Concurrent selection of internal goals and external sensations during visual search

Flexible goal-directed behaviour relies on the selective processing of internal goal representations and external sensations. Yet, internal and external selection processes have classically been studied in isolation, leaving us in the dark how internal and external selection processes are coordinated in time to support behaviour. To address this, we developed a novel visual-search task in which we could simultaneously track selection among internal search goals held in working memory and external search targets in the environment. Capitalising on sensitive gaze and neural markers of internal and external visual selection, we provide proof-of-principle evidence in humans that internal and external selection processes do not necessarily take turns in a strictly serial manner, but can develop concurrently. We further show how concurrent internal and external selection processes are associated with largely non-overlapping neural activity patterns in the human brain, and how these processes can be performed effectively even when engaging opposite spatial locations in working memory and perception. These findings challenge views portraying brain states as being either internally or externally focused and bring new insight into how internal and external selection processes work together to yield efficient search behaviour.