Search

It has been proposed that covert visual search can be fast, efficient, and stimulus driven, particularly when the target is defined by a salient single feature, or slow, inefficient, and effortful when the target is defined by a nonsalient conjunction of features. This distinction between fast, stimulus-driven orienting and slow, effortful orienting can be related to the distinction between exogenous spatial attention and endogenous spatial attention. Several studies have shown that exogenous, covert orienting is limited to the range of saccadic eye movements, whereas covert endogenous orienting is independent of the range of saccadic eye movements. The current study examined whether covert visual search is affected in a similar way. Experiment 1 showed that covert visual search for feature singletons was impaired when stimuli were presented beyond the range of saccadic eye movements, whereas conjunction search was unaffected by array position. Experiment 2 replicated and extended this effect by measuring search times at 6 eccentricities. The impairment in covert feature search emerged only when stimuli crossed the effective oculomotor range and remained stable for locations further into the periphery, ruling out the possibility that the results of Experiment 1 were due to a failure to fully compensate for the effects of cortical magnification. The findings are interpreted in terms of biased competition and oculomotor theories of spatial attention. It is concluded that, as with covert exogenous orienting, biological constraints on overt orienting in the oculomotor system constrain covert, preattentive search. [ABSTRACT FROM AUTHOR]

We typically move attention around the environment with overt eye-movements. However, it is also possible to orient attention covertly, such that the 'spotlight' of attention is moved independently of the locus of gaze. While there is enduring debate about the relationship between the mechanisms controlling covert and overt attention, one influential view is that shifts of covert attention are achieved by planning (but not executing) and overt eye movement. We have previously shown that placing stimuli at locations beyond the effective oculomotor range (EOMR) interfered with covert, exogenous orienting to peripheral cues but not covert endogenous orienting driven by symbolic cues (e.g. Smith et al., 2012; Smith & Casteau 2019). Here, we examined whether the association between exogenous attention and the EOMR observed in cueing tasks generalised to visual search tasks. We first measured the EOMR for each participant, then presented search arrays that were either within or beyond their EOMR. Feature search was significantly slower when stimuli were presented beyond the range of eye-movements whereas conjunction search was unaffected. In a second study we parametrically varied the location of the array to better establish how well changes in search performance mapped onto the range of eye-movements. The results confirmed that preattentive search was restricted to the locations within the range of eye-movement. We conclude that optimal covert, exogenous orienting of attention depends on the oculomotor system, consistent with an Oculomotor Readiness hypothesis of Exogenous Orienting. [ABSTRACT FROM AUTHOR]

Biased competition theory assumes that shift of attention is biased towards visual stimuli that matched the content of the visual working memory (VWM) and this bias might be due to a competition between eye-movement motor plans and memory object location. Here, we measured the effect of holding an item in VWM on pre-saccadic shift of attention by measuring attention when the goal of an eye-movement is congruent or incongruent with the location of an object sharing properties with the VWM content. Participants performed an eye-movement towards a previously specified location (Saccade Target, ST) and make a discrimination decision (Discrimination Target, DT). They also had to retain a visual feature in VWM for the whole duration of the trial (Memory Target; MT). There were four different conditions: 1) MT congruent with ST and DT, 2) MT congruent with DT but incongruent with ST, 3) MT congruent with ST but incongruent with DT, 4) MT incongruent with ST and DT. As expected, pre-saccadic attentional facilitation was greatest when the VWM content, the saccade direction and the discrimination location were all congruent, and abolished when ST, DT and MT were at different locations. Critically, when the ST and DT were in the same location but the MT at a different location pre-saccadic attentional facilitation was significantly reduced, suggesting competition between the saccade goal and the MT. Our results suggest that, the attention bias linked to the content of VWM can be understand as a competition between different saccade goals in the oculomotor system. [ABSTRACT FROM AUTHOR]