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Categorization Task (categorization + task)
Selected AbstractsYoung Infants' Performance in the Object-Variation Version of the Above-Below Categorization Task: A Result of Perceptual Distraction or Conceptual Limitation?INFANCY, Issue 3 2002Paul C. Quinn Five experiments were conducted to examine the performance of young infants on above versus below categorization tasks. Experiments 1 and 2 showed that infants did not form abstract categorical representations for above and below when familiarized with different objects depicted in a constant spatial relation relative to a horizontal bar and tested on a novel object depicted in the familiar and novel spatial relation. Experiments 3 through 5 examined perceptual-attentional distraction versus conceptually based generalization explanations for young infant performance in the object-variation version of the above-below categorization task. Experiments 3 and 4 demonstrated that infants still did not form abstract categorical representations for above and below when object variation was removed from the familiarization trials or when object novelty was reduced during the preference test trials. However, Experiment 5 showed that 3- and 4-month-olds succeeded on the above versus below categorization task when familiarized with object variation and preference tested with a familiar versus novel object-bar relation. These results indicate that young infants can form categorical representations for above and below in the object-variation version of the above-below categorization task, but that such representations are specific to the particular objects presented. Young infant performance in the object-variation version of the above-below categorization task thus reflects a conceptually based generalization limit rather than a problem of perceptual-attentional distraction. [source] ERP and RT Delays in Long-Term Abstinent Alcoholics in Processing of Emotional Facial Expressions During Gender and Emotion Categorization TasksALCOHOLISM, Issue 7 2010George Fein Background:, There is considerable evidence that alcoholics differ from nonalcoholics in the processing of stimuli that have emotional content. The current study examines those differences that are present in multi-year abstinent individuals. Methods:, We compared reaction time (RT), accuracy, and Event Related Potentials (ERP) measures in long-term abstinent alcoholics (LTAA, n = 52) with that in age- and gender-comparable nonalcoholic controls (NAC, n = 47). Subjects were presented with male and female faces exhibiting happy, neutral, or sad facial expressions and were instructed to identify the picture gender in 1 task and the emotion being expressed in a subsequent task. Results:, LTAA had slower RTs than NAC when instructed to identify emotion, while RT was comparable when identifying gender. There were no differences between groups on task accuracy. P160 latency was increased in LTAA for both tasks compared to NAC, though P160 amplitude did not differ between groups. The P160 effect was about 5 × as large as the RT effect and was statistically independent of the RT effect, while the RT effect was no longer present after removing variance because of the P160 effect. Conclusions:, Our data demonstrate slower early processing of emotional facial stimuli in alcoholics that is unresolved by long-term abstinence and is most sensitively indexed by delayed P160 latency in LTAA. [source] Rapid categorization of achromatic natural scenes: how robust at very low contrasts?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2005Marc J.-M. Abstract The human visual system is remarkably good at categorizing objects even in challenging visual conditions. Here we specifically assessed the robustness of the visual system in the face of large contrast variations in a high-level categorization task using natural images. Human subjects performed a go/no-go animal/nonanimal categorization task with briefly flashed grey level images. Performance was analysed for a large range of contrast conditions randomly presented to the subjects and varying from normal to 3% of initial contrast. Accuracy was very robust and subjects were performing well above chance level (, 70% correct) with only 10,12% of initial contrast. Accuracy decreased with contrast reduction but reached chance level only in the most extreme condition (3% of initial contrast). Conversely, the maximal increase in mean reaction time was ,,60 ms (at 8% of initial contrast); it then remained stable with further contrast reductions. Associated ERPs recorded on correct target and distractor trials showed a clear differential effect whose amplitude and peak latency were correlated respectively with task accuracy and mean reaction times. These data show the strong robustness of the visual system in object categorization at very low contrast. They suggest that magnocellular information could play a role in ventral stream visual functions such as object recognition. Performance may rely on early object representations which lack the details provided subsequently by the parvocellular system but contain enough information to reach decision in the categorization task. [source] Neural bases of categorization of simple speech and nonspeech soundsHUMAN BRAIN MAPPING, Issue 8 2006Fatima T. Husain Abstract Categorization is fundamental to our perception and understanding of the environment. However, little is known about the neural bases underlying the categorization of sounds. Using human functional magnetic resonance imaging (fMRI) we compared the brain responses to a category discrimination task with an auditory discrimination task using identical sets of sounds. Our stimuli differed along two dimensions: a speech,nonspeech dimension and a fast,slow temporal dynamics dimension. All stimuli activated regions in the primary and nonprimary auditory cortices in the temporal cortex and in the parietal and frontal cortices for the two tasks. When comparing the activation patterns for the category discrimination task to those for the auditory discrimination task, the results show that a core group of regions beyond the auditory cortices, including inferior and middle frontal gyri, dorsomedial frontal gyrus, and intraparietal sulcus, were preferentially activated for familiar speech categories and for novel nonspeech categories. These regions have been shown to play a role in working memory tasks by a number of studies. Additionally, the categorization of nonspeech sounds activated left middle frontal gyrus and right parietal cortex to a greater extent than did the categorization of speech sounds. Processing the temporal aspects of the stimuli had a greater impact on the left lateralization of the categorization network than did other factors, particularly in the inferior frontal gyrus, suggesting that there is no inherent left hemisphere advantage in the categorical processing of speech stimuli, or for the categorization task itself. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Better Processing of Consonantal Over Vocalic Information in Word Learning at 16 Months of AgeINFANCY, Issue 4 2009Mélanie Havy Previous research using the name-based categorization task has shown that 20-month-old infants can simultaneously learn 2 words that only differ by 1 consonantal feature but fail to do so when the words only differ by 1 vocalic feature. This asymmetry was taken as evidence for the proposal that consonants are more important than vowels at the lexical level. This study explores this consonant-vowel asymmetry in 16-month-old infants, using an interactive word learning task. It shows that the pattern of the 16-month-olds is the same as that of the 20-month-olds. Infants succeeded with 1-feature consonantal contrasts (either place or voicing) but were at chance level with 1-feature vocalic contrasts (either place or height). These results thus contribute to a growing body of evidence establishing, from early infancy to adulthood, that consonants and vowels have different roles in lexical acquisition and processing. [source] Young Infants' Performance in the Object-Variation Version of the Above-Below Categorization Task: A Result of Perceptual Distraction or Conceptual Limitation?INFANCY, Issue 3 2002Paul C. Quinn Five experiments were conducted to examine the performance of young infants on above versus below categorization tasks. Experiments 1 and 2 showed that infants did not form abstract categorical representations for above and below when familiarized with different objects depicted in a constant spatial relation relative to a horizontal bar and tested on a novel object depicted in the familiar and novel spatial relation. Experiments 3 through 5 examined perceptual-attentional distraction versus conceptually based generalization explanations for young infant performance in the object-variation version of the above-below categorization task. Experiments 3 and 4 demonstrated that infants still did not form abstract categorical representations for above and below when object variation was removed from the familiarization trials or when object novelty was reduced during the preference test trials. However, Experiment 5 showed that 3- and 4-month-olds succeeded on the above versus below categorization task when familiarized with object variation and preference tested with a familiar versus novel object-bar relation. These results indicate that young infants can form categorical representations for above and below in the object-variation version of the above-below categorization task, but that such representations are specific to the particular objects presented. Young infant performance in the object-variation version of the above-below categorization task thus reflects a conceptually based generalization limit rather than a problem of perceptual-attentional distraction. [source] Relatedness proportion effects on masked associative priming: An ERP studyPSYCHOPHYSIOLOGY, Issue 1 2006Giordana Grossi Abstract The effect of relatedness proportion (the percentage of related words in a list) on associative priming was investigated in two masked priming experiments. In Experiment 1, subjects were randomly assigned to either a high (80%) or low (20%) relatedness proportion condition and performed a lexical decision task. Semantically related and unrelated primes were briefly flashed (50 ms) before the targets and were preceded by a mask that prevented their overt identification. In Experiment 2, subjects were tested in both relatedness proportion conditions in a categorization task; the N400, an electrophysiological index of lexical and semantic priming, was measured in trials that did not require a button press. Behavioral and electrophysiological priming effects were observed in both high and low relatedness proportion conditions. The observed priming effects were not modulated by relatedness proportion. The results are discussed in terms of current theories of associative priming. [source] Six-Month-Old Infants' Categorization of Containment Spatial RelationsCHILD DEVELOPMENT, Issue 3 2003Marianella Casasola Six-month-old infants' ability to form an abstract category of containment was examined using a standard infant categorization task. Infants were habituated to 4 pairs of objects in a containment relation. Following habituation, infants were tested with a novel example of the familiar containment relation and an example of an unfamiliar relation. Results indicate that infants look reliably longer at the unfamiliar versus familiar relation, indicating that they can form a categorical representation of containment. A second experiment demonstrated that infants do not rely on object occlusion to discriminate containment from a support or a behind spatial relation. Together, the results indicate that by 6 months, infants can recognize a containment relation from different angles and across different pairs of objects. [source] Accessing newly learned names and meanings in the native languageHUMAN BRAIN MAPPING, Issue 3 2009Annika Hultén Abstract Ten healthy adults encountered pictures of unfamiliar archaic tools and successfully learned either their name, verbal definition of their usage, or both. Neural representation of the newly acquired information was probed with magnetoencephalography in an overt picture-naming task before and after learning, and in two categorization tasks after learning. Within 400 ms, activation proceeded from occipital through parietal to left temporal cortex, inferior frontal cortex (naming) and right temporal cortex (categorization). Comparison of naming of newly learned versus familiar pictures indicated that acquisition and maintenance of word forms are supported by the same neural network. Explicit access to newly learned phonology when such information was known strongly enhanced left temporal activation. By contrast, access to newly learned semantics had no comparable, direct neural effects. Both the behavioral learning pattern and neurophysiological results point to fundamentally different implementation of and access to phonological versus semantic features in processing pictured objects. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Young Infants' Performance in the Object-Variation Version of the Above-Below Categorization Task: A Result of Perceptual Distraction or Conceptual Limitation?INFANCY, Issue 3 2002Paul C. Quinn Five experiments were conducted to examine the performance of young infants on above versus below categorization tasks. Experiments 1 and 2 showed that infants did not form abstract categorical representations for above and below when familiarized with different objects depicted in a constant spatial relation relative to a horizontal bar and tested on a novel object depicted in the familiar and novel spatial relation. Experiments 3 through 5 examined perceptual-attentional distraction versus conceptually based generalization explanations for young infant performance in the object-variation version of the above-below categorization task. Experiments 3 and 4 demonstrated that infants still did not form abstract categorical representations for above and below when object variation was removed from the familiarization trials or when object novelty was reduced during the preference test trials. However, Experiment 5 showed that 3- and 4-month-olds succeeded on the above versus below categorization task when familiarized with object variation and preference tested with a familiar versus novel object-bar relation. These results indicate that young infants can form categorical representations for above and below in the object-variation version of the above-below categorization task, but that such representations are specific to the particular objects presented. Young infant performance in the object-variation version of the above-below categorization task thus reflects a conceptually based generalization limit rather than a problem of perceptual-attentional distraction. [source] Evidence of rapid correlation-based perceptual category learning by 4-month-oldsINFANT AND CHILD DEVELOPMENT, Issue 5 2005Denis Mareschal Abstract 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. [source] Machine learning for Arabic text categorizationJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 8 2006Rehab M. Duwairi In this article we propose a distance-based classifier for categorizing Arabic text. Each category is represented as a vector of words in an m -dimensional space, and documents are classified on the basis of their closeness to feature vectors of categories. The classifier, in its learning phase, scans the set of training documents to extract features of categories that capture inherent category-specific properties; in its testing phase the classifier uses previously determined category-specific features to categorize unclassified documents. Stemming was used to reduce the dimensionality of feature vectors of documents. The accuracy of the classifier was tested by carrying out several categorization tasks on an in-house collected Arabic corpus. The results show that the proposed classifier is very accurate and robust. [source] | ||||||||||||||||