Observers must select goal‐directed stimuli in lieu of distractors in the environment for preferential information processing. This selection, according to the load theory of attention, is modulated by cognitive load, involving the frontal cortices, with more significant distractor interference under high cognitive load, with strained executive control resources. Evidence in support of this theory exists; however, working memory tasks were predominately used in these investigations. The influence of other types of cognitive load on distractor processing is largely unknown. An interleaved pro‐ and anti‐saccade task has often been used to investigate executive control in which subjects are instructed in advance to either automatically look at the peripheral stimulus (pro‐saccade), or to suppress the automatic response and voluntarily look in the direction opposite of the stimulus (anti‐saccade). Distinct frontal preparatory activity has been clearly characterized during preparation for pro‐ and anti‐saccades, with higher inhibition‐related activity in preparation for anti‐saccades than pro‐saccades. Here, we used an interleaved pro‐ and anti‐saccade paradigm to investigate the modulation of distractor interference by cognitive load in a group of 24 healthy young adults. Luminant distractors were used to evoke automatic pupillary responses to evaluate distractor processing. Greater pupillary dilation following dark distractor presentation was observed in the anti‐saccade than the pro‐saccade preparation. These effects, however, were absent in pupillary constriction following bright distractors. Together, our results support the load theory of attention, importantly highlighting the potential of using involuntary changes in pupil size to objectively investigate attentional selection under load.

The orienting response such as saccades and pupil size is evoked by a salient stimulus appeared in the environment to prepare the body for appropriate action for survival (Lynn, 1966;Sokolov, 1963a). The midbrain superior colliculus (SC) receives inputs from multiple cortical and subcortical structures, and projects directly to the premotor brainstem circuit to coordinate various components of orienting (Corneil & Munoz, 2014;Gandhi & Katnani, 2011).

Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes (e.g., voluntary saccade preparation) that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus (pro-saccade) or in the opposite direction of the stimulus (anti-saccade). Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior.