Memory for Animal Tracks: A Possible Cognitive Artifact of Human Evolution

1. What they did

People hunted and gathered for most of human history, and hunting needs a knowledge of tracks. The authors asked whether this past has left modern people with a built-in ease for learning animal tracks, and whether that could be tested by experiment rather than argued after the fact.

• The memory test. College students in Fresno, California, watched a slide show of 100 grayscale pictures, 20 from each of five categories, all rated unfamiliar by a separate panel: animal tracks, armored military vehicles, seashells, trees and unusual kitchen utensils. Each picture was shown for 5 seconds while a female experimenter, who did not know the purpose of the study, read out its name.
• The recall. After 10 minutes of arithmetic, students saw the pictures again and wrote down each name. Only the correct main noun counted (“poplar”, not “white”), with the same strict scoring for every category.
• Interest and experience. Students then rated their interest and experience in hunting, tracking, animals, the outdoors, cooking, seashells and the sea, trees and forests, and armored vehicles and military matters.
• Repeats. Experiment 1 had 25 students (14 men, 11 women). Experiment 2 (28 students, 7 men and 21 women) removed confusing items, such as a hare and a rabbit track that people mixed up, leaving 17 per category, and used a new order. Experiment 3 (28 students, 11 men and 17 women) reversed that order.

2. What they found

Average number of items named correctly (out of 20 per category in Experiment 1 and 17 in Experiments 2 and 3)

• Animal tracks: 5.44, 3.96 and 4.32
• Kitchen utensils: 10.08, 9.71 and 8.00
• Trees: 2.08, 2.68 and 3.14
• Armored vehicles: 1.12, 1.61 and 1.50
• Seashells: 1.12, 1.50 and 0.82

Main results

• In all three experiments, students remembered animal tracks significantly better than trees, seashells and armored vehicles, but less well than kitchen utensils.
• Men and women did equally well. In Experiment 1, women recalled slightly more tracks (6.00) than men (5.00).
• Interest and experience gave a mixed picture. In Experiment 1, recall of tracks was not linked to interest or experience in hunting or tracking. In Experiment 2 it was linked to both interest and experience in tracking and hunting, and in Experiment 3 to interest and experience in tracking and experience in hunting. Links for the other categories also changed from one experiment to the next.

3. What they concluded

• The results fit the idea of an inherited predisposition, a “holdover” from the hunter-gatherer past, that makes animal tracks relatively easy to learn and remember. The authors see this as the simplest explanation and, to their knowledge, the first experimental demonstration of a specific thinking ability predicted from human evolution.
• They argue against other explanations: presentation order (three different orders gave the same result), the choice of categories, how distinctive the pictures were, educated guessing (similar tracks such as fox and coyote would be hard to guess), and interest or experience (the correlations varied too much between experiments).
• The advantage is modest, as they would expect after many thousands of years without selection for it. Kitchen utensils were remembered better, possibly because people have some everyday familiarity with them or a kitchen framework to organize them in.
• The ability is shared by women and men, in keeping with flexible roles in the ancient past. The authors stress that they do not suggest “tracking genes” or a “man the hunter” view of evolution.
• It is not yet known whether the predisposition lies in memory, perception and pattern recognition, or motivation, or how far the results extend to other tasks and people. More research is needed.

4. How tracking was or was not used

No tracking in the field. Students learned and recalled the names of animal tracks from field guide pictures, so the study tests memory for tracks identification by people with little or no tracking experience. Interest and experience in tracking and hunting were self-rated.

6. Other technologies, skills or innovations

• Track pictures scanned with Adobe Photoshop and evened out in grayscale with the other pictures, shown as slides with an automated projection tachistoscope and electronic timer.
• A Snellen eye test screened all students for adequate eyesight.