Physically salient stimuli in the visual field tend to capture attention rapidly and automatically, leading to the perceived pop-out effect in visual search. There is much debate about if and how top-down preparatory processes influence visual attention when salient stimuli are present. Experience with a task involves learning at multiple levels of cognitive processing, and it can be difficult to distinguish these learning effects from the effect of a ‘one-shot’ act of top-down preparation on a given trial. That is, preparing to attend to a particular colour might influence search on a given trial, but that act of preparation may also become embedded in a memory representation that carries over to influence future search events. Moreover, such learning effects may accumulate with repeated experiences of preparing in a particular way. The goal of the present thesis was to examine specifically how preparation at one point in time affects pop-out search at a later point in time. To this end, I present the following empirical contributions: I introduce a novel method for studying preparation effects in search for a salient singleton target; I use this new method to explore the contribution of learning and memory to effects of preparation on singleton search, and outline a number of boundary conditions of this new method; and I distinguish between two components of the reported preparatory effects, one related to preparing to attend to a particular feature, and one related to preparing to ignore a particular feature. Together, these contributions highlight the contribution of top-down preparation to memory representations that guide attention in singleton search, and offer a novel method that researchers can use to ask unanswered questions about the roles of preparation and experience in singleton search. / Thesis / Doctor of Philosophy (PhD) / Imagine looking out over a farmer’s field. All you can see is green grass, except for a big red tractor parked off in the distance. In this scenario, the contrast of the tractor’s colour and shape against the uniform grass will tend to draw attention to the tractor, making it immediately noticeable. This pop-out effect is often thought to be driven solely by physical stimulus features. However, past experiences searching through visual scenes can also affect the degree to which salient objects pop-out, suggesting that pop-out is influenced by memory. This thesis is centered around the memory processes that influence visual search for pop-out targets. I focus specifically on how deliberate preparation for particular search targets at one moment in time can lead to learning that influences pop-out search at later moments.