青蛙公主腦洞大，選錯榜眼嫁對郎？

Lady Frogs’ Funny Choice： Let the Second-Best Win？

These little frogs live in Central America， and they’re called túngara frogs. Amanda Lea is a biologist at the University of Texas. She says only the males make these calls to 1）woo the females， and scientists have a pretty good idea of what the females like.

Amanda： They tend to like longer calls. They also like lower frequency calls. And then the other thing that’s a really big…a big one for these 2）gals is the call rate. So they love faster call rates. The faster a male can call， the better.

But in real life， love is complicated. Female frogs face countless 3）suitors， and the researchers wondered， did a female always pick the male that scored highest on the froggy love-call meter？ So to find out， they put female frogs in a room with some loudspeakers. From one came a voice that had a very fast call rate.

Fast is good， but other features in this voice were less attractive. Then the females heard a second call.

This voice was attractive， but it was slower. The ladies had to make a choice.

They picked speed. They liked the fast guy best. The researchers then repeated the experiment， but this time， they added a third option： a frog with an attractive voice that was very， very， very slow. The females didn’t pick him. Still， his 4）mere presence had a profound effect. When he was around， the superfast guy did not win. Instead， females picked the frog they had rejected the first time around.

Amanda： They actually switched their preferences， so now call rate is no longer the most important thing.

And it seems to make no sense. David Stephens is a behavioral ecologist at the University of Minnesota. He says this is an example of something called the decoy effect. That’s when adding a third 5）inferior option 6）inexplicably results in the rejection of the best choice. Scientists see it in all sorts of decision making， in humans and other animals too.

David： In humming birds and bees， and the most stunning example is actually in a…not an animal at all， but in a 7）slime mold.

Reporter： I’m sorry—a slime mold.

David： A slime mold， yeah.

Stephens says what’s interesting about this frog study is that it found the decoy effect in something as crucial as picking a mate.

David： Mate choice is， like， for many people， the goldstandard decision.

這種小青蛙生活在中美洲，它們就是南美洲泡蟾。美國德克薩斯大學的生物學家阿曼達·利說，只有雄蛙會用這種叫聲向雌蛙求愛，科學家也很清楚女士們喜歡怎樣的蛙鳴。

阿曼達：它們一般喜歡較悠長的叫聲，也喜歡較低頻的聲音。此外還有一個因素相當重要……對姑娘們來說，還有一個重要因素就是叫聲的快慢。它們喜歡叫得快的，雄蛙叫得越快越受歡迎。

不過，在現實生活中，愛情是個很復雜的問題。雌蛙要面對無數的追求者，于是研究人員不禁在想：雌蛙總會選擇在求偶蛙鳴測量儀上得分最高的雄性嗎？為了找到答案，他們將幾只雌蛙放進一個安裝了擴音器的房間里。從擴音器中傳來一段節奏很快的蛙鳴。

叫得快是挺好的，但這個聲音里的其他要素就遜色多了。接著，雌蛙聽到第二段蛙鳴。

這個聲音很有魅力，但節奏比較慢。女士們要在這兩者之間做出選擇。

它們選擇了速度，更喜歡叫得快的雄蛙。接下來，研究人員再次進行實驗，不過這一次，他們引入了第三個選項：一只叫聲動聽但叫得非常非常慢的雄蛙。雌蛙并沒有選擇它，然而，它一出現就會對雌蛙產生重大影響。只要它在場，那只叫得忒快的雄蛙就無法俘獲芳心——雌蛙們轉而選擇了第一次實驗中的落敗者。

阿曼達：它們竟然改變了偏好，現在叫聲的快慢已經不是最重要的因素了。

這看起來似乎毫無道理。美國明尼蘇達大學的行為生態學家戴維·斯蒂芬斯說，這個例子就是所謂的“誘餌效應”，也就是說，當加入第三個較差的選項時，就會莫名其妙地導致最佳選擇的落選。