In search of the focus of attention in working memory: 13 years of the retro-cue effect

The concept of attention has a prominent place in cognitive psychology. Attention can be directed not only to perceptual information, but also to information in working memory (WM). Evidence for an internal focus of attention has come from the retro-cue effect: Performance in tests of visual WM is improved when attention is guided to the test-relevant contents of WM ahead of testing them. The retro-cue paradigm has served as a test bed to empirically investigate the functions and limits of the focus of attention in WM. In this article, we review the growing body of (behavioral) studies on the retro-cue effect. We evaluate the degrees of experimental support for six hypotheses about what causes the retro-cue effect: (1) Attention protects representations from decay, (2) attention prioritizes the selected WM contents for comparison with a probe display, (3) attended representations are strengthened in WM, (4) not-attended representations are removed from WM, (5) a retro-cue to the retrieval target provides a head start for its retrieval before decision making, and (6) attention protects the selected representation from perceptual interference. The extant evidence provides support for the last four of these hypotheses

Processing resources and interplay among sensory modalities: an EEG investigation

The primary aim of the present thesis was to investigate how the human brain handles and distributes limited processing resources among different sensory modalities. Two main hypothesis have been conventionally proposed: (1) common processing resources shared among sensory modalities (supra-modal attentional system) or (2) independent processing resources for each sensory modality. By means of four EEG experiments, we tested whether putative competitive interactions between sensory modalities – regardless of attentional influences – are present in early sensory areas. We observed no competitive interactions between sensory modalities, supporting independent processing resources in early sensory areas. Consequently, we tested the influence of top-down attention on a cross-modal dual task. We found evidence for shared attentional resources between visual and tactile modalities. Taken together, our results point toward a hybrid model of inter-modal attention. Attentional processing resources seem to be controlled by a supra-modal attentional system, however, in early sensory areas, the absence of competitive interactions strongly reduces interferences between sensory modalities, thus providing a strong processing resource independence