  We give strong numerical evidence that a self-interacting probe scalar field
in AdS, with only a few modes turned on initially, will undergo fast
thermalization only if it is above a certain energetic threshold. Below the
threshold the energy stays close to constant in a few modes for a very long
time instead of cascading quickly. This indicates the existance of a Strong
Stochasticity Threshold (SST) in holography. The idea of SST is familiar from
certain statistical mechanical systems, and we suggest that it exists also in
AdS gravity. This would naturally reconcile the generic non-linear instability
of AdS observed by Bizon and Rostworowski, with the
Fermi-Pasta-Ulam-Tsingou-like quasi-periodocity noticed recently for some
classes of initial conditions. We show that our simple set-up captures many of
the relevant features of the full gravity-scalar system.
