  The butterfly velocity characterizes the spread of correlations in a quantum
system. Recent work has provided a method of calculating the butterfly velocity
of a class of boundary operators using holographic duality. Utilizing this and
a presumed extension of the canonical holographic correspondence of AdS/CFT, we
investigate the butterfly velocities of operators with bulk duals living in
general spacetimes. We analyze some ubiquitous issues in calculating butterfly
velocities using the bulk effective theory, and then extend the previously
proposed method to include operators in entanglement shadows. We explicitly
compute butterfly velocities for bulk local operators in the holographic theory
of flat Friedmann-Robertson-Walker spacetimes and find a universal scaling
behavior for the spread of operators in the boundary theory, independent of
dimension and fluid components. This result may suggest that a Lifshitz field
theory with z = 4 is the appropriate holographic dual for these spacetimes.
