Keeping the eyes on a fixation point modulates how a symbolic cue orients covert attention

Keeping the eyes on a fixation point modulates how a symbolic cue orients covert attention Michele Burigo (mburigo@cit-ec.uni-bielefeld.de) Cognitive Interaction Technology Excellence Center, University of Bielefeld, 33615, Bielefeld, Germany Pia Knoeferle (knoeferl@cit-ec.uni-bielefeld.de) Cognitive Interaction Technology Excellence Center, University of Bielefeld, 33615, Bielefeld, Germany Abstract of the paradigm, participants are asked to keep their eye gaze on a (typically centrally-presented) fixation cross while they are asked to respond behaviorally to a peripheral target stimulus to which attention is either cued (e.g., by an arrow pointing in its direction) or not. Maintaining fixation ensures that the paradigm elicits covert (rather than overt 1 ) attention shifts to the peripheral target stimulus. Overall, results from this paradigm have shown that an attentionally cued relative to an uncued non-central target stimulus elicits faster covert attention shifts and response latencies (e.g., in a binary target discrimination task). We use the spatial cuing paradigm to investigate the extent to which maintaining fixation interferes with covert shifts of attention. Following the idea of limited resources (Kahneman, 1973), performance in covert orienting should be impaired if participants are engaged in a concurrent resource-taxing fixation task. This is in line with the studies on covert attention showing that a central-monitoring task affects the property of a peripheral cue to attract attention at a short SOA (Santangelo, Olivetti Belardinelli, & Spence, 2007; Santangelo, Botta, Lupianez & Spence, 2011). Despite this evidence, a positive cueing effect (the latency difference between responding to a target at a cued location versus an uncued location) emerged even when participants maintained fixation (e.g., Downing; 1988; Eimer, 1994; Hawkins, Hillyard, Luck, Mouloua, Downing & Woodward, 1990). One possible explanation is that in these studies, participants did not receive any feedback on their fixation behavior during the experiment. In the absence of feedback, participants may not have been aware of their performance and they may thus have allocated few resources to maintaining fixation and instead focused on shifting covert attention to the cued location, eliciting a cueing effect. To the extent that this reasoning holds, post-trial feedback every time participants move their eyes away from the fixation cross should make fixating more attention- demanding. Then, according to the limited resources view, we should observe interference in the cueing task, that is a reduced cuing effect. On the other hand, if keeping the eyes Studies on covert attention usually monitor participants’ eye movements in order to prevent participants from moving their eyes away from a central fixation point. However, given our frequently dynamic attention behavior, keeping the gaze on a fixation point may be effortful and require attentional resources. If so, then trying to maintain fixation should interfere with covert attention orienting because both maintaining fixation and attention orienting require attentional resources. Here we present two eye tracking experiments showing that the amount of attentional resources involved in maintaining fixation affects how an arrow orients covert attention. Keywords: visual attention; covert attention; spatial cueing; eye movements Introduction It is an interesting fact about visual attention that people can shift their attention covertly while overtly fixating a central point (Posner, Snyder, & Davidson, 1980). Studies on covert attention shifts often instruct participants to fixate a cross in the middle of the screen while they are engaged in another task requiring them to shift their attention covertly away from the cross. However, keeping the eye on a fixation point goes against the natural tendency to explore the environment with the eyes (Hermens & Walker, 2010; Munoz, 2002; Rolfs, 2009). This suggests that maintaining fixation may involve attentional effort (Dauwels, Vialatte & Cichocki, 2010). Despite these observations, we so far do not know whether maintaining fixation does indeed require attentional resources and how it affects other attentional processes such as covert attention shifts. Attentional-based interference It is well known that attention has limited processing capacity (Kahneman, 1973) and when engaged in two concurrent activities (both requiring attentional resources), interference is observed (Pashler, 1994). Accordingly, keeping the eye on the fixation cross should interfere with any attention-demanding task performed simultaneously. The spatial cuing paradigm is a good example of such a situation. Introduced by Posner (1980), it has become an established paradigm in the investigation of covert attention shifts. In Posner’s classical study, as in more recent variants Overt attention shifts are accompanied by an eye movement while ‘covert’ attention shifts are shifts of the attention focus without a corresponding overt eye movement.