Abstract
Attention can be shifted with (overtly) or without an accompanying saccade (covertly). Thus far, it is unknown how effortful these shifts are, yet quantification of such cognitive costs is necessary to understand how and when attention is deployed overtly or covertly in a given situation. Here, we use pupillometry to show that overt shifts are more costly than shifting attention covertly, likely because executing saccades is more complex. We pose that these differential costs will, in part, determine whether attention is shifted overtly or covertly in a given context. A subsequent experiment showed that relatively complex oblique saccades are more costly than relatively simple saccades in horizontal or vertical directions. This provides a possible explanation for the cardinal direction bias of saccades. The utility of a cost-perspective as presented here is vital to further our understanding of the multitude of decisions involved in processing and interacting with the external world efficiently.