litter body brain 3 9.447 .444 3 9.780 .436 4 9.155 .417 4 9.613 .429 5 8.850 .425 5 9.610 .434 6 8.298 .404 6 8.543 .439 7 7.400 .409 7 8.335 .429 8 7.040 .414 8 7.235 .409 9 6.600 .387 9 7.260 .433 10 6.305 .410 10 6.655 .405 11 7.183 .435 11 6.133 .407 12 5.450 .368 12 6.050 .401