The colour and taste of a placebo mouth rinse alters sweetness perception, neural responses and performance in trained cyclists

Abstract We investigated whether the colour of a non-caloric, artificially sweetened mouth-rinse modulates (1) visual and gustatory sweetness perception, (2) prefrontal cortical activity using electroencephalography (EEG) in healthy individuals and trained cyclists, and (3) cycling performance in trained cyclists. Experiment 1 identified red as a sweetness-congruent colour and green as incongruent and confirmed that the congruent solution elicited higher perceived sweetness intensity despite identical sweetener content. Experiment 2 showed colour-dependent modulation of prefrontal activity exclusively in trained cyclists: the congruent solution reduced the theta–beta ratio (TBR), a proxy of attentional engagement and executive control, before taste stimulation, while both coloured solutions reduced TBR after stimulation relative to a colourless control. In Experiment 3, cyclists completed a 4-km time trial faster following the incongruent solution. These findings demonstrate that colour cues can modulate perception, neural dynamics, and exercise performance through neurocognitive mechanisms in the absence of metabolic input.