Research on musical metre perception suggests that:

a. Complex metres are always inherently more difficult to process than simple metres.
b. Infants are born with the ability to process both simple and complex metres but they only retain processing abilities for the metre type(s) to which they are exposed.
c. Infants are born with the ability to process simple metres but they later gain the ability to process complex metres.
d. Infants are born with the ability to process both simple and complex metres and they retain these abilities throughout adulthood.

Research on musical meter perception suggests that b) Infants are born with the ability to process both simple and complex meters but they only retain processing abilities for the meter type(s) to which they are exposed.

This finding aligns with how infants handle both music and language. While infants initially possess general perceptual abilities, exposure to specific metrical structures shapes their retained abilities as they grow older.

This is supported by studies showing that infants can discern different musical rhythms and structures soon after birth. Over time, with continuous exposure, their brains become specialized in the complexities of the musical and linguistic structures prevalent in their cultural environment.