What captures attention? Under which circumstances can visual attention be captured? For over a century, the control of visual attention has been examined in terms of top-down and bottom-up processes. The top-down guidance of attention derives from the knowledge one has about what one wants to find. The bottom-up guidance of attention derives from when something in an image is unique and contrasts with what surrounds it. This book first reviews the literature on the visual attributes that guide attention in visual search. The second part of this book reviews the results from a set of experiments that utilize a novel visual search procedure to address the role of top-down and bottom-up processes in visual search for conjunctions of features (for example, a real-world object may be defined as a conjunction of color and shape, like a red and round apple). The main experimental result is that bottom-up processes guide attention in a conjunction search task. These results and this method can be applied to the study of both normal cognition and special populations, such as persons with ADHD, Autism, or Schizophrenia. The book is addressed to professionals in psychology, cognitive neuroscience, vision, and philosophy. It is also directed towards clinical researchers with an interest in applying visual search and attention methods.