  Adiabatic and non-adiabatic electron dynamics have been proposed to explain
electron heating across collisionless shocks. We analyze the evolution of the
suprathermal electrons across 310 quasi-perpendicular shocks with $1.7<M_A<48$
using in-situ measurements. We show that the electron heating mechanism shifts
from predominantly adiabatic to non-adiabatic for the Alfv\'enic Mach number in
the de Hoffman-Teller $\gtrsim 30$ with the latter constituting 48\% of the
analyzed shocks. The observed non-adiabatic heating is consistent with the
stochastic shock drift acceleration mechanism.
