“Worthwhile content in PNAS”

Ben Bolker sends an email with the above subject line, a link to this article, and the following content:

Experimental evidence that hummingbirds can see purple … researchers used Stan to analyze the data …

The article in question is called “Wild hummingbirds discriminate nonspectral colors” and is by Mary Caswell Stoddard, Harold Eyster, Benedict Hogan, Dylan Morris, Edward Soucy, and David Inouye.

All four of the figures in this paper are pretty. I’ve just shared two of them.

Here’s the key bit:

We conducted a series of field experiments on nonspectral color discrimination in a population of wild, free-flying broad-tailed hummingbirds . . . we trained hummingbirds to associate one color (the reward color) with a sucrose solution and a second color (the nonreward color) with water . . . Each platform supported a tube and a clear plastic saucer partially filled with either sucrose solution or water. . . . Because hummingbirds can readily learn location cues, after each trial we swapped the locations of the reward (sucrose saucer with reward color) and nonreward (water saucer with nonreward color) setups to prevent birds from cueing on the spatial location of the reward.

It’s the bottomless soup bowl for hummingbirds! Maybe this experiment will be featured in the next edition of Nudge.