An illustration of the “fallacy of the averaged shape”. Mixtures of randomly generated quasi-linear (A) or strongly nonlinear concave-up (blue) and concave-down (red) (B) relationships between herbivore performance and plant defense level. C, D Mean (open and closed black dots) and standard deviation (black bars) of the effect size of Jensen’s Inequality based on the individual values (colored dotes) of the corresponding relationships shown in A and B.