Graham Hole

Configurational Factors in the Perception of Unfamiliar Faces

Young et al (1987) have demonstrated that the juxtaposition of top and bottom halves of different faces produces a powerful impression of a novel face. It is difficult to isolate perceptually either half of the ‘new’ face. Inversion of the stimulus, however, makes this task easier. Upright chimeric faces appear to evoke strong and automatic configurational processing mechanisms which interfere with selective piecemeal processing. In this paper three experiments are described in which a matching paradigm was used to show that Young et als findings apply to unfamiliar as well as to familiar faces. The results highlight the way in which minor procedural differences may alter the way in which subjects perform face-recognition tasks.

Featural and configurational processes in the recognition of faces of different familiarity

Previous research suggests that face recognition may involve both configurational and piecemeal (featural) processing. To explore the relationship between these processing modes, we examined the patterns of recognition impairment produced by blurring, inversion, and scrambling, both singly and in various combinations. Two tasks were used: recognition of unfamiliar faces (seen once before) and recognition of highly familiar faces (celebrities). The results provide further support for a configurational–featural distinction. Recognition performance remained well above chance if faces were blurred, scrambled, inverted, or simultaneously inverted and scrambled: each of these manipulations disrupts either configurational or piecemeal processing, leaving the other mode available as a route to recognition. However, blurred/scrambled and blurred/inverted faces were recognised at or near chance levels, presumably because both configurational processing and featural processing were disrupted. Similar patterns of effects were found for both familiar and unfamiliar faces, suggesting that the relationship between configurational and featural processing is qualitatively similar in both cases.

Biases and sensitivities in geometrical illusions

Psychometric functions were collected to measure biases and sensitivities in certain classical illusory configurations, such as the Müller-Lyer. We found that sensitivities (thresholds or just noticeable differences) were generally not affected by the introduction of illusory biases, and the implications of this for theories of the illusions are discussed. Experiments on the Müller-Lyer figure showed that the effect depends upon mis-location of the ends of the figure, rather than upon a global expansion as demanded by the size-constancy theory. A new illusion is described in which the perceived position of a dot is displaced towards the centre of a surrounding cluster of dots, even though it is clearly discriminable from other members of the cluster by their colour. We argue that illusions illustrate powerful constraints upon visual processing: they arise when subjects are instructed to carry out a task to which the visual system is not adapted.

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.

Effects of geometric distortions on face-recognition performance.

The importance of ‘configural’ processing for face recognition is now well established, but it remains unclear precisely what it entails. Through four experiments we attempted to clarify the nature of configural processing by investigating the effects of various affine transformations on the recognition of familiar faces. Experiment 1 showed that recognition was markedly impaired by inversion of faces, somewhat impaired by shearing or horizontally stretching them, but unaffected by vertical stretching of faces to twice their normal height. In experiment 2 we investigated vertical and horizontal stretching in more detail, and found no effects of either transformation. Two further experiments were performed to determine whether participants were recognising stretched faces by using configural information. Experiment 3 showed that nonglobal vertical stretching of faces (stretching either the top or the bottom half while leaving the remainder undistorted) impaired recognition, implying that configural information from the stretched part of the face was influencing the process of recognition — ie that configural processing involves global facial properties. In experiment 4 we examined the effects of Gaussian blurring on recognition of undistorted and vertically stretched faces. Faces remained recognisable even when they were both stretched and blurred, implying that participants were basing their judgments on configural information from these stimuli, rather than resorting to some strategy based on local featural details. The tolerance of spatial distortions in human face recognition suggests that the configural information used as a basis for face recognition is unlikely to involve information about the absolute position of facial features relative to each other, at least not in any simple way

Evidence for a contact-based explanation of the own-age bias in face recognition

Previous research has shown that we recognize faces similar in age to ourselves better than older or younger faces (e.g., Wright & Stroud, 2002). This study investigated whether this own-age bias could be explained by the contact hypothesis used to account for the own-race bias (see Meissner & Brigham, 2001). If the own-age bias stems from increased exposure to people of our own age, it should be reduced or absent in those with higher exposure to other age groups. Participants were asked to remember facial photographs of 8- to 11- and 20- to 25-year-olds. Undergraduates were faster and more accurate at recognizing faces of their own age. However, trainee teachers showed no such own-age bias; they recognized the children’s faces more quickly than own-age faces and with comparable accuracy. These results support a contact-based explanation of the own-age bias.

Developmental changes in the effect of inversion: Using a picture book to investigate face recognition

A novel child-oriented procedure was used to examine the face-recognition abilities of children as young as 2 years. A recognition task was embedded in a picture book containing a story about two boys and a witch. The story and the task were designed to be entertaining for children of a wide age range. In eight trials, the children were asked to pick out one of the boys from amongst eight distractors as quickly as possible. Response-time data to both upright and inverted conditions were analysed. The results revealed that children aged 6 years onwards showed the classic inversion effect. By contrast, the youngest children, aged 2 to 4 years, were faster at recognising the target face in the inverted condition than in the upright condition. Several possible explanations for this ‘inverted inversion effect’ are discussed.

Is there a linear or a nonlinear relationship between rotation and configural processing of faces

Research suggests that inverted faces are harder to recognise than upright faces because of a disruption in processing their configural properties. Reasons for this difficulty were explored by investigating peoples ability to identify faces at intermediate angles of rotation. Participants were asked to discriminate blurred famous and unfamiliar faces presented at nine angles. Blurred faces were used to minimise featural processing strategies, and to assess the effects of rotation that are specific to configural processing. The results indicate a linear relationship between angle of rotation and recognition accuracy. It appears that configural processing becomes gradually more disrupted the further a face is oriented away from the upright. The implications of these findings for competing explanations of the face-inversion effect are discussed.

An analysis of 'looked but failed to see' accidents involving parked police vehicles

Drivers who collide with a vehicle that is parked on the hard shoulder of a motorway or dual-carriageway sometimes claim not to have seen it before the collision. Previous research into vehicle conspicuity has taken such ‘looked but failed to see’ claims at face value, and concentrated on attempting to remedy the problem by making vehicles more conspicuous in sensory terms. However, the present study describes investigations into accidents of this kind which have involved stationary police cars, vehicles which are objectively highly conspicuous. Two laboratory studies showed that experienced drivers viewing a film of dual-carriageway driving were slower to respond to a parked police car as a ‘hazard’ if it was parked directly in the direction of travel than if it was parked at an angle; this effect was more pronounced when the drivers attention was distracted with a secondary reasoning task. Taken together with the accident reports, these results suggest that ‘looked but failed to see’ accidents may arise not because the parked vehicle is difficult to see, but for more cognitive reasons, such as vigilance failure, or possession by the driver of a ‘false hypothesis’ about the road conditions ahead. An emergency vehicle parked in the direction of travel, with only its blue lights flashing, may encourage drivers to believe that the vehicle is moving rather than stationary. Parking at an angle in the road, and avoiding the use of blue lights alone while parked, are two steps that drivers of parked emergency vehicles should consider taking in order to alert approaching drivers to the fact that a stationary vehicle is ahead.

The role of spatial and surface cues in the age-processing of unfamiliar faces

Two experiments investigated the importance of spatial and surface cues in the age-processing of unfamiliar faces aged between one and 80 years. Three manipulations known to affect face recognition were used, individually and in various combinations: inversion, negation, and blurring. Faces were presented either in whole or in part. Age-estimation performance was largely unaffected by most of these manipulations; age-processing appears to be a highly robust process, due to the numerous cues available. Experiment 1 showed that, in contrast to face recognition, age-perception appears to be substantially unimpaired by inversion or negation. Experiment 2 suggests that age-estimates can be made on the basis of either surface information (the 2D disposition of the internal facial features, together with texture information) or shape information (head-shape plus feature configuration, as long as shape-from-shading information is present).