Task-evoked pupillary responses were recorded during
a visual backward masking task as an index of resource
allocation. Increased pupillary dilation indicates increased
allocation of processing resources to the task. Consistent
with numerous studies, detection accuracy increased with
longer interstimulus intervals and approximated no-mask
accuracy in the 300-ms condition. Pupillary dilation responses
were significantly greater during task performance (cognitive
load) than during a passive stimulus viewing condition
(no-load) and were significantly greater in the 300-ms
condition than the no-mask condition. Consistent with models
of early visual information processing, the results suggest
that the mask demanded extra processing resources when
it followed the target by more than 100 ms. Pupillography
methods may be useful in evaluating the contribution and
timing of resource-demanding processes during early visual
information processing.