Auditory rhythm perception involves bottom-up encoding of timing information and top-down maintenance of a particular interpretation. Beats in musical rhythms can be grouped to form metres, such as duple (two-beat groupings) or triple (three-beat groupings). Subjective (top-down) metre perception can be measured using electroencephalographic responses like mismatch negativity (MMN), P3a, and Steady-State Evoked Potentials (SSEPs). Previously we showed infants could be primed to perceive an ambiguous 6-beat rhythm as either duple or triple by adding loudness accents to every second, or third beat, respectively. For the subsequently presented unaccented rhythm, infants exhibited larger mismatch responses for pitch deviants on primed strong beats, particularly after duple priming (Flaten et al., 2022). Here we applied the same protocol to adults in two experiments. In Experiment 1, adults were passively primed to perceive the rhythm as duple or triple identically as the infants in the previous study. In Experiment 2, participants actively imagined the accents. Results showed that MMN and P3a were not enhanced for strong beats; however, P3a showed significant enhancement for duple beats regardless of priming or attention, driven mainly by musically experienced participants. SSEPs were enhanced at the primed frequency but only when participants actively imagined the metre. As with infants, effects were stronger in the duple group. These results suggest a strong bias toward duple metre in adults that requires attention to overcome, and which likely relates to enculturation to Western music as it was enhanced by music and dance experience.