Fig. 2. Parallel improvement of the wheel system and of its understanding.

(A) Wheel speed over generations for nonfailure wheels and number of failures in the Speed-Only condition (gray) and in the Configurations+Speed+Noise condition (orange). (B to D) Understanding scores over generations [(B) total; (C) center-of-mass items only; (D) inertia items only]. The performance obtained by a control group is also shown [see (41); mean: yellow; standard error: blue]. Error bars indicate standard errors.