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" Positive and negative congruency effects in masked and unmasked priming: Match of representation strength, attention, and consciousness "
Ahmad Sohrabi
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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54840
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| Doc. No
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TL24794
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| Call number
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NR36793
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| Main Entry
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Ahmad Sohrabi
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| Title & Author
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Positive and negative congruency effects in masked and unmasked priming: Match of representation strength, attention, and consciousness\ Ahmad Sohrabi
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| College
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Carleton University (Canada)
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| Date
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2008
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| Degree
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Ph.D.
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| student score
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2008
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| Page No
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273
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| Abstract
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In this thesis different data were analyzed, including behavioural performance (speed and accuracy), fMRI brain activation, and modelling simulation, to investigate the underlying processes in perceptual and symbolic, masked and unmasked magnitude priming. The perceptual stimuli were either simple or Müller-Lyer lines and the symbolic stimuli were either Arabic numerals or arbitrary symbols memorized and treated as numbers. These factors and contextual information affecting attention and conflict (and factors investigated in previous studies) were all supposed to fit in the match of representation strength as the main factor. The manipulation of this factor changed the performance in decision on the magnitude in the behavioural performance measured as the congruency (priming) effects i.e., performance in the congruent compared to incongruent trials. Stimuli with high strength caused a positive congruency effect and stimuli with low strength caused a negative congruency effect, especially when both prime and target had low strength of representation. Cueing the target made these effects disappear. With regard to the difference in the masked and unmasked conditions, it will be argued that in the unmasked priming attention is drawn to the relevant, and is withdrawn from the irrelevant prime, increasing and decreasing the match of representation strength, respectively (based on the task context). The fMRI brain activations and behavioural data showed the difference between masked and unmasked and illusory and non-illusory conditions. The model illustrated the role of major factors in the match of representation strength, including the attentional modulatory effects on those factors. The model simulated both types of congruency effects in the experimental data and accounted for main factors in masked and unmasked priming including, but not limited to, the prime and target strength, the role of mask, the time and length of stimulus presentation, stimulus degradation, attention, and conflict. A prime with a strong representation caused high activations, including attentional responses, and caused a positive congruency effect when the target came early, but when the target came late or both prime and target had low strength the congruency effect was negative.
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| Subject
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Psychology; Attention; Congruency; Consciousness; Priming; Strength; Experiments; 0623:Psychology; 0623:Experiments
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| Added Entry
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Carleton University (Canada)
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