  The spins of the pentaquark states $P_c(4440)$ and $P_c(4457)$ play a
decisive role in unraveling their nature, but remain undetermined
experimentally. Assuming that they are $\Sigma_c\bar{D}^{*}$ bound states, we
demonstrate how one can determine their spins by measuring the
$\Sigma_c^+\bar{D}^{(*)0}$ correlation functions. We show that one can use the
$\Sigma_c^+\bar{D}^0$ correlation function to fix the size of the Gaussian
source and then determine the strength of the $\Sigma_c^+\bar{D}^{*0}$
interaction of spin $1/2$ and $3/2$ and therefore the spins of the $P_c(4440)$
and $P_c(4457)$ states. The method proposed can be applied to decipher the
nature of other hadronic molecules and thus deepen our understanding of the
nonperturbative strong interaction.
