Identification and classification of facial familiarity in directed lying: an ERP study

Recognizing familiar faces is essential to social functioning, but little is known about how people identify human faces and classify them in terms of familiarity. Face identification involves discriminating familiar faces from unfamiliar faces, whereas face classification involves making an intentional decision to classify faces as "familiar" or "unfamiliar." This study used a directed-lying task to explore the differentiation between identification and classification processes involved in the recognition of familiar faces. To explore this issue, the participants in this study were shown familiar and unfamiliar faces. They responded to these faces (i.e., as familiar or unfamiliar) in accordance with the instructions they were given (i.e., to lie or to tell the truth) while their EEG activity was recorded. Familiar faces (regardless of lying vs. truth) elicited significantly less negative-going N400f in the middle and right parietal and temporal regions than unfamiliar faces. Regardless of their actual familiarity, the faces that the participants classified as "familiar" elicited more negative-going N400f in the central and right temporal regions than those classified as "unfamiliar." The P600 was related primarily with the facial identification process. Familiar faces (regardless of lying vs. truth) elicited more positive-going P600f in the middle parietal and middle occipital regions. The results suggest that N400f and P600f play different roles in the processes involved in facial recognition. The N400f appears to be associated with both the identification (judgment of familiarity) and classification of faces, while it is likely that the P600f is only associated with the identification process (recollection of facial information). Future studies should use different experimental paradigms to validate the generalizability of the results of this study.     

Familiar Face Detection in 180ms

The visual system is tuned for rapid detection of faces, with the fastest choice saccade to a face at 100ms. Familiar faces have a more robust representation than do unfamiliar faces, and are detected faster in the absence of awareness and with reduced attentional resources. Faces of family and close friends become familiar over a protracted period involving learning the unique visual appearance, including a view-invariant representation, as well as person knowledge. We investigated the effect of personal familiarity on the earliest stages of face processing by using a saccadic-choice task to measure how fast familiar face detection can happen. Subjects made correct and reliable saccades to familiar faces when unfamiliar faces were distractors at 180ms—very rapid saccades that are 30 to 70ms earlier than the earliest evoked potential modulated by familiarity. By contrast, accuracy of saccades to unfamiliar faces with familiar faces as distractors did not exceed chance. Saccades to faces with object distractors were even faster (110 to 120 ms) and equivalent for familiar and unfamiliar faces, indicating that familiarity does not affect ultra-rapid saccades. We propose that detectors of diagnostic facial features for familiar faces develop in visual cortices through learning and allow rapid detection that precedes explicit recognition of identity.     

Investigating the Effect of Familiarity on Kin Recognition of Three‐Spined Stickleback (Gasterosteus aculeatus)

The ability to discriminate between related and unrelated individuals has been demonstrated in many species. The mechanisms behind this ability might be manifold and depend on the ecological context in which the species lives. In brood‐caring species, both familiarity and phenotype matching are known to be used in kin recognition. However, results of studies disentangling these two phenomena have proved contradictory. We aimed to broaden our knowledge about the mechanisms of kin recognition using shoaling preferences of three‐spined stickleback (Gasterosteus aculeatus) as a model behavior. In our first experiment, focal fish had the choice to shoal either with kin or unfamiliar non‐kin. In half of the trials, kin groups were composed of familiar individuals, while they were unfamiliar in the other half. Focal fish significantly preferred kin as shoaling partner, a result which was not reinforced by familiarity. In our second experiment, focal fish were given the choice between a shoal of familiar kin and a shoal of unfamiliar kin. Here, focal fish did not show any significant preference. These results indicate that familiarity does not impact stickleback's ability to recognize kin. Furthermore, they show that familiarity does not overrule recognition based on phenotype matching or innate recognition, underlining the importance of these mechanisms. Finally, our results lead to the assumption that individual recognition might play a minor role also in non‐kin‐based preferences for familiars.     

Spontaneous gender categorization in masking and priming studies: key for distinguishing Jane from John Doe but not Madonna from Sinatra

Facial recognition is key to social interaction, however with unfamiliar faces only generic information, in the form of facial stereotypes such as gender and age is available. Therefore is generic information more prominent in unfamiliar versus familiar face processing? In order to address the question we tapped into two relatively disparate stages of face processing. At the early stages of encoding, we employed perceptual masking to reveal that only perception of unfamiliar face targets is affected by the gender of the facial masks. At the semantic end; using a priming paradigm, we found that while to-be-ignored unfamiliar faces prime lexical decisions to gender congruent stereotypic words, familiar faces do not. Our findings indicate that gender is a more salient dimension in unfamiliar relative to familiar face processing, both in early perceptual stages as well as later semantic stages of person construal.     

Stable face representations

Photographs are often used to establish the identity of an individual or to verify that they are who they claim to be. Yet, recent research shows that it is surprisingly difficult to match a photo to a face. Neither humans nor machines can perform this task reliably. Although human perceivers are good at matching familiar faces, performance with unfamiliar faces is strikingly poor. The situation is no better for automatic face recognition systems. In practical settings, automatic systems have been consistently disappointing. In this review, we suggest that failure to distinguish between familiar and unfamiliar face processing has led to unrealistic expectations about face identification in applied settings. We also argue that a photograph is not necessarily a reliable indicator of facial appearance, and develop our proposal that summary statistics can provide more stable face representations. In particular, we show that image averaging stabilizes facial appearance by diluting aspects of the image that vary between snapshots of the same person. We review evidence that the resulting images can outperform photographs in both behavioural experiments and computer simulations, and outline promising directions for future research.     

Effects of Caricaturing in Shape or Color on Familiarity Decisions for Familiar and Unfamiliar Faces

Recent evidence suggests that while reflectance information (including color) may be more diagnostic for familiar face recognition, shape may be more diagnostic for unfamiliar face identity processing. Moreover, event-related potential (ERP) findings suggest an earlier onset for neural processing of facial shape compared to reflectance. In the current study, we aimed to explore specifically the roles of facial shape and color in a familiarity decision task using pre-experimentally familiar (famous) and unfamiliar faces that were caricatured either in shape-only, color-only, or both (full; shape + color) by 15%, 30%, or 45%. We recorded accuracies, mean reaction times, and face-sensitive ERPs. Performance data revealed that shape caricaturing facilitated identity processing for unfamiliar faces only. In the ERP data, such effects of shape caricaturing emerged earlier than those of color caricaturing. Unsurprisingly, ERP effects were accentuated for larger levels of caricaturing. Overall, our findings corroborate the importance of shape for identity processing of unfamiliar faces and demonstrate an earlier onset of neural processing for facial shape compared to color.     

The effects of habitat‐ and diet‐based cues on association preferences in the three‐spined stickleback (Gasterosteus aculeatus)

A number of recent papers have investigated the potential of familiarity to organize the distributions of free‐ranging animals. It is not clear, however, to which extent individual recognition or a more general recognition of a group odour is responsible for familiarity preferences. First, we tested the sensory basis of the recognition of familiars in three‐spined stickleback ( Gasterosteus aculeatus ). When allowed to choose between a familiar and an unfamiliar stimulus shoal on the basis of both visual and chemical communication, visual communication only and chemical communication only, the preference of focal fish for familiars was shown to be dependent on the presence of chemical cues. We subsequently investigated the mechanisms underlying such association preferences, specifically the effects of recent habitat and diet on preferences. Experimental fish were divided into four treatment groups consisting of two environment treatments (saline and freshwater) and two diet treatments ( Daphnia spp. and chironimid larvae). Focal fish subsequently showed significant association preferences for groups of unfamiliar fish that had undergone the same environment or diet treatment as themselves, suggesting self‐referent matching. These data indicate that individual recognition is not a pre‐requisite for the expression of familiarity preferences.     

Chemosensory recognition of siblings in juvenile coho salmon (Oncorhynchus kisutch)

Juvenile coho salmon, Oncorhynchus kisutch, were tested for responses to water conditioned by conspecifics in two-choice tanks. The fish preferred water conditioned by unfamiliar non-siblings over blank water, but preferred water conditioned by both familiar and unfamiliar siblings over non-siblings. These preferences suggest that coho salmon recognize their siblings by matching the phenotype of their tank-mates with unfamiliar conspecifics, and that chemical cues are sufficient for recognition.     

Orangutans (Pongo pygmaeus) Remember Old Acquaintances

Many social animals can discriminate between familiar and unfamiliar faces. Orangutans, however, lead a semi-solitary life and spend much of the day alone. As such, they may be less adept at recognizing conspecifics and are a good model for determining how social structure influences the evolution of social cognition such as facial recognition. The present study is the first report of whether orangutans can distinguish among individual faces. We adopted a preferential looking method and found that orangutans used facial discrimination to identify known conspecifics. This suggests that frequent and intense social interaction is not necessary for facial discrimination, although our findings were limited by the small number of stimuli and the unequal numbers of male and female orangutans depicted in the stimuli.     

Familiarity influences body darkening in territorial disputes between juvenile salmon

Escalated contests between animals are potentially costly because of increased energy expenditure and risk of predation or injury. Hence we would expect selection to favour any mechanism that avoids unnecessary prolonged fighting. One such means of avoiding escalated fights could be the use of information gained through individual recognition. Previous work has shown that a darkening of the body colour is closely associated with submission in contests between juvenile Atlantic salmon, Salmo salar, and it has been hypothesized that this may act as a visual signal to the opponent. We tested the hypothesis that body darkening is used to reduce the cost of contests between familiar fish such that losers darken more quickly when faced with familiar than unfamiliar opponents. In contests between unfamiliar fish, submissive darkening occurred after more escalated contests in which the loser incurred more aggression, whereas the opposite occurred when familiar fish were in conflict. In addition familiar fish either submitted quickly or engaged in protracted conflicts in which neither fish signalled submission, whereas in unfamiliar fish contests were of intermediate duration regardless of whether either fish darkened. We suggest that body darkening is used by familiar fish to signal submission to familiar dominants in order to avert a costly escalated fight, but familiarity can lead to escalation without submission if perceived competitive asymmetries are finely balanced. Copyright 2000 The Association for the Study of Animal Behaviour.     

Shoaling Decisions in Angelfish: The Roles of Social Status and Familiarity

Abstract Past research has shown that angelfish, Pterophyllum scalare , are capable of discriminating between shoals composed of familiar dominant and subordinate companions, whereas they show no preference for shoals of unfamiliar conspecifics. In this study, the relative importance of familiarity and social status (shoal factors) on the shoaling decision of juvenile angelfish, which also differed in social status (individual factor), was investigated as very little is known about such tradeoffs in fishes. Dominant and subordinate individuals were given the choice to shoal with a group of conspecifics composed of familiar dominants vs. unfamiliar dominants and composed of familiar subordinates vs. unfamiliar subordinates. The findings demonstrate that fish with different social status differed in their shoaling preference. Subordinate test fish showed a preferential association with familiar subordinates over unfamiliar subordinates, but preferred the unfamiliar shoal over the familiar one when both shoals were constituted by dominant individuals. The shoaling behaviour shown by dominant test fish, on the other hand, indicated no significant preference for any of the shoals regardless of their composition. A replicate preference test carried out 2 h 30 min after the first one indicated that the association pattern was relatively consistent. Results suggest that angelfish are able to differentiate between the stimulus shoals and demonstrate that the pervasive influence of familiarity on the shoaling decision may be restrained or overridden by the composition of the familiar shoals and the social status of the test fish.     

Nutritional state influences shoaling preference for familiars

Preferences for grouping with familiar individuals are shown in many animal species, including the three-spined stickleback (Gasterosteus aculeatus). Shoaling with familiars is advantageous because of more precise anti-predator behaviours or more stable dominance hierarchies. Additionally, associations with familiar individuals facilitate the evolution of altruistic behaviour. Thus, in situations of increased competition one might expect an increased preference for familiar fish. We gave single juvenile sticklebacks of different nutritional state the choice between shoals composed either of familiar or unfamiliar individuals. Satiated fish preferred to shoal with familiar individuals. A comparative analysis of 8 stickleback studies with 15 different tests using familiars showed that all tests gave similar results, i.e. sticklebacks of all age classes preferred to shoal with familiars in a non-sexual context. In contrast, hungry test fish did not prefer to shoal with familiar fish, but even showed a preference for the unfamiliar group. Because sticklebacks use early-life familiarity to recognize kin, the results suggest the avoidance of competition with relatives. To our knowledge, this is the first study showing an impact of nutritional state on social interactions with familiar individuals.     

Social discrimination in lambs: the role of indirect familiarization and methods of assessment

Familiarization with individuals resulting from direct exposure is the primary mechanism mediating social recognition in many vertebrates. However, discernible phenotypic similarity among close kin may provide an additional basis for recognizing previously unencountered individuals. We investigated the existence of such a mechanism of indirect familiarity among artificially reared twin lambs, Ovis aries, that were separated shortly after birth. When they were 2-3 weeks old, we tested their recognition of familiar penmates, their unfamiliar twin and twins of familiar penmates in two-choice and paired tests. Lambs responded discriminatively to familiar penmates. When allowed to choose between their twins or twins of penmates versus an unfamiliar unrelated individual, lambs did not show any preference. Nevertheless, when paired with a twin or penmate’s twin, lambs bleated less than did those paired with an unfamiliar unrelated partner, which suggests that twins and twins of penmates were recognized. Discrimination between twin and unrelated individuals could be based either on early learning of the twin's phenotypic traits (template) before separation or on a process of indirect familiarization (comparison with familiar self cues). However, indirect familiarization was clearly implicated in the discrimination of twins of penmates; that is, lambs learned the characteristic phenotypic traits of (unrelated) penmates and detected a resemblance between those familiar individuals and their twins. Overall, the two-choice and paired tests were differentially effective procedures depending on the research question being addressed, that is, relatively simple or subtle social discrimination. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Similarities and differences in Chinese and Caucasian adults' use of facial cues for trustworthiness judgments

Background

All cultural groups in the world place paramount value on interpersonal trust. Existing research suggests that although accurate judgments of another''s trustworthiness require extensive interactions with the person, we often make trustworthiness judgments based on facial cues on the first encounter. However, little is known about what facial cues are used for such judgments and what the bases are on which individuals make their trustworthiness judgments.

Methodology/Principal Findings

In the present study, we tested the hypothesis that individuals may use facial attractiveness cues as a “shortcut” for judging another''s trustworthiness due to the lack of other more informative and in-depth information about trustworthiness. Using data-driven statistical models of 3D Caucasian faces, we compared facial cues used for judging the trustworthiness of Caucasian faces by Caucasian participants who were highly experienced with Caucasian faces, and the facial cues used by Chinese participants who were unfamiliar with Caucasian faces. We found that Chinese and Caucasian participants used similar facial cues to judge trustworthiness. Also, both Chinese and Caucasian participants used almost identical facial cues for judging trustworthiness and attractiveness.

Conclusions/Significance

The results suggest that without opportunities to interact with another person extensively, we use the less racially specific and more universal attractiveness cues as a “shortcut” for trustworthiness judgments.     

Familiarity affects social network structure and discovery of prey patch locations in foraging stickleback shoals

Numerous factors affect the fine-scale social structure of animal groups, but it is unclear how important such factors are in determining how individuals encounter resources. Familiarity affects shoal choice and structure in many social fishes. Here, we show that familiarity between shoal members of sticklebacks (Gasterosteus aculeatus) affects both fine-scale social organization and the discovery of resources. Social network analysis revealed that sticklebacks remained closer to familiar than to unfamiliar individuals within the same shoal. Network-based diffusion analysis revealed that there was a strong untransmitted social effect on patch discovery, with individuals tending to discover a task sooner if a familiar individual from their group had previously done so than if an unfamiliar fish had done so. However, in contrast to the effect of familiarity, the frequency with which individuals had previously associated with one another had no effect upon the likelihood of prey patch discovery. This may have been due to the influence of fish on one another''s movements; the effect of familiarity on discovery of an empty ‘control’ patch was as strong as for discovery of an actual prey patch. Our results demonstrate that factors affecting fine-scale social interactions can also influence how individuals encounter and exploit resources.     

Effects of Gender and Personality on First Impression

The present study explores whether and to what extent individual differences (i.e., gender and personality traits of perceiver) predict inferences of trustworthiness from emotionally neutral unfamiliar faces and the related confidence in judgment. Four hundred and ten undergraduate students participated in the study. Personality was assessed using the Big Five model (i.e., Extraversion, Neuroticism, Conscientiousness, Agreeableness and Openness to experience) and measures of trait anxiety and aggression. The results suggest that trustworthiness judgments are affected by the gender of the perceiver, although this effect depends on the valence of the face. Women tend to judge trustworthy-looking faces as significantly more trustworthy than men do, and this is particularly pronounced for judgments of female faces. There were no gender differences for judgments of untrustworthy-looking or neutral faces. Gender also seems to affect the confidence in judgment. Specifically, women were generally less confident than men in judging trustworthiness of unfamiliar faces. Personality also affected judgment. Both low agreeable individuals and high trait aggressive individuals tend to perceive unfamiliar faces as less trustworthy. The present findings suggest that both gender and personality traits are relevant for understanding how people evaluate the trustworthiness of others. Whom we decide to trust is a function not only of their facial features but also of gender and individual differences in personality traits.     

Individual Recognition in Domestic Cattle (Bos taurus): Evidence from 2D-Images of Heads from Different Breeds

Background

In order to maintain cohesion of groups, social animals need to process social information efficiently. Visual individual recognition, which is distinguished from mere visual discrimination, has been studied in only few mammalian species. In addition, most previous studies used either a small number of subjects or a few various views as test stimuli. Dairy cattle, as a domestic species allow the testing of a good sample size and provide a large variety of test stimuli due to the morphological diversity of breeds. Hence cattle are a suitable model for studying individual visual recognition. This study demonstrates that cattle display visual individual recognition and shows the effect of both familiarity and coat diversity in discrimination.

Methodology/Principal Findings

We tested whether 8 Prim''Holstein heifers could recognize 2D-images of heads of one cow (face, profiles, ¾ views) from those of other cows. Experiments were based on a simultaneous discrimination paradigm through instrumental conditioning using food rewards. In Experiment 1, all images represented familiar cows (belonging to the same social group) from the Prim''Holstein breed. In Experiments 2, 3 and 4, images were from unfamiliar (unknown) individuals either from the same breed or other breeds. All heifers displayed individual recognition of familiar and unfamiliar individuals from their own breed. Subjects reached criterion sooner when recognizing a familiar individual than when recognizing an unfamiliar one (Exp 1: 3.1±0.7 vs. Exp 2: 5.2±1.2 sessions; Z = 1.99, N = 8, P = 0.046). In addition almost all subjects recognized unknown individuals from different breeds, however with greater difficulty.

Conclusions/Significance

Our results demonstrated that cattle have efficient individual recognition based on categorization capacities. Social familiarity improved their performance. The recognition of individuals with very different coat characteristics from the subjects was the most difficult task. These results call for studies exploring the mechanisms involved in face recognition allowing interspecies comparisons, including humans.     

Interactions between Males of the Lizard Liolaemus tenuis: Roles of Familiarity and Memory

For territorial organisms, recognition of familiar individuals can reduce the frequency and intensity of aggressive encounters (‘dear enemy’ phenomenon), stabilize social systems, and reduce the cost of territory maintenance. Here, we investigated the behavioural events displayed during contests between familiar and unfamiliar individuals in the lizard Liolaemus tenuis (Liolaemidae), a species in which males are territorial. The behaviours recorded were attack, warning, evasion, and submission, and the latencies to the first aggressive (attack or warning) behaviour. Additionally, we assessed the ability of individuals to remember a familiar conspecific after a period without social interaction. Individual males reduced and delayed aggressive behaviour directed towards socially familiar individuals compared with unfamiliar ones. These results suggest that males distinguished between familiar and unfamiliar conspecific males and are in agreement with the ‘dear enemy’ phenomenon. Other behaviours were similar in the contests between familiar and unfamiliar individuals. Recognition of familiar conspecifics was lost after 20 d without social interactions. This may be relevant for interactions with floater males or with neighbours that lose their territory and subsequently attempt to fight for their ex‐neighbour's territory.     

Kin discrimination in sticklebacks is mediated by social learning rather than innate recognition

Theory predicts several advantages for animals to recognize kin. These include inbreeding avoidance and an increase in inclusive fitness. In shoaling species, kin recognition may lead to an increased amount of altruism among shoal members. Adult, non‐reproductive three‐spined sticklebacks, Gasterosteus aculeatus, prefer to shoal with kin. This preference was shown for familiar as well as for unfamiliar individuals. However, whether it is based on learned cues of familiar individuals or on innate mechanisms like self‐referent phenotype matching or ‘true’ kin recognition through recognition alleles remains unknown. In our experiments, juvenile fish were given the choice between shoals that differed in relatedness and familiarity. The number of testfish who joined each group indicated that sticklebacks prefer to shoal with familiar kin when the alternative shoal was composed of unfamiliar non‐kin. When one shoal consisted of familiar kin while the second consisted of familiar non‐kin testfish did not show any preference. Kin recognition in sticklebacks is thus most likely mediated by social learning.     

Social recognition and approach in the chick: lateralization and effect of visual experience

Chicks, Gallus gallus domesticus, tested monocularly on day 3 after hatching recognize familiar versus unfamiliar conspecifics and choose to approach one or other when they use the left eye, whereas they approach familiar and unfamiliar chicks at random when they use the right eye. In experiment 1 we investigated the effects of light exposure of embryos prior to hatching on this particular form of lateralization. Irrespective of whether they hatched from eggs incubated in the dark or from eggs exposed to light during the final days of incubation, chicks using the left eye had higher choice scores (meaning they chose to approach either a familiar or an unfamiliar chick) than chicks using the right eye or both eyes. Therefore, light experience prior to hatching did not influence the lateralization of individual recognition or choice behaviour, although it did affect latency to move out of, and time spent in, the centre of the runway. Experiment 2 showed that visual/social experience posthatching influences choice behaviour: chicks housed in a group in the light for 12 h on day 1 posthatching made a clear choice between familiar and unfamiliar chicks when tested on day 3, but chicks kept in a group in the dark on day 1 did not make a choice, instead alternating between the two stimuli. In experiment 3 we found that posthatching visual/social experience increased the choice scores of chicks using the right eye and thereby removed any lateralization of choice behaviour. The results suggest that visual experience of a social group is required before chicks using their right eye (and left hemisphere) will pay attention to the cues that distinguish one chick from another. Chicks using their left eye (and right hemisphere) recognize the difference between individuals without requiring visual experience with other chicks. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.