Category invention in unsupervised learning.

This research aimed to discriminate between 2 general approaches to unsupervised category learning, one based on learning explicit correlational rules or associations within a stimulus domain (autocorrelation) and the other based on inventing separate categories to capture the correlational structure of the domain (category invention). An "attribute-listing" paradigm was used to index unsupervised learning in 3 experiments. Each experiment manipulated the order in which instances from 2 different categories were presented and evaluated the effects of this manipulation in terms of the 2 competing theoretical approaches to unsupervised learning. Strong evidence was found for the use by Ss of a discrete category invention process to learn the categories in these experiments. These results also suggest that attribute listing may be a valuable method for future investigations of unsupervised category learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attribute conjunctions and the part configuration advantage in object category learning.

Five experiments demonstrated that in object category learning people are particularly sensitive to conjunctions of part shapes and relative locations. Participants learned categories defined by a part's shape and color (part-color conjunctions) or by a part's shape and its location relative to another part (part-location conjunctions). The statistical properties of the categories were identical across these conditions, as were the salience of color and relative location. Participants were better at classifying objects defined by part-location conjunctions than objects defined by part-color conjunctions. Subsequent experiments revealed that this effect was not due to the specific color manipulation or the role of location per se. These results suggest that the shape bias in object categorization is at least partly due to sensitivity to part-location conjunctions and suggest a new processing constraint on category learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The formation of stereotypic beliefs: Further evidence for distinctiveness-based illusory correlations.

Investigated the processes underlying illusory correlations based on the co-occurrence of infrequent stimulus events in 2 experiments with 104 undergraduates. In Exp I, 4 groups of 20 Ss were assigned to 1 of 4 conditions. Group 1 read a series of stimulus sentences describing desirable and undesirable behaviors performed by members of Groups A and B. Group 2 read the same sentences but had a different order of presentation. Group 3 read the sentences and were shown a frequency table summarizing the information they had just read. Group 4 was given only the summary table showing the frequency distribution of desirable and undesirable behaviors for Groups A and B and asked to imagine that they had read sentences. Analysis of Ss' ratings showed that the bias producing the illusory correlation occurred during the encoding of serially presented stimulus items and was not due to biased integration of information at the time of judgment. In Exp II, 24 Ss were used to assess recall of stimulus information. Results show that Ss recalled a higher proportion of items representing the co-occurrence of distinctive stimuli than of the other categories of items. The central role of these items in establishing the illusory correlations was further substantiated by correlational evidence. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Better learning with more error: Probabilistic feedback increases sensitivity to correlated cues in categorization.

Despite the fact that categories are often composed of correlated features, the evidence that people detect and use these correlations during intentional category learning has been overwhelmingly negative to date. Nonetheless, on other categorization tasks, such as feature prediction, people show evidence of correlational sensitivity. A conventional explanation holds that category learning tasks promote rule use, which discards the correlated-feature information, whereas other types of category learning tasks promote exemplar storage, which preserves correlated-feature information. Contrary to that common belief, the authors report 2 experiments that demonstrate that using probabilistic feedback in an intentional categorization task leads to sensitivity to correlations among nondiagnostic cues. Deterministic feedback eliminates correlational sensitivity by focusing attention on relevant cues. Computational modeling reveals that exemplar storage coupled with selective attention is necessary to explain this effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning correlations in categorization tasks using large, ill-defined categories.

The experiments revealed whether individual participants are sensitive to exemplar information in the form of within-category correlations between stimulus dimensions after training on large overlapping categories. Participants were trained in 1 of 2 categorization conditions. The sign of the correlation between dimensions differed across conditions, but the categorization rules that best separated the categories were identical. An unannounced attribute-prediction task followed categorization training. Several participants produced predictions consistent with the correct correlation between the dimensions. For other participants, the predictions reflected the correlation only within the region they had associated with the given category, even though the categories overlapped, suggesting that the decision boundary was explicitly represented in memory. Finally, for other participants, no correlational information appeared to be accessible for the prediction task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ideals and category typicality.

Barsalou (1985) argued that exemplars that serve category goals become more typical category members. Although this claim has received support, we investigated (a) whether categories have a single ideal, as negatively valenced categories (e.g., cigarette) often have conflicting goals, and (b) whether ideal items are in fact typical, as they often have unusual attributes. Because past studies on ideals were largely correlational and often used categories not strongly associated to goals (e.g., tree, bird, fish), we took an experimental approach, using categories with obvious goals. Our results indicated that exemplars having goal-fulfilling characteristics are generally judged as less typical than exemplars with average features. Also, although subjects had a general consensus on the ideals of neutral and positive categories, they held opposing opinions on the ideals of the negatively valenced categories. We found that this bimodality in idealness perception was due to differing perspectives taken on the categories; however, perspectives that changed idealness of category exemplars did not influence their typicality. In short, ideal exemplars that best serve category goals are not necessarily perceived as typical. We contrast the goal-fulfilling aspect of ideals with the structural notion of extreme values (e.g., very tall trees), which may influence typicality through other mechanisms. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Make the first move: How infants learn about self-propelled objects.

In 3 experiments, the author investigated 16- to 20-month-old infants' attention to dynamic and static parts in learning about self-propelled objects. In Experiment 1, infants were habituated to simple noncausal events in which a geometric figure with a single moving part started to move without physical contact from an identical geometric figure that possessed a single static part. Infants were then tested with an event in which the parts of the objects were switched. In Experiments 2 and 3, infants were habituated and tested with identical events except that the part possessed by each object during habitation was switched relative to the first experiment. Results of the experiments revealed that 16-month-olds failed to encode the relation between an object's part and its onset of motion, 18-month-olds were unconstrained in the relations involving self-propulsion that they would encode, and 20-month-olds were constrained in the relations they would encode. The results are discussed with regard to the developmental trajectory of learning about motion properties and the mechanism involved in early concept acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does Information About What Things Are Influence Children's Memory for Where Things Are?

Two experiments examined how information about what objects are influences memory for where objects are located. Seven-, 9-, and 11-year-old children and adults learned the locations of 20 objects marked by dots on the floor of a box. The objects belonged to 4 categories. In one condition, objects belonging to the same category were located in the same quadrant of the box. In another condition, objects and locations were randomly paired. After learning, participants attempted to replace the objects without the aid of the dots. Children and adults placed the objects in the same quadrant closer together when they were related than when they were unrelated, indicating that object information led to systematic biases in location memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive categorization in unsupervised learning.

In 3 experiments, the authors provide evidence for a distinct category-invention process in unsupervised (discovery) learning and set forth a method for observing and investigating that process. In the 1st 2 experiments, the sequencing of unlabeled training instances strongly affected participants' ability to discover patterns (categories) across those instances. In the 3rd experiment, providing diagnostic labels helped participants discover categories and improved learning even for instance sequences that were unlearnable in the earlier experiments. These results are incompatible with models that assume that people learn by incrementally tracking correlations between individual features; instead, they suggest that learners in this study used expectation failure as a trigger to invent distinct categories to represent patterns in the stimuli. The results are explained in terms of J. R. Anderson's (1990, 1991) rational model of categorization, and extensions of this analysis for real-world learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The remembering of auditory event durations.

Three experiments examined the incidental remembering of event durations. In each study, Ss engaged in an initial learning phase in which they performed a set of perceptual ratings on events for a varying number of trials. These events consisted of tonal sequences or ecological sounds that varied in their internal structure and ending. Ss were then given a surprise memory task in which they were asked to recognize the duration of each event (Exps 1 and 3) or extrapolate its completion (Exp 2). Results showed that in contrast to irregularly timed events, those filled with regularly timed or continuous pitch information yielded high levels of accuracy that increased with greater learning experience. In addition, durations marked by a nonarbitrary ending were more accurately remembered than those marked by an arbitrary ending which, in fact, were misremembered as shorter than their actual duration. These findings are discussed in terms of an approach that emphasizes the role of event structure on perceiving and remembering activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young children extend novel words at the basic level: Evidence for the principle of categorical scope.

If young children approached the task of word learning with a specific hypothesis about the meaning of novel count nouns, they could make the problem of word learning more tractable. Six experiments were conducted to test children's hypotheses about how labels map to object categories. Findings indicated that (a) 3- and 4-year-olds function with an antithematic bias; (b) children do not reliably extend novel nouns to superordinate exemplars when perceptual similarity is controlled until approximately age 7; and (c) children expect novel nouns to label taxonomic categories at the basic level, even in the presence of a perceptually compelling distractor. Results are interpreted as supporting the principle of categorical scope (R. M. Golinkoff, C. B. Mervis, & K. Hirsh-Pasek; see record 1994-40565-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of background knowledge on object categorization and part detection.

Previous research has shown that background knowledge affects the ease of concept learning, but little research has examined its effects on speeded categorization of instances after the category is well learned. Subjects in 4 experiments first learned novel categories. At test, they categorized a new set of novel stimuli that were either consistent or inconsistent with background knowledge given about the categories. Background knowledge affected categorization responses in an untimed task, with usual reaction time instructions, with a response deadline, or when the stimuli were presented for 50 ms followed by a mask. Three other experiments using a part-detection task showed that subjects were more likely to notice missing parts that were critical than noncritical according to background knowledge. The mechanisms by which background knowledge affects categorization and part detection are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading chimpanzee faces: Evidence for the role of verbal labels in categorical perception of emotion.

Categorical perception (CP) occurs when continuously varying stimuli are perceived as belonging to discrete categories. Thereby, perceivers are more accurate at discriminating between stimuli of different categories than between stimuli within the same category (Harnad, 1987; Goldstone, 1994). The current experiments investigated whether the structural information in the face is sufficient for CP to occur. Alternatively, a perceiver's conceptual knowledge, by virtue of expertise or verbal labeling, might contribute. In two experiments, people who differed in their conceptual knowledge (in the form of expertise, Experiment 1; or verbal label learning, Experiment 2) categorized chimpanzee facial expressions. Expertise alone did not facilitate CP. Only when perceivers first explicitly learned facial expression categories with a label were they more likely to show CP. Overall, the results suggest that the structural information in the face alone is often insufficient for CP; CP is facilitated by verbal labeling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inferring category attributes from exemplar attributes: Geometric shapes and social categories.

Three experiments tested the hypothesis that judgments about the attributes of categories are disproportionately based on the characteristics of exemplars that fit the category. In the first 2 experiments, subjects were presented with good and bad exemplars of categories with defining attributes (rectangles, triangles, pentagons, and ellipses) in which different colors were arbitrarily paired with the good and poor exemplars. In both experiments, subjects erroneously judged the colors paired with the good exemplars as more frequent than colors paired with the poor exemplars. A third experiment, using social categories, examined whether attributes associated with a single category member were more likely to generalize to the category as a whole for prototypical than for nonprototypical category members. Subjects were presented with information about individual fraternity members who varied in prototypicality, and the tendency to infer a target behavior (liberal vs. conservative voting behavior) from the individual fraternity member to the fraternity as a whole increased with the prototypicality of the category member. Implications for the contact hypothesis, category–exemplar relations, and belief stability are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Attentional consequences of object appearance and disappearance.

This study compared the attentional effects of object appearances (onsets) and disappearances (offsets) in moderately complex displays. Four experiments showed that onsets produce the inhibition of return (IOR) effect that has been found with simpler displays. In contrast, although offsets did produce inhibitory effects, these effects did not follow the spatial or temporal pattern of IOR. Two further experiments used a very salient object disappearance to determine whether the typical pattern for IOR could be instantiated; it was not. The results indicate that object appearances are more potent perceptual events than object disappearances. In addition, object disappearances have different attentional consequences than object appearances: Disappearances provoke earlier and spatially narrower inhibition. The results are consistent with the view that inhibition serves a functional role in increasing the efficiency of visual search processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event memory: Temporal-order judgments of personal life experiences.

Three experiments with undergraduate subjects investigated the mental representations that people form when they recall and chronologically order their personal experiences. Subjects in each study first recalled five events that occurred to them in two general periods of their life (e.g., high school and college). Later, they saw pairs of these events and judged the order in which they occurred. It typically took less time to compare events that occurred in different time periods than events that occurred in the same period. However, response times depended on the serial positions of the compared events in each time period, and the distance between them, in ways that varied over the three experiments. These effects were interpreted in terms of a model of event memory and judgment proposed by Wyer, Shoben, Fuhrman, and Bodenhausen (1985). Specifically, subjects appear to organize the events they are asked to recall into categories defined by the periods of life in which they occurred and assign temporal codes to these categories. However, they do not perform a more detailed temporal coding of the events they recall unless a coherent temporal representation of these events is difficult to construct. A direct comparison between judgments of personal experiences and judgments of others' experiences suggested that people may make more detailed temporal coding of others' experiences than they do of their own. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vroom's expectancy models and work-related criteria: A meta-analysis.

This meta-analysis integrates the correlations of 77 studies on V. H. Vroom's (1964) original expectancy models and work-related criteria. Correlations referring to predictions with the models and the single components—valence, instrumentality, and expectancy—were included in relation to 5 types of criterion variables: performance, effort, intention, preference, and choice. Within-subjects correlations and between-subjects correlations were included separately. Overall, the average correlations were somewhat lower than reported in previous narrative reviews. In certain categories, moderators pertaining to the measurement of the concepts were analyzed with a hierarchical linear model, but these moderators did not explain heterogeneity. The results show a differentiated overview: the use of the correlational material for the validity of expectancy theory is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blocking in category learning.

Many theories of category learning assume that learning is driven by a need to minimize classification error. When there is no classification error, therefore, learning of individual features should be negligible. The authors tested this hypothesis by conducting three category-learning experiments adapted from an associative learning blocking paradigm. Contrary to an error-driven account of learning, participants learned a wide range of information when they learned about categories, and blocking effects were difficult to obtain. Conversely, when participants learned to predict an outcome in a task with the same formal structure and materials, blocking effects were robust and followed the predictions of error-driven learning. The authors discuss their findings in relation to models of category learning and the usefulness of category knowledge in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)