Contributions from 19th Century scholars to binocular rivalry research are well recognized, however, observations concerning the phenomenon commenced centuries earlier and suggest a rich seam of research that is much less well known. This chapter discusses these early investigations, along with conflicting views and observations thereafter. We also discuss the early application of notions of attention and consciousness to rivalry. Such notions have more recently been the subject of concerted investigation into distinguishing brain activity mediating the rivaling states from that underlying visual stimulation. Observations in the literature that preceded this key principle are discussed. We also trace the rivalry studies that followed and note their relevance to current thinking on the phenomenon. * TTN supported by NHMRC (ID 490976). We thank Steven Miller and Jakob Hohwy for providing helpful comments on the manuscript.

Visual attention is used to select part of the visual array for higher-level processing. Visual selection can be based on spatial location, but it has also been demonstrated that multiple locations can be selected simultaneously on the basis of a visual feature such as color. One task that has been used to demonstrate feature-based attention is the judgement of the symmetry of simple four-color displays. In a typical task, when symmetry is violated, four squares on either side of the display do not match. When four colors are involved, symmetry judgements are made more quickly than when only two of the four colors are involved. This indicates that symmetry judgements are made one color at a time. Previous studies have confounded lightness, hue, and saturation when defining the colors used in such displays. In three experiments, symmetry was defined by lightness alone, lightness plus hue, or by hue or saturation alone, with lightness levels randomised. The difference between judgements of two- and four-color asymmetry was maintained, showing that hue and saturation can provide the sole basis for feature-based attentional selection.

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