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Previous studies have produced contradictory findings regarding whether emotion exerts facilitative effects or inhibitory effects on perception. In the present study, we hypothesized that attention can be separated into the initial selection stage and the latter consolidation stage, and emotion plays a different role in each of these two stages. To test this hypothesis, we adopted the dual-stream rapid serial visual presentation paradigm (Goodbourn & Holcombe, Journal of Experimental Psychology: Human Perception and Performance, 41(2), 364-384, 2015), which provided separate measurements for selection latency (how delayed the attentional selection process is) and efficacy (how much information can be successfully consolidated for conscious report). The results suggested emotion's dual role on perception. Firstly, the presence of negatively charged visual targets (which were Chinese characters in the present study) accelerated attention selection, and the acceleration effect could spread to different locations in the visual field. Secondly, negatively charged characters preoccupied attentional resources for consolidation, yielding location-specific facilitative and inhibitory effects.

Perceptual grouping is the process through which the perceptual system combines local stimuli into a more global perceptual unit. Previous studies have shown attention to be a modulatory factor for perceptual grouping. However, these studies mainly used explicit measurements, and, thus, whether attention can modulate perceptual grouping without awareness is still relatively unexplored. To clarify the relationship between attention and perceptual grouping, the present study aims to explore how attention interacts with perceptual grouping without awareness. The task was to judge the relative lengths of two centrally presented horizontal bars while a railway-shaped pattern defined by color similarity was presented in the background. Although the observers were unaware of the railway-shaped pattern, their line-length judgment was biased by that pattern, which induced a Ponzo illusion, indicating grouping without awareness. More importantly, an attentional modulatory effect without awareness was manifested as evident by the observer's performance being more often biased when the railway-shaped pattern was formed by an attended color than when it was formed by an unattended one. Also, the attentional modulation effect was shown to be dynamic, being more pronounced with a short presentation time than a longer one. The results of the present study not only clarify the relationship between attention and perceptual grouping but also further contribute to our understanding of attention and awareness by corroborating the dissociation between attention and awareness.

Based on the finding that perception is lagged by attention split on multiple features (Lo et al., 2012), this study investigated how the feature-based lag effect interacts with the target spatial arrangement. Participants were presented with gratings the spatial frequencies of which constantly changed. The task was to monitor two gratings of the same or different colors and report their spatial frequencies right before the stimulus offset. The results showed a perceptual lag wherein the reported value was closer to the physical value some time prior to the stimulus offset. This lag effect was larger when the two gratings were of different colors than when they were the same color. Furthermore, the feature-based lag effect was statistically significant when the two gratings were horizontally arranged but not when they were vertically or diagonally arranged. A model is proposed to explain the effect of target arrangement: When targets are horizontally arranged, selecting an additional feature delays perception. When targets are vertically or diagonally arranged, target selection for the lower field is prioritized. This prioritization on the lower target might prompt observers to only select the lower target and ignore the upper one, and this causes more perceptual errors without delaying perception., (© 2017 Elsevier B.V. All rights reserved.)

In a previous study Lo, Howard, & Holcombe (Vision Research 63:20-33, 2012), selecting two colors did not induce a performance cost, relative to selecting one color. For example, requiring possible report of both a green and a red target did not yield a worse performance than when both targets were green. Yet a cost of selecting multiple colors was observed when selection needed be contingent on both color and location. When selecting a red target to the left and a green target to the right, superimposing a green distractor to the left and a red distractor to the right impeded performance. Possibly, participants cannot confine attention to a color at a particular location. As a result, distractors that share the target colors disrupt attentional selection of the targets. The attempt to select the targets must then be repeated, which increases the likelihood that the trial terminates when selection is not effective, even for long trials. Consistent with this, here we find a persistent cost of selecting two colors when the conjunction of color and location is needed, but the cost is confined to short exposure durations when the observer just has to monitor red and green stimuli without the need to use the location information. These results suggest that selecting two colors is time-consuming but effective, whereas selection of simultaneous conjunctions is never entirely successful.

According to a limited-resource account of feature-based attention, dividing feature-based attention by selecting targets on the basis of different features dilutes its power. Multiple-feature costs have been documented previously, but it is not clear whether the multiple-feature cost arose at the selection (segregating targets from non-targets) stage predicted by the limited-resource account. The cost might instead result from a post-selection difficulty in processing or accessing the contents of the targets. By defining the targets with a selection attribute (color) that is very distinct from the attribute participants must access and report (spatial period), we were able to manipulate the selection process independently from the access stage. We still found a cost for different selection features (colors), suggesting that multiple-feature costs can arise at the selection stage. The cost was only significant however when distracters were present that shared the selection features. The cost manifested not only as greater errors or less precision in reporting the access attribute (spatial period), but also as an increased temporal lag between the physical stimuli and the reported percept. In summary, splitting selection among different features incurred little or no penalty by itself, but selection interference by distracters sharing target features could be large and could slow processing., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Studies showing human behavior influenced by subliminal stimuli mainly focus on implicit processing per se, and little is known about its interaction with explicit processing. We examined this by using the Simon effect, wherein a task-irrelevant spatial distracter interferes with lateralized response. Lo and Yeh (2008) found that the visual Simon effect, although it occurred when participants were aware of the visual distracters, did not occur with subliminal visual distracters. We used the same paradigm and examined whether subliminal and supra-threshold stimuli are processed independently by adding a supra-threshold auditory distracter to ascertain whether it would interact with the subliminal visual distracter. Results showed auditory Simon effect, but there was still no visual Simon effect, indicating that supra-threshold and subliminal stimuli are processed separately in independent streams. In contrast to the traditional view that implicit processing precedes explicit processing, our results suggest that they operate independently in a parallel fashion., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Consciousness researchers are interested in distinguishing between mental activity that occurs with and without awareness (i.e., explicit versus implicit processes). The inattentional blindness (IB) paradigm is an excellent tool for this question because it permits the independent manipulation of processing time and awareness. In the present study, we show that implicit texture segregation can occur during inattentional blindness, provided that the texture is exposed for a sufficient duration. In contrast, a Simon effect does not occur during inattentional blindness, even with similar exposure duration of the critical stimulus. This reveals a dissociation between processing time and awareness, consistent with the possibility of separate processing streams for explicit and implicit visual perception.