Dynamic prioritisation of attention when external and internal demands compete

Abstract

Attention enables the prioritisation of task-relevant information, whether encountered in the external world or maintained as internal representations. While the mechanisms of attention have been extensively studied within perception and working memory, everyday cognition often confronts us with competing demands from both domains simultaneously. How attention is divided under such cross-domain demands remains poorly understood. Here, participants performed a combined perception and working-memory task in which an informative cue appeared between a working-memory display and a subsequent perceptual display. On most trials, this cue simultaneously indicated two items for prioritisation: either two encoded working-memory items or two upcoming perceptual items (within-domain attention), or one item from each domain (cross-domain attention). Combining behavioural measures with electroencephalography allowed us to characterise how dividing attention across domains shapes performance and neural activity relative to dividing attention within one domain. Behaviourally, we observed a striking asymmetry: perceptual performance benefited from cross-domain versus within-domain attention, whereas working-memory performance showed the opposite pattern. Mirroring this behavioural imbalance, time-resolved decoding revealed distinct cross-versus within-domain competition in both perception and working memory, suggesting that external and internal attention are neurally separable even when engaged simultaneously. This competition between domains was also evident in neural markers of spatial attentional orienting: while initially impaired during cross-domain attention, orienting progressively favoured external over internal information. Together, these findings show that when perception and working memory compete, attention is not divided evenly. Instead, cross-domain attention constitutes a distinct attentional state, with its own prioritisation dynamics and neural representation. Significance statementPerception and working memory are typically studied as separate targets of attention, yet real-world behaviour requires continuous negotiation between what is currently available in the external environment and what is held in mind. This study addresses how that negotiation unfolds when both sources of information become relevant at once. By directly comparing divided attention across versus within domains, we show that competition between perception and working memory is not neutral: it produces asymmetric behavioural consequences, distinct neural states, and a progressive bias in attentional prioritisation towards upcoming perceptual input. These findings suggest that cross-domain attention is not a balanced extension of within-domain attention, but a domain-biased prioritisation regime in which perception and working memory systematically trade off against each other.