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In the Introduction, we developed the hypothesis that the selection of a given spatial reference frame in position priming of pop-out search is contingent on the display factors, such as the predictability of the placement of the items across trials. A related idea is that positional priming is always supported by multiple �C spatiotopic and object-centered �C reference frames, but that their relative contributions to overall priming differ as a function of the predictability of the item placements. Based on an evaluation of previous investigations of the position priming task, the two experiments reported here tested the assumption that target location priming is more strongly supported by object-centered representations (Maljkovic and Nakayama, 1996) and that predictability  can determine  whether a spatiotopic reference frame can be used and, if so, to which extent it would contribute to positional priming (Ball et al., 2009, 2010). The results obtained were in line with these predictions. To our knowledge, this is the first time that the effects of the predictability of item sequences have been shown to influence positional priming. Earlier studies have looked at the effects of predictability of repetitions on immediate position and feature priming effects (Maljkovic and Nakayama, 1994, 2000; Maljkovic and Martini, 2005; Geyer and M��ller, 2009). These studies typically show that re-presentation of the target at a previous location (or, respectively, re-presentation of the target color) across [http://www.selleckchem.com/products/dinaciclib-sch727965.html SCH727965 purchase] longer sequences of trials leads to larger, that is, cumulative, priming effects. Geyer and M��ller (2009) found that priming increased with each stimulus repetition and that this increase was larger when position/color repetitions occurred on the majority of trials and, thus, were expected (they compared priming effects in this high-repeat condition with priming effects in a baseline condition in which position/color repetitions vs. changes were equally likely �C importantly, priming effects in the two conditions were compared between  identical sequences of repeat trials). They interpreted this result as evidence for an effect of top�Cdown expectancy on color and position priming. However, the transition of target location priming from an object-centered to a spatiotopic reference frame as a function of expectation is a novel finding and adds to the existing evidence on top�Cdown controlled priming. For example, Summerfield et al. (2008) compared responses to repeated and non-repeated face stimuli measured by functional magnetic resonance imaging (fMRI). The important finding was that of reductions of blood oxygen level-dependent (BOLD) responses on repeated compared to non-repeated trials (i.e., repetition suppression, Grill-Spector et al., 2006) being larger when repetitions were frequent and thus expected.