Abstract
Limited attention capacity results that not all the stimuli present in the visual field are equally processed. While processing of salient stimuli is automatically boosted by bottom‑up attention, processing of task‑relevant stimuli can be boosted volitionally by top‑down attention. Usually, both top‑down and bottom‑up influences are present simultaneously, which creates acompetition between these two types of attention. We examined this competition using both behavioral and electrophysiological measures. Participants responded to letters superimposed on background pictures. We assumed that responding to different conditions of the letter task engages top‑down attention to different extent, whereas processing of background pictures of varying salience engages bottom‑up attention to different extent. To check how manipulation of top‑down attention influences bottom‑up processing, we measured evoked response potentials (ERPs) in response to pictures (engaging mostly bottom‑up attention) during three conditions of aletter task (different levels of top‑down engagement). Conversely, to check how manipulation of bottom‑up attention influences top‑down processing, we measured ERP responses for letters (engaging mostly top‑down attention) while manipulating the salience of background pictures (different levels of bottom‑up engagement). The correctness and reactiontimes in response to letters were also analyzed. As expected, most of the ERPs and behavioral measures revealed atrade‑off between both types of processing: adecrease of bottom‑up processing was associated with an increase of top‑down processing and, similarly, adecrease of top‑down processing was associated with an increase in bottom‑up processing. Results proved competition between the two types of attentions.
Highlights
Top‐down and bottom‐up competitionAttention is traditionally perceived as a filter which limits the overwhelming amount of information we receive every second
The more resources utilized by the top‐down system, the less are available for bottom‐up processing (Berger et al 2005, Hopfinger and West 2006, Okon‐Singer et al 2007)
To check how intensification of top‐down attention influ‐ ences bottom‐up processing, we measured evoked response potentials (ERPs) respons‐ es for pictures while manipulating task conditions, and, to check how intensification of bottom‐up attention influences top‐down processing, we mea‐ sured ERP responses for task‐letters while manipulating salience of pictures presented as a background
Summary
Top‐down and bottom‐up competitionAttention is traditionally perceived as a filter which limits the overwhelming amount of information we receive every second. The choice of information for further processing is guided by: i) stimulus salience (related to emotional arousal, novelty, suddenness and gener‐ al distinctiveness from other competing stimuli), and ii) behavioral relevance to the current task and estab‐ lished goals (Mayer et al 2004) This dichotomy be‐ tween automatically and voluntarily guided attention reflects the functional distinction between the bot‐ tom‐up and top‐down systems. Both of them constant‐ ly interact with each other in order to maintain the ef‐ ficiency of goal‐related actions whilst simultaneously monitoring the environment to allow for processing of unexpected but important events (Corbetta and Shul‐ man 2002, Theeuwes 2010). By means of evoked potentials we measured how bottom‐up and top‐down processing of visual stimuli is affected by competition between systems during processing of visual stimuli
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