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Benjamin A. Guenther, James M. Brown, Shruti Narang, Aisha P. Siddiqui; Studying object-based attention with a steady/pulsed-pedestal paradigm. Journal of Vision 2010;10(7):175. doi: 10.1167/10.7.175.
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The steady/pulsed-pedestal paradigm has been shown to be an effective manipulation of relative magnocellular (M) and parvocellular (P) activity (e.g., Leonova, Pokorny, & Smith, 2003; McAnany & Levine, 2007). However, this manipulation has primarily been used with contrast sensitivity measures. The purposes of the present study were to evaluate the effectiveness of this manipulation using a simple reaction time (RT) measure and then test previous findings showing specific influences on space- and object-based attention under M- and P-biased conditions. Cuing studies investigating object-based attention have shown the cost for shifting attention within an object is less than equidistant shifts between two objects (object advantage = within-object RTs <between-object RTs). We previously reported this object advantage is eliminated under equiluminant (P-biased) conditions because of increased within-object RTs (Boyd, Guenther, & Brown, VSS 2007). The first experiment measured simple RTs to a square target presented at center screen on a square pedestal (20% catch trials) to see if the pulsed-pedestal would cause increased RTs expected from P-biased conditions. The steady/pulsed-pedestal manipulation produced reliable differences in RTs consistent with M- and P-biased conditions with overall RTs longer for the pulsed (P-biased) compared to the steady (M-biased) pedestal condition. A second experiment tested for an object advantage using pairs of rectangular bars (tilted 45° left or right of vertical) as objects. Again overall RTs were greater for pulsed compared to steady pedestal conditions. A similar magnitude validity effect (valid RTs <invalid RTs) was found for both conditions indicating that, in general, the pulsed condition did not interfere with shifting attention. However, the pulsed condition had a greater influence on RTs for within- compared to between-object shifts. Similar to our previous study, RTs for within-object shifts increased for P-biased conditions eliminating the object advantage.
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