The effect of category variability in perceptual categorization

Exemplar and distributional accounts of categorization make differing predictions for the classification of a critical exemplar precisely halfway between the nearest exemplars of 2 categories differing in variability. Under standard conditions of sequential presentation, the critical exemplar was classified into the most similar, least variable category, consistent with an exemplar account. However, if the difference in variability is made more salient, then the same exemplar is classified into the more variable, most likely category, consistent with a distributional account. This suggests that participants may be strategic in their use of either strategy. However, when the relative variability of 2 categories was manipulated, participants showed changes in the classification of intermediate exemplars that neither approach could account for.     

It is who you know that counts: Intergroup contact and judgments about race‐based exclusion

Intergroup contact and evaluations about race‐based exclusion were assessed for majority and minority students in grades 4, 7 and 10 (N = 685). Scenarios depicting cross‐race relations in contexts of dyadic friendship, parental discomfort and peer group disapproval were described to participants. Participants reporting higher levels of intergroup contact gave higher ratings of wrongfulness of exclusion and lower frequency estimations of race‐based exclusion than did participants reporting lower levels of such contact. Intergroup contact also predicted students' attributions of motives in two out of the three scenarios. Findings are discussed in terms of the extant literature on peer relations, moral reasoning and intergroup contact.     

Evidence of rapid correlation‐based perceptual category learning by 4‐month‐olds

Young infants are very sensitive to feature distribution information in the environment. However, existing work suggests that they do not make use of correlation information to form certain perceptual categories until at least 7 months of age. We suggest that the failure to use correlation information is a by‐product of familiarization procedures that encourage infants to over encode individual exemplars rather than relations across exemplars. By changing the exemplar presentation regime to one in which exemplars are rapidly (2 s durations) and repeatedly presented we find that 4‐month‐olds can form perceptual categories on the basis of feature correlation information. In addition, this ability emerges rapidly between 114 and 134 days. We argue that the ability to process correlation information is present very early on but that the demonstration of that ability in categorization tasks is mediated by the demands of the task the infant is tested with. Copyright © 2005 John Wiley & Sons, Ltd.     

Unsupervised categorization with a child sample: category cohesion development

Studies into categorization have demonstrated that the ability to form concepts is an essential ability in cognitive development. For example, before a decision about anything can be made, firstly category concepts need to be acquired in order to make efficient decisions about that situation. The present study explored a particular type of category learning, not previously explored in this particular context – unsupervised categorization with 16 items and two dimensions, and comparing specifically children vs. adults. Previous studies have typically focused on simpler designs such as three items of two dimensions in the triad tasks, or a greater number of dimensions but with much fewer items per category in other unsupervised settings. This study investigated unsupervised categorization with two levels of task difficulty, and compared two different populations, children and adults. The findings revealed that adults performed better for the easy condition but there was no difference between these groups for the more difficult category task. The findings also revealed that unsupervised categorization in more complex settings result in more one dimensional sorting, for both children and adults. The results are discussed in the context of unsupervised categorization development abilities in children.     

Domain differences in absolute judgments of category membership: evidence for an essentialist account of categorization

There has been some debate about the correspondence between typicality gradients and category membership. The present study investigates the relationship between these two measures in the domains of animals and artifacts. Forty-two adults judged the degree of typicality or category membership of 293 animals and artifacts. The subjects’ tendency for animals, but not for artifacts, was to make more absolute ratings on category membership (i.e., judging exemplars as definitely members or definitely not members of their respective category) than on typicality. More importantly, at almost every level of typicality, subjects were more likely to make absolute judgments of category membership for animals than for artifacts. These results indicate that people treat category membership of animals as relatively absolute (which best fits an essentialist model of categorization) and treat category membership of artifacts as relatively graded (which best fits a prototype model of categorization). These domain differences add crucial supporting evidence for claims about the domain-specificity of essentialism.     

The effects of perceptual similarity and category membership on early word-referent identification

We investigated the impact of perceptual and categorical relatedness between a target and a distracter object on early referent identification in infants and adults. In an intermodal preferential looking (IPL) task, participants looked at a target object paired with a distracter object that could be perceptually similar or dissimilar and drawn from the same or different global category. The proportion of target looking measures revealed that infants and adults were sensitive to the interplay between category membership and perceptual similarity. Online latency measures demonstrated an advantage for perceptually dissimilar items regardless of their categorical status, indicating that different IPL measures index different processes during target identification. Results suggest that perceptual similarity and category membership of the objects lead to competition effects in word recognition and referent identification in both adults and infants and that lexical categorization and nonlinguistic categorization processes are closely related during infancy.     

The ontogeny of intent‐based normative judgments

When evaluating norm transgressions, children begin to show some sensitivity to the agent's intentionality around preschool age. However, the specific developmental trajectories of different forms of such intent‐based judgments and their cognitive underpinnings are still largely unclear. The current studies, therefore, systematically investigated the development of intent‐based normative judgments as a function of two crucial factors: (a) the type of the agent's mental state underlying a normative transgression, and (b) the type of norm transgressed (moral versus conventional). In Study 1, 5‐ and 7‐year‐old children as well as adults were presented with vignettes in which an agent transgressed either a moral or a conventional norm. Crucially, she did so either intentionally, accidentally (not intentionally at all) or unknowingly (intentionally, yet based on a false belief regarding the outcome). The results revealed two asymmetries in children's intent‐based judgments. First, all age groups showed greater sensitivity to mental state information for moral compared to conventional transgressions. Second, children's (but not adults') normative judgments were more sensitive to the agent's intention than to her belief. Two subsequent studies investigated this asymmetry in children more closely and found evidence that it is based on performance factors: children are able in principle to take into account an agent's false belief in much the same way as her intentions, yet do not make belief‐based judgments in many existing tasks (like that of Study 1) due to their inferential complexity. Taken together, these findings contribute to a more systematic understanding of the development of intent‐based normative judgment.     

Early development of perceptual expertise: Within-basic-level categorization experience facilitates the formation of subordinate-level category representations in 6- to 7-month-old infants

A behavioral manifestation of perceptual expertise is the shift in recognition downward toward the subordinate level. Here, a familiarization-novelty preference procedure was used to determine whether 6- to 7-month-old infants could be induced to form category representations for cats and dogs at the subordinate level. In Experiment 1, the infants succeeded in forming subordinate-level category representations for beagle dogs and Siamese cats, but only when provided with previous experience on a subordinate-level category-formation task from within the same basic-level category (i.e., Saint Bernard dogs or tabby cats). When the prior category-formation task involved a different basic-level category, subsequent subordinate-level category learning was not in evidence. The preferences in Experiment 1 were shown in Experiments 2 and 3 not to be attributable to a priori preference or within-category discrimination failure. The findings suggest that within-basic-level categorization experience can facilitate the formation of subordinate-level category representations in the first half-year of life.     

The prioritization of perceptual processing in categorization

In three experiments, the effects of selective attention on perceptual processes in a complex multidimensional object categorization task were investigated. In each experiment, participants completed a perceptual-matching task to gain estimates of the perceptual salience of each stimulus dimension, then a categorization task using the same stimuli. In Experiments 1 and 2, the perceptual processing of stimulus dimensions was faster when dimensions were more diagnostic of category membership, regardless of their perceptual salience. Experiment 3 demonstrated that this prioritization of perceptual processing was evident even when stimuli were presented in unpredictable locations during categorization, indicating that the physical characteristics of the stimulus guide selective attention to diagnostic stimulus dimensions.     

The perceptual basis of loudness ratio judgments

In Experiment 1, subjects were required to estimateloudness ratios for 45 pairs of tones. Ten 1,200-Hz tones, differing only in intensity, were used to generate the 45 distinct tone pairs. In Experiment 2, subjects were required to directly compare two pairs of tones (chosen from among the set of 45) and indicate which pair of tones had the greaterloudness ratio. In both Experiments 1 and 2, the subjects’ judgments were used to rank order the tone pairs with respect to their judged loudness ratios. Nonmetric analyses of these rank orders indicated that both magnitude estimates of loudness ratios and direct comparisons of loudness ratios were based on loudnessintervals ordifferences where loudness was a power function of sound pressure. These experiments, along with those on loudness difference judgments (Parker & Schneider, 1974; Schneider, Parker, & Stein, 1974), support Torgerson’s (1961) conjecture that there is but one comparative perceptual relationship for ioudnesses, and that differences in numerical estimates for loudness ratios as opposed to loudness intervals simply reflect different reporting strategies generated by the two sets of instructions.     

The impact of category separation on unsupervised categorization

Most previous research on unsupervised categorization has used unconstrained tasks in which no instructions are provided about the underlying category structure or in which the stimuli are not clustered into categories. Few studies have investigated constrained tasks in which the goal is to learn predefined stimulus clusters in the absence of feedback. These studies have generally reported good performance when the stimulus clusters could be separated by a one-dimensional rule. In the present study, we investigated the limits of this ability. Results suggest that even when two stimulus clusters are as widely separated, as in previous studies, performance is poor if within-category variance on the relevant dimension is nonnegligible. In fact, under these conditions, many participants failed even to identify the single relevant stimulus dimension. This poor performance is generally incompatible with all current models of unsupervised category learning.     

Evolutionary models of color categorization based on discrimination

Specifying the factors that contribute to the universality of color categorization across individuals and cultures is a longstanding and still controversial issue in psychology, linguistics, and anthropology. This article approaches this issue through the simulated evolution of color lexicons. It is shown that the combination of a minimal perceptual psychology of discrimination, simple pragmatic constraints involving communication, and simple learning rules is enough to evolve color-naming systems. Implications of this result for psychological theories of color categorization and the evolution of color-naming systems in human societies are discussed.     

The dimensionality of perceptual category learning: A state-trace analysis

State-trace analysis was used to investigate the effect of concurrent working memory load on perceptual category learning. Initial reanalysis of Zeithamova and Maddox (2006, Experiment 1) revealed an apparently two-dimensional state-trace plot consistent with a dual-system interpretation of category learning. However, three modified replications of the original experiment found evidence of a single resource underlying the learning of both rule-based and information integration category structures. Follow-up analyses of the Zeithamova and Maddox data, restricted to only those participants who had learned the category task and performed the concurrent working memory task adequately, revealed a one-dimensional plot consistent with a single-resource interpretation and the results of the three new experiments. The results highlight the potential of state-trace analysis in furthering our understanding of the mechanisms underlying category learning.     

The role of skin color and facial physiognomy in racial categorization: Moderation by implicit racial attitudes

Previous research has not sufficiently addressed factors that define and moderate racial categorization judgments. This study independently manipulated skin color and facial physiognomy to determine their relative weighting in racial categorization. Participants (N = 250) judged faces varying on 10 levels of facial physiognomy (from Afrocentric to Eurocentric) and 10 levels of skin color (from dark to light) under either no time constraints, a modest time constraint, and under a stringent time constraint. Skin color was a powerful predictor of racial typicality ratings at all levels of facial physiognomy, but participants relied upon facial physiognomy more when rating faces of light than dark skin color. Skin color was a more important cue than facial physiognomy under no time constraints, but as time constraints became more severe, skin color's importance decreased, yet it remained a more important cue at extreme physiognomy levels. The relationship between skin color and racial typicality ratings was stronger for those with more negative implicit racial attitudes. These findings suggest the primary role of skin color in racial categorization and underscore the importance of implicit attitudes in explicit categorization judgments.     

Quantitative judgments of color: The square root rule

Judgments of the appearance of colored papers blended with different proportions of white were obtained using a rotating color mixer. Responses consisted of a mark on a line labeled with the appropriate color name at one end and “white” at the other. Prior context was avoided by obtaining only single judgments. It was found for all six color displays that distance from the colored end of the line was proportional to the square root of the proportion of white present in the mixture. This square root relation is in keeping with the physical correlate theory and with other experiments involving gray papers, point sources, and luminous fields.     

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.     

An investigation of the link between attributional judgments and stereotype‐based judgments

Three experiments investigated the relationship between the attributions made for stereotype‐relevant behavior and stereotype‐based judgments. In Experiment 1 participants were presented with a short scenario describing a single stereotypic behavior and were given either a situational or a dispositional explanation for the behavior, before evaluating both the target and the group as a whole on stereotype‐based dimensions. As predicted, participants given a situational explanation for the stereotypic behavior described in the target and the group in less stereotype‐based terms than did baseline participants. In Experiment 2 and 3 participants were presented with a short scenario describing either a single stereotypic or counter‐stereotypic behavior but were asked to provide an explanation for the behavior, rather than being given one. As predicted, stereotypic behavior was attributed more strongly to dispositional than situational factors and counter‐stereotypic behavior more strongly to situational than dispositional factors. No overall moderation of group‐based beliefs relative to baseline was seen in either experiment. Correlations between the attributions and stereotypic‐based judgments did, however, show a relationship between the strength of the attributions made for the behaviors and stereotype‐based judgements. Implications for the moderation of stereotype‐based judgments are discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

The calibration and resolution of confidence in perceptual judgments

Carleton University, Ottawa, Ontariot Canada Confidence rating based calibration and resolution indices were obtained in two experiments requiring perceptual comparisons and in a third with visual gap detection. Four important results were obtained. First, as in the general knowledge domain, subjects were underconfident when judgments were easy and overconfident when they were difficult. Second, paralleling the clear dependence of calibration on decisional difficulty, resolution decreased with increases in decision difficulty arising either from decreases in discriminability or from increasing demands for speed at the expense of accuracy. Third, providing trial-by-trial response feedback on difficult tasks improved resolution but had no effect on calibration. Fourth, subjects can accurately reportsubjective errors (i.e., trials in which they have indicated that they made an error) with their confidence ratings. It is also shown that the properties of decision time, conditionalized on confidence category, impose a rigorous set of constraints on theories of confidence calibration.     

Dissimilarity is used as evidence of category membership in multidimensional perceptual categorization: a test of the similarity-dissimilarity generalized context model

In exemplar models of categorization, the similarity between an exemplar and category members constitutes evidence that the exemplar belongs to the category. We test the possibility that the dissimilarity to members of competing categories also contributes to this evidence. Data were collected from two 2-dimensional perceptual categorization experiments, one with lines varying in orientation and length and the other with coloured patches varying in saturation and brightness. Model fits of the similarity-dissimilarity generalized context model were used to compare a model where only similarity was used with a model where both similarity and dissimilarity were used. For the majority of participants the similarity-dissimilarity model provided both a significantly better fit and better generalization, suggesting that people do also use dissimilarity as evidence.     

The language environment of the young infant: implications for early perceptual development

The purpose of this article is to review recent research on the young infant's use of voice-specific as well as voice-nonspecific auditory information during early language processing, to suggest a possible mechanism that biases the young infant towards this information, and to discuss potential implications of the early saliency of this information for later language development. Auditory preferences expressed by young infants are of interest because they demonstrate which properties of complex auditory events are effective in capturing the infant's attention. Moreover, the presence of such auditory preferences has led to speculations about their possible origins in both pre- and postnatal auditory experience. Research examining the role of early auditory experience in the formation of preferences is presented, along with a discussion of how the constrained nature of early auditory experience (particularly prenatal) may bias the young infant towards specific features of maternal as well as nonmaternal speech.