Why are some people’s names easier to learn than others? The effects of face similarity on memory for face-name associations

Using synthetic faces that varied along four perceptual dimensions (Wilson, Loffler, & Wilkinson, 2002), we examined the effects of face similarity on memory for face-name associations. The nature of these stimuli allowed us to go beyond the categorical similarity manipulations used in previous verbal associative memory studies to trace out the parametric relation between similarity and various performance measures. In Experiment 1, we found that recall performance diminished as a function of how many studied faces were in the vicinity of the cue face in similarity space. Also, incorrect recalls were more likely to come from nearby positions in face space. Experiments 2 and 3, respectively, demonstrated analogous effects with a set of more distinguishable, photorealistic faces, and in an associative recognition task. These results highlight the similarity between associative recall and associative recognition, and between face-name association and other domains of associative memory.     

The fidelity of visual memory for faces and non-face objects

The fidelity of visual working memory was assessed for faces and non-face objects. In two experiments, four levels of memory load (1, 2, 3, or 4 items) were combined with four perceptual distances between probe and study items, with maximum item confusability occurring for the minimum memory load. Under these conditions, recognition memory for multiple faces exceeded that of a single face. This result was primarily due to the higher false alarm rates for faces than non-face objects, even though the two classes of stimuli had been matched for perceptual discriminability. Control experiments revealed that this counterintuitive result emerged only for old–new recognition choices based on near-threshold image differences. For non-face objects, instead, recognition performance decreased with increasing memory load. It is speculated that the low memorial discriminability of the transient properties of a face may serve the purpose of enhancing recognition at the individual-exemplar level.     

Physical and Psychological Representations of Faces: Evidence FromMorphing

Models of face recognition and classification often adopt a framework in which faces are represented as points in a multi-dimensional space. This psychological face space organizes the faces according to similarity and makes predictions for representational theories of faces. A variety of image-processing techniques have been used to create novel stimuli in this space that represent the average of a population or make a face appear more distinctive. The current research examined the relation between the stimuli created by these image-processing techniques and the underlying psychological representation as measured by multidimensional scaling (MDS) procedures. Morphing procedures were used to create 16 faces that were embedded in a set of 84 other faces. Similarity ratings between all possible pairs of faces were collected, and the data were analyzed using MDS procedures. Dimensions that emerged from the MDS solution included age, race, adiposity, and facial hair. In the MDS space, the morphs appeared more typical than the parents, as predicted by the geometric model. A number of biases were examined, including the tendency of the morphs to be less typical than predicted, which may be attributed to the effects of density near the center of face space. In addition, age and facial-adiposity biases were found. The results support the use of the face-space framework for models of face recognition, although image-processing techniques that are designed to create novel stimuli in this space may introduce systematic biases.     

Directed forgetting: differential effects on typical and distinctive faces

Directed forgetting (DF) occurs when stimuli presented during the study phase are followed by "forget" and "remember" cues. On a subsequent memory test, poor memory is observed for stimuli followed by the forget cues, compared to stimuli followed by the remember cues. Although DF is most commonly observed with verbal tasks, the present study extended intentional forgetting research for nonverbal stimuli and examined whether faces were susceptible to DF. Results confirmed that the presentation of a forget cue significantly reduced recognition for faces, as compared to faces followed by a remember cue. Additionally, a well-established finding in face recognition is that distinctive faces are better remembered than typical faces, and Experiment 2 assessed whether face appearance influenced the degree of DF. Results indicate that the DF effect observed in Experiment 1 was replicated in Experiment 2 and that the effect was more pronounced for those faces that were typical in appearance.     

Infants' delayed recognition memory and forgetting

Infants 21- to 25-weeks-old devoted more visual fixation to novel than to previously exposed stimuli on immediate and delayed tests of recognition. Abstract black and white patterns were recognized following a 48-hour delay and photos of faces after a 2-week delay. A decline in recognition over 3 hours for targets (face masks) most akin to objects (real faces) in S's environment led to studies of the effect on delayed recognition of exposure to stimuli similar to those to be retained. One-minute delayed recognition for face photos was disrupted by intervening exposure to intermediate similarity stimuli (rotated photos) but was unaffected by exposure to either high (upright photos) or low (rotated line drawings) similarity stimuli. Differentiation among intervening stimuli occurred only for the upright photos used as high-similarity intervening material. In addition, immediate exposure to rotated photos also prevented 3-hour-delayed recognition of upright photos but had no such effect when delayed for 3 hours. The present experiments confirm the existence of long-term recognition memory for pictorial stimuli in the early months of life and show that one source of forgetting is due to a diversion of the infant's attention to material bearing some perceptual similarity to the material to be retained. This diversion of attention must occur soon after immediate recognition testing to produce a reduction of recognition and such deleterious effects last for an appreciable period of time.     

Serial position effects in short-term visual memory: A SIMPLE explanation?

A version of Sternberg's (1966) short-term visual memory recognition paradigm with pictures of unfamiliar faces as stimuli was used in three experiments to assess the applicability of the distinctiveness-based SIMPLE model proposed by Brown, Neath, and Chater (2002). Initial simulations indicated that the amount of recency predicted increased as the parameter measuring the psychological distinctiveness of the stimulus material (c) increased and that the amount of primacy was dependent on the extent of proactive interference from previously presented stimuli. The data from Experiment 1, in which memory lists of four and five faces varying in visual similarity were used, confirmed the predicted extended recency effect. However, changes in visual similarity were not found to produce changes in c. In Experiments 2 and 3, the conditions that influence the magnitude of c were explored. These revealed that both the familiarity of the stimulus class before testing and changes in familiarity, due to perceptual learning, influenced distinctiveness, as indexed by the parameter c. Overall, the empirical data from all three experiments were well fit by SIMPLE.     

The flip side of the other‐race coin: They all look different to me

Poorer recognition of other‐race faces than own‐races faces has been attributed to a problem of discrimination (i.e., telling faces apart). The conclusion that ‘they all look the same to me' is based on studies measuring the perception/memory of highly controlled stimuli, typically involving only one or two images of each identity. We hypothesized that such studies underestimate the challenge involved in recognizing other‐race faces because in the real world, an individual's appearance varies in a number of ways (e.g., lighting, expression, hairstyle), reducing the utility of relying on pictorial cues to identity. In two experiments, Caucasian and East Asian participants completed a perceptual sorting task in which they were asked to sort 40 photographs of two unfamiliar identities into piles such that each pile contained all photographs of a single identity. Participants perceived more identities when sorting other‐race faces than own‐race faces, both when sorting celebrity (Experiment 1) and non‐celebrity (Experiment 2) faces, suggesting that in the real world, ‘they all look different to me'. We discuss these results in the light of models in which each identity is represented as a region in a multidimensional face space; we argue that this region is smaller for other‐race than own‐race faces.     

Perceptual asymmetries in face recognition

Four experiments were carried out to investigate perceptual asymmetries in face recognition. Perceptual asymmetries favoring the half-face on the observer's left were found under free viewing conditions for both unfamiliar faces (Experiment 1) and famous faces (Experiment 3). For unfamiliar faces, this asymmetry was not obtained when fixation was controlled by presenting faces tachistoscopically (Experiment 2). For famous faces, the perceptual asymmetry favoring the half-face normally seen on the left did not appear to be retained in memory (Experiments 3 and 4). Asymmetries in face perception have been explained in terms of a direct access model of laterally effects. However, these results raise the possibility that asymmetric scanning or attentional factors may be important.     

Domain‐specific development of face memory but not face perception

How does the remarkable human ability for face recognition arise over development? Competing theories have proposed either late maturity (beyond 10 years) or early maturity (before 5 years), but have not distinguished between perceptual and memory aspects of face recognition. Here, we demonstrate a perception–memory dissociation. We compare rate of development for (adult, human) faces versus other social stimuli (bodies), other discrete objects (cars), and other categories processed in discrete brain regions (scenes, bodies), from 5 years to adulthood. For perceptual discrimination, performance improved with age at the same rate for faces and all other categories, indicating no domain‐specific development. In contrast, face memory increased more strongly than non‐face memory, indicating domain‐specific development. The results imply that each theory is partly true: the late maturity theory holds for face memory, and the early maturity theory for face perception.     

Intentionally remembering or forgetting own- and other-race faces: Evidence from directed forgetting

People are better at remembering faces of their own relative to another ethnic group. This so-called own-race bias (ORB) has been explained in terms of differential perceptual expertise for own- and other-race faces or, alternatively, as resulting from socio-cognitive factors. To test predictions derived from the latter account, we examined item-method directed forgetting (DF), a paradigm sensitive to an intentional modulation of memory, for faces belonging to different ethnic and social groups. In a series of five experiments, participants during learning received cues following each face to either remember or forget the item, but at test were required to recognize all items irrespective of instruction. In Experiments 1 and 5, Caucasian participants showed DF for own-race faces only while, in Experiment 2, East Asian participants with considerable expertise for Caucasian faces demonstrated DF for own- and other-race faces. Experiments 3 and 4 found clear DF for social in- and outgroup faces. These results suggest that a modulation of face memory by motivational processes is limited to faces with which we have acquired perceptual expertise. Thus, motivation alone is not sufficient to modulate memory for other-race faces and cannot fully explain the ORB.     

Recognizing distinctive faces: A hybrid-similarity exemplar model account

In recognition memory experiments, Nosofsky and Zaki (2003) found that adding discrete distinctive features to continuous-dimension color stimuli helped participants to identify old items as old (the old-item distinctiveness effect), as well as to identify new items as new. The present study tests the extent to which these results generalize to the domain of face recognition. Two experiments were conducted, one using artificial faces and one using natural faces. Artificial faces were used to test memory for faces with discrete distinctive features while controlling the similarity of the faces themselves on more continuous dimensions. The natural-face experiment used the faces of 40 bald men categorized into three groups (typical, isolated, and distinctive) based on experimental ratings of distinctiveness. In both experiments, there were strong effects of the distinctive features on recognition performance. The data were accounted for reasonably well by a hybrid-similarity version of an exemplar recognition model (Nosofsky and Zaki, 2003), which includes a feature-matching mechanism that can provide boosts to an item's self-similarity.     

Long-term effects of covert face recognition

Covert face recognition has previously been thought to produce only very short-lasting effects. In this study we demonstrate that manipulating subjects' attentional load affects explicit, but not implicit memory for faces, and that implicit effects can persist over much longer intervals than is normally reported. Subjects performed letter-string tasks of high vs. low perceptual load (Lavie, N. (1995). Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Perfomance. 21, 451-468.), while ignoring task-irrelevant celebrity faces. Memory for the faces was then assessed using (a) a surprise recognition test for the celebrities' names, and (b) repetition priming in a face familiarity task. The load manipulation strongly influenced explicit recognition memory, but had no effect on repetition priming from the same items. Moreover, faces from the high load condition produced the same amount of priming whether they were explicitly remembered or not. This result resolves a long-standing anomaly in the face recognition literature, and is discussed in relation to covert processing in prosopagnosia.     

A hybrid-similarity exemplar model for predicting distinctiveness effects in perceptual old-new recognition

In 2 sets of experiments, the authors investigated the basis for old-item distinctiveness effects in perceptual recognition, whereby distinctive old items are recognized with higher probability than are typical old items. In Experiment 1, distinctive old items were defined as those lying in isolated regions of a continuous-dimension similarity space. In this case, any beneficial effects of distinctiveness were absent or small, regardless of the structure of the test list used to assess recognition memory. In Experiment 2, distinctive items were defined as those objects containing certain discrete, individuating features. In this case, large old-item distinctive effects were observed, with the nature of the effects being modulated by the structure of the test lists. A hybrid-similarity exemplar model, combining elements of continuous-dimension distance and discrete-feature matching, was used to account for these distinctiveness effects in the recognition data.     

Identification of own-race and other-race faces: Implications for the representation of race in face space

Own-race faces are recognized more easily than faces of a different, unfamiliar race. According to the multidimensional space (MDS) framework, the poor discriminability of other-race faces is due to their being more densely clustered in face space than own-race faces. Multidimensional scaling analyses of similarity ratings (Caucasian participants, n = 22) showed that other-race (Chinese) faces are more densely clustered in face space. We applied a formal model to test whether the spatial location of face stimuli could account for identification accuracy of another group of Caucasian participants (n = 30). As expected, own-race (Caucasian) faces were identified more accurately (higher hit rate, lower false alarms, and higher A) than other-race faces, which were more densely clustered than ownrace faces. A quantitative model successfully predicted identification performance from the spatial locations of the stimuli. The results are discussed in relation to the standard MDS account of race effects and also an alternative “race-feature” hypothesis.     

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.     

Independent influences of verbalization and race on the configural and featural processing of faces: a behavioral and eye movement study

Describing a face in words can either hinder or help subsequent face recognition. Here, the authors examined the relationship between the benefit from verbally describing a series of faces and the same-race advantage (SRA) whereby people are better at recognizing unfamiliar faces from their own race as compared with those from other races. Verbalization and the SRA influenced face recognition independently, as evident on both behavioral (Experiment 1) and eye movement measures (Experiment 2). The findings indicate that verbalization and the SRA each recruit different types of configural processing, with verbalization modulating face learning and the SRA modulating both face learning and recognition. Eye movement patterns demonstrated greater feature sampling for describing as compared with not describing faces and for other-race as compared with same-race faces. In both cases, sampling of the eyes, nose, and mouth played a major role in performance. The findings support a single process account whereby verbalization can influence perceptual processing in a flexible and yet fundamental way through shifting one's processing orientation.     

Perceptibility of schematic face stimuli: Evidence for a perceptual Gestalt

The perceptibility of face, scrambled face, and single-feature stimuli was investigated in three experiments. Stimuli were presented tachistoscopically, followed by a visual noise mask and a forced-choice test of one of three features (eyes, nose, and mouth). In Experiment I, two processing strategies which have been proposed for word perception (involving expectancy and redundancy) were investigated for the stimuli employed here. In Experiments II and III, experimentally induced familiarity was studied for its effect on recognition and perception, and an immediate and delayed perceptual test was employed. Across all three experiments, perception of single-feature and face stimuli were consistently superior to scrambled faces; in Experiment III, differences between single features and faces were eliminated. The effects of perceptual expectancy, internal feature redundancy, familiarity, guessing biases, etc., were shown to be insufficient to account for the superiority of face to scrambled face stimuli. It was argued that the perceptibility of nonredundant features are enhanced when those features are aligned in a well-defined form class. The view that familiarity operates directly on recognitive processes but indirectly on perceptual ones was discussed.     

Perceptual representations in false recognition and priming of pictures

Using a new procedure, we investigate whether imagination can induce false memory by creating a perceptual representation. Participants studied pictures and words with and without an imagery task and at test performed both a direct recognition test and an indirect perceptual identification test on pictorial stimuli. Corrected false recognition rates were 7% for pictures studied in word form (Experiment 1), 26% for pictures imagined once (Experiment 2), and 48% for pictures imagined multiple times (Experiment 3), although on the indirect test, no priming was found for these items. Furthermore, a perceptual/conceptual imagery manipulation did not affect the tendency to claim that imagined items had been studied as pictures (Experiment 4). These results suggest that the false memories reported on direct tests are not driven by perceptual representations.     

Applying the attractor field model to social cognition: Perceptual discrimination is facilitated, but memory is impaired for faces displaying evaluatively congruent expressions

A new model of mental representation is applied to social cognition: the attractor field model. Using the model, the authors predicted and found a perceptual advantage but a memory disadvantage for faces displaying evaluatively congruent expressions. In Experiment 1, participants completed a same/different perceptual discrimination task involving morphed pairs of angry-to-happy Black and White faces. Pairs of faces displaying evaluatively incongruent expressions (i.e., happy Black, angry White) were more likely to be labeled as similar and were less likely to be accurately discriminated from one another than faces displaying evaluatively congruent expressions (i.e., angry Black, happy White). Experiment 2 replicated this finding and showed that objective discriminability of stimuli moderated the impact of attractor field effects on perceptual discrimination accuracy. In Experiment 3, participants completed a recognition task for angry and happy Black and White faces. Consistent with the attractor field model, memory accuracy was better for faces displaying evaluatively incongruent expressions. Theoretical and practical implications of these findings are discussed.