A study by Stella Gerdemann and Dr. Annie Wertz
One key adaptive problem that humans had to solve was to identify safe plants while avoiding dangerous ones. The ability to reliably categorize plants was likely critical to accomplishing this task and avoid confusing non-toxic plants with similar-looking toxic ones. Here, they investigated which cues 18-month-old infants (Study 1, N = 40) from Germany, and adults (Study 2, N = 145) recruited online use to categorize plants and manmade artifacts. To this end, in Study 1, we presented infants with plants with different leaf shapes in brightly colored pots and feature-matched artifacts that had the same variation in shape and color as the plants. The results of the categorization task indicate that infants relied on variation in leaf shape to categorize plants more than they relied on similar variation in shape to categorize artifacts.
In Study 2, using a modified version of the task from Study 1, Gerdemann and Dr. Wertz found that adults were less willing to categorize plants using features other than leaf shape, while they were more willing to do so for artifacts. We conclude that infants use different features to categorize plants and artifacts and that aspects of this categorization strategy persist into adulthood. The features infants use to categorize plants would have reliably differentiated between plant types over ancestral time and thus reliance on these features may be based on their conceptual relevance to plants.