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  • 1
    Online Resource
    Online Resource
    A Study of the Effect of Structural Information and Familiarity in Form Perception
    SAGE Publications ; 1991
    In:  The Quarterly Journal of Experimental Psychology Section A Vol. 43, No. 2 ( 1991-05), p. 223-248
    Details
    In: The Quarterly Journal of Experimental Psychology Section A, SAGE Publications, Vol. 43, No. 2 ( 1991-05), p. 223-248
    Abstract: Two experiments were carried out to investigate the influence of structural information and familiarity on the processing of visual forms. Pairs of “well” structured and nameable and “poorly” structured and non-nameable fragmented forms were employed as stimuli. The effects of structure and familiarity were assessed by manipulating the visual hemifield of presentation and the task. In Experiment 1 stimuli were judged as being either in the same orientation or mirror-reversed, a task that does not require high-level semantic information to be processed. Experiment 2 required physically identical forms to be matched, which may use either physical or name information. In Experiment 1 “same” judgements were equivalent for both types of stimuli, and “different' judgements were longer for the “poorly” structured (non-nameable) forms. In Experiment 2 there was little overall difference between “well” and “poorly” structured forms, though response times to “well” structured (nameable) forms were slowed for right-visual-field presentations. It is suggested that familiarity may not be sufficient to provide a perceptual advantage for nameable forms, as the advantage for nameable stimuli was confined to “same” judgements in Experiment 1 and response times were shorter for non-nameable stimuli in Experiment 2. Rather, performance depends upon factors such as the computation of global shape (due to structural properties of collinearity and closure) and on the use of different kinds or representations (physical versus name) in matching.
    Type of Medium: Online Resource
    ISSN: 0272-4987 , 1464-0740
    URL: Article
    DOI: 10.1080/14640749108400968
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1991
    detail.hit.zdb_id: 1467172-4
    SSG: 5,2
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  • 2
    Online Resource
    Online Resource
    Integration of Physical and Semantic Information in Object Processing
    SAGE Publications ; 1997
    In:  Perception Vol. 26, No. 9 ( 1997-09), p. 1197-1209
    Details
    In: Perception, SAGE Publications, Vol. 26, No. 9 ( 1997-09), p. 1197-1209
    Abstract: Physiological studies report independent processing pathways for form and colour information. A more-complex picture on human subjects has previously been reported. A sequential matching task was used that was based on a physical property of an object and in which semantic relations between stimuli were manipulated. Performance was affected by semantic information when matching was based on a property of the form of an object (its orientation, shape, or size). Effects of semantic information were eliminated when matching was based on the colour of a local part of an object but were found again when subjects matched pictures on the basis of the percentage of a colour integrated across the shape boundary. The results suggest independent selection mechanisms in vision in which selection by local colour can be based on inhibition of the form-processing pathway whilst processing of the global configuration of the form of an object activates automatically the identification process.
    Type of Medium: Online Resource
    ISSN: 0301-0066 , 1468-4233
    URL: Article
    DOI: 10.1068/p261197
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1997
    detail.hit.zdb_id: 2013004-1
    SSG: 5,2
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  • 3
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    Online Resource
    Influence of Physical and Semantic Information in a Categorisation Task of Fragmented Forms
    SAGE Publications ; 1991
    In:  Perception Vol. 20, No. 3 ( 1991-06), p. 403-414
    Details
    In: Perception, SAGE Publications, Vol. 20, No. 3 ( 1991-06), p. 403-414
    Abstract: Two experiments were carried out to investigate the influence of structural and semantic information in the categorisation of visual forms. In experiment 1 the stimuli were pairs of ‘well structured’ or ‘poorly structured’ fragmented forms differing in structural properties including convexity, collinearity, and closure of the elements, and in their ‘name-ability’. The influence of structural and semantic information was tested by means of a task involving the presentation to both visual hemifields separately of stimuli having within-category physical similarity. For well structured forms, subjects were asked to judge if two sequentially presented forms belonged to the same semantic category. For poorly structured forms, subjects were required to decide if two stimuli belonged to the same previously learnt category of forms. For the two types of stimuli, one category was composed of physically similar items, and the other was composed of physically dissimilar items. The results show a marked advantage for the category composed of physically similar forms when the stimuli are well structured but no differences between the two categories when the stimuli are poorly structured. This suggests a facilitation in the computation of global shape information for forms having collinear and closed elements. The only effect of semantic information was a tendency towards a right visual field advantage for same-category pairs of well structured forms. The pattern of results for well structured fragmented forms (experiment 1) and forms in which fragments had been joined in order to complete the contour (experiment 2) were similar, suggesting that structured incomplete forms can be processed in the same way as forms having a continuous contour. Hypotheses about the organisational processes of forms are proposed in the discussion.
    Type of Medium: Online Resource
    ISSN: 0301-0066 , 1468-4233
    URL: Article
    DOI: 10.1068/p200403
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1991
    detail.hit.zdb_id: 2013004-1
    SSG: 5,2
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  • 4
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    Online Resource
    Effects of Methylphenidate on Default-Mode Network/Task-Positive Network Synchronization in Children With ADHD
    SAGE Publications ; 2017
    In:  Journal of Attention Disorders Vol. 21, No. 14 ( 2017-12), p. 1208-1220
    Details
    In: Journal of Attention Disorders, SAGE Publications, Vol. 21, No. 14 ( 2017-12), p. 1208-1220
    Abstract: Objective: A failure of the anti-phase synchronization between default-mode (DMN) and task-positive networks (TPN) may be involved in a main manifestation of ADHD: moment-to-moment variability. The study investigated whereby methylphenidate may improve TPN/DMN synchronization in ADHD. Method: Eleven drug-naive ADHD children and 11 typically developing (TD) children performed a flanker task during functional magnetic resonance imaging. The ADHD group was scanned without and 1 month later with methylphenidate. The signal was analyzed by independent component analysis. Results: The TD group showed anti-phase DMN/TPN synchronization. The unmedicated ADHD group showed synchronous activity in the posterior DMN only, which was positively correlated with response time variability for the flanker task. Methylphenidate initiated a partial anti-phase TPN/DMN synchronization, reduced variability, and abolished the variability/DMN correlation. Conclusion: Although results should be interpreted cautiously because the sample size is small, they suggest that a failure of the TPN/DMN synchronization could be involved in the moment-to-moment variability in ADHD. Methylphenidate initiated TPN/DMN synchronization, which in turn appeared to reduce variability.
    Type of Medium: Online Resource
    ISSN: 1087-0547 , 1557-1246
    URL: Article
    DOI: 10.1177/1087054713517542
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
    detail.hit.zdb_id: 2188086-4
    SSG: 5,2
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  • 5
    Online Resource
    Online Resource
    The Computation of Contour Information in Complex Objects
    SAGE Publications ; 1994
    In:  Perception Vol. 23, No. 4 ( 1994-04), p. 399-409
    Details
    In: Perception, SAGE Publications, Vol. 23, No. 4 ( 1994-04), p. 399-409
    Abstract: Perceptual organisation, and especially the computation of contour information, has been the object of considerable interest in the last few years. In the first part of the paper we review recent accounts on the mechanisms involved in the processing of contour. In the second part we report an experiment designed to examine (1) how physical parameters such as spatial proximity and collinearity of elements affect the integration of global contour in objects and (2) whether the activation of stored representations of objects facilitates the computation of contour. Incomplete forms varying in the spacing and the alignment of line segments on their contour were used as stimuli in a matching task. Subjects were asked to decide which of two laterally displayed figures matched a reference form presented previously. The matching target and the distractor were physically identical but differed in their orientation. In one condition the reference object was always an outline drawing of an object. In a second condition the reference object was either a complete object or a more or less identifiable incomplete form. Little variation in performance was found for forms having continuous and discontinuous contour up to a spacing of 5 pixels (10.8 min) between elements. Response times and errors increased abruptly beyond this limit. This effect occurred in the two conditions of reference stimulus, suggesting that the computation of contour information is more affected by physical constraints at early processes than by high-level processes involving activation of stored structural representations of objects.
    Type of Medium: Online Resource
    ISSN: 0301-0066 , 1468-4233
    URL: Article
    DOI: 10.1068/p230399
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1994
    detail.hit.zdb_id: 2013004-1
    SSG: 5,2
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