How do people order stimuli?

People may find it easier to construct an order after first representing stimuli on a scale or categorizing them, particularly when the number of stimuli to be ordered is large or when some of them must be remembered. Five experiments tested this hypothesis. In two of these experiments (1 and 3), we asked participants to rank line lengths or to rank photographs by artistic value. The participants provided evidence of how they performed these tasks, and this evidence indicated that they often made use of some preliminary representation—either a metric or a categorization. Two further experiments (2 and 4) indicated that people rarely produced rankings when given a choice of assessment measures for either the length of lines or the artistic value of photographs. In Experiment 5, when the number of lines was larger or lines were only visible one at a time, participants were faster at estimating line lengths as a percentage of the card covered than at rank ordering the lengths. Overall, the results indicate that ordering stimuli is not an easy or natural process when the number of stimuli is large or when the stimuli are not all perceptible at once. An implication is that the psychological measures available to individuals are not likely to be purely ordinal when many of the elements being measured must be recalled.     

Classification behavior and measures of intelligence: dimensional identity versus overall similarity

Individuals tend to adopt either analytic or holistic modes of categorizing objects. In two studies, we examined the relation between these categorization tendencies and cognitive abilities as measured by standard psychometric instruments. The participants in both studies were pretested with a restricted classification task in which it was possible for them to classify simple stimuli by dimensional identity or overall similarity. Those making a large number of either type of categorization were then tested with subtests of the WAIS-R and with the Raven's progressive matrices. Across both studies, the analytic individuals (many dimensional identity classifications) scored higher than the holistic individuals (many overall similarity classifications) on some but not all of the subtests. The results are consistent with the idea that holistic modes of categorization may be more "primitive" than analytic modes. The findings are discussed in terms of the association between categorization mode and either general or specific cognitive abilities.     

Faces, flowers and football boots: capacity limits in distractor processing

While visual attention can be attracted by task-irrelevant stimuli, questions remain regarding how many irrelevant items can be processed simultaneously and whether capacity limits are equivalent for all types of stimuli. To explore these issues, participants were required to classify verbal stimuli that were flanked by either one or two response-matching or response-mismatching faces (Expts. 1 and 2) or objects (Expt. 2). The results revealed that when stimulus categorization was sufficient to trigger flanker interference, distractor processing was insensitive to the number of irrelevant stimuli. When, however, stimulus identification was needed to drive flanker interference, distractor processing was attenuated when two task-irrelevant items were presented. The theoretical implications of these findings are considered.     

Strategy development and learning differences in supervised and unsupervised categorization

The processes that determine unsupervised categorization, the task of classifying stimuli without guidance or feedback, are poorly understood. Two experiments examined the emergence and plasticity of unsupervised strategies using perceptual stimuli that varied along two separable dimensions. In the first experiment, participants either classified stimuli into any two categories of their choice or learned identical classifications by supervised categorization. Irrespective of the complexity of classification, supervised and unsupervised learning rates differed little when both modes of learning were maximally comparable. The second experiment examined the plasticity of unsupervised classifications by introducing novel stimuli halfway through training. Whether or not people altered their strategies, they responded to novel stimuli in a gradual manner. The gradual and continuous evolution and adaptation of strategies suggests that unsupervised categorization involves true learning which shares many properties of supervised category learning. We also show that the choice of unsupervised strategy cannot be predicted from the properties of early learning trials, but is best understood as a function of the initial distribution of dimensional attention.     

Comparing categorization models

Four experiments are presented that competitively test rule- and exemplar-based models of human categorization behavior. Participants classified stimuli that varied on a unidimensional axis into 2 categories. The stimuli did not consistently belong to a category; instead, they were probabilistically assigned. By manipulating these assignment probabilities, it was possible to produce stimuli for which exemplar- and rule-based explanations made qualitatively different predictions. F. G. Ashby and J. T. Townsend's (1986) rule-based general recognition theory provided a better account of the data than R. M. Nosofsky's (1986) exemplar-based generalized context model in conditions in which the to-be-classified stimuli were relatively confusable. However, generalized context model provided a better account when the stimuli were relatively few and distinct. These findings are consistent with multiple process accounts of categorization and demonstrate that stimulus confusion is a determining factor as 10 which process mediates categorization.     

Prior experience with negative spectral correlations promotes information integration during auditory category learning

Complex sounds vary along a number of acoustic dimensions. These dimensions may exhibit correlations that are familiar to listeners due to their frequent occurrence in natural sounds—namely, speech. However, the precise mechanisms that enable the integration of these dimensions are not well understood. In this study, we examined the categorization of novel auditory stimuli that differed in the correlations of their acoustic dimensions, using decision bound theory. Decision bound theory assumes that stimuli are categorized on the basis of either a single dimension (rule based) or the combination of more than one dimension (information integration) and provides tools for assessing successful integration across multiple acoustic dimensions. In two experiments, we manipulated the stimulus distributions such that in Experiment 1, optimal categorization could be accomplished by either a rule-based or an information integration strategy, while in Experiment 2, optimal categorization was possible only by using an information integration strategy. In both experiments, the pattern of results demonstrated that unidimensional strategies were strongly preferred. Listeners focused on the acoustic dimension most closely related to pitch, suggesting that pitch-based categorization was given preference over timbre-based categorization. Importantly, in Experiment 2, listeners also relied on a two-dimensional information integration strategy, if there was immediate feedback. Furthermore, this strategy was used more often for distributions defined by a negative spectral correlation between stimulus dimensions, as compared with distributions with a positive correlation. These results suggest that prior experience with such correlations might shape short-term auditory category learning.     

Better late than never: how onsets and offsets influence prior entry and exit

The three experiments presented in the paper examine visual prior entry (determining which of two stimuli appeared first) and prior exit (determining which of two stimuli disappeared first) effects with a temporal order judgment (TOJ) task. In addition to using onset and offset targets, the preceding cues also consisted of either onset or offset stimuli. Typical, and equivalent, prior entry effects were found when either onset or offset cues preceded the onset targets. Unexpectedly large prior exit effects where found with the offset targets, with offset cues producing greater capture effects than onset cues. These findings are consistent with the notion that more attention is allocated to searching the visual field when targets are more difficult to find. In addition, the results indicate that attentional control settings may be more likely to occur with more difficult searches. In addition, these findings demonstrate that TOJ tasks provide extremely precise measures of the allocation of attention and are very sensitive to a range of task manipulations.     

Geometric and featural representations in semantic concepts

We explore the adequacy of two types of similarity representation in the context of semantic concepts. To this end, we evaluate different categorization models, assuming either a geometric or a featural representation, using categorization decisions involving familiar and unfamiliar foods and animals. The study aims to assess the optimal stimulus representation as a function of the familiarity of the stimuli. For the unfamiliar stimuli, the geometric categorization models provide the best account of the categorization data, whereas for the familiar stimuli, the featural categorization models provide the best account. This pattern of results suggests that people rely on perceptual information to assign an unfamiliar stimulus to a category but rely on more elaborate conceptual knowledge when assigning a familiar stimulus.     

Blinded by the accent! The minor role of looks in ethnic categorization

The categories that social targets belong to are often activated automatically. Most studies investigating social categorization have used visual stimuli or verbal labels, whereas ethnolinguistic identity theory posits that language is an essential dimension of ethnic identity. Language should therefore be used for social categorization. In 2 experiments, using the "Who Said What?" paradigm, the authors investigated social categorization by using accents (auditory stimuli) and looks (visual stimuli) to indicate ethnicity, either separately or in combination. Given either looks or accents only, the authors demonstrated that ethnic categorization can be based on accents, and the authors found a similar degree of ethnic categorization by accents and looks. When ethnic cues of looks and accents were combined by creating cross categories, there was a clear predominance of accents as meaningful cues for categorization, as shown in the respective parameters of a multinomial model. The present findings are discussed with regard to the generalizability of findings using one channel of presentation (e.g., visual) and the asymmetry found with different presentation channels for the category ethnicity.     

Comparing Exemplar- and Rule-Based Theories of Categorization

ABSTRACT— We address whether human categorization behavior is based on abstracted rules or stored exemplars. Although predictions of both theories often mimic each other in many designs, they can be differentiated. Experimental data reviewed does not support either theory exclusively. We find participants use rules when the stimuli are confusable and exemplars when they are distinct. By drawing on the distinction between simple stimuli (such as lines of various lengths) and complex ones (such as words and objects), we offer a dynamic view of category learning. Initially, categorization is based on rules. During learning, suitable features for discriminating stimuli may be gradually learned. Then, stimuli can be stored as exemplars and used to categorize novel stimuli without recourse to rules.     

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.     

Individual variability in the perception of cues to place contrasts in initial stops

Synthetic continua of two minimal pairs, BAIT-DATE and DATE-GATE, closely modeled on natural utterances by a female speaker, were presented to a group of 16 listeners for identification in full-cue and reduced-cue conditions. Grouped results showed that categorization curves for full- and reduced-cue conditions differed significantly in both contrasts. However, an averaging of results obscures marked variability in labeling behavior. Some listeners showed large changes in categorization between the full- and reduced-cue conditions, whereas others showed relatively small or no changes. In a follow-up study, perception of the BAIT-DATE contrast was compared with the perception of a highly stylized BA-DA continuum. A smaller degree of intersubject and between-condition variability was found for these less complex synthetic stimuli. The amount of variability found in the labeling of speech contrasts may be dependent on cue salience, which will be determined by the speech pattern complexity of the stimuli and by the vowel environment.     

Sex differences in categorization of tactile stimuli

This experiment investigated the effect of sex differences in categorization of tactile stimuli. 9 men and 9 women rated the perceived similarity between pairs of stimuli varying in texture and shape. The magnitudes of sex-related differences, using omega 2 and d, were relatively large and indicated that men had better categorical abilities in processing haptic information.     

愉快面孔识别优势及其认知神经机制

愉快面孔识别优势表现为被试对高兴面孔比对其他情绪面孔的识别正确率更高、反应时更短。大量研究以简笔画和面孔图片为材料, 在情绪分类任务和视觉搜索任务中均发现这一优势。该优势存在诊断性价值假说、情绪独特性假说和出现频率假说三种不同的理论解释。近年来, 研究者采用ERP技术发现这一优势形成于反应选择阶段, 但其起始阶段尚无一致结论。未来可借助fMRI技术进一步研究其认知神经机制。     

The role of background knowledge in speeded perceptual categorization

We examined the time-course of the influence of background knowledge on perceptual categorization by manipulating the meaningfulness of labels associated with categories and by manipulating the amount of time provided to subjects for making a categorization decision. Extending a paradigm originally reported by Wisniewski and Medin (1994) (Cog. Sci. 18 (1994) 221), subjects learned two categories of children's drawings that were given either meaningless labels (drawings by children from 'group 1' or 'group 2') or meaningful labels (drawings by 'creative' or 'non-creative' children); the meaningfulness of the label had a significant effect on how new drawings were classified. In addition, half of the subjects were provided unlimited time to respond, while the other half of the subjects were forced to respond quickly; speeded response conditions had a relatively large effect on categorization decisions by subjects given the meaningless labels but had relatively little effect on categorization decisions by subjects given the meaningful labels. These results suggest that some forms of background knowledge can show an influence at relatively early stages in the time-course of a categorization decision.     

Rapid categorization of foveal and extrafoveal natural images: associated ERPs and effects of lateralization

Humans are fast and accurate at performing an animal categorization task with natural photographs briefly flashed centrally. Here, this central categorization task is compared to a three position task in which photographs could appear randomly either centrally, or at 3.6 degrees eccentricity (right or left) of the fixation point. A mild behavioral impairment was found with peripheral stimuli with no evidence in support of hemispheric superiority; but enlarging the window of spatial attention to three possible stimuli locations had no behavioral cost on the processing of central images. Performance in the central categorization task has been associated with a large difference between the potentials evoked to target and non-target correct trials, starting about 150 ms after stimulus onset on frontal sites. Present results show that this activity originates within extrastriate visual cortices and probably reflects perceptual stimuli differences processed within areas involved in object recognition. Latencies, slopes, and peak amplitudes of this differential activity were invariant to stimulus position and attentional load. Stimulus location uncertainty and lateralization did not affect speed of visual processing.     

Acquired Equivalence Changes Stimulus Representations

Acquired equivalence is a paradigm in which generalization is increased between two superficially dissimilar stimuli (or antecedents) that have previously been associated with similar outcomes (or consequents). Several possible mechanisms have been proposed, including changes in stimulus representations, either in the form of added associations or a change of feature salience. A different way of conceptualizing acquired equivalence is in terms of strategic inference: Confronted with a choice on which it has no evidence, the organism may infer from its history of reinforcement what the best option is, and that inference is observed as acquired equivalence. To test this account, we combined an incremental learning task with an episodic memory test. Drawings of faces were made equivalent through acquired equivalence training, and then paired with words in a list learning paradigm. When participants were asked to recognize specific face-word pairings, they confused faces more often when they had been made equivalent. This suggests that prior acquired equivalence training does influence how memories are coded. We also tested whether this change in coding reflected acquisition of new associations, as suggested by the associative mediation account, or whether stimuli become more similar through a reweighting of stimulus features, as assumed by some categorization theories. Results supported the associative mediation view. We discuss similarities between this view and exemplar theories of categorization performance.     

刻板印象激活效应对社会分类的影响

采用改进的flanker范式,探讨了刻板印象激活效应对社会分类的影响,并考察了匹配刺激出现概率对刻板印象激活效应影响社会分类的调节作用。实验一发现,性别刻板印象激活后,按性别分类时,匹配刺激中和不匹配刺激中面孔分类反应时之间的差异是显著的,但按年龄分类时,二者间的差异不显著。实验二表明,匹配刺激出现概率为80%时和50%时,匹配刺激中和不匹配刺激中面孔分类反应时之间的差异是显著的;但当匹配刺激出现概率为20%时,二者间的差异不显著。结果表明,刻板印象激活效应对与该刻板印象对应的社会分类有显著的影响,对与该刻板印象无关社会分类不会产生影响。刻板印象激活效应对社会分类的影响受匹配刺激出现概率的调节。     

The effect of prolonged viewing on the recognition of global and local levels of hierarchically constructed patterns

Two experiments were carried out to examine delays in the recognition of test patterns after prolonged (25 s) viewing of an adaptation pattern which was composed of either the same or different local components and global structures. In the case of geometric patterns that contained a few relatively large elements, there were significant delays of about 70 ms in the global decision task when the test and adaptation stimuli (TS and AS) were of the same pattern, or when they had the same structure but different components. In contrast, in the case of geometric patterns that were composed of many relatively small elements, such a figural relation between the AS and the TS did not affect the recognition speed of the TSs either in the global or in the local decision task. These results suggest that prolonged viewing reduces the efficiency of global processing and that such a disruptive effect occurs depending upon the number and the relative size of the elements that make up the whole pattern.     

Accentuation and sensitization effects in the categorization of multifaceted stimuli

Categorization affects perceptions in ways that are assumed to underlie social stereotypes. Research on categorization, however, has focused either on very simple stimuli or on judgmental tasks that focus attention only on single dimensions. To more fully understand the role of categorization in social perception, it is important to examine its effects in the case of multifaceted stimuli and holistic judgments. In 3 studies, participants formed an impression of a focal category of multifaceted stimuli either by itself or in the context of another category. They then judged the typicality of exemplars to the focal category. Results showed that categorization in the presence of a context produced both accentuation and sensitization effects: Participants accentuated between-category differences on relevant dimensions, and they were less sensitive to exemplar differences on irrelevant dimensions.