  We use $N$-body simulations to compare the evolution of spatial distributions
of stars and brown dwarfs in young star-forming regions. We use three different
diagnostics; the ratio of stars to brown dwarfs as a function of distance from
the region's centre, $\mathcal{R}_{\rm SSR}$, the local surface density of
stars compared to brown dwarfs, $\Sigma_{\rm LDR}$, and we compare the global
spatial distributions using the $\Lambda_{\rm MSR}$ method. From a suite of
twenty initially statistically identical simulations, 6/20 attain
$\mathcal{R}_{\rm SSR} << 1$ $and$ $\Sigma_{\rm LDR} << 1$ $and$ $\Lambda_{\rm
MSR} << 1$, indicating that dynamical interactions could be responsible for
observed differences in the spatial distributions of stars and brown dwarfs in
star-forming regions. However, many simulations also display apparently
contradictory results - for example, in some cases the brown dwarfs have much
lower local densities than stars ($\Sigma_{\rm LDR} << 1$), but their global
spatial distributions are indistinguishable ($\Lambda_{\rm MSR} = 1$) and the
relative proportion of stars and brown dwarfs remains constant across the
region ($\mathcal{R}_{\rm SSR} = 1$). Our results suggest that extreme caution
should be exercised when interpreting any observed difference in the spatial
distribution of stars and brown dwarfs, and that a much larger observational
sample of regions/clusters (with complete mass functions) is necessary to
investigate whether or not brown dwarfs form through similar mechanisms to
stars.
