Abstract
Hierarchical letters are large letters composed of smaller letters that form the global and local levels respectively. Our study uses these letters to study attentional control of multi-level item perception. A key aspect of attentional control is shielding, or the inhibition of irrelevant information (Neill, 1977). Studies show that irrelevant global information can interfere with local level processing, producing slower response times (RTs) for the local level (e.g., Navon, 1977). This indicates poor attentional control during local level processing. Interestingly, overall response times become faster when the relevant level is repeated, and especially with multiple repetitions (Lamb et al. 1998; Ward, 1982). Our study tests whether multiple repetitions can increase attentional control, by aiding the shielding of irrelevant global information. The experiment was organized into blocks, or runs, of seven trials; trials were identified by their sequential position within the run (e.g., the first trial is position one). At the beginning of each run, participants were given a target letter (A, E, G, K, U) and relevant level (global or local). Critical runs contained six congruent letters (e.g., large A made of smaller A’s) and one incongruent letter (e.g., large A made of smaller E’s). For each position, participants had to verify target letter presence at the relevant level. On the critical runs, every position in the run contained the target letter. Conditions varied based on whether positions two or six presented the incongruent letter, representing the single and multiple repetition conditions respectively. RTs for every position were recorded. For both global- and locally-focused runs, RTs became faster with each repetition. However, there was no increase in attentional control for the local runs; equal amounts of global interference occurred at position two and position six. These results show that multiple repeated exposures did not improve attentional control.