accuracy on a line-up task when the target is known to be present (Dowsett et al., 2016, Q J Exp Psychol, 69, 1), suggesting that exposure to within-person variability in appearance is key to face learning. Across three experiments, we show that viewing multiple images of a target identity also improves accuracy for other-race faces on target-present trials. However, viewing multiple images decreases accuracy (i.e., increases false alarms) on target-absent trials for both own- and other-race faces. We discuss the implications of our findings for models of face recognition and for forensic settings.     

The own‐age face recognition bias is task dependent

The own‐age bias (OAB) in face recognition (more accurate recognition of own‐age than other‐age faces) is robust among young adults but not older adults. We investigated the OAB under two different task conditions. In Experiment 1 young and older adults (who reported more recent experience with own than other‐age faces) completed a match‐to‐sample task with young and older adult faces; only young adults showed an OAB. In Experiment 2 young and older adults completed an identity detection task in which we manipulated the identity strength of target and distracter identities by morphing each face with an average face in 20% steps. Accuracy increased with identity strength and facial age influenced older adults' (but not younger adults') strategy, but there was no evidence of an OAB. Collectively, these results suggest that the OAB depends on task demands and may be absent when searching for one identity.     

Not looking yourself: The cost of self‐selecting photographs for identity verification

Photo‐identification is based on the premise that photographs are representative of facial appearance. However, previous studies show that ratings of likeness vary across different photographs of the same face, suggesting that some images capture identity better than others. Two experiments were designed to examine the relationship between likeness judgments and face matching accuracy. In Experiment 1, we compared unfamiliar face matching accuracy for self‐selected and other‐selected high‐likeness images. Surprisingly, images selected by previously unfamiliar viewers – after very limited exposure to a target face – were more accurately matched than self‐selected images chosen by the target identity themselves. Results also revealed extremely low inter‐rater agreement in ratings of likeness across participants, suggesting that perceptions of image resemblance are inherently unstable. In Experiment 2, we test whether the cost of self‐selection can be explained by this general disagreement in likeness judgments between individual raters. We find that averaging across rankings by multiple raters produces image selections that provide superior identification accuracy. However, benefit of other‐selection persisted for single raters, suggesting that inaccurate representations of self interfere with our ability to judge which images faithfully represent our current appearance.     

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.     

What happens to our representation of identity as familiar faces age? Evidence from priming and identity aftereffects

Matching identity in images of unfamiliar faces is error prone, but we can easily recognize highly variable images of familiar faces – even images taken decades apart. Recent theoretical development based on computational modelling can account for how we recognize extremely variable instances of the same identity. We provide complementary behavioural data by examining older adults’ representation of older celebrities who were also famous when young. In Experiment 1, participants completed a long-lag repetition priming task in which primes and test stimuli were the same age or different ages. In Experiment 2, participants completed an identity after effects task in which the adapting stimulus was an older or young photograph of one celebrity and the test stimulus was a morph between the adapting identity and a different celebrity; the adapting stimulus was the same age as the test stimulus on some trials (e.g., both old) or a different age (e.g., adapter young, test stimulus old). The magnitude of priming and identity after effects were not influenced by whether the prime and adapting stimulus were the same age or different age as the test face. Collectively, our findings suggest that humans have one common mental representation for a familiar face (e.g., Paul McCartney) that incorporates visual changes across decades, rather than multiple age-specific representations. These findings make novel predictions for state-of-the-art algorithms (e.g., Deep Convolutional Neural Networks).     

Smiles in face matching: Idiosyncratic information revealed through a smile improves unfamiliar face matching performance

Unfamiliar face matching is a surprisingly difficult task, yet we often rely on people's matching decisions in applied settings (e.g., border control). Most attempts to improve accuracy (including training and image manipulation) have had very limited success. In a series of studies, we demonstrate that using smiling rather than neutral pairs of images brings about significant improvements in face matching accuracy. This is true for both match and mismatch trials, implying that the information provided through a smile helps us detect images of the same identity as well as distinguishing between images of different identities. Study 1 compares matching performance when images in the face pair display either an open-mouth smile or a neutral expression. In Study 2, we add an intermediate level, closed-mouth smile, to identify the effect of teeth being exposed, and Study 3 explores face matching accuracy when only information about the lower part of the face is available. Results demonstrate that an open-mouth smile changes the face in an idiosyncratic way which aids face matching decisions. Such findings have practical implications for matching in the applied context where we typically use neutral images to represent ourselves in official documents.     

In the Dock: Chimeric Image Composites Reduce Identification Accuracy

The aim of presenting chimeric images (formed from opposing halves of a pair of same or different faces) in court settings is to optimise the accuracy of identification decisions based on CCTV evidence. The experiments reported here examined the utility of this technique. Experiment 1 examined the accuracy of face matching with vertically split, aligned chimeric images, misaligned hemi‐faces and full‐face images. Experiment 2 replicated the first experiment but replaced the misaligned images with opposing hemi‐faces separated by a gap. The final experiment used horizontally split faces. All three experiments showed that matching was less accurate with aligned chimeric images than with full‐face images. Furthermore, the pattern of responses obtained with chimeric images differed significantly from full‐face matching and misaligned/separated hemi‐face matching. Chimeric images produced a bias towards same responses even when the face halves were different. The results suggest caution in the use of chimeric images in court. Copyright © 2011 John Wiley & Sons, Ltd.     

Dominance of texture over shape in facial identity processing is modulated by individual abilities

For face recognition, observers utilize both shape and texture information. Here, we investigated the relative diagnosticity of shape and texture for delayed matching of familiar and unfamiliar faces (Experiment 1) and identifying familiar and newly learned faces (Experiment 2). Within each familiarity condition, pairs of 3D‐captured faces were morphed selectively in either shape or texture in 20% steps, holding the respective other dimension constant. We also assessed participants’ individual face‐processing skills via the Bielefelder Famous Faces Test (BFFT), the Glasgow Face Matching Test, and the Cambridge Face Memory Test (CFMT). Using multilevel model analyses, we examined probabilities of same versus different responses (Experiment 1) and of original identity versus other/unknown identity responses (Experiment 2). Overall, texture was more diagnostic than shape for both delayed matching and identification, particularly so for familiar faces. On top of these overall effects, above‐average BFFT performance was associated with enhanced utilization of texture in both experiments. Furthermore, above‐average CFMT performance coincided with slightly reduced texture dominance in the delayed matching task (Experiment 1) and stronger sensitivity to morph‐based changes overall, that is irrespective of morph type, in the face identification task (Experiment 2). Our findings (1) show the disproportionate importance of texture information for processing familiar face identity and (2) provide further evidence that familiar and unfamiliar face identity perception are mediated by different underlying processes.     

Face learning with multiple images leads to fast acquisition of familiarity for specific individuals

Matching unfamiliar faces is a difficult task. Here we ask whether it is possible to improve performance by providing multiple images to support matching. In two experiments we observe that accuracy improves as viewers are provided with additional images on which to base their match. This technique leads to fast learning of an individual, but the effect is identity-specific: Despite large improvements in viewers’ ability to match a particular person's face, these improvements do not generalize to other faces. Experiment 2 demonstrated that trial-by-trial feedback provided no additional benefits over the provision of multiple images. We discuss these results in terms of familiar and unfamiliar face processing and draw out some implications for training regimes.     

The contribution of external and internal features to the matching of unfamiliar faces

The relative efficacy of external and internal features in matching unfamiliar faces was studied in three experiments in which the subjects matched target and test faces differing in terms of external or internal features, or both. In Experiment 1 only full congruency between target and test faces was considered a match; in Experiments 2 and 3 faces sharing the same external and internal features were also considered to be matches. A total of 100 subjects matched 192 pairs of target and test faces in a same-different task. Reaction times and matching errors were recorded for analyses of variance. In all three experiments performance was best when either all features matched or all features mismatched, with mismatches having a slight edge. When matches of external and internal features with the target faces were inconsistent with each other, mismatches of external features led to faster responses in Experiments 1 and 2, and mismatches of internal features led to faster responses in Experiment 3. The results suggest that since faces are configurational stimuli, face matching is influenced by the non-relevant set of features; and that mismatches, especially of external features, influence face matching more than matches do.     

Face detection dissociates from face identification

We describe three experiments in which viewers complete face detection tasks as well as standard measures of unfamiliar face identification. In the first two studies, participants viewed pareidolic images of objects (Experiment 1) or cloud scenes (Experiment 2), and their propensity to see faces in these scenes was measured. In neither case is performance significantly associated with identification, as measured by the Cambridge Face Memory or Glasgow Face Matching Tests. In Experiment 3 we showed participants real faces in cluttered scenes. Viewers’ ability to detect these faces is unrelated to their identification performance. We conclude that face detection dissociates from face identification.     

特征关联的类别间面孔适应

研究通过系列实验探讨了面孔适应不仅仅发生在形状选择性上, 也能发生在任务相关的特征上有内在关联的两个不同类别的物体间。实验1以带有明显性别倾向的物品图片作为适应刺激, 让被试对男女之间morphing程度不同的图片面孔进行性别辨别, 考察了不同适应刺激呈现时间的类别间面孔适应。结果表明适应刺激呈现时间大于50 ms时均存在类别间面孔适应效应。实验2评估了“性别”这一特征以及适应刺激形式在类别间面孔适应中所起的作用, 结果发现带有性别倾向的物品图片、相应的物品名称和性别文字(“男性”、“女性”) 3种适应刺激类型均能产生类别间适应。实验3通过操纵适应刺激上的注意负荷(高负荷、低负荷和无负荷), 探究了注意对类别间面孔适应的影响。结果表明随着注意负荷的增加, 类别间面孔适应效应减小。3个实验报告了一个新异的类别间适应后效, 证明了适应也能发生于在任务相关特征上有内在关联的两个不同类别的物体间。     

Feedback training for facial image comparison

People are typically poor at matching the identity of unfamiliar faces from photographs. This observation has broad implications for face matching in operational settings (e.g., border control). Here, we report significant improvements in face matching ability following feedback training. In Experiment 1, we show cumulative improvement in performance on a standard test of face matching ability when participants were provided with trial-by-trial feedback. More important, Experiment 2 shows that training benefits can generalize to novel, widely varying, unfamiliar face images for which no feedback is provided. The transfer effect specifically benefited participants who had performed poorly on an initial screening test. These findings are discussed in the context of existing literature on unfamiliar face matching and perceptual training. Given the reliability of the performance enhancement and its generalization to diverse image sets, we suggest that feedback training may be useful for face matching in occupational settings.     

A bottleneck in face identification: repetition priming from flanker images

There is evidence that face processing is capacity-limited in distractor interference tasks and in tasks requiring overt recognition memory. We examined whether capacity limits for faces can be observed with a more sensitive measure of visual processing, by measuring repetition priming of flanker faces that were presented alongside a face or a nonface target. In Experiment 1, we found identity priming for face flankers, by measuring repetition priming across a change in image, during task-relevant nonface processing, but not during the processing of a concurrently-presented face target. Experiment 2 showed perceptual priming of the flanker faces, across identical images at prime and test, when they were presented alongside a face target. In a third Experiment, all of these effects were replicated by measuring identity priming and perceptual priming within the same task. Overall, these results imply that face processing is capacity limited, such that only a single face can be identified at one time. Merely attending to a target face appears sufficient to trigger these capacity limits, thereby extinguishing identification of a second face in the display, although our results demonstrate that the additional face remains at least subject to superficial image processing.     

The Effect of Image Pixelation on Unfamiliar‐Face Matching

Low‐resolution, pixelated images from closed‐circuit television (CCTV) can be used to compare the perpetrators of crime with high‐resolution photographs of potential suspects. The current study investigated the accuracy of person identification under these conditions, by comparing high‐resolution and pixelated photographs of unfamiliar faces in a series of matching tasks. Performance decreased gradually with different levels of pixelation and was close to chance with a horizontal image resolution of only 8 pixels per face (Experiment 1). Matching accuracy could be improved by reducing the size of pixelated faces (Experiment 2) or by varying the size of the to‐be‐compared‐with high‐resolution face image (Experiment 3). In addition, pixelation produced effects that appear to be separable from other factors that might affect matching performance, such as changes in face view (Experiment 4). These findings reaffirm that criminal identifications from CCTV must be treated with caution and provide some basic estimates for identification accuracy with different pixelation levels. This study also highlights potential methods for improving performance in this task. Copyright © 2013 John Wiley & Sons, Ltd.     

背景性质对7-10岁自闭症谱系障碍儿童面孔搜索与加工的作用

为了考察背景性质对ASD者搜索面孔的影响,设计两个眼动实验任务,要求14名7~10岁ASD儿童和20名同年龄正常儿童观看图片。实验一采用将面孔嵌入风景图片中引起语义不一致的刺激;实验二采用含有面孔的无意义背景乱序图片刺激。结果发现：（1）面孔与背景语义不一致并不能促进ASD儿童对面孔的搜索;（2）乱序背景对ASD儿童面孔搜索与加工没有产生干扰作用,但使正常儿童的搜索时间变长;（3）一旦觉察到面孔后,ASD儿童对面孔的注视时间少于正常儿童。表明正常儿童对面孔的搜索与加工受背景性质的影响,而ASD儿童不受背景性质的影响;一旦发现面孔,ASD儿童的注意维持较短,但面孔加工模式与正常儿童相似。     

Performance of typical and superior face recognizers on a novel interactive face matching procedure

Unfamiliar simultaneous face matching is error prone. Reducing incorrect identification decisions will positively benefit forensic and security contexts. The absence of view-independent information in static images likely contributes to the difficulty of unfamiliar face matching. We tested whether a novel interactive viewing procedure that provides the user with 3D structural information as they rotate a facial image to different orientations would improve face matching accuracy. We tested the performance of ‘typical’ (Experiment 1) and ‘superior’ (Experiment 2) face recognizers, comparing their performance using high-quality (Experiment 3) and pixelated (Experiment 4) Facebook profile images. In each trial, participants responded whether two images featured the same person with one of these images being either a static face, a video providing orientation information, or an interactive image. Taken together, the results show that fluid orientation information and interactivity prompt shifts in criterion and support matching performance. Because typical and superior face recognizers both benefited from the structural information provided by the novel viewing procedures, our results point to qualitatively similar reliance on pictorial encoding in these groups. This also suggests that interactive viewing tools can be valuable in assisting face matching in high-performing practitioner groups.     

Facial comparison behaviour of forensic facial examiners

Facial examiners make visual comparisons of face images to establish the identities of persons in police investigations. This study utilised eye-tracking and an individual differences approach to investigate whether these experts exhibit specialist viewing behaviours during identification, by comparing facial examiners with forensic fingerprint analysts and untrained novices across three tasks. These comprised of face matching under unlimited (Experiment 1) and time-restricted viewing (Experiment 2), and with a feature-comparison protocol derived from examiner casework procedures (Experiment 3). Facial examiners exhibited individual differences in facial comparison accuracy and did not consistently outperform fingerprint analysts and novices. Their behaviour was also marked by similarities to the comparison groups in terms of how faces were viewed, as evidenced from eye movements, and how faces were perceived, based on the made feature judgements and identification decisions. These findings further understanding of how facial comparisons are performed and clarify the nature of examiner expertise.     

Improving Discrimination and Face Matching with Caricature

Identification of faces from photographs is a common security measure, but matching unfamiliar faces produces high rates of error. Caricatures of familiar people are highly identifiable because they exaggerate distinctive features. We investigated whether exaggerating unfamiliar faces through caricaturing could also improve face‐matching accuracy. In Experiment 1, face‐matching arrays were caricatured relative to an average by 30%, 50% and 70%. Correct rejection of the target‐absent arrays was improved at all levels. Accurate matches increased at 30%, but at 70%, the transformation was too extreme, and all of the arrays were more likely to be rejected. In Experiment 2, photographic identification (ID) images were caricatured by 30% and 50% and matched to life‐size photographs. Rejection of foils improved, but the ID of matching images was impaired. Modest levels of caricature may improve discrimination in unfamiliar face matching, but at stronger levels, a conservative response bias may inhibit accurate ID. Copyright © 2013 John Wiley & Sons, Ltd.     

Sustained conscious access to incidental memories in RSVP

In visual search of natural scenes, differentiation of briefly fixated but task-irrelevant distractor items from incidental memory is often comparable to explicit memorization. However, many characteristics of incidental memory remain unclear, including the capacity for its conscious retrieval. Here, we examined incidental memory for faces in either upright or inverted orientation using Rapid Serial Visual Presentation (RSVP). Subjects were instructed to detect a target face in a sequence of 8–15 faces cropped from natural scene photographs (Experiment 1). If the target face was identified within a brief time window, the subject proceeded to an incidental memory task. Here, subjects used incidental memory to discriminate between a probe face (a distractor in the RSVP stream) and a novel, foil face. In Experiment 2 we reduced scene-related semantic coherency by intermixing faces from multiple scenes and contrasted incidental memory with explicit memory, a condition where subjects actively memorized each face from the sequence without searching for a target. In both experiments, we measured objective performance (Type 1 AUC) and metacognitive accuracy (Type 2 AUC), revealing sustained and consciously accessible incidental memory for upright and inverted faces. In novel analyses of face categories, we examined whether accuracy or metacognitive judgments are affected by shared semantic features (i.e., similarity in gender, race, age). Similarity enhanced the accuracy of incidental memory discriminations but did not influence metacognition. We conclude that incidental memory is sustained and consciously accessible, is not reliant on scene contexts, and is not enhanced by explicit memorization.