Search

Visual search requires the maintenance of a search template in visual working memory in order to guide attention towards the target. This raises the question whether a search template is essentially the same as a visual working memory representation used in tasks that do not require attentional guidance, or whether it is a qualitatively different representation. Two experiments tested this by comparing electrophysiological markers of visual working memory maintenance between simple recognition and search tasks. For both experiments, responses were less rapid and less accurate in search task than in simple recognition. Nevertheless, the contralateral delay activity (CDA), an index of quantity and quality of visual working memory representations, was equal across tasks. On the other hand, the late positive complex (LPC), which is sensitive to the effort invested in visual working memory maintenance, was greater for the search task than the recognition task. Additionally, when the same target cue was repeated across trials (Experiment 2), the amplitude of visual working memory markers (both CDA and LPC) decreased, demonstrating learning of the target at an equal rate for both tasks. Our results suggest that a search template is qualitatively the same as a representation used for simple recognition, but greater effort is invested in its maintenance. [ABSTRACT FROM AUTHOR]

Prominent theories of attention claim that visual search is guided through attentional templates stored in working memory. Recently, the contralateral delay activity (CDA), an electrophysiological index of working memory storage, has been found to rapidly decrease when participants repeatedly search for the same target, suggesting that, with learning, the template moves out of working memory. However, this has only been investigated with pop-out search for distinct targets, for which a strong attentional template may not be necessary. More effortful search tasks might rely more on an active attentional template in working memory, leading to a slower handoff to long-term memory and thus a slower decline of the CDA. Using ERPs, we compared the rate of learning of attentional templates in pop-out and effortful search tasks. In two experiments, the rate of decrease in the CDA was the same for both search tasks. Similar results were found for a second component indexing working memory effort, the late positive complex. However, the late positive complex was also sensitive to anticipated search difficulty, as was expressed in a greater amplitude before the harder search task. We conclude that the amount of working memory effort invested in maintaining an attentional template, but not the rate of learning, depends on search difficulty. [ABSTRACT FROM AUTHOR]

Trial-to-trial feature repetition speeds response times in pop-out visual search tasks. These priming effects are often ascribed to a short-term memory system. Recently, however, it has been reported that a 'build-up' sequence of repetitions could facilitate responses over 16 trials later - well beyond twice the typically reported time course (Vision Research, 2011, 51, 1972-1978). Here, we first report two replication attempts that yielded little to no support for such long-term priming of pop-out. The results instead fell in line with the predictions of a previously proposed computational model that describes priming as short-lived facilitation that decays over approximately eight trials (Vision Research, 2010, 50, 2110-2115). In the second part of this study, we show that these data are consistent with a simple formulation of decay with a single timescale, and that there is no significant priming beyond eight trials. [ABSTRACT FROM AUTHOR]