Bigger animals live longer, think slower and bite harder — but not in proportion. Here every animal is ranked by how far it beats what its body size predicts, with the textbook rule next to our own line.
22
traits fitted
12
with a textbook value
Who punches above their weight: brain mass
The tightest relationship we can fit — what a scaling law looks like before the messy ones.
Below predictedactual ÷ predicted (1.0× = on the line)Above predicted
Showing 14 of 345 ranked animals — the full list is in the table view.
Fitted to the 345 animals with both measurements. Textbook: +0.750 (Encephalisation — Jerison 1973; the residual from this line is the EQ). Each animal’s score is actual ÷ predicted from the line through these 345 animals. 981 animals have no brain mass measurement and aren’t ranked. Most animals land within a factor of 1.7 of the line, so anything inside that is ordinary.
What the textbook says · n = 50
fitted exponent +0.662 (95% CI +0.605 to +0.719) against a textbook +0.75 -- the textbook value is outside our interval; R2 = 0.92 over 50 species. A quadratic in log-mass fits better (R2 = 0.93) -- do not draw the straight line.
That comes from the original 50-species study. Our numbers use the 345 animals here, so the two won’t always match.
Tap a bar to pick an animal, or open the table.
▶Customize this chart
Trait
Sample
Numbers refit for whatever group you pick. Mixing birds, mammals and reptiles blurs the picture, so try one class at a time.
Which traits follow the textbook rule
Filled = our fit. Hollow = textbook. The pale bar is the uncertainty. Tap a row to send its trait to the ranking above.
Our fit
Textbook
22 traits fitted over all animals; 5 weak (R² below 0.30); 4 of 11 match the textbook. Traits with no textbook value show our marker alone. 1 trait has too few animals for the uncertainty to mean anything, so it appears in the table only.
How it works
We fit a line through all the animals with a given trait, compare its slope with the textbook value, and rank each animal by its distance from the line. A weak fit is marked as such.
