Volitional Attention to Color: Breaking Willed Attention out of the Spatial Domain

Attention can be guided by either voluntary (top-down) or involuntary (bottom-up) influences. In real-world vision, voluntary attention can be directed by a wide range of influences such as reward, priming, meaning, experience, selection history, and volition. Laboratory studies of voluntary attention have commonly used attention-directing cues to induce or instruct human subjects to attend one class of stimuli while ignoring others. In recent years, free choice conditions of attention have been introduced, where self-generated volitional shifts of attention (willed attention) are possible (for a review, see Nadra & Mangun, 2023). Prior willed attention studies have focused on mechanisms of covert spatial attention, investigating the neurophysiological correlates of willed attention related to both post-decision processing, and the pre-decision brain activity patterns that predict participants' free choices about where to attend. Much less work, however, has been done on willed non-spatial attention. In this study, in a fashion similar to prior willed spatial attention studies, we investigated willed attention to stimulus color. In a trial-by-trial cueing design, subjects were either cued what color to attend or were allowed to freely choose what color to attend, in order to subsequently discriminate visual features of the cued or willfully chosen target. Behavioral measures showed that the subjects were selectively attending the cued or willed color. Using support vector machine decoding on EEG alpha (8-12 Hz) signals, we found significant post-decision differences in alpha-band power and broadband EEG voltage when participants chose to attend to orange versus purple. However, in contrast to the findings in prior work on willed spatial attention, no pre-decision EEG signals could be identified that predicted which color participants would choose to attend to.