Introduction to the Special Issue on Binding

In many ways visual processing acts as a prism, splitting visual information from the retinal image into separately processed visual features such as colours, shapes, sizes, or orientations. Binding refers to the set of cognitive and neural mechanisms that re-integrate these features to create a holistic representation of the objects in the visual field. The binding problem in vision refers to how this integration is achieved. Because binding processes must be applied to virtually every level of visual processing, the binding problem is a ubiquitous one that applies to perception, attention, working memory, and long-term memory systems. It is more appropriate, therefore, to conceptualize the binding problem not as a singular problem, but as a constellation of interrelated problems. For example, how does one perceive and represent the fact that features a, b, and c belong to object X while features q, r, and s belong to object Y? How does one perceive and represent the relationships among objects such as the fact that object Y is to the left of object X and to the right of object Z? How does one perceive and represent that events x and y are temporally related to each other, but are distinct from events p and q? What happens to bound representations when the relations among features, objects, or events change? How functional are these representations in the service of visuallyguided tasks? This special issue of Visual Cognition provides a sampling of current work being done in visual perception and visual memory to understand how human observers accomplish the appropriate binding of features within objects, the relational binding among objects, and the binding between temporally related events. Within these broad areas, the articles cover a wide range of topics including the role of attention in feature binding, the representation of static and moving multi-feature objects in memory, the binding of objects to scenes, binding processes involved in learning and longterm memory, binding of information about objects perceived in visual and non-visual modalities, the development of binding abilities, and the neural substrates involved in binding processes. The goal of this special issue is not to disseminate conclusive solutions to the various instantiations of the binding problem. Although this collection of articles converges on several theoretical points, there are also examples of clear divergence. It is our hope, rather, that this collection of work will describe the current state-of-the-science regarding binding processes in visual perception and memory, outline the critical issues that have yet to be resolved, and highlight the interconnections between the binding problems and the approaches taken to solve them. In this single volume readers will encounter work with children, young adults, and patients, and work that uses traditional behavioural measures, eye movement recording, functional imaging, and transcranial magnetic stimulation. The special issue begins by examining the role attention plays in binding. Although attention will be important in many of the articles in this volume, the first set of papers make it their primary focus and take up the classic and hotly debated question regarding the degree to which, and conditions under which, binding relies on focused attention. Hyun, Woodman, and Luck examined the attentional requirements of explicitly binding surface features to their spatial locations in visual perception. The authors asked observers to either indicate whether a target color was present in a display, or to report the location of the target color. While the first task simply required observers to detect a feature, the second task additionally