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Animal Brains

Alignments to Content Standards: 8.SP.A.1 8.SP.A.2


Is there an association between the weight of an animal’s body and the weight of the animal’s brain? 1. Make a scatterplot using the following data.

Body and brain weight by animal. Source: http://mste.illinois.edu/malcz/DATA/BIOLOGY/Animals.html
Animal Body Weight (kg) Brain Weight (g)
Mountain beaver 1.35 8.1
Cow 465 423
Grey wolf 36.33 119.5
Goat 27.66 115
Guinea pig 1.04 5.5
Asian elephant 2547 4603
Donkey 187.1 419
Horse 521 655
Potar monkey 10 115
Cat 3.3 25.6
Giraffe 529 680
Gorilla 207 406
Human 62 1320
African elephant 6654 5712
Rhesus monkey 6.8 179
Kangaroo 35 56
Golden hamster 0.12 1
Mouse 0.023 0.4
Rabbit 2.5 12.1
Sheep 55.5 175
Jaguar 100 157
Chimpanzee 52.16 440
Mole 0.122 3
Pig 192 180
  1. Do there appear to be outliers in this data? Which animals appear to be outliers? Explain how you identified these outliers.
  2. Removing the outliers from the data set, make a new scatterplot of the remaining animal body and brain weights.
  3. Does there appear to be a relationship between body weight and brain weight? If yes, write a brief description of the relationship.
  4. Take a piece of uncooked spaghetti and use that spaghetti to informally fit a line to the data. Attempt to place your line so that the vertical distances from the points to the line are as small as possible.
  5. How well does the spaghetti line appear to fit the data? Explain.

IM Commentary

This task is designed as an instructional task. You will need to provide each student with a piece of uncooked spaghetti.

The purpose of this task is for students to create scatterplots, and think critically about associations and outliers in data as well as informally fit a trend line to data. This task provides an example of how students could informally fit a line to bivariate data without using technology to “magically” make the line appear. By using spaghetti rather than drawing a line, students can easily make adjustments on the placement of the line. They can also easily see points on both sides of the line as they are trying to fit the line to the data.


  1. Sol1_b99aeec067fb05e519047a43a9c67f0c
    Yes there appear to be two outliers. The outliers are the African Elephant and the Asian Elephant. The points corresponding to these two animals are very far away from the rest of the data.

  2. Sol2_ad912a72fc946c1cc85f0894bc86b8f0
  3. Yes, there appears to be a relationship between body weight and brain weight of animals. The relationship looks roughly linear and the relationship is positive. Larger brain weights tend to be paired with larger body weights.

  4. Sol3_caa89c04e9ae8ba41841688307576b76
  5. The spaghetti line fits the data fairly well although the human has a brain weight that is very large given the weight of the body.

Matt says:

almost 3 years

I have a hard time believing that the "mountain beaver" has a brain weight that is around 34% of it's body weight. Wikipedia identifies no such creature but does state that the average beaver weighs in around 20kg.

Cam says:

almost 3 years

Excellent catch! It looks like our data was correctly transcribed from the sourced linked, but that source had a typo when transcribing from the original research. It's been fixed now.

Jana says:

over 3 years

What are the units for body weight and brain weight?

Kristin says:

over 3 years

Good question--I've added that back in from the original source.