Infants' formation and use of categories to segregate objects

Four- and-a-half-month-old infants' (N = 100) category formation and use was studied in a series of five experiments. For each experiment, the test events featured a display composed of a cylinder and a box. Previous research showed that this display is not clearly parsed as a single unit or as two separate units by infants of this age. Immediately prior to testing, infants were shown a set of category exemplars. Knowledge about this category could help infants disambiguate the test display, which contained a novel exemplar of this category. Clear interpretation of the test display as composed of two separate units (as indicated by infants' longer looking at the move-together than at the move-apart test event) was taken as evidence of category formation and use. In Experiments 1 and 5, infants' prior experience with a set of three different boxes that were similar to the test box facilitated their segregation of the test display. Experiment 2 showed that three different exemplars are necessary: prior experience with any two of the three boxes used in Experiment 1 did not facilitate infants' segregation of the test display. Experiment 3 showed that variability in the exemplar set is necessary: prior experience with three identical boxes did not facilitate infants' segregation of the test display. Experiment 4 showed that under these conditions of very brief prior exposure, similarity between the exemplar set and test box is necessary: prior experience with three different boxes that were not very similar to the test box did not facilitate infants' segregation of the test display. Together, these findings suggest that: (a) number of exemplars, variability, and similarity in the exemplar set are important for infants' category formation, and (b) infants use their category knowledge to determine the boundaries of the objects in a display.     

Typicality in logically defined categories: Exemplar-similarity versus rule instantiation

A rule-instantiation model and a similarity-to-exemplars model were contrasted in terms of their predictions of typicality judgments and speeded classifications for members of logically defined categories. In Experiment 1, subjects learned a unidimensional rule based on the size of objects. It was assumed that items that maximally instantiated the rule were those farthest from the category boundary that separated small and large stimuli. In Experiment 2, subjects learned a disjunctive rule of the form "x or y or both". It was assumed that items that maximally instantiated the rule were those with both positive values (x and y). In both experiments, the frequency with which different exemplars were presented during classification learning was manipulated across conditions. These frequency manipulations exerted a major impact on subjects' postacquisition goodness-of-example judgments, and they also influenced reaction times in a speeded classification task. The results could not be predicted solely on the basis of the degree to which the rules were instantiated. The goodness judgments were predicted fairly well by a mixed exemplar model involving both relative-similarity and absolute-similarity components. It was concluded that even for logically defined concepts, stored exemplars may form a major component of the category representation.     

Metacognitive monitoring during category learning: how success affects future behaviour

The purpose of this study was to see how people perceive their own learning during a category learning task, and whether their perceptions matched their performance. In two experiments, participants were asked to learn natural categories, of both high and low variability, and make category learning judgements (CLJs). Variability was manipulated by varying the number of exemplars and the number of times each exemplar was presented within each category. Experiment 1 showed that participants were generally overconfident in their knowledge of low variability families, suggesting that they considered repetition to be more useful for learning than it actually was. Also, a correct trial, for a particular category, was more likely to occur if the previous trial was correct. CLJs had the largest increase when a trial was correct following an incorrect trial and the largest decrease when an incorrect trial followed a correct trial. Experiment 2 replicated these results, but also demonstrated that global CLJ ratings showed the same bias towards repetition. These results indicate that we generally identify success as being the biggest determinant of learning, but do not always recognise cues, such as variability, that enhance learning.     

Distributional expectations and the induction of category structure

Previous research on how categories are learned from observation of exemplars has largely ignored the possible role of prior expectations concerning how exemplars will be distributed. The experiments reported here explored this issue by presenting subjects with category-learning tasks in which the distributions of exemplars defining the categories were varied. In Experiments 1 and 2 the distributional form of a category was found to affect speed of learning. Learning was faster when a category's distribution was normal than when it was multimodal. Also, subjects in the early stages of learning a multimodal category responded as if it were unimodal. These results suggested that subjects enter category-learning tasks with expectations of unimodal, possibly normal, distributions of exemplars. Experiments 3 and 4 attempted to manipulate subjects' prior expectations by varying the distribution of exemplars in the first of two consecutive category-learning tasks. Learning a multimodal category was influenced by the shape of a previously learned distribution and was facilitated when the earlier distribution was either multimodal or skewed, rather than normal. These results are interpreted as support for a dual-process model of category learning that incorporates the effects of prior expectations concerning exemplar distributions.     

The impact of stereotype-incongruent information on perceived group variability and stereotype change

Three experiments showed increases in the perceived variability of social groups after perceivers received stereotype-incongruent information about group members. In Experiment 1, participants generated flatter distributions after exposure to incongruent information, compared with equally deviant congruent information, in the form of typical verbal materials. Experiment 2 indicated similar changes in dispersion after the presentation of numeric information about a single group member. In Experiment 3, the authors manipulated cognitive load at encoding or at the time group judgments were requested. Under conditions of cognitive constraint, stereotype-incongruent information ceased to promote more dispersed group representations. These results are consistent with the idea that incongruent information triggers more deliberative and comprehensive retrieval and generation of exemplars. The authors discuss the implications of these findings for stereotype change.     

知道与不知道要学多少：类别学习中样例量的预期作用

采用“5/4模型”类别结构探讨了类别学习中样例量的预期作用。设置了两种学习条件(“知道样例量”和“不知道样例量”), 分别探讨两种学习条件下的学习效率、学习策略以及所形成的类别表征。106名大学生参加了实验, 结果表明：在类别学习中, 样例量的预期作用显著, 知道样例量组的学习效率高于不知道样例量组; 样例量的预期作用对类别学习效率的影响是通过影响学习过程中使用的策略来实现的; 样例量的预期作用不影响两种学习条件的学习后形成的类别表征, 且两种学习条件的被试自始至终表现出样例学习的表征模式。     

Adult age differences in the perception and learning of artistic style categories

Adult age differences in conceptual behavior were studied using informationally complex stimuli from real-world categories: paintings by two impressionist artists. In Experiment 1 we examined perceptions of category structure by having subjects sort paintings according to style similarity. Young adults were observed to depend more on abstract information in making style judgments, whereas older adults relied more on similarity in content. This resulted in different category structures between age groups, but similarity judgments in both groups appeared to correspond to actual style differences between the two artists. In Experiment 2, learning efficiency was shown to increase with a painting's category centrality, but older adults had particular trouble learning noncentral items. At transfer, both age groups were able to use abstracted central tendency information to categorize new paintings, although young adults appeared to have better access to information about specific category exemplars from acquisition. The results are generally consistent with those from studies using simpler artificial stimuli.     

A rose in any other font would not smell as sweet: effects of perceptual fluency on categorization

Fluency--the ease with which people process information--is a central piece of information we take into account when we make judgments about the world. Prior research has shown that fluency affects judgments in a wide variety of domains, including frequency, familiarity, and confidence. In this paper, we present evidence that fluency also plays a role in categorization judgments. In Experiment 1, participants judged a variety of different exemplars to be worse category members if they were less fluent (because they were presented in a smaller typeface). In Experiment 2, we found that fluency also affected judgments of feature typicality. In Experiment 3, we demonstrated that the effects of fluency can be reversed when a salient attribution for reduced fluency is available (i.e., the stimuli are hard to read because they were printed by a printer with low toner). In Experiment 4 we replicated these effects using a within-subject design, which ruled out the possibility that the effects were a statistical artifact caused by aggregation of data. We propose a possible mechanism for these effects: if an exemplar and its category are closely related, activation of one will cause priming of the other, leading to increased fluency. Over time, feelings of fluency come to be used as a valid cue that can become confused with more traditional sources of information about category membership.     

Ratio scale measurement of the perceived lengths of lines.

In Experiments 1 and 2, magnitude and category estimates of perceived line length difference were used to rank order 36 pairs of lines with respect to the psychological length difference between the lines forming a pair. In Experiment 3 magnitude estimates of line length ratios were used to order the same 36 pairs with respect to the psychological length ratio between the lines comprising a pair. A nonmetric analysis of the rank-order of the difference and ratio judgments was used to construct a ratio scale of perceived line length. Perceived line length was found to be a power function of physical line length with an exponent of .46. In Experiments 4 and 5, magnitude and category estimates of line length similarity were obtained. A nonmetric analysis of these data indicated that similarity judgments were monotonic inverses of judgments of psychological ratios.     

Cross-category structure in semantic memory

In Experiment I, subjects made similarity judgments about all 56 category terms listed in the Battig and Montague (1969) norms. These judgments were then subjected to a hierarchical clustering analysis. Experiment II demonstrated that the relations among the category labels are very similar to the relations among the high dominance exemplars of these categories. Experiment III showed that the distances between the category terms in the hierarchical clustering analysis could predict RTs in a same-different paradigm.     

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     

Inadequacy of recall as a basis for frequency knowledge.

Subjects studied a word list comprising varying numbers of words from distinct semantic categories. The category names (trees, colors, etc.) were then re-presented, and for each name subjects either recalled as many exemplars as they could or estimated how many had been included in the list (Experiments 1 and 2). Recall was not sufficiently informative about actual category sizes to account for performance in the frequency estimation task. Moreover, it remained insufficiently informative when efforts were made to induce a recall-estimate strategy by requiring overt recall prior to estimation (Experiments 3-5), by using very small categories (Experiment 4), and by not showing the category name at study (Experiment 5), even though it did allow a partial account of estimation when the category exemplars were individually cued (Experiment 6). It is concluded that the role of recall in frequency estimation is much exaggerated.     

Subtyping as a knowledge preservation strategy in category learning

Subtyping occurs when atypical examples are excluded from consideration in judging a category. In three experiments, we investigated whether subtyping can influence category learning. In each experiment, participants learned about a category where most, but not all, of the exemplars corresponded to a theme. The category structure included a subtyping dimension, which had one value for theme-congruent exemplars and another for exception exemplars. On the basis of work by Hayes, Foster, and Gadd (2003) and studies on social stereotyping, we hypothesized that this subtyping dimension would enable the participants to discount the exception exemplars, thereby facilitating category learning. Contrary to expectations, we did not find a subtyping effect with traditional category-learning procedures. By introducing the theme prior to learning, however, we observed increased effects on typicality ratings (Experiment 1) and facilitated learning of the category (Experiment 2). Experiment 3 provided direct evidence that introducing the theme prior to learning enhanced the subtyping effect and provided support for a knowledge-gating explanation of subtyping. We conclude that subtyping effects are strongest on already-learned concepts and that subtyping is unlikely to aid in the learning of new concepts, except in particular circumstances.     

Accuracy in the judgment of in-group and out-group variability

The accuracy of in-group and out-group variability judgments was examined by comparing those judgments with the variability of self-ratings provided by random samples of group members. Following Park and Judd (1990), perceptions of both group dispersion and group stereotypicality were examined. Accuracy was examined both by within-subject sensitivity correlations and by simple discrepancies between perceived and actual variability estimates. In-group-out-group differences in sensitivity were shown, particularly for judgments of stereotypicality. These differences were related to differences in the degree to which out-group variability is underestimated relative to in-group variability (i.e., the out-group homogeneity effect). Out-group stereotypicality judgments were overestimated, supporting the view that out-group stereotypes are overgeneralizations. Whether dispersion judgments were over- or underestimated depended on their measurement.     

样例多样性和流畅性信念对类别学习判断的影响

目的:通过三个实验考查样例特征、流畅性和信念对类别学习及其元认知判断的影响。方法:实验1采用2(样例特征)×2(测试类型)的组内设计以检验样例特征的作用; 实验2采用2(样例特征)×2(测试类型)×2(流畅性)的组内设计以检验流畅性的作用; 实验3采用2(样例特征)×2(测试类型)×2(流畅性信念)的混合设计以检验信念对类别学习判断的作用。结果表明:样例特征影响学习成绩、类别学习判断和流畅感; 流畅性不会影响类别学习判断; 原理解释能够有效建立“关于流畅性的信念”,且“关于流畅性的信念”对类别学习判断起作用。即样例多样性和流畅性信念对类别学习判断起作用,支持信念假说。     

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.     

Study preferences for exemplar variability in self-regulated category learning

Increasing exemplar variability during category learning can enhance classification of novel exemplars from studied categories. Four experiments examined whether participants preferred variability when making study choices with the goal of later classifying novel exemplars. In Experiments 1–3, participants were familiarised with exemplars of birds from multiple categories prior to making category-level assessments of learning and subsequent choices about whether to receive more variability or repetitions of exemplars during study. After study, participants classified novel exemplars from studied categories. The majority of participants showed a consistent preference for variability in their study, but choices were not related to category-level assessments of learning. Experiment 4 provided evidence that study preferences were based primarily on theoretical beliefs in that most participants indicated a preference for variability on questionnaires that did not include prior experience with exemplars. Potential directions for theoretical development and applications to education are discussed.     

The role of graded category structure in imaginative thought

Participants generated lists of exemplars from the categories of animals, tools, and fruit, and their lists were used to determine the relative accessibility of individual exemplars. Measures of accessibility included output dominance (the number of participants who listed an exemplar), rank (how early instances were listed), and two scores that reflect their combination-output precedence and dominance/rank. Other participants drew and described novel exemplars of those categories that might exist on an imaginary planet and reported on the factors that influenced their creations. References to Earth animals, tools, or fruit were used to determine imagination frequency (the number of participants who mentioned relying on particular Earth exemplars). Items high in accessibility were also high in imagination frequency, implying that those items that come to mind most readily are the ones most likely to serve as starting points for the development of novel ideas. This result held even when task constraints weighed against the use of such items (Experiment 2) and when participants were encouraged to be as creative as possible (Experiment 4), suggesting that it is difficult to avoid the influence of highly accessible category exemplars. Other measures of category structure, including the rated typicality, familiarity, and frequency of exemplars, did not predict imagination frequency as well. The results are discussed in terms of expanding concept boundaries and the inadvertent application of knowledge that is readily accessible.     

Perceived distributions of the characteristics of in-group and out-group members: empirical evidence and a computer simulation

This research studied 2 properties of perceived distributions of the characteristics of social category members: the probability of differentiating (making distinctions) among category members and the perceived variability (variance) of category members. The results of 4 experiments supported the hypothesis that greater familiarity with a social group leads to greater perceived differentiation and variability regarding that group. In-group members formed more differentiated and variable distributions for groups defined by age and more differentiated distributions for groups defined by nationality. For gender (where students were roughly equally familiar with people of both genders), no in-group--out-group differences occurred. Also, students perceived greater differentiation and variability among classmates over the course of a semester. To explain these results, we developed PDIST, a multiple exemplar model that assumes that people form perceived distributions by activating a set of category exemplars and then judging the relative likelihoods of different feature values on the basis of the relative activation strengths of these feature values. The results of a computer simulation experiment indicated that PDIST is sufficient to explain the results of our 4 experiments. According to the perceived distributions formed by PDIST, increasing familiarity leads to greater differentiation and variability, has a concave impact, and has greater impact on differentiation than on variability.