Fig. 11. Predicting navigational prowess, NP. (A) Tail stiffness k predicts NP. Predicted values of NP were generated from values of kinematic variables R, t, U and W predicted by k in univariate regressions (Table 4). Stiffness predicts 40% of the variance in NP. (B) Stiffness-independent correlates of NP. Residuals (observed minus predicted value) of NP, by definition independent of k, are correlated with the residuals of two of the four kinematic variables, orbital radius R (P<0.0001) and swimming speed U (P<0.001) as determined by stepwise linear regression (r²=0.81). Residuals for kinematic variables from regression onto k. All observed values are means of 12 trials for each of three tails for ten generations (N=30).