Why is it so hard to find a needle in a haystack? Is it because the needle is small? Likely not, if the needle were red, or the needle were shaped like a ball, it would be pretty easy to find, needles get lost in haystacks because in order to be distinguished from the hay around them two features, colour and shape, must be processed at the same time, and this takes attention. This topic has been explored experimentally using the ‘visual search’ paradigm (e.g., Treisman and Gelade (1980)). In this paradigm participants are asked to look for a specific target among distractor stimuli. The target may differ from distractors in one or more of its features and there may be a few or a large number of distractors. Differences in response times for target detection across condition has helped psychologists better understand many aspects of visual information processing.