Is preattentive search constrained by the oculomotor system?

Yes. At least, that’s what we claim in the latest paper from the Durham arm of the MotorBias project, which has now been accepted for a special issue of Attention, Perception & Psychophysics honouring Anne Triesman. In this study we explored what happened to visual search when we presented search arrays at positions that can be seen but are beyond the Effective Oculomotor Range (EOMR; ie. positions that could not be reached with saccadic eye movement). In short, we found that preattentive, feature search was significantly impaired but conjunction search was not. The twist on our previous projects which used cueing tasks (e.g. Casteau & Smith 2020) or the eye-abduction technique (Smith et al., 2014)  was that we parametrically varied the eccentricity of the search array across 6 different positions. This meant we could precisely localise the eccentricity at which feature search became impaired in relation to each participants EOMR. Critically, the drop in feature search performance occurred when the arrays were moved from just within the range of eye-movements to just beyond the range of eye-movements, and was stable at more eccentric locations (see figure 1) . The latter finding is important, as it mean we can rule out the possibility that people simply got worse at search tasks as stimuli are presented further into the periphery.

Figure 1: Time to detect a colour feature singleton. The X axis illustrate the position of the search array relative to the participants EOMR. -1 is the location just within the EOMR, +1 and +2 are the two locations just beyond the EOMR.

It therefore seems that the EOMR imposes a significant constraint on the ability to reflexively orient to salient stimuli, but not on the voluntary shifts of attention associated with conjunction or ‘attentive’ search. This pattern of data is echoes our other findings (reviewed in Casteau & Smith 2019), and is consistent with the broader claim that Oculomotor theories of spatial attention such as OMRH and Premotor Theory are only tenable for exogenous, covert orienting.  Thanks to the ESRC and Durham University the paper is open access, and you can read it by clicking here


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