Evidence for object-based attention is based mainly on studies using object displays that remain unchanged throughout, with the assumption that object representation should be completed and stabilized before it is selected for further processing. We used the modified double-rectangle cuing paradigm of Egly, Driver, and Rafal (Journal of Experimental Psychology: General, 123, 161-177, 1994) but introduced a configuration change to the cued-object display to test whether object-based attention is determined by the cued- or, alternatively, the changed-object display. Four small rectangles were presented in the initial display; critically, after one was cued, an occluder was presented to make the four small rectangles amodally completed into the double-rectangle configuration. Results show that object-based attention is determined by the changed display, but not by the cued display. This suggests that object-based attention is an interactively evolving process between object representation and attention, rather than a serial process in which attention operates after object representation is completed.
To show that, in reading, a fundamental and unconscious perceptual process occurs beyond the current fixation, we examined whether peripherally presented characters of Chinese words in such extreme viewing conditions could be grouped when some characters were rendered invisible while others were visible. We presented a pair of two-character Chinese words and indexed whether the visible and invisible characters that formed a word could be grouped together by the effect of same-object advantage-an index used to indicate the formation of perceptual grouping and the basis for attentional selection (i.e. object-based attention). Results revealed a difference in the judgments of prior entry that would otherwise be equivalent between two concurrent targets in a cued temporal-order judgment task: the target that appeared in the cued word was judged to appear first more frequently than the other target that appeared in the uncued word. The results suggest that a perceptual grouping was formed for two-character words between visible and invisible constituent characters. While grouping within two-character words occurred, the invisible characters remained invisible in most of the trials, suggesting that this grouping occurred unconsciously. This implies that, in reading, characters presented in the peripheral region can be grouped into words even without the readers' awareness of all the constituent characters, and such unconscious grouping can facilitate fluent reading by aggregating the texts into fewer meaningful units and thus reduce the number of fixations needed.
Interocular grouping occurs when different parts of an image presented to each eye bound into a coherent whole. Previous studies anticipated that these parts are visible to both eyes simultaneously (i.e., the images altered back and forth). Although this view is consistent with the general consensus of binocular rivalry (BR) that suppressed stimuli receive no processing beyond rudimentary level (i.e., adaptation), it is actually inconsistent with studies that use continuous flash suppression (CFS). CFS is a form of interocular suppression that is more stable and causes stronger suppression of stimuli than BR. In the present study, we examined whether or not interocular grouping needs to occur at a conscious level as prior studies suggested. The modified double-rectangle paradigm used by Egly, Driver, and Rafal (1994) was adopted, and object-based attention was directed for successful grouping. To induce interocular grouping, we presented complementary parts of two rectangles dichoptically for possible interocular grouping and a dynamic Mondrian in front of one eye (i.e., CFS). Two concurrent targets were presented after one of the visible parts of the rectangles was cued. Participants were asked to judge which target appeared first. We found that the target showed on the cued rectangle after interocular grouping was reported to appear first more frequently than the target on the uncued rectangle. This result was based on the majority of trials where the suppressed parts of the objects remained invisible, which indicates that interocular grouping can occur without all the to-be-grouped parts being visible and without awareness.
Detection of a target is faster when it is presented on an attended rather than an unattended object (i.e., objectbased attention). Using the double-rectangle cuing paradigm (Egly, Driver, & Rafal, 1994), we previously showed that object-based attention operates on a dynamic representation: Object-based attentional guidance is affected by subsequent changes occurring to an attended object (Lin & Yeh, 2011). The present study provides further support for our dynamicupdating hypothesis, demonstrating that changes are indeed updated into the existing object representation. After a cue display, we introduced changes between the initial display (four hashes) and the final display (four squares with an occluder between them). We found object-based attention only with smooth transitions between the initial and final displays, not when transitions were in the reverse order (Exp. 1) or contained any single disruption of the smooth transition (Exp. 2). These results confirm our hypothesis that attention operates on a dynamic object representation that is constantly and continuously updated.
We investigated the spatial summation effect on pedestals with difference luminance. The targets were luminance modulation defined by Gaussian functions. The size of the Gaussian spot was determined by the scale parameter (standard deviation, σ) which ranged from 0.13 o to 1.04 o . The local luminance pedestal (2 o radius) had mean luminance ranged from 2.9 to 29cd/m 2 . The no-pedestal condition had a mean luminance 58cd/m 2 . We used a QUEST adaptive threshold seeking procedure and 2AFC paradigm to measure the target contrast threshold at different target sizes (spatial summation curve) and pedestal luminance. The target threshold decreased as the target spatial extent increased with a slope -0.5 on log-log coordinates.However, if the target size was large enough (σ >0.3 o ), there was little, if any, threshold reduction as the target size further increased. The spatial summation curve had the same shape at all pedestal luminance levels. The effect of the pedestal was to shift the summation curve vertically on log-log coordinates. Hence, the size and the luminance effects on target detection are separable. The visibility of the Gaussian spot can be modeled by a function with a form f(L)*g(σ) where f(L) is a function of local luminance and g(σ) is a function of size.
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