The limitations of the visual short-term memory (VSTM) system have become an increasingly popular ﬁeld of study. One line of inquiry has focused on the way attention selects objects for encoding into VSTM. Using the framework of the Theory of Visual Attention (TVA; Bundesen, 1990 Psychological Review 97 523–547) diﬀerent components of attention were measured while arousal was systematically varied by manipulating temporal expectancies of the observer. The results showed increments in both overall speed of encoding into VSTM and eﬃciency of visual selection as the level of arousal was increased, whereas VSTM capacity showed some decrease with increasing arousal. Furthermore, attentional weights seemed to be modulated such that, as arousal increased, the attentional focus narrowed around fewer, highly relevant objects. Arousal seems to interact with attention in two diﬀerent ways: Through a scaling mechanism modulating the decision bias of the observer and also through an accentuation-suppression mechanism that modulates the degree of subjective relevance of objects, contracting attention around fewer, highly relevant objects while suppressing less relevant objects. These mechanisms may aﬀord an evolutionary advantage for an observer, ensuring that the most relevant objects are selected and encoded faster under high arousal, and making later processing more focused as the capacity of VSTM is decreased.