Selective attention enables the prioritisation of task-relevant visual information, including among internal contents in working memory. Studies targeting the foundational mechanisms of covert selective attention often consider situations where to-be-attended and to-be-ignored visual contents are presented or memorised in distinct directions from fixation — rendering direction sufficient for covert selection. Yet, in everyday life, direction alone is typically insufficient for selection because multiple potential objects of attention compete along any given direction. To gain insight into the mechanisms of covert attention when direction is sufficient versus insufficient for selection, we cued participants to select memorised visual items that were encoded near or far from fixation while manipulating whether direction was sufficient (no competition along direction) or insufficient (competition along direction) for selection. To uncover the nature of spatial coding for covert attention, we tapped into directional biasing of fixational gaze behaviour as a non-invasive read-out of the brain's oculomotor system — a brain system widely recognised for its contribution to covert attention. This unveiled the principle of 'efficient spatial coding' whereby covert internal selective attention considers just direction when sufficient and considers the distance of the attended target only when necessary.

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