Analysis of experiments performed at different heating powers and magnetic field intensities shows that the existence of internal transport barriers in JET can be inferred in regions of space-time where the ratio of the ion gyroradius to the local gradient scale length exceeds some critical value. A possible interpretation leading to the theoretical relevance of this dimensionless parameter as a local indicator of a bifurcated plasma state is the stabilization of turbulence by the E×B shear flows associated with large pressure gradients and plasma rotation. Large database analysis and real time plasma control are envisaged as attractive applications.