UC Davis

When searching for a target object (e.g., a friend at a party), we engage in a continuous “look-identify” cycle in which we use known features (e.g., hair color) to guide attention and eye gaze towards potential targets and then to decide if it is indeed the target. Theories of attention refer to the information about the target in memory as the “target” or “attentional” template and typically characterize it as a single, fixed, source of information. In this doctoral thesis, I provide evidence that templates do not necessarily represent the veridical properties of the target item, but rather are adapted to the current context (e.g., distractors, task demands, etc.) to improve visual search efficiency. In Chapter 2, I investigated the behavioral mechanisms by which modulations in the target template might increase the representational distinctiveness of targets from expected distractors. I argue that template shifting and asymmetrical sharpening are two mechanisms that increase the template-to-distractor distinctiveness, which makes target selection and decisions more efficient. In Chapter 3, I assessed the brain mechanisms that support these changes in target representations to optimize target-match decisions. I found that sensory-veridical target information is transformed in lateral prefrontal cortex into an adaptive code of target-relevant information that optimize decision processes during visual search. In Chapter 4 and 5, I investigated how template information operates to guide attention and make identity decisions during visual search. I argue that attentional guidance operates on a coarser code to weight sensory information and target match decisions use a more precise representation to determine identity. Across these studies, the results reveal the flexible nature of target templates that are used to guide visual search.