The contribution of category relationships to similarity ratings.

Two experiments produced evidence that category relationships contribute to similarity ratings. In Experiment 1, participants gave similarity ratings with respect to a semantic category (VEGETABLE) and a set of exemplars, some of which were members of the category (e.g., BROCCOLI) and some of which were not (e.g., BANANA). A regression analysis was used to predict the similarity ratings in terms of numbers of common and distinctive features, as reported by other participants. Perceived similarity was greater for examplars that were members of the category, independently of feature overlap. Experiment 2 examined similarity ratings with respect to pairs of exemplars. In some cases, both exemplars were members of the same category (e.g., BROCCOLI/CUCUMBER). In other cases, one exemplar was a member of the category and the other was not (e.g., BROCCOLI/BANANA). A regression analysis was used to predict the similarity ratings in terms of numbers of common and distinctive features. Perceived similarity was greater when both exemplars were members of the same category, independently of feature overlap.     

The role of exemplar distribution in infants'' differentiation of categories

Three experiments investigated how the frequency of exposure to particular exemplars influenced 10-month-old infants' differentiation of land and sea animals in an object-examining task. In Experiments 1 and 2, one category exemplar was presented more frequently than the others during familiarization (i.e., that exemplar was presented on 6 of 12 familiarization trials, and 3 other exemplars were each presented on 2 familiarization trials). For half of the infants, the frequent exemplar was similar to other category exemplars (e.g., a zebra if the familiarization category was land animals), and for half the frequent exemplar was not similar to many other category exemplars (e.g., a rabbit). Infants who frequently experienced the similar exemplar formed an exclusive category, and differentiated land and sea animals. Infants who frequently experienced a dissimilar exemplar, in contrast, formed an inclusive category, and failed to differentiate between land and sea animals. In Experiment 3, infants received frequent experience with a set of similar or dissimilar exemplars, and the same pattern was observed. Thus, 10-month-old infants are sensitive to the distribution of the exemplars to which they are exposed, and they form different category boundaries depending on that distribution.     

Remembering can cause inhibition: retrieval-induced inhibition as cue independent process

Previous experiments have mostly relied on recall as a dependent measure to assess whether retrieval of information from memory causes inhibition of related information. This study aimed to measure this inhibition in a more direct way. In Experiment 1, it was shown that repeated retrieval of exemplars from a category resulted in longer recognition latencies to nonretrieved exemplars from that same category, compared with recognition latencies to control exemplars. Experiment 2 obtained the same pattern of results using a lexical decision task. This was the 1st time that retrieval-induced forgetting was demonstrated on an implicit test of memory. To exclude noninhibitory explanations of the data, the exemplars were presented in both experiments without their categories as cues.     

Operativity and the superordinate categorization of artifacts.

Relations between typical and atypical exemplars of superordinate categories are low in figurative similarity, i.e., similarity based in appearance or in spatial/temporal context. Operativity, as an emergent competence to overcome figurative cues and establish nonfigurative relations, might be expected to contribute to superordinate categorization. The present study assessed the relative consistency of age-equivalent preoperational and concrete-operational groups of first graders across two categorization tasks employing color drawings of exemplars of superordinate artifact categories. Concrete-operational subjects categorized two exemplars together on a Sample-Match Task if they had previously included both exemplars under the same category on a Category-Membership Task. In addition to membership in the same category, preoperational subjects required that both exemplars be typical before categorizing them together on the Sample-Match Task. The cognitive levels did not differ in their category membership decisions. Results are discussed in terms of both utilization and acquisition of superordinate knowledge.     

Object manipulation facilitates kind-based object individuation of shape-similar objects

Five experiments investigated the importance of shape and object manipulation when 12-month-olds were given the task of individuating objects representing exemplars of kinds in an event-mapping design. In Experiments 1 and 2, results of the study from Xu, Carey, and Quint (2004, Experiment 4) were partially replicated, showing that infants were able to individuate two natural-looking exemplars from different categories, but not two exemplars from the same category. In Experiment 3, infants failed to individuate two shape-similar exemplars (from Pauen, 2002a) from different categories. However, Experiment 4 revealed that allowing infants to manipulate objects shortly before the individuation task enabled them to individuate shape-similar objects from different categories. In Experiment 5, allowing object manipulation did not induce infants to individuate natural-looking objects from the same category. These findings suggest that object manipulation facilitates kind-based individuation of shape-similar objects by 12-month-olds.     

Retention performance as a function of the distinctiveness of memory traces and retention task

Summary In the acquisition phase of an incidental learning paradigm, words that are exemplars of categories were judged as to whether or not they belonged to a specified category. This was followed by a forced choice recognition task. The effects of three variables were studied: a) whether the acquisition task called for a positive or a negative response; b) the number of exemplar words per category; and c) whether distractor items in the recognition test came from the same category as the target words or from other categories. The results showed that recognition errors were influenced by all three variables. Unlike the variables a) and c) which showed significant main effects, the effect of number of exemplars per category was significant only for the same category distractor condition. In this condition more exemplars per category led to more recognition errors. The results are explained by assuming that retention performance is determined by two factors. The first factor is the distinctiveness of the memory traces. This is supposed to be a joint product of task-specific encoding and stimulus characteristics. The second factor is the distinctive similarity between the retrieval information and the stored memory traces. Although the results show some sublte effects that are not easy to explain, it is argued that this model offers a good account of the general findings.     

Learning words in space and time: probing the mechanisms behind the suspicious-coincidence effect

A major debate in the study of word learning centers on the extension of categories to new items. The rational approach assumes that learners make structured inferences about category membership, whereas the mechanistic approach emphasizes the attentional and memory processes that form the basis of generalization behaviors. Recent support for the rational view comes from observations of the suspicious-coincidence effect: People generalize category membership narrowly when presented with three subordinate-level exemplars that share the same label and generalize category membership broadly when presented with one exemplar. Across three experiments, we examined the mechanistic basis of this effect. Results showed that the presentation of multiple subordinate-level exemplars led to narrow generalization only when the exemplars were presented simultaneously, even when the number of exemplars was increased from three to six. These data demonstrate that the suspicious-coincidence effect is firmly grounded in the general cognitive processes of attention, memory, and visual comparison.     

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.     

That's More Like It: Multiple Exemplars Facilitate Word Learning

Previous research indicates learning words facilitates categorisation. The current study explores how categorisation affects word learning. In the current study, we investigated whether learning about a category facilitates retention of newly learned words by presenting 2‐year‐old children with multiple referent selection trials to the same object category. In Experiment 1, children either encountered the same exemplar repeatedly or encountered multiple exemplars across trials. All children did very well on the initial task; however, only children who encountered multiple exemplars retained these mappings after a short delay. Experiment 2 replicated and extended this finding by exploring the effect of within‐category variability on children's word retention. Children encountered either narrow or broad exemplars across trials. Again, all children did very well on the initial task; however, only children who encountered narrow exemplars retained mappings after a short delay. Overall, these data offer strong evidence that providing children with the opportunity to compare across exemplars during fast mapping facilitates retention. Copyright © 2013 John Wiley & Sons, Ltd.     

Two routes for activation in the priming of categorical coordinates

The authors operationalized category priming as participants' recognition facilitation of nonstudied, low semantically similar exemplars by studied exemplars in a category. The existing literature either does not examine the effect of studied exemplars on nonstudied exemplars in a category or fails to show an appreciable amount of category priming. In 2 experiments, the authors demonstrated a unique process to account for the category priming effect and distinguish it from the semantic priming effect, facilitation of semantically similar exemplars, in the context of a category. In Experiment 1A, the authors used a multidimensional scaling technique to examine participants' internal structure of different categories. In Experiment 1B, the authors used a lexical decision task that used these internal structures to show that semantic encoding of category exemplars causes activation of existing category knowledge in memory. Consequently, participants easily recognized nonstudied, low semantically similar exemplars in a category. However, recognition facilitation between high semantically similar exemplars did not require category knowledge activation.     

On the relationship between categorical frequency estimation and cued recall

In a categorical frequency-estimation task, subjects have to indicate the number of exemplars from particular categories that have been shown on a list. In three experiments, the relationship between this task and the recall of exemplars with category names as cues was investigated. Three variables (generation, blocking of category exemplars, and provision of extralist cues) were shown to have identical effects on the two tasks. These results support a model of categorical frequency estimation in which subjects use a category name to retrieve exemplars and then base their frequency estimate on a count of the exemplars that have been retrieved.     

The differing roles of comparison and contrast in children’s categorization

Comparison of perceptually similar exemplars from an object category encourages children to overlook compelling perceptual similarities and use relational and functional properties more relevant for taxonomic categorization. This article investigates whether showing children a contrasting object that is perceptually similar but out of kind serves the same function as comparison in heightening children’s attention to taxonomically relevant features. In this study, 4-year-olds completed a forced-choice categorization task in which they viewed exemplars from a target category and then selected among (a) a perceptually similar out-of-kind object, (b) a category member that differed perceptually from the exemplars, and (c) a thematically related object. Children were assigned to one of four conditions: No-Compare/No-Contrast, Compare/No-Contrast, No-Compare/Contrast, or Compare/Contrast. As in previous work, comparison increased the frequency of category responses, but there was no effect of contrast on categorization. However, only those in the Compare/Contrast condition displayed consistently taxonomic patterns of responding. Follow-up studies revealed that the effect of comparison plus contrast was evident only when comparison preceded, rather than followed, contrast information and that the value added by providing contrastive information is not attributable to the perceptual similarity between the category exemplars and the contrast object. Comparison and contrast make differing contributions to children’s categorization.     

Asymmetries in categorization, cerceptual discrimination, and visual search for reference and nonreference exemplars

In two experiments, we examined the representation, treatment, and attention devoted to the members of reference (i.e., club members) and nonreference (i.e., not club members) categories. Consistent with prior work on category interrelatedness (e.g., Goldstone, 1996; Goldstone, Steyvers, and Rogosky, 2003), the findings reveal the existence of asymmetric representations for reference and nonreference categories, which, however, decreased as expertise and familiarity with the categories increased (Experiments 1 and 2). Participants also more readily judged two reference exemplars as being the same than they did two nonreference exemplars (Experiment 1) and were better at detecting reference than nonreference exemplars in a set of novel, category-unspecified exemplars (Experiment 2). These findings provide evidence for the existence of a feature asymmetry in the representation and treatment of exemplars from reference and nonreference categories. Membership in a reference category acts as a salient feature, thereby increasing the perceived similarity and detection of faces that belong in the reference, in comparison with the nonreference, category.     

Measuring the perceptual magnet effect in the perception of /i/ by German listeners

In a study of the internal category structure of the vowel /i/, Kuhl found a “perceptual magnet effect”: Discrimination sensitivity was poorer for category instances that were acoustically similar to the category prototype than it was for category instances that were not. The typicality of category exemplars was determined by goodness judgments and was found to correlate with the acoustics of average production. Analysis and interpretation of discrimination performance relied on two important assumptions: that listeners perceived all stimuli presented as exemplars of the same vowel category and that, apart from the influence of phonetic coding, discrimination sensitivity was the same across the investigated part of the vowel space. In the present study, it is shown that production and perception estimates of the category prototype may diverge, possibly because listeners seem to prefer hyperarticulated variants of vowel categories. An approach towards measurement of intra-category discrimination minima is put forward and tested that protects against intercategory confounds and avoids the isosensitivity assumption. Received: 26 November 1997 / Accepted: 25 May 1998     

An investigation of time course of category and semantic priming

Low semantically similar exemplars in a category demonstrate the category-priming effect through priming of the category (i.e., exemplar-category-exemplar), whereas high semantically similar exemplars in the same category demonstrate the semantic-priming effect (i.e., direct activation of one high semantically similar exemplar by another). The author asked whether the category- and semantic-priming effects are based on a common memory process. She examined this question by testing the time courses of category- and semantic-priming effects. She tested participants on either category- or semantic-priming paradigm at 2 different time intervals (6 min and 42 min) by using a lexical decision task using exemplars from categories. Results showed that the time course of category priming was different from that of semantic priming. The author concludes that these 2 priming effects are based on 2 separate memory processes.     

Form categorization in 10-month-olds

In five experiments, 10-month-olds were habituated to exemplars of a form category and tested for categorization in paired-comparison trials involving in-category versus out-of-category stimuli. Across these experiments, color was systematically manipulated during habituation and/or test trials. Infants categorized form when color was either held constant or varied during habituation, but failed to categorize form when exposed to color-constant stimuli during habituation and tested for categorization with novel-color form exemplars. Two subsequent experiments traced this failure to the narrow experience of exposure to color-constant exemplars during habituation. These results suggest that (a) infants' internal representation for a category will not include a stimulus dimension not varied in the exemplars from which the category was derived, but (b) if variation in that dimension is experienced, exemplars constructed of novel instances of that dimension will still be regarded as belonging to the category.     

Contextual memory and skill transfer in category search

In three experiments, we examined transfer and contextual memory in a category search task. Each experiment included two phases (training and test), during which participants searched through category and exemplar menus for targets. In Experiment 1, the targets were from one of two domains during training (grocery store or department store); the domain was either the same or changed at test. Also, the categories were organized in one of two ways (alphabetically or semantically); the organization either remained the same or changed at test. In Experiments 2 and 3, domain and organization were held constant; however, categories or exemplars were the same, partially replaced, or entirely replaced across phases in order to simulate the dynamic nature of category search in everyday situations. Transfer occurred at test when the category organization or domain was maintained and when the categories or exemplars matched (partially or entirely) those at training. These results demonstrate that transfer is facilitated by overlap in training and testing contexts.     

A little labeling goes a long way: Semi‐supervised learning in infancy

There is considerable evidence that labeling supports infants' object categorization. Yet in daily life, most of the category exemplars that infants encounter will remain unlabeled. Inspired by recent evidence from machine learning, we propose that infants successfully exploit this sparsely labeled input through “semi‐supervised learning.” Providing only a few labeled exemplars leads infants to initiate the process of categorization, after which they can integrate all subsequent exemplars, labeled or unlabeled, into their evolving category representations. Using a classic novelty preference task, we introduced 2‐year‐old infants (n = 96) to a novel object category, varying whether and when its exemplars were labeled. Infants were equally successful whether all exemplars were labeled (fully supervised condition) or only the first two exemplars were labeled (semi‐supervised condition), but they failed when no exemplars were labeled (unsupervised condition). Furthermore, the timing of the labeling mattered: when the labeled exemplars were provided at the end, rather than the beginning, of familiarization (reversed semi‐supervised condition), infants failed to learn the category. This provides the first evidence of semi‐supervised learning in infancy, revealing that infants excel at learning from exactly the kind of input that they typically receive in acquiring real‐world categories and their names.     

The influence of category representations on exemplar generation

The present study examined the influence of category representations on exemplar generation, which has been neglected in previous category research. An experiment on college students manipulated the category representation of insects in three conditions (prototypes, exemplars, and the hybrid of prototypes and exemplars). Participants were asked to generate as many exemplars as possible. The results demonstrate that category representations affect and constrain exemplar generation. The new findings are as follows. In the prototype and hybrid conditions with the prototype representation, people tend to generate more valid exemplars by using the prototype mutation mechanism, and exemplar generation conforms to the family resemblance structure. Exemplar generation in the hybrid condition is additionally constrained by known exemplars. In the exemplar condition, people tend to generate fewer valid exemplars by using miscellaneous strategies, and their exemplar generation may not conform to the family resemblance structure.