How Temporal Preparation Influences Spatial Selection

Abstract

Studies provide evidence that temporal preparation facilitates spatial selection in visual search. According to visual search models, spatial selection of stimuli can be influenced by several factors such as bottom-up salience, top-down goals, and prior selection history. The question is how temporal preparation facilitates spatial selection. To this end, this dissertation investigated whether temporal preparation affects spatial selection by influencing bottom-up and/or top-down processing. To manipulate temporal preparation, a constant foreperiod (FP) paradigm was applied in which the interval between an auditory warning signal and a subsequent search display was varied (i.e., short or long FP). Study 1, a series of behavioral experiments, aimed to investigate whether temporal preparation interacts with target salience, examining bottom-up processing, or with prior knowledge of the target constancy, corresponding to the formation of a top-down representation. Participants’ (experiment 1: N = 24, experiment 2: N = 32) task was to find a pop-out target among homogeneous distractors. Replicating previous findings, Study 1 showed an FP effect in reaction time (RT), i.e., an indicator of temporal preparation. Most importantly, this FP effect did not interact with target salience or target constancy. These RT results do not support a direct influence of temporal preparation on bottom-up or top-down processing in visual search. In Study 2, event-related potentials (ERPs) were measured to investigate whether temporal preparation facilitates spatial selection as a function of target salience, and thus bottom-up processing. Participants (N = 24) searched for a salient target among homogeneous distractors, with the N2pc being measured as an index of spatial selection. Temporal preparation accelerated the spatial selection of the target, as indexed by a reduction of the onset latency of the target N2pc. Furthermore, temporal preparation reduced the onset latency of the N2pc to a greater extent for low salient targets than for high salient targets. This result provides evidence that temporal preparation facilitates spatial selection as a function of stimulus salience. In addition, Study 3 aimed to further investigate the influence of temporal preparation on bottom-up and top-down processes in spatial selection. Therefore, participants (N = 24) performed a visual search task for a shape target while ignoring a color singleton distractor. Interestingly, temporal preparation also modulated the amplitude of the N2pc elicited by the salient but task-irrelevant distractor. This finding supports the notion that temporal preparation influences the processing of all salient stimuli in spatial selection, regardless of their task-relevance. Taken together, the results of the two ERP studies (Studies 2 and 3) provide evidence that temporal preparation facilitates spatial selection by influencing bottom-up processing.