What's behind different kinds of kinds: Effects of statistical density on learning and representation of categories.

This research examined how differences in category structure affect category learning and category representation across points of development. The authors specifically focused on category density--or the proportion of category-relevant variance to the total variance. Results of Experiments 1-3 showed a clear dissociation between dense and sparse categories: Whereas dense categories were readily learned without supervision, learning of sparse categories required supervision. There were also developmental differences in how statistical density affected category representation. Although children represented both dense and sparse categories on the basis of the overall similarity (Experiment 4A), adults represented dense categories on the basis of similarity and represented sparse categories on the basis of the inclusion rule (Experiment 4B). The results support the notion that statistical structure interacts with the learning regime in their effects on category learning. In addition, these results elucidate important developmental differences in how categories are represented, which presents interesting challenges for theories of categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Teaching phonological awareness to young children with learning disabilities

This study examined the feasibility of teaching phonological manipulation skills to preschool children with disabilities. Forty-seven children, 4-6 years old, enrolled in a special education preschool, were randomly assigned to receive training in one of three categories of phonological tasks (rhyming, blending, and segmenting) or a control group. Results indicated that children were able to make significant progress in each experimental category, but that they demonstrated little or no generalization either within a category (e.g., from one type of blending task to another type of blending task) or between categories (e.g., from blending to segmenting). Although the children's level of cognitive development significantly predicted some learning outcomes, it did not appear to limit the learning of phonological tasks.     

Attention and retrieval from long-term memory.

Conducted 9 experiments with 152 female volunteers (mean age 44.4 yrs) to investigate the disrupting effect of a secondary task on retrieval from long-term memory. Exps I–V studied the influence of concurrent card sorting or digit span on free recall or paired-associate learning of word lists. Exp VI explored recall probability using a recognition paradigm in which accuracy and latency could be measured simultaneously. Exp VII explored the latency effect with a semantic memory paradigm, and Exp VIII required Ss to make semantic category judgments while retaining sequences of 6 digits. Exp IX examined the effect of concurrent digital load on the rate of generating items from semantic categories. Overall findings reveal that a demanding concurrent task did not reduce the probability of retrieving an item from semantic or episodic memory. However, concurrent load during learning substantially effected recall performance. A concurrent task during retrieval did not have a clear effect on latency. The contrast between the pattern shown by errors and by that shown by latencies suggests that attempts to estimate the attentional demands of any task should be interpreted with considerable caution when based on a single measure, such as performance errors, performance latency, or a response to a probe RT signal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual tempo, activity, and concept learning in hyperactive and normal children.

Conducted an experiment with 40 hyperactive and 80 normal 8-11 yr old males which examined the relations among activity, conceptual tempo, and diagnostic category on a concept learning and transfer task. Results reveal a small but significant performance decrement by the hyperactive group on the learning task. However, this decrement did not carry over to the transfer task, in which a group difference was not found. Activity and conceptual tempo were related to diagnosis, with the hyperactive group being more active and having a greater percentage classified as impulsive. Nonetheless, activity and conceptual tempo were not related to the performance tasks. Rather than accept a label of "brain damage" as an explanation for the learning problems of hyperactive children, it is suggested that future research might focus on cognitive styles and performance characteristics of hyperactive children. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dispensability of member effort and group motivation losses: Free-rider effects.

Three experiments tested the hypothesis that group members exert less effort as the perceived dispensability of their efforts for group success increases. The resultant motivation losses were termed "free-rider effects." In Exp I, 189 undergraduates of high or low ability performed in 2-, 4-, or 8-person groups at tasks with additive, conjunctive, or disjunctive demands. As predicted, member ability had opposite effects on effort under disjunctive and conjunctive task demands. The failure to obtain a relationship between group size and member effort in Exp I was attributed to a procedural artifact eliminated in Exp II (73 Ss). As predicted, as groups performing conjunctive and disjunctive tasks increased in size, member motivation declined. This was not a social loafing effect; group members were fully identifiable at every group size. Exp III (108 Ss) explored the role that performance feedback plays in informing group members of the dispensability of their efforts and encouraging free riding. Results are generally consistent with those of Exps I and II. (24 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)     

Supervised and unsupervised learning of multidimensional acoustic categories.

Learning to recognize the contrasts of a language-specific phonemic repertoire can be viewed as forming categories in a multidimensional psychophysical space. Research on the learning of distributionally defined visual categories has shown that categories defined over 1 dimension are easy to learn and that learning multidimensional categories is more difficult but tractable under specific task conditions. In 2 experiments, adult participants learned either a unidimensional or a multidimensional category distinction with or without supervision (feedback) during learning. The unidimensional distinctions were readily learned and supervision proved beneficial, especially in maintaining category learning beyond the learning phase. Learning the multidimensional category distinction proved to be much more difficult and supervision was not nearly as beneficial as with unidimensionally defined categories. Maintaining a learned multidimensional category distinction was only possible when the distributional information that identified the categories remained present throughout the testing phase. We conclude that listeners are sensitive to both trial-by-trial feedback and the distributional information in the stimuli. Even given limited exposure, listeners learned to use 2 relevant dimensions, albeit with considerable difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of concurrent verbal and visual tasks on category learning.

Current theories of category learning posit separate verbal and nonverbal learning systems. Past research suggests that the verbal system relies on verbal working memory and executive functioning and learns rule-defined categories; the nonverbal system does not rely on verbal working memory and learns non-rule-defined categories (E. M. Waldron & F. G. Ashby, 2001; D. Zeithamova & W. T. Maddox, 2006). However, relatively little research has explored the importance of visual working memory or visual processing for either system. The authors investigated the role of working memory (Experiment 1a and 1b), visual processing (Experiment 2), and executive functioning for each system, using a concurrent task methodology. It was found that visual tasks with high executive functioning demands and verbal tasks with high or low executive demands disrupted rule-defined learning, whereas any visual task, regardless of executive functioning demand, disrupted non-rule-defined learning. Taken together, these results confirm the importance of verbal working memory and executive functioning for the verbal system and provide new evidence for the importance of visual processing for the nonverbal system. These results help to clarify understanding of the nonverbal system and have implications for multiple systems theories of category learning (F. G. Ashby, L. A. Alfonso-Reese, A. U. Turken, & E. M. Waldron, 1998). (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit and explicit category learning by macaques (Macaca mulatta) and humans (Homo sapiens).

An influential theoretical perspective differentiates in humans an explicit, rule-based system of category learning from an implicit system that slowly associates different regions of perceptual space with different response outputs. This perspective was extended for the 1st time to the category learning of nonhuman primates. Humans (Homo sapiens) and macaques (Macaca mulatta) learned categories composed of sine-wave gratings that varied across trials in bar width and bar orientation. The categories had either a single-dimensional, rule-based solution or a two-dimensional, information-integration solution. Humans strongly dimensionalized the stimuli and learned the rule-based task far more quickly. Six macaques showed the same performance advantage in the rule-based task. In humans, rule-based category learning is linked to explicit cognition, consciousness, and declarative reports about the contents of cognition. These results demonstrate an empirical continuity between human and nonhuman primate cognition, suggesting that nonhuman primates may have some structural components of humans’ capacity for explicit cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category knowledge in Alzheimer's disease: Normal organization and a general retrieval deficit.

Three hypotheses that could account for deficits in the retrieval of category information in Alzheimer's disease (AD) were evaluated: abnormal organization, class- or category-specific vulnerability, and limitation by general factors, such as decreased processing speed. Relative to 18 elderly control Ss, 18 patients with AD produced fewer items in a category fluency task and had longer reaction times in a category decision task. The pattern of performance across categories on both tasks was normal in the AD group: The same categories elicited the most (or fastest) responses in both the control group and the AD group. AD patients showed normal performance in ranking of category exemplars by typicality. There was no evidence for differential accessibility by category or by class of information (animate vs inanimate). The authors conclude that a general factor or factors limit(s) retrievability equally across all categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prior knowledge and correlational structure in unsupervised learning.

Prior knowledge has been shown to facilitate both supervised and unsupervised category learning, but questions remain about how this facilitation occurs. This article describes two experiments that investigate the effects of prior knowledge on unsupervised learning, using the exemplar-memory task of Clapper and Bower (2002). Experiment 1 demonstrates that prior knowledge facilitates learning in this task, as expected, and that this facilitation extends to both knowledge-relevant and knowledge-irrelevant features of the new categories. Experiment 2 shows that knowledge facilitates learning not only by increasing the probability that people will discover separate categories, but also by making the features of different categories seem less interchangeable, thereby reducing interference and confusion among them. Taken together, these experiments demonstrate that prior knowledge has multiple effects on unsupervised learning and suggests that the exemplar-memory task may provide a useful procedure for disentangling and investigating these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of place learning in children as measured in the Radial Arm Maze, Morris Search Task, and Open Field Task.

Children and adults were tested on 3 place learning tasks. Children under the age of 7 yrs were inferior to older Ss in solving the tasks by using spatial relational solutions, but Ss of all ages were equally proficient in solving the task by using simple stimulus-reward associations (cued solutions). Accurate performance on the cued versions suggests that neither the general response demands nor the large size of testing environments rendered the tasks differentially inappropriate for young children. Instead, the nature of the cognitive demands were responsible for different levels of performance across the age groups. Because, in animal studies, spatial relational solutions but not cued solutions of these tests require mature and undamaged medial temporal lobe structures, the results suggest that these systems are not fully developed in humans before approximately 7 yrs of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An adaptive approach to human decision making: Learning theory, decision theory, and human performance.

Describes a general model of decision rule learning, the rule competition model, composed of 2 parts: an adaptive network model that describes how individuals learn to predict the payoffs produced by applying each decision rule for any given situation and a hill-climbing model that describes how individuals learn to fine tune each rule by adjusting its parameters. The model was tested and compared with other models in 3 experiments on probabilistic categorization. The 1st experiment was designed to test the adaptive network model using a probability learning task, the 2nd was designed to test the parameter search process using a criterion learning task, and the 3rd was designed to test both parts of the model simultaneously by using a task that required learning both category and cutoff criteria. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do children profit from looking beyond looks? From similarity-based to cue abstraction processes in multiple-cue judgment.

The authors investigated the ability of 9- to 11-year-olds and of adults to use similarity-based and rule-based processes as a function of task characteristics in a task that can be considered either a categorization task or a multiple-cue judgment task, depending on the nature of the criterion (binary vs. continuous). Both children and adults relied on similarity-based processes in the categorization task. However, adults relied on cue abstraction in the multiple-cue judgment task, whereas the majority of children continued to rely on similarity-based processes. Reliance on cue abstraction resulted in better judgments for adults but not for children in the multiple-cue judgment task. This suggests that 9- to 11-year-olds may have defaulted to similarity-based processes because they were not able to employ a cue abstraction process efficiently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning mode and exemplar sequencing in unsupervised category learning.

Exemplar sequencing effects in incidental and intentional unsupervised category learning were investigated to illuminate how people form categories without an external teacher. Stimuli were perfectly separable into 2 categories based on 1 of 2 dimensions of variation. Sequencing of the first 20 training stimuli was manipulated. In the blocked condition, 10 Category A stimuli were followed by 10 Category B stimuli. In the intermixed condition, these 20 stimuli were ordered randomly. Experiment 1 revealed an interaction between learning mode and sequence, with better intentional learning for intermixed sequences but better incidental learning for blocked sequences. Experiment 2 showed that manipulating trial-to-trial variability along each dimension can impact intentional learning. Training sequences that emphasized variation along the category-relevant dimension resulted in better performance than sequences that emphasized variation along the category-irrelevant dimension. The results suggest that unsupervised category learning is influenced by the mode of learning and the order and nature of encountered exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-category discontinuity interacts with verbal rule complexity in perceptual category learning.

A test of the predicted interaction between within-category discontinuity and verbal rule complexity on information-integration and rule-based category learning was conducted. Within-category discontinuity adversely affected information-integration category learning but not rule-based category learning. Model-based analyses suggested that some information-integration participants improved performance by recruiting more "units" in the discontinuous condition. Verbal rule complexity adversely affected rule-based category learning but not information-integration category learning. Model-based analyses suggested that the rule based effect was on both decision criterion learning and variability in decision criterion placement. These results suggest that within-category discontinuity and decision rule complexity differentially impact information-integration and rule-based category learning and provide information regarding the detailed processing characteristics of these two proposed category learning systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed Feedback Disrupts the Procedural-Learning System but Not the Hypothesis-Testing System in Perceptual Category Learning.

W. T. Maddox, F. G. Ashby, and C. J. Bohil (2003) found that delayed feedback adversely affects information-integration but not rule-based category learning in support of a multiple-systems approach to category learning. However, differences in the number of stimulus dimensions relevant to solving the task and perceptual similarity failed to rule out 2 single-system interpretations. The authors conducted an experiment that remedied these problems and replicated W. T. Maddox et al.'s findings. The experiment revealed a strong performance decrement for information-integration but not rule-based category learning under delayed feedback that was due to an increase in the number of observers using hypothesis-testing strategies to solve the information-integration task, and lower accuracy rates for the few observers using information-integration strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of performance evaluation rating segmentation on motivation and fairness perceptions.

This study investigated the impact of rating segmentation (i.e., the number of alternative appraisal categories available for rating employee performance) on motivation and perceptions of fairness. Participants were 305 student volunteers who performed a catalog search task, A 2 X 4 factorial design with 2 performance rating systems--low segmentation (3 categories) and moderate segmentation (5 categories)--and 4 performance levels was used. Overall, the results indicated that the 5-category system resulted in higher self-efficacy regarding participants' ability to reach the next higher rating category, higher goals for rating improvement, and higher rating improvements than the 3-category system. The effects of rating system and performance rating on rating improvement were partially mediated by self-efficacy and personal goals. The rating system and the performance rating affected perceptions of distributive and procedural justice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)