Third option alters choice of previous alternatives
BySarah Schwartz
A trick that salesmen use to sell expensive cars may help average frogs snag mates.
Female túngara frogs often switch which of two mating calls they prefer upon hearing a third, unattractive mating call, researchers report in the Aug. 28 Science. This action resembles a human behavior known as the “decoy effect.”
“People are really interested in this because it’s such a common thing for people,” says study coauthor Amanda Lea, an evolutionary biologist at the University of Texas at Austin. The decoy effect is a well-known marketing trick, where one wholly unappealing option changes a customer’s preference between two others. For example, a customer might prefer a cheap, compact car over a spacious, expensive sedan. But if a salesman presents a third “decoy” option — a car about as large as the sedan but much more expensive — the customer often changes his mind and picks the sedan.
Just as a decoy car prompts a human buyer to change his or her mind, a decoy mating call can make a female túngara frog fickle. Lea and her Texas coauthor Michael Ryan, also of the Smithsonian Tropical Research Institute in Panama, presented 80 individual female frogs with three recorded mating calls. The calls varied in attractiveness of voice and speed of repeated calls. Females tend to prefer long, low croaks and quick repetitions, which might indicate a larger, more energetic male.
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