PJB Hancock | University of Stirling (original) (raw)

Papers by PJB Hancock

Cognition, 2021

Most people recognise and match pictures of familiar faces effortlessly, while struggling to matc... more Most people recognise and match pictures of familiar faces effortlessly, while struggling to match unfamiliar face images. This has led to the suggestion that true human expertise for faces applies only to familiar faces. This paper develops that idea to propose that we have isolated 'islands of expertise' surrounding each familiar face that allow us to perform better with faces that resemble those we already know. This idea is tested in three experiments. The first shows that familiarity with a person facilitates identification of their relatives. The second shows that people are better able to remember faces that resemble someone they already know. The third shows that while prompting participants to think about resemblance at study produces a large positive effect on subsequent recognition, there is still a significant effect if there is no such prompt. Face-spaceR (Lewis, 2004) is used to illustrate a possible computational explanation of the processes involved.

Ergonomics, 2018

Witnesses may construct a composite face of a perpetrator using a computerised interface. Police ... more Witnesses may construct a composite face of a perpetrator using a computerised interface. Police practitioners guide witnesses through this unusual process, the goal being to produce an identifiable image. However, any changes a perpetrator makes to their external facialfeatures may interfere with this process. In Experiment 1, participants constructed a composite using a holistic interface one day after target encoding. Target faces were unaltered, or had altered external-features: (i) changed hair, (ii) external-features removed or (iii) naturally-concealed external-features (hair, ears, face-shape occluded by a hooded top). These manipulations produced composites with more error-prone internal-features: participants' familiar with a target's unaltered appearance less often provided a correct name. Experiment 2 applied external-feature alterations to composites of unaltered targets; although whole-face composites contained less error-prone internal-features, identification was impaired. Experiment 3 replicated negative effects of changing target hair on construction and tested a practical solution: selectively concealing hair and eyes improved identification.

Journal of Forensic Practice, 2015

Purpose – The purpose of this paper is to assess the impact of seven variables that emerge from f... more Purpose – The purpose of this paper is to assess the impact of seven variables that emerge from forensic research on facial-composite construction and naming using contemporary police systems: EvoFIT, Feature and Sketch. Design/methodology/approach – The paper involves regression- and meta-analyses on composite-naming data from 23 studies that have followed procedures used by police practitioners for forensic face construction. The corpus for analyses contains 6,464 individual naming responses from 1,069 participants in 41 experimental conditions. Findings – The analyses reveal that composites constructed from the holistic EvoFIT system were over four-times more identifiable than composites from “Feature” (E-FIT and PRO-fit) and Sketch systems; Sketch was somewhat more effective than Feature systems. EvoFIT was more effective when internal features were created before rather than after selecting hair and the other (blurred) external features. Adding questions about the global appear...

Quarterly Journal of Experimental Psychology, 2012

Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but c... more Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but comparative studies with monkeys suggest that these may be the result of recent evolutionary adaptations. The present study utilized the novel approach of face space, a powerful theoretical framework used to understand the representation of face identity in humans, to further explore species differences in face processing. According to the theory, faces are represented by vectors in a multidimensional space, the centre of which is defined by an average face. Each dimension codes features important for describing a face's identity, and vector length codes the feature's distinctiveness. Chimpanzees and rhesus monkeys discriminated male and female conspecifics’ faces, rated by humans for their distinctiveness, using a computerized task. Multidimensional scaling analyses showed that the organization of face space was similar between humans and chimpanzees. Distinctive faces had the lo...

Perception, 2011

One of the ways to demonstrate a caricature preference is to ask participants to adjust a face im... more One of the ways to demonstrate a caricature preference is to ask participants to adjust a face image over a range from anti-caricature to caricature until it shows the best likeness to a specific individual. Since facial adaptation, whereby exposure to a face influences subsequent perception of faces, is rapid, it is possible that adaptation promotes the selection of a caricatured image. We tested whether giving participants a reference average face image, to counteract any adaptation, would reduce the degree of caricature selected for famous faces. Results confirmed a significant decrease but, even without an average, participants chose an anti-caricatured image. These data suggest a role for adaptation in generating caricature preferences while also suggesting such preferences are not inevitable.

Cognitive neuropsychiatry, 2014

Existing eye-tracking literature has shown that both adults and children with autism spectrum dis... more Existing eye-tracking literature has shown that both adults and children with autism spectrum disorders (ASD) show fewer and slower fixations on faces. Despite this reduced saliency and processing of other faces, recognition of their own face is reported to be more "typical" in nature. This study uses eye-tracking to explore the typicality of gaze patterns when children with ASD attend their own faces compared to other familiar and unfamiliar faces. Eye-tracking methodology was used to explore fixation duration and time taken to fixate on the Eye and Mouth regions of familiar, unfamiliar and Self Faces. Twenty-one children with ASD (9-16 years) were compared to typically developing matched groups. There were no significant differences between children with ASD and typically matched groups for fixation patterns to the Eye and Mouth areas of all face types (familiar, unfamiliar and self). Correlational analyses showed that attention to the Eye area of unfamiliar and Self Fac...

2017 Seventh International Conference on Emerging Security Technologies (EST), 2017

Accurate identification of criminal suspects by witnesses is vital for police investigations. Met... more Accurate identification of criminal suspects by witnesses is vital for police investigations. Methods such as Cognitive Interviewing techniques have been employed for this reason to enhance witness recall. In the current project, we demonstrate the benefit of including a focused breathing exercise during face construction using the EvoFIT recognition-based facial composite system. Twenty participants, half of whom received the focused breathing instruction, each constructed a facial composite of an unfamiliar face seen the previous day. A further 40 participants attempted to name the resulting composites. A significant increase was found in accurate identification of composites constructed by the focused breathing group.

2018 13th IEEE International Conference on Automatic Face & Gesture Recognition (FG 2018), May 1, 2018

This paper investigates the evaluation of dense 3D face reconstruction from a single 2D image in ... more This paper investigates the evaluation of dense 3D face reconstruction from a single 2D image in the wild. To this end, we organise a competition that provides a new benchmark dataset that contains 2000 2D facial images of 135 subjects as well as their 3D ground truth face scans. In contrast to previous competitions or challenges, the aim of this new benchmark dataset is to evaluate the accuracy of a 3D dense face reconstruction algorithm using real, accurate and high-resolution 3D ground truth face scans. In addition to the dataset, we provide a standard protocol as well as a Python script for the evaluation. Last, we report the results obtained by five state-of-the-art 3D face reconstruction systems on the new benchmark dataset. The competition is organised along with the 2018 13th IEEE Conference on Automatic Face & Gesture Recognition. This is an extended version of the original conference submission with two additional 3D face reconstruction systems evaluated on the benchmark.

2019 Eighth International Conference on Emerging Security Technologies (EST), Jul 1, 2019

This paper assesses use of EvoFIT facial composites by police practitioners in the UK and oversea... more This paper assesses use of EvoFIT facial composites by police practitioners in the UK and overseas. Results reveal that this composite system is used extensively: a total of 2,440 times since September 2013. With a suspect identification rate of 60% and a conviction rate of 17%, the impact of this forensic technique is appreciable for helping the police to identify and convict offenders. It was also found that empirically-driven enhancement techniques were used frequently by police practitioners-including use of detailed context reinstatement and holistic techniques during interview, asking the witness to focus on the eye-region during construction, or presenting a stretched image for identification. Research evaluating EvoFIT composites published by police in the media also reveals that composites were deployed almost exclusively for serious offences, and most often for sexual crimes. In addition, the vast majority were of male offenders, in their early 30's; victims were female (aged mid 20's to mid 30's). A similar outcome was observed for composites published from another recognition system, EFIT-V / 6. Although this overall exercise revealed that EvoFIT composites were sometimes presented to the public in an optimal, stretched fashion, it was also apparent that a worrying number of composites were presented in a way that did not faithfully represent the constructed image, specifically, with the external features cropped.

Neuropsychologia, Jan 7, 2018

Are all faces recognized in the same way, or does previous experience with a face change how it i... more Are all faces recognized in the same way, or does previous experience with a face change how it is retrieved? Previous research using human scalp-recorded Event-Related Potentials (ERPs) demonstrates that recognition memory can produce dissociable brain signals under a variety of circumstances. While many studies have reported dissociations between the putative 'dual processes' of familiarity and recollection, a growing number of reports demonstrate that recollection itself may be fractionated into component processes. Many recognition memory studies using lexical materials as stimuli have reported a left parietal ERP old/new effect for recollection; however, when unfamiliar faces are recollected, an anterior effect can be observed. This paper addresses two separate hypotheses concerning the functional significance of the anterior old/new effect: perceptual retrieval and semantic status. The perceptual retrieval view is that the anterior effect reflects reinstatement of perc...

Police require reliable facial-composite systems to help identify, arrest and convict criminals. ... more Police require reliable facial-composite systems to help identify, arrest and convict criminals. Recent developments, however, have allowed newer versions of the EvoFIT composite system to be made available for policing. The outcome is an online (cloud-based) version and a new system called Witness At Home, both using a simpler interface. Here, we formally compare these two versions to establish potential benefits to policing. Two experiments were conducted. In Experiment 1, participants observed a target identity for 1 minute and returned 4 hours (Witness At Home) or 24 hours (EvoFIT Online) to construct a composite from memory. No significant difference in composite accuracy was found. In Experiment 2, participants constructed a composite 24 hours after seeing a target identity using either EvoFIT Online or Witness At Home. A significant increase in accurate identification was found for EvoFIT Online, with some utility for the self-administered procedure, together indicating benef...

Replication efforts in psychological science sometimes fail to replicate prior findings. If repli... more Replication efforts in psychological science sometimes fail to replicate prior findings. If replications use methods that are unfaithful to the original study or ineffective in eliciting the phenomenon of interest, then a failure to replicate may be a failure of the replication protocol rather than a challenge to the original finding. Formal pre-data collection peer review by experts may address shortcomings and increase replicability rates. We selected 10 replications from the Reproducibility Project: Psychology (RP:P; Open Science Collaboration, 2015) in which the original authors had expressed concerns about the replication designs before data collection and only one of which was “statistically significant” (p < .05). Commenters on RP:P suggested that lack of adherence to expert review and low-powered tests were the reasons that most of these failed to replicate (Gilbert et al., 2016). We revised the replication protocols and received formal peer review prior to conducting new...

ABSTRACT Eyewitnesses often construct a “composite” face of a person they saw commit a crime, a p... more ABSTRACT Eyewitnesses often construct a “composite” face of a person they saw commit a crime, a picture that police use to identify suspects. We described a technique (Frowd, Bruce, Ross, McIntyre, & Hancock, 2007) based on facial caricature to facilitate recognition of these images: Correct naming substantially improves when composites are seen with progressive positive caricature, where distinctive information is enhanced, and then with progressive negative caricature, the opposite. Over the course of four experiments, the underpinnings of this mechanism were explored. Positive-caricature levels were found to be largely responsible for improving naming of composites, with some benefit from negative-caricature levels. Also, different frame-presentation orders (forward, reverse, random, repeated) facilitated equivalent naming benefit relative to static composites. Overall, the data indicate that composites are usually constructed as negative caricatures.

Royal Society Open Science

Convolutional neural networks (CNNs) give the state-of-the-art performance in many pattern recogn... more Convolutional neural networks (CNNs) give the state-of-the-art performance in many pattern recognition problems but can be fooled by carefully crafted patterns of noise. We report that CNN face recognition systems also make surprising ‘errors'. We tested six commercial face recognition CNNs and found that they outperform typical human participants on standard face-matching tasks. However, they also declare matches that humans would not, where one image from the pair has been transformed to appear a different sex or race. This is not due to poor performance; the best CNNs perform almost perfectly on the human face-matching tasks, but also declare the most matches for faces of a different apparent race or sex. Although differing on the salience of sex and race, humans and computer systems are not working in completely different ways. They tend to find the same pairs of images difficult, suggesting some agreement about the underlying similarity space.

Cognitive Research: Principles and Implications

The role of image colour in face identification has received little attention in research despite... more The role of image colour in face identification has received little attention in research despite the importance of identifying people from photographs in identity documents (IDs). Here, in two experiments, we investigated whether colour congruency of two photographs, shown side by side, affects face-matching accuracy. Participants were presented with two images from the Models Face Matching Test (experiment 1) and a newly devised matching task incorporating female faces (experiment 2) and asked to decide whether they show the same person or two different people. The photographs were either both in colour, both in grayscale, or mixed (one in grayscale and one in colour). Participants were more likely to accept a pair of images as a "match", i.e. same person, in the mixed condition, regardless of whether the identity of the pair was the same or not. This demonstrates a clear shift in bias between "congruent" colour conditions and the mixed trials. In addition, there was a small decline in accuracy in the mixed condition, relative to when the images were presented in colour. Our study provides the first evidence that the hue of document photographs matters for face-matching performance. This finding has important implications for the design and regulation of photographic ID worldwide.

The Quarterly Journal of Experimental Psychology

Research has established that a perceived eye gaze produces a concomitant shift in a viewer's spa... more Research has established that a perceived eye gaze produces a concomitant shift in a viewer's spatial attention in the direction of that gaze. The two experiments reported here investigate the extent to which the nature of the eye movement made by the gazer contributes to this orienting effect. On each trial in these experiments participants were asked to make a speeded response to a target that could appear in a location toward which a centrally presented face had just gazed (a cued target), or in a location that was not the recipient of a gaze (an uncued target). The gaze cues consisted of either fast saccadic eye movements or slower smooth pursuit movements. Cued targets were responded to faster than uncued targets, and this gaze-cued orienting effect was found to be equivalent for each type of gaze shift both when the gazes were un-predictive of target location (Experiment 1) and counterpredictive of target location (Experiment 2). The results offer no support for the hypothesis that motion speed modulates gaze-cued orienting. However, they do suggest that motion of the eyes per se, regardless of its type, may be sufficient to trigger an orienting effect.

Psychonomic bulletin & review, Jan 22, 2017

This study examined the effects of ego depletion on ambiguous figure perception. Adults (N = 315)... more This study examined the effects of ego depletion on ambiguous figure perception. Adults (N = 315) received an ego depletion task and were subsequently tested on their inhibitory control abilities that were indexed by the Stroop task (Experiment 1) and their ability to perceive both interpretations of ambiguous figures that was indexed by reversal (Experiment 2). Ego depletion had a very small effect on reducing inhibitory control (Cohen's d = .15) (Experiment 1). Ego-depleted participants had a tendency to take longer to respond in Stroop trials. In Experiment 2, ego depletion had small to medium effects on the experience of reversal. Ego-depleted viewers tended to take longer to reverse ambiguous figures (duration to first reversal) when naïve of the ambiguity and experienced less reversal both when naïve and informed of the ambiguity. Together, findings suggest that ego depletion has small effects on inhibitory control and small to medium effects on bottom-up and top-down perc...

Recent research has provided evidence for the role of norm-based coding in face recognition (e.g.... more Recent research has provided evidence for the role of norm-based coding in face recognition (e.g. Leopold et al., 2001). In such a model, any given face can be represented by a vector from the norm, with the difference between two faces being the difference between the two vectors. However, as has previously been suggested it is also possible to conceive of a model in which the angle between two vectors provides relevant information for differentiating faces. Two experiments investigated this possibility using a face matching paradigm. Discrimination was found to be better when two faces lay on different vectors than when they were the same physical distance apart but lying on the same vector. The results favour a specific type of norm-based model suggesting that vector angle is important in face perception.