Attention biases the appearance of rapidly alternating stimuli

Abstract Attentional selection not only increases behavioural performance and neural information for attended stimuli but, in some instances, induces changes in stimulus appearance. While reported appearance changes have mostly concerned the effects of attending to a particular spatial location, here we report a shift in appearance that occurs when attention is directed to one component of a rapidly alternating stimulus. Our stimuli included two frames of different colours, which alternated at 3.75Hz or 7.5Hz. Participants reported the perceived dominance of one frame’s colour in the target stimulus, by comparison with a reference stimulus. We found that when one stimulus frame was more salient than the other, capturing exogenous attention, there was an illusory perception that the frame was physically present for a greater proportion of time. When the frames were matched in salience, endogenously directing attention to one frame produced a smaller shift in appearance. Our results add to the body of literature demonstrating that attention can change appearance, in this case altering the appearance of attended versus unattended stimuli that are presented at the same spatial location. Furthermore, our results support the notion that in ‘temporal transparency’, where rapidly alternating stimuli are perceived as two translucent surfaces, attentional selection of one surface can account for the apparent paradox that feature conjunctions are perceived at stimulus alternation rates higher than predicted by the temporal limits of feature binding for other stimuli. Competing Interest Statement The authors have declared no competing interest.