You’re in the Psychology section looking for a book. You know it is big and red. How long will it take you to search for it? It probably depends on how many big books there are, and how many red books there are. If there are lots, your search might take a while. Why can’t just process all the books at the same time and home in immediately on just the one we want? The factors that make a ‘visual search’ task hard, or easy, reveal the functions and the limitations of our attention. This lecture will trace the history of visual search theories, and the clever solutions that each have proposed to explain the complexities of visual search behaviour, though not always very successfully.