Spearman rank correlation between the tidal anisotropy and the overdensity as a function of halo mass. Different fixed Gaussian smoothing scales, S, have been used, as indicated by the legend. The solid black line indicates the Spearman rank correlation at a variable scale corresponding to the radius of the halo, i.e. $4·R_{200b}/\sqrt{5}$. Our chosen smoothing scale for the tidal anisotropy, 4·R_200b, corresponds to the maximum correlation for any mass range considered, and the correlation at this scale envelopes the correlations computed at other smoothing scales.