Matching familiar and unfamiliar faces on identity and expression

Summary Subjects were asked to decide whether or not simultaneously presented photographs of pairs of faces were pictures of the same person or of different people (identity matching), or to decide whether or not the pairs of face showed the same expressions or different expressions (expression matching). Faces of familiar and unfamiliar people were used as stimuli. For identity matching, reaction times to familiar faces were faster than reaction times to unfamiliar faces, but there was no difference between familiar and unfamiliar faces for expression matching. These results support the view derived from neuropsychological and neurophysiological studies that analyses of facial expressions proceed independently from processes involved in establishing the person's identity.This research was supported by the ESRC (Grant C 0023 2075)     

Recognizing familiar and unfamiliar faces

These experiments addressed why, in episodic-memory tests, familiar faces are recognized better than unfamiliar faces. Memory for faces of well-known public figures and unfamiliar persons was tested, not only with old/new recognition tests, in which initially viewed faces were discriminated from dis tractors, but also with tests of memory for specific information. These included: detail recall, in which a masked feature had to be described; orientation recognition, in which discrimination between originally seen faces and mirror-image reversals was required; and recognition and recall of labels for the public figures. Experiments 1 and 2 showed that memory for orientation and featural details was not robustly related either to facial familiarity or to old/new recognition rates. Experiment 3 showed that memory for labels was not the exclusive determinant of the famous-face advantage in recognition, since famous faces were highly recognizable even they were not labelable or when labels were forgotten. These results suggest that the familiarity effect, and face recognition in general, may reflect a nonverbal memory representation that is relatively abstract.     

Multiple contributions to priming effects for familiar faces: analyses with backward masking and event-related potentials

The model of face recognition by Bruce and Young postulates a pool of structural representations for familiar faces in long-term memory, so-called face recognition units (FRUs). Event-related brain potentials show early repetition priming effects for familiar faces around 250-300 ms [N250r or early repetition effect (ERE)], which are thought to reflect the activation of these FRUs. However, small N250r effects are also seen for unfamiliar faces suggesting that priming of perceptual codes (i.e., pictorial and structural codes) also contributes to early repetition effects. Using a face-familiarity task in Experiment 1, we aimed to eliminate these perceptual contributions to face priming by backward masking the prime face with a different, unfamiliar face. As expected, a repetition priming effect appeared only for familiar faces. Experiment 2 used a semantic-decision task and compared the effects of different kinds of masks that interfered with either pictorial codes or with pictorial and structural codes. Our findings indicate that both structural codes and memory representations contribute to the N250r and that unfamiliar-face masks interfere only with structural codes. Face-masks may therefore provide a useful tool to extract the pure contributions of memory representations (i.e., FRUs) to repetition priming.     

Semantic priming of familiar faces

A series of experiments to explore the effect of priming by semantically related items in familiarity judgement tasks using faces and names that are analogous to lexical decision tasks is reported. In the first experiment, the semantic priming effect in face recognition reported by Bruce (1983) was explored in more detail by including neutral as well as associated and unrelated primes and by varying the prime-target SOA from 250 to 1,000 msec. Significant facilitation effects, with no inhibition, were found at all three SOAs. To explore the analogy between the processing of faces and verbal materials, a second experiment used names rather than faces. The difference between related and unrelated conditions at 250- and 1,000-msec SOA was similar to that found for faces in Experiment 1, but for names there was some evidence of inhibition. To investigate the locus of the priming effect with faces, in Experiment 3 the effect of degrading face targets was examined. An interaction between stimulus quality and semantic priming was observed, suggesting that the locus of the facilitation might lie at a relatively early stage in face processing. The results of these experiments illustrate further similarities between the processing of faces and verbal materials (cf. Bruce 1979, 1981).     

Viewpoint-dependent recognition of familiar faces

The question whether object representations in the human brain are object-centered or viewer-centered has motivated a variety of experiments with divergent results. A key issue concerns the visual recognition of objects seen from novel views. If recognition performance depends on whether a particular view has been seen before, it can be interpreted as evidence for a viewer-centered representation. Earlier experiments used unfamiliar objects to provide the experimenter with complete control over the observer's previous experience with the object. In this study, we tested whether human recognition shows viewpoint dependence for the highly familiar faces of well-known colleagues and for the observer's own face. We found that observers are poorer at recognizing their own profile, whereas there is no difference in response time between frontal and profile views of other faces. This result shows that extensive experience and familiarity with one's own face is not sufficient to produce viewpoint invariance. Our result provides strong evidence for viewer-centered representations in human visual recognition even for highly familiar objects.     

Automatic identification of familiar faces

Much research has suggested that facial identification has some characteristics of automaticity, in that it is rapid, nonconscious, and mandatory. However, little research has tested whether it can occur even if attention is already devoted to the demanding central processes of another task. In the present study, we addressed this type of automaticity using the psychological refractory period paradigm. In Experiments 1 and 2, participants successfully identified familiar faces, even while they were engaged with another task, indicating the automaticity of familiar-face identification. In Experiments 3 and 4, however, participants could not identify unfamiliar faces as automatically as they could identify the familiar faces. We concluded that automatic face identification is possible, but dependent on prior familiarity.     

Mental representations of familiar faces

The Bruce and Young (1986) framework makes a number of important distinctions between the types of representation needed to recognize a familiar face. Here, we return to these, focussing particularly on face recognition units. We argue that such representations need to incorporate idiosyncratic within-person variability, asking questions such as 'What counts as a picture of Harrison Ford?'. We describe a mechanism for achieving this, and discuss the relation between image variability and episodic face memories, in the context of behavioural and neurophysiological data.     

Expression influences the recognition of familiar faces

Face recognition has been assumed to be independent of facial expression. We used familiar and unfamiliar faces that were morphed from a happy to an angry expression within a given identity. Participants performed speeded two-choice decisions according to whether or not a face was familiar. Consistent with earlier findings, reaction times for classifications of unfamiliar faces were independent of facial expressions. In contrast, expression clearly influenced the recognition of familiar faces. with fastest recognition for moderately happy expressions. This suggests that representations of familiar faces for recognition preserve some information about typical emotional expressions.     

Determining the influence of Gaussian blurring on inversion effects with talking faces

Perception of visual speech and the influence of visual speech on auditory speech perception is affected by the orientation of a talker's face, but the nature of the visual information underlying this effect has yet to be established. Here, we examine the contributions of visually coarse (configural) and fine (featural) facial movement information to inversion effects in the perception of visual and audiovisual speech. We describe two experiments in which we disrupted perception of fine facial detail by decreasing spatial frequency (blurring) and disrupted perception of coarse configural information by facial inversion. For normal, unblurred talking faces, facial inversion had no influence on visual speech identification or on the effects of congruent or incongruent visual speech movements on perception of auditory speech. However, for blurred faces, facial inversion reduced identification of unimodal visual speech and effects of visual speech on perception of congruent and incongruent auditory speech. These effects were more pronounced for words whose appearance may be defined by fine featural detail. Implications for the nature of inversion effects in visual and audiovisual speech are discussed.     

Hemisphere-dependent holistic processing of familiar faces

In two behavioral experiments involving lateralized stimulus presentation, we tested whether one of the most commonly used measures of holistic face processing—the composite face effect—would be more pronounced for stimuli presented to the right as compared to the left hemisphere. In experiment 1, we investigated the composite face effect in a verbal identification task, similar to its original report (Young, Hellawell, & Hay, 1987). Aligning top and bottom halves of composite face stimuli led to performance decreases irrespective of hemifield, indicating holistic processing of comparable magnitude for inputs provided separately to either hemisphere. However, when matching of the same top parts was required in experiment 2, an alignment-dependent performance decrease was found for stimuli presented in the left, but not right visual field. These observations suggest that the right hemisphere dominates in early stages of holistic processing, as indexed by the composite face effect, but that later processes such as face identification and naming are based on unified representations that are independent of input lateralization. Moreover, the composite face effect may not rely on the exact same representation(s) when measured in matching and identification tasks.     

Context effects in the processing of familiar faces

Summary In this paper we report five experiments that investigate the influence of prime faces upon the speed with which familiar faces are recognized and named. Previously, priming had been reported when the prime and target faces were closely associated, e.g., Prince Charles and Princess Diana (Bruce & Valentine, 1986). In Experiment 1 we show that there is a reliable effect of relatedness on a double-familiarity decision, even when the faces are only categorially related, e. g., Kirk Douglas and Clint Eastwood. Then it was shown that such an effect emerges only on a double decision task (Experiments 2 and 3). Experiment 4 showed that on a primed naming task, faces preceded by a categorially related prime were responded to more quickly than those preceded by an unrelated prime, and the effect was due to inhibition. Experiment 5 replicated this effect and also showed that when associatively related primes were used, a facilitatory, and not an inhibitory, effect is found. It is argued that the facilitation of associative priming arises at an earlier locus than the inhibition of categorial priming.     

Matching familiar and unfamiliar faces on internal and external features

Two experiments are reported in which subjects were asked to match a photograph of a complete face and a simultaneously presented photograph of internal or external features of a face, deciding whether or not the two photographs were pictures of the same person. In experiment 1 'same' pairs were derived from different pictures of the same face, so that subjects had to match the faces and not the particular photographs used. Matches based on internal features were found to be faster for familiar than for unfamiliar faces, whereas there was no difference in reaction time between matches based on the external features of familiar and unfamiliar faces. Faster matching of internal features of familiar faces was found to hold equally for pairs of photographs that differed in orientation of the face or in facial expression. In experiment 2 'same' pairs were derived from the same photographs, which gave subjects the choice of matching on the basis of the features of the depicted faces or matching the photographs. Reaction times were faster than in experiment 1, and there were no differences between familiar and unfamiliar faces. The study confirms reports of differential saliency of the internal features of familiar faces, and shows that this only holds when stimuli are treated as faces. The finding thus reflects properties of structural rather than pictorial codes.     

Order of feature recognition in familiar and unfamiliar faces

Three experiments measured order of processing for single faces presented to the left or right visual field (VF) using a same-different matching task. In contrast to earlier studies, the stimuli in the present experiments were carefully matched for overall similarity prior to the actual experiments. Experiments 1 and 2 showed that a significant top-to-bottom order of processing occurred for line drawings of unfamiliar faces but not for line drawings of familiar faces. Experiment 3 found evidence supporting top-to-bottom processing for unfamiliar photographic face stimuli. The photographic stimuli in Experiment 3 were matched more quickly when presented in the left VF (right hemisphere); however, this VF asymmetry was not related to previously reported differences in order of processing. It is suggested that under some conditions faces presented to the right hemisphere may be processed more like familiar faces than faces presented to the left hemisphere; however, this difference is not critical for the left VF (right hemisphere) superiority often found in face recognition tasks.     

The speed of recognition of personally familiar faces

Despite the generally accepted notion that humans are very good and fast at recognising familiar individuals from their faces, the actual speed with which this fundamental brain function can be achieved remains largely unknown. Here, two groups of participants were required to respond by finger-lift when presented with either a photograph of a personally familiar face (classmate), or an unfamiliar one. This speeded manual go/no-go categorisation task revealed that personally familiar faces could be categorised as early as 380 ms after presentation, about 80 ms faster than unfamiliar faces. When response times were averaged across all 8 stimulus presentations, we found that minimum RTs for both familiar and unfamiliar face decisions were substantially lower (310 ms and 370 ms). Analyses confirmed that stimulus repetition enhanced the speed with which faces were categorised, irrespective of familiarity, and that repetition did not affect the observed benefit in RTS for familiar over unfamiliar faces. These data, representing the elapsed time from stimulus onset to motor output, put constraints on the time course of familiar face recognition in the human brain, which can be tracked more precisely by high temporal resolution electrophysiological measures.     

Second-order isomorphism of internal representations of familiar faces

Following a suggestion by Shepard and Chipman (1970), photographs and names of 15 well-known faces were used as stimuli in judgments of similarity. Ss ranked all pairs of stimuli in terms of facial similarity either from memory when presented with pairs of names, or from photographs. There was a highly significant positive correlation between these two types of judgment. A simple classificatory analysis of the 15 faces in terms of the physical features provided evidence that judgments based on the internal representation of the faces utilized pictorial information. These results extend the generality of Shepard and Chipman’s findings and confirm the usefulness of an approach to the problem of mental images based on the concept of second-order isomorphism.     

Reduced fixation on the upper area of personally familiar faces following acquired prosopagnosia

Selective impairment of face recognition following brain damage, as in acquired prosopagnosia, may cause a dramatic loss of diagnosticity of the eye area of the face and an increased reliance on the mouth for identification ( Caldara et al., 2005 ). To clarify the nature of this phenomenon, we measured eye fixation patterns in a case of pure prosopagnosia (PS, Rossion et al., 2003 ) during her identification of photographs of personally familiar faces (27 children of her kindergarten). Her age‐matched colleague served as a control. Consistent with previous evidence, the normal control identified the faces within two fixations located just below the eyes (central upper nose). This pattern (location and duration) of fixations remained unchanged even by increasing difficulty by presenting anti‐caricatures of the faces. In contrast, the great majority of the patient's fixations, irrespective of her accuracy, were located on the mouth. Overall, these observations confirm the abnormally reduced processing of the upper area of the face in acquired prosopagnosia. Most importantly, the prosopagnosic patient also fixated the area of the eyes spontaneously in between the first and last fixation, ruling out alternative accounts of her behaviour such as, for example, avoidance or failure to orient attention to the eyes, as observed in autistic or bilateral amygdala patients. Rather, they reinforce our proposal of a high‐level perceptual account ( Caldara et al., 2005 ), according to which acquired prosopagnosic patients have lost the ability to represent multiple elements of an individual face as a perceptual unit (holistic face perception). To identify a given face, they focus very precisely on local features rather than seeing the whole of a face from its diagnostic centre (i.e. just below the eyes). The upper area of the face is particularly less attended to and less relevant for the prosopagnosic patient because it contains multiple features that require normal holistic perception in order to be the most diagnostic region. Consequently, prosopagnosic patients develop a more robust representation of the mouth, a relatively isolated feature in the face that may contain more information than any single element of the upper face area, and is thus sampled repeatedly for resolving ambiguity in the process of identification.     

Repetition priming for familiar and unfamiliar faces in a sex-judgment task: evidence for a common route for the processing of sex and identity

Repetition priming for faces was examined in a sex-judgment task given at test. Priming was found for edited, hair-removed photos of unfamiliar and familiar faces after a single presentation at study. Priming was also observed for the edited photos when study and test faces were different exemplars. Priming was not observed, however, when sex judgments were made at test to photos of complete, hair-included faces. These findings were interpreted by assuming that, for edited faces, internal features are attended, thereby activating face-recognition units that support performance. With complete faces, however, participants provided speeded judgments based primarily on the hairstyle. It is suggested that, for both familiar and unfamiliar faces, a common locus exists for the processing of the identity of a face and its sex. A single face-recognition model for the processing of familiar and unfamiliar faces is advocated.     

Adaptation effects of highly familiar faces: Immediate and long lasting

A central problem of face identification is forming stable representations from entities that vary--both in a rigid and nonrigid manner--over time, under different viewing conditions, and with altering appearances. Three experiments investigated the underlying mechanism that is more flexible than has often been supposed. The experiments used highly familiar faces that were first inspected as configurally manipulated versions. When participants had to select the veridical version (known from TV/media/movies) out of a series of gradually altered versions, their selections were biased toward the previously inspected manipulated versions. This adaptation effect (face identity aftereffect, Leopold, Rhodes, Müller, & Jeffery, 2005) was demonstrated even for a delay of 24 h between inspection and test phase. Moreover, the inspection of a specific image version of a famous person not only changed the veridicality decision of the same image, but also transferred to other images of this person as well. Thus, this adaptation effect is apparently not based on simple pictorial grounds, but appears to have a rather structural basis. Importantly, as indicated by Experiment 3, the adaptation effect was not based on a simple averaging mechanism or an episodic memory effect, but on identity-specific information.     

Electrodermal discrimination of familiar but not unfamiliar faces in prosopagnosia

It has been previously shown that prosopagnosics can electrodermally "recognize" faces they cannot verbally identify and with which they feel no familiarity. This study extended previous results by showing that electrodermal discrimination of faces exists only on a famous face identification task, and not on a matching-to-sample task involving unfamiliar faces. This suggests that electrodermal recognition reflects the activation of stored identity-specific information built up on the basis of past contact with faces, and provides a psychophysiological distinction between familiar and unfamiliar face processing. Implications for cognitive models of face recognition, and for understanding the nature of prosopagnosia, are discussed.