Human information processing is limited by attentional resources. That is, via
attentional mechanisms, humans select a limited amount of sensory input to
process while other sensory input is neglected. In multisensory research, a
matter of ongoing debate is whether there are distinct pools of attentional
resources for each sensory modality or whether attentional resources are shared
across sensory modalities. Recent studies have suggested that attentional
resource allocation across sensory modalities is in part task-dependent. That
is, the recruitment of attentional resources across the sensory modalities
depends on whether processing involves object-based attention
(e.g., the discrimination of stimulus attributes) or spatial
attention (e.g., the localization of stimuli). In the present
paper, we review findings in multisensory research related to this view. For the
visual and auditory sensory modalities, findings suggest that distinct resources
are recruited when humans perform object-based attention tasks, whereas for the
visual and tactile sensory modalities, partially shared resources are recruited.
If object-based attention tasks are time-critical, shared resources are
recruited across the sensory modalities. When humans perform an object-based
attention task in combination with a spatial attention task, partly shared
resources are recruited across the sensory modalities as well. Conversely, for
spatial attention tasks, attentional processing does consistently involve shared
attentional resources for the sensory modalities. Generally, findings suggest
that the attentional system flexibly allocates attentional resources depending
on task demands. We propose that such flexibility reflects a large-scale
optimization strategy that minimizes the brain’s costly resource expenditures
and simultaneously maximizes capability to process currently relevant
information.