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.     

A probabilistic account of exemplar and category generation

People are capable of imagining and generating new category exemplars and categories. This ability has not been addressed by previous models of categorization, most of which focus on classifying category exemplars rather than generating them. We develop a formal account of exemplar and category generation which proposes that category knowledge is represented by probability distributions over exemplars and categories, and that new exemplars and categories are generated by sampling from these distributions. This sampling account of generation is evaluated in two pairs of behavioral experiments. In the first pair of experiments, participants were asked to generate novel exemplars of a category. In the second pair of experiments, participants were asked to generate a novel category after observing exemplars from several related categories. The results suggest that generation is influenced by both structural and distributional properties of the observed categories, and we argue that our data are better explained by the sampling account than by several alternative approaches.     

Recognizing disguised faces

Across three experiments, we evaluated the effects of “disguises” on observers’ face identification performance using naturalistic images in which individuals posed with a variety of wigs and eyeglasses. Experiment 1 tested recognition memory performance with and without disguises and showed that any changes in these facial attributes hindered performance, replicating previous findings. More interestingly, Experiment 1 revealed that a change in hairstyle or the removal of eyeglasses had more impact on performance than did the addition of eyeglasses. In Experiment 2, disguised and undisguised faces were presented upright or inverted to examine whether the performance decrements seen in Experiment 1 were attributable to disruption of processing strategies for faces. Despite showing an overall effect of disguise on performance, there was no interaction between inversion and disguise. This suggests that disguises are not directly affecting processing strategies, but instead disguises are likely encoded as part of the overall representation. Similarly, in Experiment 3, the composite face paradigm was used to examine whether the impact of disguises is attributable to disruption of holistic processing for faces. Again, we found an overall effect of disguise on performance, but here we also observed that the presence of disguises interacted with participants’ tendency to form holistic face representations.     

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.     

Recognizing faces defined by texture gradients

Texture gradients can reveal surface orientation in a manner similar to shape from shading, and therefore provide an important cue for object recognition. In this study, we tested whether a complex 3-D object, such as a face, can be identified from texture gradients alone. The stimuli were laser-scanned faces for which the texture element was a fractal-noise pattern mapped onto the 3-D surface. An eight-alternative forced choice task was used in which participants matched a face defined by texture gradients to one of eight faces defined by shape from shading (Experiment 1) or by texture gradients (Experiment 2). On average, participants scored 24% and 18%, respectively, above chance in these experiments. Although this performance was much poorer than the performance based entirely on shape-from-shading stimuli (Experiment 3), the results suggest that texture gradient information may be used to recover surface geometry of complex objects.     

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.     

Recognizing faces in and out of context

Two experiments are reported which examined the influence of context on face recognition accuracy for novel and familiar faces respectively. Context was manipulated by varying the physical background against which the faces appeared. In Experiment I, 80 student subjects observed 18 faces before attempting to recognize them in a sequence of 36 alternatives. For half the subjects, the backgrounds changed from study to test, while for the remainder they stayed the same. In addition, for half the subjects, both the pose and expression of the face also changed, while for the others it remained constant. Changes in pose plus expression and context significantly reduced recognition accuracy for the target faces. Experiment II used an identical design, except that the faces of celebrities replaced the novel faces. The influence of context was eliminated but the effects of pose and expression were maintained. However, when only faces which were actually identified by subjects were considered, the effects of pose and expression, too, were eliminated. The significance of these findings for theories of contextual memory are discussed.     

Recognizing faces in and out of context

Two experiments are reported which examined the influence of context on face recognition accuracy for novel and familiar faces respectively. Context was manipulated by varying the physical background against which the faces appeared. In Experiment I, 80 student subjects observed 18 faces before attempting to recognize them in a sequence of 36 al ternatives , For half the subj ects, the backgrounds changed from study to test, while for the remainder they stayed the same. In addition, for half the subjects, both the pose and expression of the face also changed, while for the others it remained constant. Changes in pose plus expression and context significantly reduced recognition accuracy for the target faces. Experiment 11 used an identical design, except that the faces of celebrities replaced the novel faces. The influence of context was eliminated but the effects of pose and expression were maintained. However, when only faces which were actually identified by subjects were considered, the effects of pose and expression, too, were eliminated. The significance of these findings for theories of contextual memory are discussed.     

Recognizing emotion in faces: developmental effects of child abuse and neglect

The contributions to the recognition of emotional signals of (a) experience and learning versus (b) internal predispositions are difficult to investigate because children are virtually always exposed to complex emotional experiences from birth. The recognition of emotion among physically abused and physically neglected preschoolers was assessed in order to examine the effects of atypical experience on emotional development. In Experiment 1, children matched a facial expression to an emotional situation. Neglected children had more difficulty discriminating emotional expressions than did control or physically abused children. Physically abused children displayed a response bias for angry facial expressions. In Experiment 2, children rated the similarity of facial expressions. Control children viewed discrete emotions as dissimilar, neglected children saw fewer distinctions between emotions, and physically abused children showed the most variance across emotions. These results suggest that to the extent that children's experience with the world varies, so too will their interpretation and understanding of emotional signals.     

An exemplar account of the bow and set-size effects in absolute identification

The extended generalized context model for response times (K. Lamberts, 2000) was designed to account for choice proportions and response times in perceptual categorization. In this article, the hypothesis that the model also offers an account of accuracy and response times in absolute identification was investigated. The model was applied to the data from 2 absolute identification experiments and provided a good account of the bow and the set-size effects in accuracy and response time data from individual participants, including the response time distributions for individual stimuli. The model applications demonstrated that exemplar-based process models offer a viable account of absolute identification data.     

Attractiveness, distinctiveness, and recognition of faces: attractive faces can be typical or distinctive but are not better recognized

The debate surrounding the relationship between facial attractiveness and distinctiveness appears to arise from different definitions of distinctiveness. In our study unfamiliar faces were rated for attractiveness, age, and distinctiveness. Two measures of distinctiveness were used: ease of spotting the face in a crowd (traditional) and deviation from an average face (deviation). Recognition was not predicted by attractiveness. The traditional ratings produced a complex relationship with attractiveness, where unattractive faces were distinctive, but attractive faces were rated at all levels of distinctiveness. When the effects of age were partialled out, attractiveness no longer predicted traditional distinctiveness. However, deviation ratings produced a strong negative correlation with attractiveness, even when the effects of age were removed.     

Familiarity breeds attraction: effects of exposure on the attractiveness of typical and distinctive faces

Several studies have shown that facial attractiveness is positively correlated with both familiarity and typicality. Here we manipulated the familiarity of typical and distinctive faces to measure the effect on attractiveness. In our first experiment, we collected ratings of attractiveness, distinctiveness, and familiarity using three different groups of participants. Our stimuli included 84 images of female faces, presented in a full-face view. We replicated the finding that attractiveness ratings negatively correlate with distinctiveness ratings. In addition, we showed that attractiveness ratings were positively correlated with familiarity ratings. In our second experiment, we demonstrated that increasing exposure to faces increases their attractiveness, although there was no differential effect of exposure on typical and distinctive faces. Our results suggest that episodic familiarity affects attractiveness ratings independently of general or structural familiarity. The implications of our findings for the 'face-space' model are discussed.     

Differences in attentional involvement underlying the perception of distinctive and typical faces

Differences in human faces can be evaluated along a continuum that ranges from 'distinctive' to 'typical.' We examined processing differences between distinctive and typical faces by two attentional tasks that induce attentional blink (AB). Given that AB is believed to reflect temporal or capacity limits of attention, stimuli that survive AB are believed to be associated with greater processing efficiency. In a change-detection task, participants were required to detect changes in the two pairs of faces that were presented in rapid succession. Changes involving the distinctive face of a pair were more likely to be detected than those involving a typical face. In a face-identification task, distinctive faces embedded in a rapid serial visual presentation (RSVP) stream were identified with a greater accuracy than typical faces. Together, our results suggest that distinctive faces are associated with greater processing efficiency and may be explained in terms of perceptual salience, a stimulus dimension known to attract attention.     

Recognizing people from the inner or outer parts of their faces: Developmental data concerning ‘unfamiliar’ faces

Existing data demonstrate a developmental trend in the way in which highly familiar faces are recognized, such that young children rely more on the outer facial features (the hairline, chin and ears) than the inner facial features (the eyes, nose and mouth) and adults demonstrate the reverse pattern. However, little is known about the developmental pattern of importance of inner and outer facial features for recognizing people who are not highly familiar. Here we report a study which attempts to describe this pattern. Using a two‐alternative forced‐choice procedure, we presented 5‐, 7‐, and 9‐year‐olds and adults (N = 22 in each group) with the task of recognizing an experimentally familiarized face (initially seen in a short video) from a still picture of either the whole face, just the inner, or just the outer parts. The results showed that, for all ages, recognition was faster (and in most cases, more accurate) for outer features alone than for inner features alone (and was fastest for whole faces). These data demonstrate the importance of outer facial features for the recognition of relatively unfamiliar faces. Taken together with previous findings, they enhance our picture of the effects of age and experience with individual faces on recognition and configural processing.     

From exemplar to grammar: a probabilistic analogy-based model of language learning

While rules and exemplars are usually viewed as opposites, this paper argues that they form end points of the same distribution. By representing both rules and exemplars as (partial) trees, we can take into account the fluid middle ground between the two extremes. This insight is the starting point for a new theory of language learning that is based on the following idea: If a language learner does not know which phrase-structure trees should be assigned to initial sentences, s/he allows (implicitly) for all possible trees and lets linguistic experience decide which is the "best" tree for each sentence. The best tree is obtained by maximizing "structural analogy" between a sentence and previous sentences, which is formalized by the most probable shortest combination of subtrees from all trees of previous sentences. Corpus-based experiments with this model on the Penn Treebank and the Childes database indicate that it can learn both exemplar-based and rule-based aspects of language, ranging from phrasal verbs to auxiliary fronting. By having learned the syntactic structures of sentences, we have also learned the grammar implicit in these structures, which can in turn be used to produce new sentences. We show that our model mimicks children's language development from item-based constructions to abstract constructions, and that the model can simulate some of the errors made by children in producing complex questions.     

Rule-based extrapolation: A continuing challenge for exemplar models

Erickson and Kruschke (1998, 2002) demonstrated that in rule-plus-exception categorization, people generalize category knowledge by extrapolating in a rule-like fashion, even when they are presented with a novel stimulus that is most similar to a known exception. Although exemplar models have been found to be deficient in explaining rule-based extrapolation, Rodrigues and Murre (2007) offered a variation of an exemplar model that was better able to account for such performance. Here, we present the results of a new rule-plus-exception experiment that yields rule-like extrapolation similar to that of previous experiments, and yet the data are not accounted for by Rodrigues and Murre's augmented exemplar model. Further, a hybrid rule-and-exemplar model is shown to better describe the data. Thus, we maintain that rule-plus-exception categorization continues to be a challenge for exemplar-only models.     

Recognizing melodies: A dynamic interpretation

Two experiments explore hypotheses about rhythm and contour in recognition of simple pitch strings (melodies). Target melodies that differed with respect to pitch relationships (interval and contour pitch differences) and rhythm, were presented to ordinary listeners who were told to learn the melodies (Phase I). In a subsequent recognition test (Phase II), listeners had to recognize these same target melodies although they were transposed to a different musical key. In recognition, target melodies appeared in the original rhythm or in new rhythms that simulated some pause properties of the original rhythm. Target melodies were interspersed with decoy melodies that either preserved the pitch contour of targets or did not; all appeared in the original rhythm and in new rhythms. Results indicated that a new rhythmic context lowered recognizability of target melodies, and that decoys were most confusing when they possessed the same “dynamic shape” (contour-plus-rhythm) as targets (Experiment 1). Also, target recognition improved with Phase I familiarity (Experiment 2), although rhythmic shifts remained detrimental across levels of target familiarity. Confusions based on “dynamic shape” accounted for a relatively high proportion of errors where familiarity with targets is low. Findings were interpreted in terms of a theory of context-sensitive dynamic attending in which remembering is assumed to involve recapitulation of the original rhythmical activities involved in attending to melodies.     

Applying an exemplar model to the artificial-grammar task: inferring grammaticality from similarity

We present three artificial-grammar experiments. The first used position constraints, and the second used sequential constraints. The third varied both the amount of training and the degree of sequential constraint. Increasing both the amount of training and the redundancy of the grammar benefited participants' ability to infer grammatical status; nevertheless, they were unable to describe the grammar. We applied a multitrace model of memory to the task. The model used a global measure of similarity to assess the grammatical status of the probe and captured performance both in our experiments and in three classic studies from the literature. The model shows that retrieval is sensitive to structure in memory, even when individual exemplars are encoded sparsely. The work ties an understanding of performance in the artificial-grammar task to the principles used to understand performance in episodic-memory tasks.