The pair backlit each panel with either blue, yellow, or green light or a shade visible to insects known as UV-yellow.
Lotto and Wicklein then placed a sugar solution at every blue flower. This trained forager bees to selectively visit the blue blossoms amid the riot of multicolored, plastic flowers.
Once trained, the bees were given what Wicklein, an expert on insect biology and behavior, describes as a "multiple-choice exam." The researchers rearranged the blossoms and removed all traces of the sugar solution.
When they let the bumblebee foragers loose on the array, the insects showed a preference for visiting the blue flowers.
Even when the scientists backlit the flowers with a color of light the bees had never seen before, the bugs still made a beeline for the blue blossoms.
"We were kind of surprised," Wicklein said of the insects' performance. "It's a hard task, but it looks as if bumblebees can solve the problem very easily."
So how do the bees pick out the blue flowers amid a kaleidoscope of choices?
"What we've discovered is that the way the bees are solving this problem is that they're using relationships between the flowers," Lotto said. Whether it's within the context of a backlit green array or a backlit yellow array, the bees survey the panel and go for the bluest looking flower.
Dale Purves, director of Duke University's Center for Cognitive Science, said via e-mail that the "highly imaginative" study is important because it shows "that relatively simple invertebrates use the same empirical strategy that humans employ."
"The ability to manipulate the environment of bees in ways that would be impossible in human studies promises many additional insights about the deeper nature of vision across a wide range of animals," he added.
Because the bees are able to tackle such a complex task and have only a million neurons in their tiny brains, Lotto thinks robots could evolve a similar system.
One of his students has already created a virtual bee computer program, like the matrix described in the study, that's populated with virtual bees. In the virtual system, the bees evolve their ability to use color relationships. Those that can pick out the blue flowers eat, live, and reproduce. Those that can't starve and die off.
"In this next year we're trying to take those virtual robots into the real world," Lotto said.
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